CHAPTER VI.

Voyage from Buenos Ayres to Santos--Tropical vegetation in Brazil--Visit to San Paulo--Journey from San Paulo to Rio Janeiro--Valley of the Parahyba do Sul--Ancient mountains of Brazil--Rio Janeiro--Visit to Petropolis--Falls of Itamariti--Struggle for existence in a tropical forest--The hermit of Petropolis--Morning view over the Bay of Rio--A gorgeous flowering shrub--Visit to Tijuca--Yellow fever in Brazil--A giant of the forest--Voyage to Bahia and Pernambuco--Equatorial rains--Fernando Noronha--St. Vincent in the Cape de Verde Islands--Trade winds of the North Atlantic--Lisbon--Return to England.

[_EMBARCATION AT BUENOS AYRES._]

About midday on June 30, I took my departure from Buenos Ayres. The operation was not altogether simple or to be quickly accomplished. Jolting heavily over the ill-paved streets, a hackney coach carried me and a fellow-traveller with our luggage to the riverbank. The sight was very strange. It was a busy day, and there were literally hundreds of high-wheeled carts engaged in carrying passengers and goods out to the boats, which lay fully half a mile from the shore. When, after a delay that seemed excessive, we were installed in a boat, this was pulled in a leisurely fashion to the steam-tender, which lay more than a mile farther out. When the hour fixed for the departure of the tender was long past, we at length got under way, and finally reached the Neva steamship of the Royal Mail Company, about fourteen miles below the city, at five o’clock.

With iron punctuality dinner was served at the regular hour, although none of the passengers were ready, and the luggage was not brought on board till after dinner. There was, in truth, no reason for haste, as we were appointed to call at Monte Video on the following morning. My chief business at that place was to recover possession of the chest containing my botanical collections, which I had deposited at the custom-house.

Impressed with the attractions of Brazil, and feeling the strict limits of time to which I was bound, I asked myself if I should not have done better to have omitted a visit to the Plata region, and saved nine days by proceeding direct to Brazil in the _Iberia_, which started on the 22nd of June. I should certainly recommend that course to any naturalist travelling under similar circumstances at the same season; but I am sure that, if I had done so, I should have felt regret at having missed an opportunity, and should have fancied that I had lost new and interesting experiences.

At four p.m. on the 1st of July the big ship began to move from her moorings opposite Monte Video, and for about sixty miles kept a due easterly course. Somewhere near the port of Maldonado we passed a bright light on an island which shows as a bold headland. I was told that this is known as Cape Frio, because of the cold often encountered here by those arriving from Brazil. It may be supposed that the force of the south-west wind which prevails in winter is more felt as the wide opening of the great estuary is reached. During my own short stay, the wind never rose beyond a gentle breeze, and the temperature on land was no more than agreeably cool, usually between 55° and 60° Fahr. during the day.

[_VOYAGE TO SANTOS._]

The distance from Monte Video to Santos, which is reckoned at 970 sea miles, was accomplished in about three days and eighteen hours. The voyage was uneventful. On the 3rd we approached the Brazilian coast, but the land lay low, and no objects could be distinguished. The weather was all that could be desired by the most delicate passengers, the barometer remaining almost stationary at about 30·2 inches,[42] and the temperature by day rising gradually from 57° at Monte Video to 62° in lat. 25° south. Before sunrise on the morning of July 5, we entered the bay through which the Santos river discharges itself into the Atlantic, and found ourselves in a new region. The richness of the green and the luxuriance of the foliage recalled the aspect of the coast at Jacmel, in Hayti, and as the morning advanced, while we slowly steamed towards the head of the bay, I had no difficulty in deciding on a course which had already suggested itself to my mind. I knew that Santos is connected by railway with São Paulo (better known in the form San Paulo), the chief town of this part of Brazil, and that the railway between that place and the capital was also completed; and I accordingly determined to leave the steamer, and find my way by land to Rio Janeiro.

Santos is an ancient place which had long remained obscure, until the great development of coffee-cultivation in South Brazil, and the construction of a railway to the interior, have made it the most advantageous port for the shipment to Europe of that important product. It lies at the mouth of an inconsiderable stream that enters the head of the bay. Seen from the sea, it appears to be backed by a range of lofty, flat-topped hills, but, in truth, these are no more than the seaward face of the great plateau which extends through a considerable part of the province of San Paulo. Although Santos is placed a few miles south of the Tropic of Capricorn, the aspect of the vegetation is completely tropical; and if a stranger were in doubt, the fringe of cocoa-nut palms on the shores of the bay would completely reassure him. Although the thermometer on board ship did not rise above 67°, the air seemed to us, arriving from the south, very warm, and we were surprised to hear the company’s agent, when he came on board, complain that he had found the water in his bath uncomfortably chilly.

I landed with a young German fellow-traveller who, like myself, intended to proceed to San Paulo; and, as we found that the train was not to start for three hours, we occupied the time in ascending the nearest hill. It was now nearly three months since I had enjoyed a glimpse of true tropical vegetation in the forest of Buenaventura, and the interest and delight of this renewed experience can never be forgotten. It was clear that on the slopes about Santos the native forests had been cleared, but on all the steeper parts, not reclaimed for cultivation, the indigenous vegetation had resumed the mastery. Trees and shrubs in wonderful variety contended for the mastery, and maintained, as they best could, a precarious struggle for existence with a crowd of climbers and parasites. So dense was the mass of vegetation that it was impossible to penetrate in any direction farther than a few yards, and there was no choice but to follow the track that led to the summit of the slope, on which stood a pretty house with an adjoining coffee-plantation. Among the many new forms of vegetation here seen, the most singular was that of the _Tillandsia_.[43] Long, whitish, smooth cords hang from the branches of the taller trees, and at eight or ten feet from the ground abruptly produce a rosette of stiff leaves, like those of a miniature pine-apple, with a central spike of flowers. But the most brilliant ornament of this season was a species of trumpet-flower (_Bignonia venusta_, Ker = _Pyrostegia ignea_, Presl), which, partly supporting itself, and partly climbing over the shrubs and small trees, covered them with dense masses of brilliant orange or flame-coloured flowers.

[_TROPICAL VEGETATION AT SANTOS._]

Laden with specimens, I returned to the town just in time for the afternoon train to San Paulo. The railway was constructed by an English company, and is so far remarkable that a somewhat difficult problem has been solved in an efficient and probably economical fashion. The object is, within a distance of a few miles, to raise a railway train about 2500 feet. This is done by four stationary engines. The line is laid on four rather steep inclines, with nearly level intermediate spaces, each ascending train being counterpoised by one descending in the opposite direction, and the loss of time in effecting the connections is quite inconsiderable.

On every map of Brazil that I have seen, the Serra do Mar, which we were here ascending, is represented as a range of mountains running parallel to the coast, and extending from near Rio Janeiro to the Bay of Paranagua in South Brazil, apparently dividing the strip of coast from the low country of the interior. Most travellers would probably have expected, as I did, that on reaching the summit we should descend considerably before reaching San Paulo, and it was with surprise that from the summit I saw before me what appeared to be a vast level plain, with some distant hills or mountains in the dim horizon. It is true that the drainage of the whole tract is carried westward and ultimately reaches the Paranà; but the slope is quite insensible, and I do not think that, in the space of about sixty miles that lay between us and San Paulo, the descent can exceed two or three hundred feet. There was a complete change in the aspect of the vegetation, and open tracts of moorland recalled scenes of Northern Germany.

Night had closed before we reached the station at San Paulo. There was a difficulty about a carriage to convey us to the hotel. Perhaps the demands were unreasonable, or perhaps we were too unfamiliar with the coinage of Brazil, which is that of the mother country; but on hearing from the driver a demand for several thousand rees, we indignantly resolved to walk, and engaged a man to convey our luggage to the hotel. We were favourably impressed by the appearance of this provincial capital. In the space of a mile we passed through several good streets, well lighted with gas, and better paved than any I had seen in South America. Many handsome houses with adjoining gardens were passed on the way, and, on reaching the Grand Hotel, nice clean rooms, and good food provided for the evening meal, further conduced to favourable first impressions of Brazil.

[_GERMAN COMMERCIAL TRAVELLERS._]

My young German companion, a traveller for a commercial house, was returning from a visit to the interior of Brazil. By steamer on the Paranà and Paraguay he had gone from Buenos Ayres to Cuyabà, the capital of the province of Matto Grosso, a vast region with undefined boundaries, probably larger than most of the European states. I have often been struck by the results of superior education among Germans engaged in business, as compared with men of the same class in other countries. It is not that they often merit the designation of intellectual men, and still more rarely do they show active interest in scientific inquiry; but they retain a respect for the studies they have abandoned, are ready to talk intelligently on such subjects, and, as a rule, have a regard for accuracy as to facts which is so uncommon in the world, as much because the majority are too ignorant to appreciate their importance as owing to deliberate disregard of truth. I did not learn much as to the progress of inner Brazil, but my fellow-traveller mentioned a few particulars that had struck him as singular. He found the civil population of Cuyabà solicitous in their adherence to European fashions in dress, and, as a special note of respectability, the men always appearing in what are vulgarly called chimneypot hats. The current coin in all but small transactions consisted in English sovereigns, but he was unable to explain how these have reached a region which can have so few commercial relations with this country. He departed on the following morning, while I resolved to spend a day in visiting the neighbourhood of the city.

Although San Paulo lies exactly on the southern tropic, the winter climate is positively cool, and at sunrise on July 6 the thermometer stood at 58° Fahr. On a rough estimate from a single barometric observation it stands about 2400 feet above the sea. Its appearance was altogether unlike that of all the towns seen in Spanish America. The somewhat wearisome monotony of regular square blocks gave place to the irregular arrangement of some of the provincial towns in England, several streets running out into the country and ending in detached villas. The general impression was that of comfort and prosperity. Several well-appointed private carriages were seen in the streets, and the shops were as good as one commonly sees in a European town of the same class.

I was much interested by the short country excursion, which occupied most of the day, and by an aspect of vegetation entirely new to me. The plants, with scarcely an exception, belonged to genera prevailing in tropical America, many of them now seen by me for the first time; but the species were nearly all different from those of the coast region, and the general aspect of the flora still more markedly different. There was no trace of that luxuriance which we commonly expect in tropical vegetation; monocotyledonous plants, except grasses, were very few, and, in place of the large ferns that abounded at Santos, I found but a single _Gleichenia_, allied to a species that I had gathered in the Straits of Magellan.

[_FLORA OF THE BRAZILIAN PLATEAU._]

Although a fair number of plants were still in flower, I soon came to the conclusion that night frosts must be not unfrequent at this season, and that a considerable proportion of the vegetation must be annually renewed. I found several groups of small trees, chiefly of the laurel family, and for the first time saw the _Araucaria brasiliensis_, possibly in a wild state; but none of the trees attained considerable height, and I doubt whether in a state of nature this plateau has ever been a forest region. I was rejoiced to see again, growing in some abundance, the splendid _Bignonia venusta_, and was led to doubt whether its real home may not be in the interior, and its appearance at Santos due to introduction by man.

We possess a fair amount of information as to the climate of the Brazilian coasts, but our knowledge of the meteorology of the interior provinces is miserably scanty. I was led to conjecture that, although the district surrounding San Paulo is not divided by a mountain range from the neighbouring coast region, the climate must be very much drier, and that the rainfall is mainly limited to the summer season.

In the course of my walk, I unexpectedly approached a country house about three miles from the town, and was somewhat surprised by meeting a carriage with ladies on their way to the house. As far as my experience has gone in the country parts of Portugal or Spain, such an encounter would there be regarded as a very unusual phenomenon.

The railway from San Paulo to Rio Janeiro appears to be a well-managed and prosperous concern, paying to its shareholders dividends of from ten to twelve per cent. The distance is about 380 miles, and the trains perform the distance in about thirteen and a half hours. Leaving my hotel in the dark, I found at the station a crowd of passengers contending for tickets; but good order was maintained, and we started punctually at six o’clock. For some way the line is carried at an apparent level over the plain, with occasional distant views of high hills to the north, and crosses two or three inconsiderable streams, whose waters run to the Paranà. A slight but continuous ascent, scarcely noticed by the passing, traveller, leads to the watershed which, in this direction, limits the vast basin of the Paranà. After a long but very gentle descent, we reached a stream flowing westward. I at first supposed it, like those already seen, to be a tributary of the Paranà which made its way through some depression in the low ridge over which we had passed; but I soon ascertained that this was an error. Near the spot where the railway crosses it, the stream makes a sharp turn, and thenceforth proceeds in a direction little north of east for about four hundred miles, till it falls into the Atlantic at São João da Barra, north-east of Rio Janeiro. This is the Rio Parahyba do Sul, not to be confounded with the Rio Parahyba north of Pernambuco, nor yet with the more important river Paranahyba in the province of Piauhy.

[_GEOLOGY OF EASTERN BRAZIL._]

For the greater part of the way to Rio the railway runs parallel with the river. As laid down on the maps, the valley lies between a mountain range called the Serra da Mantiqueira on the left, and a minor range, which divides the upper course of the river from the middle part, where it flows in the opposite direction. The appearance of the country through which I now passed forcibly suggested to me views respecting its geological history, which were confirmed and extended by what I afterwards saw in the neighbourhood of Rio, and by all that I have since been able to learn on the subject.

I had already been struck by what little I had seen of the plateau region of the province of San Paulo. Beneath the superficial crust of vegetable soil, the plateau appears to be formed of more or less red arenaceous deposits, such as would result from the erosion and decomposition of the gneiss or granite which is the only rock I had seen in the country. In the valley of the Parahyba, the connection was unmistakable. Every section in the valley showed thick beds of the same coarse-grained, red arenaceous deposits, and on the slopes the same material lay at the base of whatever masses of granite we approached. But what especially struck me were the forms and appearance of the mountains on either hand, if that designation could properly be given to them. I saw nothing that would elsewhere be called a mountain range. The outlines were in most places rounded and covered with vegetation, but at intervals occurred steep conical masses, of the same general type as the sugar-loaf peaks surrounding the Bay of Rio Janeiro. However steep, the rocks nowhere showed angular peaks or edges, these being always more or less rounded.

It would be rash to generalize from the partial observations of a passing traveller; but the broad outlines of the geology of Brazil, or, at least, of the eastern provinces, have now been well traced,[44] and some general conclusions may safely be drawn. It is true that large districts of the interior have been but partially explored, and remain blanks on the geological map; but the eastern half of Brazil is undoubtedly ancient land; presenting no trace of secondary strata except in small detached areas near the coast, and where more recent tertiary deposits are to be found only in a portion of the great valley of the Amazons. A mountain range, having various local designations, but which may best be called the Serra da Mantiqueira, extends from the neighbourhood of San Paulo to the lower course of the Rio San Francisco, for a distance of twelve hundred miles, and this is mainly composed of gneiss, sometimes passing into true granite, syenite, or mica schist; and the same may be said of the Serra do Mar, a less considerable range lying between the main chain and the coast. The southern limits of the Serra do Mar do not appear to be well-defined, but we may estimate its length at from five to six hundred miles. The other mountain systems of the empire are less well known; but I believe that the ranges dividing the province of Minas Geraes from Goyaz, and the so-called Cordillera Grande of the province of Goyaz, lying between the two main branches of the great river Tocantins, are largely formed of ancient sedimentary rocks of the Laurentian and Huronian groups.

[_DISINTEGRATION OF GRANITE._]

The granite of the Serra da Mantiqueira and Serra do Mar is coarse-grained, with large crystals of felspar, and is therefore much exposed to disintegration. So far as I know, the vast masses of detritus forming the plateaux of this region show no other materials than such as would be produced by the disintegration of the crystalline rocks, and there is strong reason to believe that these have never been overlaid by sedimentary deposits.

Let us now consider what must have been the past history of a region formed of such materials, exposed, during a large part of the past history of the earth, to the action of the elements. In such an inquiry one of the chief points for consideration is the amount of rainfall. The direct effect, both mechanical and chemical, of rain falling on a rock surface is perhaps not the most important. Still more essential is its action in removing the disintegrated matter, and thereby exposing a fresh surface to renewed action. The difference in the absolute result due to abundant or deficient rainfall would be found, if we could calculate it accurately, to be enormous. In a nearly rainless country, such as Egypt or Peru, we see a slope covered with _débris_, and are apt to conclude that the rock is being rapidly disintegrated; but, in truth, what we see is the work of many, perhaps many hundred, centuries, which remains _in situ_ because there is no agency to remove it. In a land of heavy rainfall the _débris_ is speedily carried to lower levels, and the work of destruction is constantly renewed.

We have scarcely any observations of rainfall in the mountain districts of Brazil. The only reliable return that I have seen is that of one year’s rainfall at Gongo Seco, in Goyaz, which amounted to more than a hundred and thirty inches; but we may safely conclude that it is everywhere very great. It is also important to note that if, as most geologists now believe, the Atlantic valley has existed since an early period of the earth’s history, Eastern Brazil must always have been a land of heavy rainfall. A great mountain range on the eastern side of the continent might have created a desert region in the interior, but would have received in the past as much aqueous precipitation as it does at the present time.

We have, therefore, to consider what must have been the ancient condition of a region subjected throughout vast periods of geological time to the utmost force of disintegrating agencies applied to a rock very liable to yield to them, and where, without reckoning the large proportion which must have been carried by rivers to the sea, we see such vast deposits of the disintegrated materials formed out of the same matrix. To my mind the conclusion is irresistible that ancient Brazil was one of the greatest mountain regions of the earth, and that its summits may very probably have exceeded in height any now existing in the world. What we now behold are the ruins of the ancient mountains, and the singular conical peaks are, as Liais has explained, the remains of some harder masses of metamorphic gneiss, of which the strata were tilted at a high angle. As the same writer has remarked, although the crystalline rocks are for the most part easily disintegrated, some portions are formed of much more resisting materials, and these have to some extent survived the incessant action of destructive forces.

[_RUINS OF THE ANCIENT MOUNTAINS._]

We are far from possessing the materials for a rational estimate of the probable extent and elevation of the ancient mountain ranges of Brazil. In the first place, we have a plateau region occupying a large part of the upper basin of the Paranà, with an area of fully 100,000 square miles, covered with detritus to an unknown, but certainly considerable, depth. In addition to this, it cannot be doubted that the finer constituents carried down by that river, and its tributary the Paraguay, from the same original home, have largely contributed to the formation of the Argentine pampas and Paraguay, including the northern portion of the Gran Chaco. Borings and chemical analysis of the soil may hereafter give us reliable data; but in the mean time we may safely reckon that an area of 200,000 square miles has been mainly formed from the materials derived from the ancient mountains whose importance I endeavour to point out. In addition to all this, we should further reckon the soluble matter and fine silt carried to the ocean during the long course of geological history, and take into account that the same great mountain region also furnished materials to streams which flowed northward and eastward.

In attempting to speculate on the past history of this region it is important to remark that, so far as evidence is available, there is reason to believe that Brazil has undergone less considerable changes of level than most other parts of the earth’s surface. Even if we go back to the period of the earlier secondary rocks, there is no evidence to show that movements of elevation or depression have exceeded a few hundred feet.

I have attempted elsewhere[45] to give a sketch of the views which I hold as to the probable origin of the chief types of phanerogamous vegetation. I there pointed out that, at a period when physical conditions in the lower regions of the earth’s surface were widely different, and the proportion of carbonic acid gas present in the atmosphere was very much greater than it has been since the deposition of the coal measures, it was only in the higher region of great mountain countries that conditions prevailed at all similar to those now existing. I further argued that, if the early types of flowering plants were confined, as I believe they were, to the high mountains, we could not expect to find their remains in deposits formed in shallow lakes and estuaries until after the probably long period during which they were gradually modified to adapt them to altered physical conditions.

[_VALLEY OF THE PARAHYBA._]

A general survey of the South American flora shows, along with elements derived from distant regions, a large number of types either absolutely peculiar to that continent, or which, in some cases, appear to have spread from that centre to other areas. Of these peculiar types some may probably have originated in the Andean chain, but as to the majority, it seems far more probable that their primitive home was in Brazil; and it is precisely on the ancient mountains of this region that I should look for the ancestors of many forms of vegetation which have stamped their character on the vegetation of the continent.

I should be the first to admit that the views here expressed have no claim to rank as more than probable conjectures; but I hold that these, when resting on some positive basis of facts, are often serviceable to the progress of science, by stimulating inquiry and leading observers to co-ordinate facts whose connection had not previously been apparent.

In following the valley, in places where the siliceous soil supported only a scanty vegetation, I was struck by the singular appearance of scattered piles, usually about four feet in height, having much the appearance of rude milestones, occurring here and there in some abundance, but never very near each other. I was often able to avail myself of the short halts of the train at wayside stations to secure specimens of interesting plants, but I was not able to approach near to these unknown objects. I have no doubt, however, that they were habitations of termites, or, as they are commonly called, white ants. I have never been able to conjecture the origin of the instinct that induces so many species of termites in different parts of the world to construct dwellings in this form, nor what advantage they can derive from it.

As the Parahyba appeared to be a rapid-flowing stream, it is probable that in following the valley the railway descends considerably before it reaches the point, about eighty miles north of Rio, where it abruptly turns away from the river to make its way to the capital. The appearance of the vegetation announced a change of climate, but I did not notice any palms by the way. The country between the Parahyba valley and the coast appears to be an irregular mountain tract, nowhere of any great height, with projecting summits rising here and there of the same general character as those already described, and the railway follows a sinuous course so as to select the lowest depressions between the neighbouring bosses of granite. As we wound to and fro, constantly changing our direction amid scenes of increasing loveliness, night closed with that suddenness to which one becomes accustomed in the tropics, and the last part of the way was unfortunately passed in darkness. The approach to Rio must be surpassingly beautiful, but, beyond the fantastic outlines of the surrounding mountains, little could be discerned save the lights of the city, visible for many miles before we reached the railway station.

After a long drive through paved streets, I reached the English hotel (Carson’s), and was curtly informed that the house was full. The next in rank is the Fonda dos Estrangeiros, to which I proceeded, and found quarters in a rather shabby room, not overclean. The general style of the establishment and the food provided answered the same description. It is generally admitted that the accommodation for strangers in the capital of Brazil does not come up to the reasonable expectations of travellers.

[_THE BAY OF RIO JANEIRO._]

By quitting the steamer at Santos, and travelling to Rio by land, I had gained some slight acquaintance with a new region, but I was well aware that I had suffered a considerable loss. The view on first entering the Bay of Rio Janeiro is one of those spectacles that leave an ineffaceable impression even on persons not very sensitive to natural beauty, and one on which my fancy from early youth onwards had most often dwelt. The pursuits of a naturalist, besides their own fascination, offer additional rewards to all who worship in the temple of Nature, but they also sometimes exact a sacrifice. Sallying forth on the morning of July 8, a little under the impression of the unattractive quarters of the night, I had but very moderate expectations as to what might be enjoyed of the scenery in the midst of a large city and its surroundings, but I was speedily disabused. Man has certainly done little to set off the unequalled fascinations of the place, but he has been powerless to conceal them. I passed a delightful day, partly strolling much at random on foot, and occasionally availing myself of the street-cars, which are frequented by all classes, and afford a stranger the best opportunity for seeing something of the very mixed population.

The famous Bay of Rio Janeiro may properly be described as a salt-water lake, so completely is it landlocked and cut off from the open sea. About thirty miles long and twenty in breadth, it is large enough to allow of spacious views, yet not so large as to lose in distance the marvellous background that is presented in every direction by the fantastic peaks that surround it. Numerous islands stud the surface, the larger telling their history in piles of huge blocks, either simulating rude Cyclopean architecture, or lying in wild confusion--granite pinnacles, half-decayed or fallen into utter ruin. The shores are everywhere a maze of coves and inlets, in which land and water are interlaced; and over all--the mainland and the islands alike--the wild riot of tropical vegetation holds its sway, defying the efforts of man to tame it to trimness. Even within the limits of the city, which stretches for about four miles along the shore, four or five coves present a ceaseless variety of outline. Of necessity the plan is completely irregular. Where a space of level ground opens out between the shore and the rocks, the city has spread out; where the rocks approach the water’s edge, it is narrowed in places to a single street. In architecture, since the great era of Alcobaça and Batalha, the Portuguese have not achieved much, and their descendants in South America have done little to adorn the capital of their great empire. The largest building, the imperial palace, might easily be taken for a barrack. Nature has undertaken the decoration of the city, and, amid the palms, and under the shade of large-leaved tropical trees in the public walks and gardens, the absence of sightly buildings is not felt.

The suburb of Botafogo, which is the fashionable quarter, lies on the shores of the most beautiful of the coves round which the city has grown up. It mainly consists of a range of handsome villas facing the sea, each with a charming garden, and, in this season, must be a delightful residence. But it is generally admitted that the climate of Rio is debilitating to European constitutions. As compared with most coast stations in the tropics the heat is not excessive--the mean temperature of the warmest month (February) is not quite 80° Fahr., and that of the coldest (July) about 70°; but most Europeans, and especially those of Germanic stock, require to be braced by intervals of cold, if they are to endure a hot climate with impunity. The annual appearance of yellow fever in the city supplies a still stronger motive to many of the foreign residents for fixing their abode amongst the hills. The chief resort, which in summer is frequented by most of the wealthier classes, is the well-known Petropolis, in the Organ Mountains, or Serra dos Orgãos, that rise beyond the northern shores of the bay.

[_THE AVENUE OF PALMS._]

From Botafogo I directed my steps towards the Botanic Garden, and, as usual among people of Portuguese descent, found great readiness in giving information to strangers. Following a road that turned away from the shore, I seemed to have left the city far behind, and be quite in the country; but presently another beautiful dark blue cove opened out before me, and again turning inland I reached the garden. I must confess to a feeling of something like disappointment at the famous avenue of palms. It has been correctly described as reproducing the effect of the aisle of a great Gothic cathedral, and the defect, as it seemed to me, is that the reproduction is too faithful. The trees of _Oreodoxa regia_, which are about a hundred feet in height, are all exactly of the same form and dimensions, so much alike that they appear to have been cast in the same mould, and it is difficult to persuade one’s self that they are not artificial productions. It may not be easy to say why the same uniformity which satisfies the eye in a construction of stone, should fail to do so when similar forms are represented by natural objects. I suppose the fact to be that in all æsthetic judgments the mind is unconsciously influenced by trains of association. Our admiration is aroused not merely by given combinations of colour or form--by the mere visual image formed on the retina--but is controlled by our sense of fitness. We should resent as a caprice of the architect an irregularity in a vista of arches: among objects endowed with life we expect some manifestation of the universal tendency to variation.

With an intention, never fulfilled, to make a second visit to the garden, and, under the guidance of the director, Dr. Glaziou, to make nearer acquaintance with some of the vegetable wonders there brought together, I returned to my hotel. Before reaching Rio, I had decided to devote most of my short remaining time to a visit to the Organ Mountains, and to make Petropolis my head-quarters. As there was no especial reason for delay, I started for that place on the morning of the following day, July 9.

I shall make no attempt to describe the beauties of the bay as they were successively unfolded during the short passage to and from Petropolis. From early youth the Bay of Naples has ever appeared to me so perfectly beautiful that I was very reluctant to admit the pretensions of a rival. Even now I can well understand that some may find the pictures presented to the eye on the charmed coasts of our Mediterranean bay more complete, and the tints of the shores and sea and sky more harmonious; but there could be no doubt as to the gorgeous vesture that everywhere adorns this land. The vegetation of the Mediterranean coasts seems but poor and homely after the eye has dwelt on the luxuriance of tropical life, as though one were to compare a garb of homespun with trappings of velvet and embroidery. The islands of the bay present a ceaseless variety. Some are mere rocks, on which sea-birds of unknown aspect stood perched. Many of the larger are inhabited, and one, as I heard, has a population of thirteen hundred souls, and several charming villas showed it to be a favourite resort.

[_THE ORGAN MOUNTAINS._]

In about an hour and a half from the city, the little steamer ran alongside of a wooden jetty at a spot on the northern side of the bay facing the bold range of the Organ Mountains, which extend for over twenty miles in an easterly direction. Between the northern shore and the foot of the mountains is a level swampy tract, evidently filled up by the detritus borne down by the numerous streams, and beyond this the mountain range rises very abruptly from the plain. Somewhat to my disappointment, I ascertained that Petropolis lies at a considerable distance from the higher part of the Organ range to which my attention had hitherto been directed. It is towards its eastern extremity that the Serra shows that remarkable series of granitic pinnacles of nearly equal height, appearing vertical from a distance, that suggested the likeness to the pipes of an organ whence these mountains obtained their name. The height of the loftier part has been estimated at 7500 feet above sea-level. I do not think that any of the summits near Petropolis can surpass the level of 5000 feet.

A short train with a small locomotive carried passengers for Petropolis across the low tract to the point where the ascent abruptly commences, a distance of nine or ten miles. The marshy plain is doubtless fever-stricken, and we passed very few houses on the way to the terminus, which is appropriately named Raiz da Serra. The construction of a railway on the slope leading thence to Petropolis, up which trains should be drawn by a wire rope, had been commenced, but at the time of my visit passengers were conveyed in carriages, each drawn by six or eight mules. A well-kept and well-engineered road--by far the best mountain road that I have seen in any part of America--leads to the pass or summit of the ridge that divides Petropolis from the Bay of Rio. The views during the ascent, especially in looking back over the bay, were entrancing, and new and strange forms of vegetation showed themselves at each turn of the road. From the summit, a gentle descent of a couple of miles leads to the main street of Petropolis.

The place lies about 2900 feet above the sea, in a basin or depression amidst forest-covered hills. The abundant rains of this region have carved the surface into a multitude of little dells and recesses, separated by hills and knolls of various size and height, leaving in their midst one comparatively broad space, where most of the buildings are grouped. The streamlets that issue from every nook in the mountains are finally united in two streams that flow in opposite directions, but both, I believe, ultimately find their way northward to the Parahyba. The streamlets have been turned to account by the inhabitants, for on each side of the main streets a rivulet of crystal water serves to maintain the vigour of a line of trees supplying the one need of the long summer--shelter from the vertical midday sun. In the present season (mid-winter) only one hotel was open; but in summer, when all who can do so escape from the oppressive heat of Rio, two or three others are generally crowded. It is at once apparent that Petropolis is a place for rest and enjoyment, not for business. The few shops and hotels are all in the main street, Rua do Imperador; the other streets, or roads, lie between ranges of detached villas, each with a garden, and here and there some more secluded habitation is withdrawn into some nook on the margin of the forest.

[_ATTRACTIONS OF PETROPOLIS._]

The large majority of the trees and shrubs of this region have persistent leaves, but a few lose their foliage annually in winter, and a few others, I believe, during the heat of summer. The only prominent reminder of the fact that we were in winter was the appearance of the _Bombax_ trees that line the main street, now completely bare of foliage. The tree commonly planted in this part of Brazil is, I believe, the _Bombax pubescens_ of botanists. The fruit, with its copious silky appendage to the seeds, alone remained at this season; but when covered with a mass of large white flowers, it must have a gorgeous appearance.

I cannot feel sure that every naturalist will approve of the resolution, which I very soon formed, to remain as long as was possible at Petropolis. To reach the higher summits of the Organ Mountains would have required at least three or four days’ travel, and at this season I could expect to see very little of the vegetation of the higher zone. In the mean time, I found in the immediate neighbourhood, within a radius of four or five miles, an unexhausted variety of objects of interest, and the attractions of the place were doubtless heightened by the fortunate circumstances in which I found myself. It is certain that the ten days that I spent at this fascinating spot remain in my memory as the nearest approach to a visit to the terrestrial paradise that I can expect to realize. Besides the British minister, Mr. Corbett, I was fortunate enough to make the acquaintance of two English families, whose constant kindness and hospitality largely contributed to the enjoyment of my stay. To find in the midst of the marvels of tropical nature the charms of cultivated society, was a combination that I had not ventured to promise to myself.

Although I never went farther than five or six miles from my head-quarters, the variety of delightful walks in every direction seemed to be inexhaustible; go where one would, it seemed certain that one could not go wrong. I soon ascertained, indeed, that it is useless to attempt to penetrate the forests, except by following a road or cleared path. My first lesson was on the slope of a little hill some three hundred feet in height that overlooks the town. I was told that there was a path on the farther side, but, seeing the ground partly open, with trees of small stature not much crowded together, I resolved to follow the straight course. The ascent cost me over two hours of hard work, and I accomplished it only with the help of a sharp knife, by which to cut through the tangle of vegetation. In the midst of this I was surprised to find tall fronds of our common English bracken (_Pteris aquilina_), a fern that has been able to adapt its constitution to all but the most extreme climates of the world. The little hill that cost me so much labour had been completely cleared ten years before, so that all the trees and shrubs had grown up since that time.

[_THE STRUGGLE FOR EXISTENCE._]

The first excursion recommended to every stranger at Petropolis is that to the Falls of Itamariti. I went there twice, varying somewhat my course--the first time with a horse, which I found quite unnecessary and rather an incumbrance; the second time alone. The falls are not very considerable. A stream so slender that it can be passed by stepping-stones falls over two ledges of granite rock, together about forty feet in height; but, framed in a mass of the most luxuriant tropical vegetation, the whole forms a lovely picture. For some reason which I did not learn, the forest on the slopes of the lower part of the glen below the falls had been felled just before my visit, and its beauty had vanished, but fortunately the arm of the destroyer was arrested before reaching the falls.

As happens to every stranger in a tropical forest, I was bewildered amidst the great variety of trees that struggle for supremacy, the one condition for victory being to get a full share of the glorious sunshine overhead. By vigorous tugging at one of the _lianes_ that hung like a rope from a branch sixty feet above my head, I succeeded in breaking off a fragment, and identifying one of the larger trees as a species of fig, with large, oval, leathery leaves somewhat like those of a magnolia. It is needless to say that each tree is invaded by a host of enemies--parasites that fatten on its substance, comparatively harmless epiphytes that cling to the branches, and hosts of climbing lianes that mount to the topmost branches, robbing them of their share of sunlight, and hang down, often twined together, and in the deep shade are generally mere bare flexible stems. It was strange to observe that one of the deadliest enemies, a small parasite, fixing itself near the ground on the trunks of the larger trees, is a species of fig, belonging to the same genus as some of the giants of the forest, and doubtless tracing its descent from a common ancestor. It is in the tropical forest that one feels the force of Darwin’s phrase “struggle for existence,” as applied to the vegetable world. In our latitudes it is by an effort of the imagination that we realize the fact that in our fields and woodlands there is a contest going on between rival claimants for the necessary conditions of life. Here we see ourselves in the midst of a scene of savage warfare. The great climbers, like monstrous boas, that twine round and strangle the branch, remind one of the Laocoon; the obscure parasite that eats into the trunk of a mighty tree till a great cavity prepares its downfall, testifies to the destructive power of an insidious enemy.

[_THE HERMIT OF PETROPOLIS._]

It is only in the more open spots that a botanist is able to make close acquaintance with the smaller trees and shrubs. Near to the stream I was able to hook down a branch and secure flowering specimens of a _Begonia_ that grew to a height of over twenty feet. In such situations _Melastomaceæ_ were everywhere abundant, but for variety of forms the ferns surpassed any of the families of flowering plants. I was surprised to find that the beautiful tree ferns, that add so much to the charm of the tropical flora, were rarely to be found with fructification, and the huge fronds being of quite unmanageable dimensions, I did not attempt to collect specimens. Of the smaller kinds, when I was able, with the kind assistance of Mr. Baker, of Kew, to name my specimens, I found that I had collected thirty-five species in the neighbourhood of Petropolis.

During my stay here I visited a German gentleman whose singular manner of life excites the interest and curiosity of the European residents. I am ignorant of the motives that have led Mr. Doer, evidently an educated and cultivated man, to lead the life of a hermit far from his native country. He has built for himself a small house in the forest, on one of the hills that enclose the basin of Petropolis, and lives quite alone, except for the daily visit of a boy who carries the provisions that satisfy his very moderate wants. He seems to be entirely occupied in studying the habits of the native animals of the country, and especially those of the Lepidopterous insects--butterflies and moths--that adorn this region. By attention to the habitual food of the various species, he has succeeded in keeping in his house the caterpillars that in due time produce the perfect insect, and has preserved in cabinets large collections of fine specimens.

At the suggestion of the friend who accompanied me, Mr. Doer was good enough to introduce me to the family of small monkeys which he has raised and domesticated. The senior members had been brought from some place in Northern Brazil, but they had multiplied, some of the offspring being born in his house, and now formed a rather numerous party. The creatures habitually passed the day in the forest, never, in Mr. Doer’s belief, wandering to a distance from the house, and at night came in and nestled among the rafters of the roof. The call was by a peculiar note, somewhat resembling a low whistle, repeated two or three times, and before a minute had elapsed the little creatures came swarming about the open window. They were decidedly pretty, their large black eyes giving an impression of intelligence, but I did not detect any indication of attachment to their master. I cannot say to what species they belonged. They had large ears like those of the marmoset, but differed in having a prehensile tail. One of them hung with his head downward, suspended by the tail from some projection above the window. After receiving some fragments of sweetmeat they soon departed, returning to their favourite haunts among the trees of the forest.

Starting early one morning, and reaching the crest of the range that divides Petropolis from the Bay of Rio Janeiro, I enjoyed in great perfection a spectacle that is commonly visible at this season when the weather is clear and settled. Before sunrise a stratum of mist extends over the bay and the low country surrounding it. As I saw it, this may have been about a thousand feet in thickness when the sun first reached it, and the fantastic summits of the mountains rose like islets from a sea of dazzling white. As the sun’s rays began to act, the mist appeared to melt away from above; the lower hills and the rocky islands of the bay emerged in succession, and finally the veil completely disappeared, and the whole wondrous view was completely disclosed.

[_A SEA OF MIST._]

The beautiful effects displayed in the gradual disappearance of mist as seen from a height in early morning must be familiar to every genuine mountaineer, and may be enjoyed amongst the hills of the British Islands. Among my own recollections, a certain morning, when I stood alone at sunrise on the highest peak of the Pilatus, near Lucerne, showed the phenomenon in a most striking way, accompanied as it was by the coloured halo that surrounds the shadow of the observer thrown on the cloud-stratum below. But in my previous experience the disappearance of the mist was always accompanied by the upward movement of some portions of the mass. The surface appears to heave under the action of force acting from below, and some masses are generally carried up so as temporarily to envelope the observer. In the view over the Bay of Rio I was much farther away from the surface of the mist than in previous experiences of the kind, and I may have been misled by distance from the scene of action, but, though watching attentively, I saw no appearance of heaving of the surface or any break in its regular form. The waste seemed to proceed altogether from the upper surface, and the emergence of the prominent objects in regular succession gave direct evidence to that effect.

During the first five days of my visit the weather at Petropolis was perfectly enjoyable. The temperature varied from about 60° Fahr. at sunrise to about 70° in the afternoon; but the effect of radiation must have been intense, as in an exposed situation a minimum thermometer descended on one night to 46°, and on the next to 44°, and the dew was heavier than I have ever seen it elsewhere, so that in some places the quantity fallen from the leaves of the trees made the ground perfectly wet in the morning. The barometer varied very little, even after the weather changed, and stood as nearly as possible three inches lower than at Rio, showing a difference of level of about 2900 feet. On the 16th of July the sky became overcast, and some rain fell in the afternoon, the thermometer rising at two p.m. to 73° Fahr., and moderate rain fell on each succeeding day until the evening of the 19th, but scarcely any movement of the air was perceptible. There is a remarkable difference in the distribution of rainfall between the part of Brazil lying within about fifteen degrees of the equator and the region south of that limit. At Pernambuco (south lat. 8° 4′), out of an annual rainfall of about a hundred and ten inches, nearly ninety inches fall during the six months from March to August, and at Bahia, with less total rainfall, the proportion is nearly the same. But at Rio Janeiro the rainy season falls in summer, from November to March, and winter is the dry season. Of an annual rainfall of forty-eight and a half inches, only five and a half inches fall in the winter months, June, July, and August, and less than an inch and a half in July. No doubt the amount of rain is greater at a mountain station such as Petropolis, while the proportion falling in the different seasons must be about the same.

[_THE DEVELOPMENT OF INDOLENCE._]

At Petropolis, as well as elsewhere in South America, I was struck by the fact that the children of European parents born in the country speedily acquire the indolent habits of the native population of Spanish or Portuguese origin. The direct influence of climate is doubtless one cause of the change of disposition, but I suspect that the chief share is due to the great difference in the conditions of life which are the indirect results of climate. Where mere existence is so enjoyable, where physical wants are so few and so easily supplied, the chief stimulus to exertion is wanting, and the natural distaste for labour prevails over the hope of gain. A boy will prefer to pick up a few pence by collecting flowers, or roots, or butterflies in the forest near his home, to earning ten times as much by walking to a distance, especially if expected to carry a light weight. On my first visit to Itamariti I took with me a German boy, whom I left in charge of the superfluous horse that I had been advised to take with me. Finding the occupation a bore, and probably fearing that he would have to carry back the portfolio and vasculum that I had taken for plant-collecting, he fastened the bridle to a tree and disappeared, never coming to claim the pay promised for his unaccomplished day’s work.

All delightful times come to an end, and, as I resolved to visit Tijuca before departing from Brazil, I quitted Petropolis on the morning of July 20, and made my return to Rio amid brilliant sunshine, in which the glorious scenery of the bay renewed its indelible impression on my memory. In passing over the tract of low land between Raiz da Serra and the shore, partly overgrown by shrubs or small trees ten or twelve feet in height, I found them covered with masses of large flowers of the most brilliant purple hue, where ten days before not a single flower had been visible. The train halted for half a minute at a solitary half-way house, and I was able to break off a branch from the nearest plant. It belonged, as I suspected, to the family of _Melastomaceæ_, and is known to botanists as _Pleroma granulosum_ of Don; but one seeing dried specimens in a European herbarium, could form no conception of the gorgeous effect of the masses of rich colour that were here displayed, outshining the splendours of the Indian rhododendrons now familiar to European eyes. I again found the same species at Tijuca; but the soil and situation were, I suppose, less favourable, and the show of bloom was neither so rich nor so abundant.

I was told that the local name of this splendid plant is _quaresma_, because it flowers in Lent, which in Brazil falls in autumn; but I afterwards ascertained that the same name is given to several other species of _Melastomaceæ_ having brilliant flowers, and it seems improbable that the same species which I found bursting into flower in mid-winter should have also flowered three or four months before. The only remains of fruit that I found were dry, empty capsules that had apparently survived the preceding summer.

[_THE EMPEROR DOM PEDRO._]

Although I reached Rio some time before midday, so many matters required my attention that I found it impossible to return for a fuller visit to the Botanic Garden. Mr. Corbett had kindly offered to present me to the emperor, and, if time had permitted, I should have gladly taken the opportunity of making the personal acquaintance of a sovereign who stands alone among living rulers for the extent and variety of his scientific attainments, and for the active interest he has shown in the progress of natural knowledge. Irrespective of the qualities that appeal to the sympathies of men of science, Dom Pedro is evidently one of the remarkable men of our time. His exceptional energies, physical and mental, are incessantly devoted to every branch of public affairs, and it is said that he has even succeeded in inspiring some of his subjects with a share of his own zeal. But, so far as I could learn, he cannot be said to have achieved popularity. Among indolent and listless people, indefatigable industry produces an unpleasant effect. Improvements may or may not be desirable, but they are certain to give some trouble: it would be far pleasanter to let things remain as they are. Perhaps, whenever the time comes for Brazil to be deprived of the guidance of the present emperor, its people will become sensible of the loss they have sustained.

The steamer of the Royal Mail Company was to depart on July 24, so that no time was to be lost in making my visit to Tijuca. That place lies among the hills north-west of the city, about nine hundred feet above the sea, and the distance is quite inconsiderable; but the arrangements for visitors are inconvenient. A tramway runs over the flat country to the foot of the hill, and from the terminus the remainder of the way is accomplished by carriage or omnibus. But no luggage is taken by the tramway, and this has to be forwarded on the previous day. When I reached the station, about eleven a.m. on the 21st, I had an unpleasant quarter of an hour, during which it appeared that the case containing most of my Petropolis collections was lost or mislaid. At length it was found lying in an outhouse; no omnibus was available, but I soon succeeded in hiring a carriage to convey me to Tijuca.

The country between the city and the lower slopes of the hills is covered with the villas of wealthy natives, many of them large and handsome houses, each surrounded by a garden or pleasure-ground. In these grounds the mango, bread-fruit tree, and others, with large thick leaves giving dense shade, were invariably planted; and here and there palms, of which I thought I could distinguish four or five species, gave to the whole the aspect of completely tropical vegetation. Amidst the mass of trees, it was rarely possible to get a glimpse of the exquisite scenery surrounding Rio on every side, and it was only towards the top of the hill that I gained a view of the bay. Tijuca lies on the farther, or westward, slope, nearly surrounded by forest, and consists of only a few houses, of which the chief is White’s Hotel. As I afterwards learned, Mr. White, who is engaged in business in the city, was in the habit of hospitably entertaining his friends at a spot which naturally attracted frequent visits, and at length judiciously turned his house into an hotel, where a moderate number of guests find charming scenery, comparative coolness in the hot season, and far more of creature-comforts than are to be had in the hotels of Rio.

[_TREATMENT OF YELLOW FEVER._]

Time allowed me no more than a short stroll in the immediate neighbourhood before the hour of dinner, at which I met several intelligent and well-informed gentlemen, and amongst them three English engineers, from whom I received much information as to the country which they have made their home.

Amongst other questions discussed was that, so important to Europeans, regarding the annual visitation of yellow fever and the best method of treatment. I was especially struck by the experiences of the youngest of the party, who had come out from England a few years before to superintend some considerable new works for the drainage of Rio. For two years he lived altogether in the city, constantly requiring to go below, and sometimes remaining for hours in the main sewers. During that time he was never attacked by the fever, and no fatal cases arose among the workmen engaged in the same work. Since its completion this gentleman had been engaged on other works of a more ordinary character, and had habitually slept in the country during the hot season; but, under conditions apparently more favourable, he had been twice stricken by the fever. The first attack, which was probably slight, was at once cut short by a large dose of castor oil and aconite administered by a friend. In the following year he experienced a more serious attack, and had been treated by a doctor of good repute, mainly with tartar emetic. It appears that professors of the healing art in Brazil regulate their charges, not by the amount of time or labour which they give, but by the estimated value of the patient’s life. If he survives, it is considered that the remuneration should be in the nature of salvage--a considerable percentage on the amount of his income. In the present case the young engineer had been required to pay a fee of £180. In some cases, where the doctor’s demand appeared utterly unreasonable, foreigners have attempted to appeal to the tribunals, but it appears that the results of litigation have not encouraged others to resort to the protection of the law.

In answer to my inquiries, most of my informants made light of the difficulties of exploring the interior of Brazil, but they agreed in the opinion that much time must be given by any traveller wishing to break new ground. Even in the more or less fully settled provinces, the spaces to be traversed are so great, and the means of communication so imperfect, that a large margin must be left for unexpected delays. One gentleman, who had travelled far in Goyaz and Matto Grosso, assured me that he had never encountered any difficulty as to provisions. Three articles of European origin are to be found, so he assured me, at every inhabited place in the interior--Huntley and Palmer’s biscuits, French sardines, and Bass’s pale ale.

[_VEGETATION OF TIJUCA._]

July 22 was a day of great enjoyment, devoted to the immediate neighbourhood of Tijuca, where objects of interest were so abundant as to furnish ample occupation for many days. I have said that the place is almost surrounded by the forest which spreads over the adjoining hills. I now learned that less than fifty years before, at a time when coffee-planting in Brazil became a mania, and was counted on as everywhere a certain source of wealth, the aboriginal forest which covered the country was completely cleared, and coffee-planting commenced on the largest scale. Experience soon proved that the conditions either of soil or climate were unfavourable, and after a few years the land was again abandoned to the native vegetation. About thirty-five years had sufficed to produce a new forest, which in other lands might be supposed to be the growth of centuries. The trees averaged from two to three feet in diameter, and many were at least seventy feet in height. One of the largest is locally called _ipa_; it belongs to the leguminous family, has a trunk nearly quite bare, and the upper branches bore masses of cream-coloured flowers; but, finding it impossible to obtain flower or fruit, I have been unable to identify it. The vegetation here appeared to be even more luxuriant than that of Petropolis, and to indicate a somewhat higher mean temperature. The proportion of tree ferns was decidedly greater, and a good many conspicuous plants not seen there were here abundant. Some of these, such as _Bignonia venusta_, _Allamanda_, etc., may have strayed from the gardens; but many more appeared to be certainly indigenous. Of flowering plants the family of _Melastomaceæ_ was decidedly predominant, and within a small area I collected fifteen species, eight of which belonged to the beautiful genus _Pleroma_. One of these (_P. arboreum_ of Gardner) is a tree growing to a height of forty feet; but the species of this family are more commonly shrubs not exceeding ten or twelve feet in height.

I was unfortunately not acquainted at that time with the observations made near Tijuca by Professor Alexander Agassiz, which appear to him to give evidence of glacial action in this part of Brazil. It would be rash, especially for one who has not been able to examine the deposits referred to, to controvert conclusions resting on such high authority; but I may remark that the evidence is confessedly very imperfect, and that the characteristic striations, either on the live rock or on the transported blocks, which are commonly seen in the theatre of glacial action, have not been observed. I lean to the opinion that the deposits seen near Tijuca are of the same character as those described by M. Liais[46] as frequent in Brazil. The crystalline rocks are of very unequal hardness, and while some portions are rapidly disintegrated, the harder parts resist. The disintegrated matter is washed away, and the result is to leave a pile of blocks of unequal dimensions lying in a confused mass.

On the following day, my last in Brazil, one of my new acquaintances was kind enough to guide me on a short excursion in the forest, which enabled me to approach one of the giants of the vegetable kingdom. At the time of the clearing of the aboriginal forest two great trees were spared. One of these had been blown down some years before my visit, and but one now remained. It was easily recognized from a distance, as it presented a great dome of verdure that rose high above the other trees of the forest. The greater part of the way was perfectly easy. A broad track, smooth enough to be passable in a carriage, has been cleared for a distance of many miles over the forest-covered hills.

[_A GIANT TREE._]

Following this amid delightful scenery, we reached a point scarcely two hundred yards distant from the great tree. I had already learned that even two hundred yards in a Brazilian forest are not very easily accomplished, but I was assured that a path had been cut a year or two before which allowed easy access to the foot of the tree. We found the path, but it was soon apparent that it had been neglected during the past season, and in this country a few months suffice to produce a tangle of vegetation not easily traversed.

When at length we effected our object, we found ourselves at the base of a cylindrical column or tower, with very smooth and uniform surface, tapering very slightly up to the lowest branch, which was about eighty feet over our heads. We measured the girth, and found it just twenty-nine feet at five feet from the ground. It is needless to say that I could form no conjecture as to the species, or even the family, to which this giant belongs, as I was quite unable to make out the character of the foliage. While near to it we could form no guess as to the height; but my companion, whose profession made him used to accurate estimates, and who had observed it from many points of view, reckoned the height at between 180 and 200 feet. I had not then seen the giant conifers of western North America, but, excluding the two Sequoias, I have not found any single tree to equal this. In the valleys of the Alleghany Mountains in Tennessee, I have indeed beheld not unworthy rivals. The _Liriodendron_ there sends up a stem more than seven feet in diameter, and frequently exceeds 150 feet in height.

To diminish my regret at quitting this beautiful region, the morning of July 24 broke amid dark clouds and heavy rain, which continued till the afternoon. I had counted on enjoying a few hours in Rio before my departure, but, that being impossible, I went directly from Tijuca to the landing-place, and thence on board the steamer of the Royal Mail Company, which was to take me back to England. This was the _Tagus_, and I had much pleasure in finding her under the command of Captain Gillies, with whom I had made the voyage from Southampton to Colon. In the afternoon we slowly steamed out of the bay. Its glories were veiled, heavy clouds rested on the Organ Mountains; but the Corcovado and the other nearer summits appeared from time to time, and the last impression was that of fleeting images of beauty the like of which I cannot hope again to behold.

The course for steamers from Rio Janeiro to England is as nearly as possible direct. The coast of Brazil from Rio to Pernambuco runs from south-south-west to north-north-east, in the same direction that leads to Europe; and from the headland of Cabo Frio to the entrance of the English Channel at Ushant, a distance of about 72° of latitude and 38° of longitude, the helm is scarcely varied from the same course. It is somewhat remarkable that in so long a voyage, in which one passes from the Tropic of Capricorn to the region of the variable anti-trade-winds of the northern hemisphere, it not very rarely happens, as I was assured by our experienced captain, that north-north-east winds are encountered throughout the entire distance. This was nearly verified in the present case. For comparatively short periods the wind shifted occasionally to the north and north-west; more rarely, and at brief intervals, light breezes from the south and south-east were experienced; but the north-east and north-north-east winds predominated, even on the Brazilian coast, until we reached the latitude of Lisbon.

[_WINDS OF THE ATLANTIC._]

It is an admitted fact in meteorology, that the trade-winds of the northern are--at least in the Atlantic--stronger than those of the southern hemisphere; but at the winter season of the south, the south-east trade-winds prevail in the equatorial zone, and are not rarely felt as far as eight or even ten degrees north of the equator. But in investigating the extremely complex causes that determine the direction of air currents, and especially those slight movements that make what is called a breeze, it is difficult to trace the separate effect of each agent. The neighbourhood of a coast constantly brings local causes into play, and it may well be that the rapid condensation of large masses of vapour, such as occurs at each heavy fall of rain, may determine temporary currents in the air in directions opposed to the general and ordinary march of the winds. Irrespective, however, of any such local causes, we must bear in mind the general tendency of air currents towards motion of a circular or spiral character. When we meet a breeze blowing in a direction contrary to that which ordinary experience leads us to expect, we must not forget the possibility that it may be a portion of the ordinary current which has formed an eddy. The main facts of meteorology are now well established, but the local deviations may give room for prolonged study.

Although I knew that the delay at both places would be short, I looked forward with much interest to the prospect of landing at Bahia and Pernambuco. The latter place especially is known to be the chief mart for the natural productions of Equatorial America. Skins of animals, birds living and dead, gorgeous butterflies and shells, are easily procurable; and a mere visit to the fish and vegetable markets is sure to make a visitor acquainted with objects of interest. But my expectations were doomed to disappointment.

We reached Bahia on the morning of July 27. The city stands on a point of land north of the entrance to an extensive bay, called by the Portuguese Bahia de Todos Santos, and the proper name of the city is São Salvador; but the concurrent practice of foreigners has established the name now in general use. The steamer lay in the roadstead nearly a mile from the shore, and the heavy boats, carrying some passengers for Europe, moved slowly as they pitched to and fro in the swell of the sea. Just as they came alongside, rain suddenly burst in a torrent from the clouds, which had formed in the course of a few minutes. For the first time in my journey, I regretted the omission to have supplied myself with a waterproof cloak. A thorough wetting in tropical countries usually entails an attack of fever, and for that I was not prepared; so, along with two or three other passengers who wished to go ashore, I remained in the main deck. The rain ceased, and there was an interval of sunshine; but the torrential showers were renewed two or three times before we resumed our voyage in the afternoon.

[_COAST CLIMATE OF BRAZIL._]

I have already noticed the contrast that exists between the winter and summer climate of this part of Brazil and that of Rio and the southern provinces. In the latter the rainy season is in summer, while nearer the equator, although no season can be called dry, the chief rainfall occurs in winter--that is to say, in the season when the sun is farthest from the zenith. While passing through the equatorial zone, when intervals of bright weather alternated with extremely heavy rain, I frequently consulted the barometer, but was unable to trace the slightest connection between atmospheric pressure and rainfall, the slight oscillations observed being due to the diurnal variation everywhere sensible in the tropics.

The temperature on this part of the coast was only moderately warm, varying from 76° to 78° Fahr. on this and the following day, when we called at Maceio, a place of increasing commercial importance. Our stay was so short that no one attempted to go ashore, although the weather was favourable. Several whales were seen both on the 27th and 28th, but I failed to ascertain to what species they belonged.

On the evening of the 28th we experienced a decided rise of temperature; three hours after sunset the thermometer still stood at 81° Fahr., and, with two remarkable intervals, it did not fall below 80° during the following eight days. During that time my attention was often directed to the physiological effects of heat on the human economy, and both my own experience and the conflicting testimony of travellers lead me to conclude that there are many facts not yet satisfactorily explained.

On the enfeebling effect of moist tropical climates there is a general agreement, both as to the fact and the chief cause; but, as I have remarked in a preceding page, the circumstance that this is little or not at all experienced at sea is apparently anomalous. With regard to the direct effect of the sun’s rays on the surface of the body, and especially in the production of sun-stroke, the evidence of scientific travellers is conflicting, and the explanations offered are by no means satisfactory. On the one hand, it is asserted on good authority that in the equatorial zone the direct effect of the sun is far greater than it is in Europe at the same elevation above the horizon. The rapid reddening and blistering of the skin where exposed, and sun-stroke from exposure of the head, are said to be the ordinary effects. Being extremely sensitive to solar heat, I have always carefully protected my head, and have avoided rash experiments. Of the reddening and blistering of the skin I have had very frequent experience in Europe, upon the Alps and other mountains; but I observed none but very slight effects of this kind in the tropics, even with a nearly vertical sun, either on land or while at sea. Dr. Hann[47] cites many statements on the subject. In the West Indies cases of sun-stroke are rare, and the inhabitants expose themselves without danger. In nearly all parts of British India, as is too well known, the danger of exposing the head to the sun is notorious, and the same is certainly true of most parts of tropical Africa.

[_SUN-STROKE._]

The most obvious suggestion is that, inasmuch as dry air absorbs less of the solar heat than air charged with aqueous vapour, the injurious effects should be more felt in dry climates than in damp ones. But, so far as what is called sun-stroke is concerned, the balance of evidence is opposed to this conclusion. Sir Joseph Fayrer, who has had wide experience in India, expressly asserts that the hot dry winds in Upper India induce less cases of sun-stroke than the moist though cooler climate of Bengal and Southern India. Dr. Hann quotes Borius for a statement that in Senegambia the rainy season is that in which sun-stroke commonly occurs, while he further asserts that on the Loango coast, in very similar climatal conditions, the affection is almost unknown, and that Europeans even expose the head to the sun with impunity.

My own conclusion, fortified by that of eminent authorities, is that the phenomena here discussed are of a very complex nature; that different physical agencies are concerned in the various effects produced on the body; and that most probably there are many different pathological affections which have been classed together, but which, when more fully studied, will be recognized as distinct.

In the first place, I apprehend that the action of the sun which causes discolouration and blistering of the skin has no relation to that which causes sun-stroke. It is a local effect confined to the surfaces actually exposed, and, if it could be accurately registered, would serve the purpose of an actinometer, depending as it does on the amount of radiant heat reaching the surface in a unit of time.

Sun-stroke proper is, I believe, an affection of the cerebro-spinal system arising from the overheating of those parts of the body. It is by no means confined to the tropics, or to very hot countries, as many cases occur annually in Europe, and still more frequently in the eastern states of North America.

Nearly allied to sun-stroke, but perhaps sufficiently different to deserve separate classification, are those attacks which some writers style cases of thermic fever, which arise mainly in places where the body is for a continuance exposed to temperatures exceeding the normal amount of the human body. In producing thermic fever, it would appear that the depressing effect of a hot moist climate acts powerfully as a predisposing cause, and such cases not uncommonly arise where there has been no exposure whatever to the direct rays of the sun.

[_PERNAMBUCO._]

It is easy to understand that, as a general rule, seamen are less exposed than other classes to any of the injurious effects of heat, but it is remarkable that they should enjoy complete exemption. Cases are not very uncommon among seamen going ashore in hot countries, but I have not found a well-authenticated case of sun-stroke arising on board ship; and cases of thermic fever in the Red Sea usually arise in the engine-room of a steamer rather than among the men on deck.

On the morning of July 29 we reached Pernambuco, to which I had looked forward as the last Brazilian city that I was likely to see. It had been described to me as the Venice of South America, and the comparison is to a slight extent justified by its position on a lagoon of smooth water, separated from the open roadstead by a coral reef several miles in length. It enjoys the further distinction, unusual in a place within eight degrees of the equator, of being remarkably healthy. But on this occasion fortune was against me.

No doubt for some sufficient reason, we did not enter the rather intricate passage leading inside the reef, but lay to in rough water outside. For a short time the scene was brilliant. The hot sun beat down on the deep blue water, and lit up the foam on the crests of the dancing waves, and the sky overhead showed such a pure azure that one could not suppose the air to be saturated with vapour. Before long boats were seen approaching, tossed to and fro in the broken water; but before they drew near, heavy clouds had gathered in the course of a few minutes, and a torrent of water was discharged such as I had never experienced except in passing under a waterfall. As each boat came alongside, a seat was let down from the upper deck, and the passengers were hoisted up in turn, those who had not efficient waterproofs being as thoroughly drenched as if they had been dipped in the sea. Four or five times during the day the sky cleared, the blazing sun returned, and the decks were nearly dry, when another downpour of torrential rain drove us all to seek shelter, each shower lasting only from ten to fifteen minutes.

During the hotter hours of the day a rather strong breeze set in towards the shore, and I have no doubt that it is to its full exposure to this ordinary sea-breeze that the city owes its comparative healthiness. It was interesting to watch the manœuvres of the _catamarans_, in which the native fishermen were pursuing their avocations. This most primitive of sea-craft is formed of two or three logs well spliced together, with some weight to serve as ballast fastened underneath. In the forepart a stout stick some ten feet long stands up as a mast and supports a small sail, and amid-ships a short rail, supported on two uprights, enabled the two men who form the crew to hold on when much knocked about by the waves. A single paddle seems to serve as a rudder, but it is not easy to understand how such a rude substitute for a boat is able to work out to sea against the breeze which commonly sets towards the shore.

A large proportion of the steerage passengers who came on board at Bahia and Pernambuco were Portuguese returning to their native country after a residence, either as artisans or as agricultural settlers, in Brazil. My command of the language is unfortunately so limited that I failed to extract from these fellow-passengers any interesting information. With scarcely an exception, each carried at least one parrot, usually intended for sale at Lisbon, where it appears that they are in some request. Comparatively high prices are given for birds that freely simulate human speech.

[_THE ANEROID BAROMETER._]

We were under steam in the afternoon of the 29th, and soon lost to view the South American continent. On the following day the barometer for the first time showed the diminution of pressure which is normally found in the equatorial zone. Between nine a.m. and four p.m. the ship’s mercurial barometer fell about a quarter of an inch from 30·30 to 30·06 inches, and my aneroid showed nearly the same amount of difference. It must be remembered, however, that nearly one-half of the effect (at least one-tenth of an inch) must be set down to the daily oscillation of the height of the barometer, which so constantly occurs within the tropics, the highest pressures recurring at ten a.m. and ten p.m., and the lowest about four p.m. and four a.m.

I carried with me on this journey only a single aneroid barometer, an excellent instrument by Casella, whose performance was very satisfactory, and which in a very short time returned to its normal indication after exposure to diminished pressure in the Andes; but it had the defect, which, so far as I know, is common to the aneroid instruments by the best makers, that the temperature at which the scale is originally laid down by comparison with a standard mercurial barometer is not indicated on the face of the instrument. Assuming that the aneroid is compensated for variations of temperature, and I have found this to be the case within ordinary limits in good instruments, there remains the question to what height of mercury at what temperature a given reading of the aneroid corresponds. For scientific purposes it is customary to reduce the reading of the mercurial barometer to the temperature of the freezing-point of water, and it is often supposed that the aneroid reading corresponds to that figure. But we may feel pretty confident that the maker, in laying down the scale, did not work in a room at freezing-point. I have been accustomed to assume 15° Cent., or 59° Fahr., as about the probable temperature with instruments made in our climate.

In the present case, the barometer-reading of 30·06 inches at the temperature of 84° Fahr. would (neglecting the small correction for capillarity) be reduced by about fourteen-hundredths of an inch, in order to give the correct figure at freezing-point; but for comparison with an aneroid, supposed to have been laid down at 59° Fahr., the correction would be a fraction over seven-hundredths of an inch. As a matter of fact, my aneroid marked at four p.m. 29·89 inches, or, allowing for the correction, just one-tenth of an inch less than the ship’s mercurial barometer, and, as I believe, was more nearly correct.

As the sun was declining on the evening of July 30, we sighted the remarkable island of Fernando Noronha. It lies about four degrees south of the equator, and more than two hundred miles from the nearest point of the Brazilian coast. The outline is singular, for the rough hills which cover most of the surface terminate at the western end of the island in a peak surmounted by a column, in the form of a gigantic lighthouse, which must rise over a thousand feet above the sea-level.[48] Although Darwin passed some hours on the island in 1832, it remains to the present day one of the least known of the Atlantic islands, so far as regards its natural productions. A fellow-passenger who had landed there assured me that he had found granite; but I have no doubt that the island is exclusively of volcanic origin, for such is the opinion of the few scientific men who have visited it.

[_FERNANDO NORONHA._]

The island has been converted by the Brazilian Government into a convict station, and in consequence access by strangers has become very difficult. Such information as we possess is mainly to be found in Professor Moseley’s account of the voyage of the _Challenger_. On landing there with Sir G. Nares, he at first obtained permission from the governor to visit the island and to collect natural objects; but the permission was very soon retracted, and he was unable to obtain specimens of several singular shrubs that abound and give the island the appearance of being covered with forest.

Now that the attention of naturalists has been directed to the especial interest attaching to the fauna and flora of oceanic islands, and their liability to extinction owing to competition from species introduced by settlers, it may be hoped that the exploration of this small but remarkable island will before long be undertaken by a competent naturalist. For that purpose it would be, in the first place, necessary to obtain the permission of the Brazilian Government, and to secure the means of existence during a stay of ten or twelve days on the island. The most effectual means would be through direct personal application to the emperor, who is well known to take a lively interest in all branches of natural science.

With the thermometer standing about 82°, the passengers naturally preferred the upper deck to the close air of the saloon, and were resting in their ship-chairs between nine and ten p.m., when suddenly there came an outburst of coughing and sneezing, followed by demands for muffling of every kind. There was no sensible movement in the air, but I found that the thermometer had fallen to 79° Fahr., and there was a feeling of chilliness which was not easily explained by that slight fall of temperature.

The mystery was explained on consulting the chief officer, who throughout the voyage paid much attention to the temperature of the sea. Since leaving Pernambuco, the thermometer in buckets brought up from the surface had varied only between 82° and 83°. On this evening we had abruptly encountered a relatively cold current, with a temperature somewhat below 76°, and the effect of being surrounded by a body of cool water when the skin was in the condition usual in the tropics was felt by nearly all the passengers.

[_M. GEORGES CLARAZ._]

With slight variation, this comparatively cool current must have extended over a large area on both sides of the equator, as the temperature of the water remained nearly the same for about forty-eight hours.

Throughout the voyage from Brazil to Europe, I was fortunate in enjoying the society of a man of remarkable intelligence, who has been a diligent and accurate observer of nature in a region still imperfectly known. M. Georges Claraz, by birth a Swiss, belonging to a family of small proprietors in the Canton of Fribourg, had gone out as a young man to improve his fortune in South America. He had received a fair scientific education, having followed the lectures of the eminent men who have adorned the Polytechnic School at Zurich; but, what is much more rare, he appeared to have retained everything that he had ever learned, and to have had a clear perception of the scientific value of the observations that a stranger may make in a little-known region. After passing some time in the state of Entrerios, he had settled at Bahia Blanca, close to the northern border of Patagonia. He had established friendly relations with the Indians, and made frequent excursions in the interior of Patagonia and southward as far as, and even beyond, the river Chubat.

During the entire time, although engaged in the work of a settler, M. Claraz seems to have made careful notes of his observations--on the native Indians and their customs; on the indigenous and the domestic animals; on the plants and their uses; on the mineral structure of the country, not omitting to take specimens of the mud brought down by the different rivers; and on general physics. Of his large collections I trust that the greater part have safely reached Switzerland. A considerable collection of dried plants, sent home while he resided at Bahia Blanca, was unfortunately lost. He was good enough, after his return, to send me a smaller collection remaining in his hands, of which I gave an account in the _Journal of the Linnæan Society_ for 1884.

As I trust that the great store of information collected by M. Claraz will before long be given to the world, I should not wish to anticipate the appearance of his work, but I may say that among many interesting particulars, several of which I noted at the time, I was especially struck by the evidence collected among the Indians, which seemed to prove that the _Glyptodon_ survived in Patagonia down to a comparatively recent period, and that the tradition of its presence is preserved in the stories and songs of the natives.

Early on July 31 we passed the equator, but it was not till ten p.m. on the following day that we escaped from the area of cool water and found the ordinary equatorial temperature of 82·5°. During the three following days the weather was hot and relaxing, the thermometer ranging by day between 84° and 85°. For some hours on the 2nd of August the wind came from south-south-east, but before evening it backed to west, and blew from that point rather freshly at night. On the following day we appeared to have met the north-east trade-wind, which was, however, a gentle breeze, and occasionally veered to the north-west.

[_ISLAND OF ST. VINCENT._]

In the afternoon of August 4 we made out the picturesque outline of the Cape Verde Islands, and before sunset entered the channel between St. Vincent and St. Antão, finally dropping anchor for the night in the outer part of the fine harbour of St. Vincent. Having been selected as a coaling station, this has become the chief resort of steamers plying between Europe and the Southern Atlantic, and we were led to expect that the operation would take up great part of the following day. Here a fresh disappointment awaited me. I had confidently reckoned upon spending several hours ashore, and seeing something of the curious vegetation of the island, which includes a scanty representation of tropical African types, with several forms allied to the characteristic plants of the Canary Islands.

I had not duly taken account of the perverse temper of the officers of health, whose chief object in life seems everywhere to be to make their authority felt by the needless annoyance they cause to unoffending fellow-creatures. We had left Rio with a clean bill of health; not a single case of yellow fever had occurred for months before our departure; but Brazil is regarded as permanently “suspected,” and quarantine regulations were strictly enforced in our case.

I am far from believing that in certain conditions, and as regards certain diseases, judicious quarantine regulations may not be effective; but, reckoning up all the loss and inconvenience, and the positive damage to health, arising from the sanitary regulations now enforced, I question whether it would not be better for the world if the system were entirely abolished.

The view of St. Vincent, backed by a bold and stern mountain mass, on which scarcely a trace of vegetation is visible from a distance, was for some time sufficiently interesting; but as the day wore on, and the sun beat down more fiercely, life on board became less agreeable. To keep out the penetrating coal dust all the ports were closed, and, with the thermometer at 90°, the air below was stifling, and the passengers generally preferred to remain on deck, and breathe the hot air mixed with the coal dust that arose from the open bunkers.

I offered two of the boatmen who hung about the ship three milreis if they would land on an uninhabited part of the bay, which I pointed out to them, and collect for me every plant they found growing, and I was well pleased when, after two or three hours, they returned with a respectable bundle of green foliage. Under the vigilant eyes of the officers of health the specimens were hauled up to the deck, while the three dollars were thrown into the boat. It is remarkable that coin is nowhere supposed to convey contagion.

When I came to examine it, I found to my disgust that the bouquet included only the leaves of two species, with no trace of flower or fruit. One was most probably _Nicotiana glauca_, introduced from tropical America; the other a leguminous shrub, possibly a _Cassia_, but quite uncertain.

The rest of the passengers spent most of the day in bargaining with the hucksters who flocked round the ship. Ornaments made from palm leaves, sweetmeats of very suspicious appearance, photographs, and tobacco in various forms, were the chief articles of traffic, and the main object seemed to be to prolong the chaffering and bargaining over each article so as to kill as much time as possible. More attractive in appearance were the tropical fruits, of which those suitable to a dry climate grow here in perfection. In spite of persevering efforts, I have never developed much appreciation of the banana as an article of diet, but I thought those obtained here much the best that I have anywhere eaten.

[_ATLANTIC TRADE WINDS._]

General satisfaction was felt when, the work of coaling being finished, the ship was again in motion, with her head set towards Europe. On returning to the channel between the islands, and still more when we had got well out to sea, we encountered a rather strong breeze right ahead, which with varying force continued for the next four days. This was, of course, the regular trade-wind of the North Atlantic, and had the agreeable effect of lowering the temperature, which at once fell to 78°. Along with the trade-wind, the sea-current apparently travels in the same direction. It is certain that the temperature of the water was here much lower. Before reaching St. Vincent we found it between 80° and 81° Fahr., while after leaving the islands it had fallen to 74°. This temperature remained nearly constant for three days, but on the evening of the 9th, in about 27° north latitude, we abruptly encountered another current of still cooler water, in which the thermometer fell to 69°.

The force of the wind never, I think, exceeded what seamen describe as a fresh breeze, but it sufficed to cause at times considerable disturbance of the surface; and on the afternoon of the 6th we shipped some heavy seas, so that it was found expedient to slacken speed for a time.

I have alluded in a former page to the ordinary observation that in the track of the trade-winds the breeze usually falls off about sunset. It is more difficult to account for the opposite phenomenon, which we experienced on three successive evenings from the 7th to the 9th of August, when the force of the wind increased in a marked degree after nightfall.

I was also struck by the fact that the temperature of the air throughout the voyage from St. Vincent to the mouth of the Tagus seemed to be unaffected either by the varying force of the wind or by the fall in surface-temperature of the sea, to which I have above referred. On board ship in clear weather it is very difficult to ascertain the true shade temperature when the sun is much above the horizon, but the observations made at sunrise and after nightfall from the evening of the 5th to the morning of the 11th varied very slightly, the utmost range being from 77·5° to 73°.

Some points in the Canary Islands are often visible in the voyage from Brazil to Europe, especially the lofty peak of Palma; but we passed this part of the course at night, and nothing was seen. As we drew near to Europe, the wind, through keeping the same direction, gradually fell off to a gentle breeze, and the surface of the water became glassy smooth, heaving gently in long undulations. The relative effect of smooth or rough water on the speed of steamers is remarkable, and was shown by the fact that during the twenty-four hours ending at noon on the 11th of August the _Tagus_ accomplished a run of 295 knots, while three days before, with only a gentle breeze but rougher water, the run to noon was only 240 knots.

[_THE TOWER OF BELEM._]

Early in the afternoon of the 11th, the Rock of Lisbon at the mouth of the Tagus was distinctly visible, and we slowly entered the river and cast anchor at the quarantine station below Belem. Our captain, after the experience of St. Vincent, did not expect to obtain pratique at Lisbon, and with more or less grumbling the passengers had made up their minds to remain on board, when, after a long deliberation, the unexpected news, “admitted to pratique,” was rapidly spread through the ship, and we moved up to the anchorage opposite the picturesque old tower of Belem, which the true mariner must always regard as one of his holy places. It marks the spot wherefrom Vasco de Gama and his companions, after a night spent in prayer in the adjoining chapel, embarked on their memorable voyage, and here, after years of anxious uncertainty, King Manuel greeted the survivors on their return to their country.

The sun was sinking when such passengers as wished to see something of Lisbon took the opportunity for going ashore, while others, like myself, preferred to remain on board. Hoping to receive letters at the post-office, I landed early next morning, and found a tramcar to carry me to the centre of the town. Early hours are not in much honour at Lisbon. I found the post-office closed, and, after several vain efforts, was informed that letters could not be delivered until ten o’clock, the precise hour fixed for our departure from the anchorage at Belem.

The voyage from Lisbon along the coasts of Portugal and Galicia is usually enjoyed, even by fair-weather sailors. The case is often otherwise with the Bay of Biscay, but on this occasion there was nothing of which the most fastidious could complain. I have sometimes doubted whether injustice has not been done to that much-abused bay, which, in truth, is not rightly so called by those bound from the north to the coast of Portugal. It is simply a part of the Atlantic Ocean, adjoining the coast of Europe between latitudes 43° 46′ and 48° 28′. I have not been able to ascertain that the wind blows harder, or that the sea runs higher there than elsewhere in the same latitudes, and am inclined to rank the prejudice against that particular tract of sea-water among vulgar errors.

The adventurer who has attempted to open up a trade with some distant region is accustomed, as he returns home, to count up the profits of his expedition; and in somewhat the same spirit the man who pursues natural knowledge can scarcely fail to take stock of the results of a journey. It is his happy privilege to reckon up none but gains, and those of a kind that bring abiding satisfaction. He may feel some regret that outer circumstance or his own shortcoming have allowed opportunities to escape, and lessened the store that he has been able to accumulate; but as for the positive drawbacks, which seemed but trivial at the time, they absolutely disappear in the recollection of his experiences. Thinking of these things as the journey drew to a close, I could not help feeling how great are the rewards that a traveller reaps, even irrespective of anything he may learn, or of the suggestions to thought that a voyage of this kind cannot fail to bear with it. How much is life made fuller and richer by the stock of images laid up in the marvellous storehouse of the brain, to be summoned, one knows not when or how, by some hidden train of association--shifting scenes that serve to beautify many a common and prosaic moment of life!

[_PSEUDO-PESSIMISM._]

Often during this return voyage my thoughts recurred to an article in some periodical lent to me by my kind friends at Petropolis, wherein the writer, with seeming gravity, discussed the question _whether life is worth living_. My first impression, as I well remember, was somewhat contemptuous pity for the man whose mind could be so profoundly diseased as even to ask such a question, as for a soldier who, with the trumpet-call sounding in his ear, should stop to inquire whether the battle was worth fighting. When one remembers how full life is of appeals to the active faculties of man, and how the exertion of each of these brings its correlative satisfaction; how the world, in the first place, needs the daily labour of the majority of our race; how much there is yet to be learned, and how much to be taught to the ignorant; what constant demand there is for the spirit of sympathy to alleviate suffering in our fellows; how much beauty exists to be enjoyed, and, it may be, to be brought home to others;--one is tempted to ask if the man who halts to discuss whether life is worth living can have a mind to care for truth, or a heart to feel for others, or a soul accessible to the sense of beauty.

Recurring to the subject, as I sometimes did during the homeward voyage, it seemed to me that I had perhaps treated the matter too seriously, and that the article I had read was an elaborate hoax, by which the writer, while in truth laughing at his readers, sought merely to astonish and to gain repute as an original thinker. However the fact may be, when taken in connection with the shallow pessimism which, through various channels, has of late filtered into much modern literature, there does appear to be some real danger that the disease may spread among the weaker portion of the young generation. A new fashion, however absurd or mischievous, is sure to have attractions for the feebler forms of human vanity. It is true that there is little danger that the genuine doctrine will spread widely, but the mere masquerade of pessimism may do unimagined mischief. The better instincts of man’s nature are not so firmly rooted that we should wish to see the spread of any influence that directly allies itself with his selfish and cowardly tendencies.

To any young man who has been touched by the contagion of such doctrines, I should recommend a journey long enough and distant enough to bring him into contact with new and varied aspects of nature and of human society. Removed from the daily round of monotonous occupation, or, far worse, of monotonous idleness, life is thus presented in larger and truer proportions, and in a nature not quite worthless some chord must be touched that will stir the springs of healthy action. If there be in truth such beings as genuine and incurable pessimists, the stern believer in progress will be tempted to say that the sooner they carry out their doctrine to its logical result the better it will be for the race. Their continued existence, where it is not merely useless, must be altogether a mischief to their fellow-creatures.

[_RETURN TO ENGLAND._]

On the morning of the 16th of August, all but completing five months since I quitted her shores, the coast of England was dimly descried amid gusts of cold wind and showers of drizzling rain. My winter experiences in the Straits of Magellan were forcibly recalled to my mind, and I felt some partial satisfaction in the seeming confirmation of the conclusion which I had already reached--that the physical differences between the conditions of life in the northern and southern hemispheres are not nearly so great as has generally been supposed.

APPENDIX A.

ON THE FALL OF TEMPERATURE IN ASCENDING TO HEIGHTS ABOVE THE SEA-LEVEL.

The remarkable features of the climate of Western Peru referred to in the text seem to me to admit of a partial explanation from the local conditions affecting that region. The most important of these are the prevalence of a relatively cold oceanic current, and of accompanying southerly breezes along the Peruvian coast. These not only directly affect the temperature of the air and the soil in the coast-zone, but, by causing fogs throughout a considerable part of the year, intercept a large share of solar radiation. It has been found in Northern Chili, some fifteen degrees farther south than Lima, but under similar climatal conditions, that, although the land rises rather rapidly in receding from the coast, the mean temperature increases with increasing height for a considerable distance. It is stated on good authority[49] that at Potrero Grande, a place about fifty miles distant, and 850 metres above the sea, the mean annual temperature is higher by 2·5° C. than at Copiapò, or at the adjoining port of Caldera. It is probable that in the valley of the Rimac the mean temperature at a height of 1000 metres is at least as high as it is at Lima. Taking the mean temperature of the lower station at 19·2° C., and that of Chicla at 12·2° C., that would give a fall of 7° for a difference of level of 2724 metres, or an average fall of 1° for 387 metres, instead of 1° for 512 metres, as given in the text.

A further peculiarity in the climate, which tends to diminish below the normal amount the rate of decrease of temperature, is the comparative absence of strong winds, and the feebleness of the sea-breezes which are usually so conspicuous in the tropics. For reasons that will be further noticed, the fall in temperature in ascending mountain ranges is largely due to currents of air carried up from the lower region. In mountain countries an air-current, encountering a range transverse to its own direction, is mechanically forced to rise along the slopes, and thus raises large masses of air to a higher level; the same effect in a less degree occurs with isolated peaks. But in the Peruvian Andes, as well as in many other parts of the great range, although storms arise from local causes on the plateau, westerly winds from the ocean are infrequent and feeble; and the sea-breezes, due to the heating of the soil by day, much less sensible than usual in warm countries.

Making full allowance for the operation of the two causes here specified, it yet appears that the difference of temperature between the coast and the higher slopes of the Peruvian Andes is exceptionally small. It is not merely due to the abnormal cooling of the coast-zone, but to the exceptionally high temperature found in the zone ranging from 3500 to 4000 metres. I should not have attached much importance to the few observations of the thermometer that I was able to make during a hurried visit, if the conclusion which they suggest had not been strongly confirmed by the character and aspect of the vegetation.

When I found that the table given by Humboldt, which has been copied and adopted by so many writers on physics, in which the mean temperature at a height of 2000 toises, or 3898 metres, in the Andes of Ecuador, close to the equator, is set down at 7°, while at Chicla, thirteen degrees of latitude south, at a height less only by 174 metres, there is reason to believe that we find a mean annual temperature of not less than 12°, I was led to enter more fully into the subject.

The result of somewhat careful study has been to convince me that, while the physical principles involved in the attempt to discover the vertical distribution of temperature in the atmosphere prove the problem to be one of extreme complexity, the results hitherto obtained from observation are altogether insufficient to guide us to an approximate law of distribution. I may remark that the problem has not merely a general interest in connection with the physics of the globe, but has a direct bearing on two practical applications of science. The observations of the astronomer and the surveyor require a knowledge of the amount of atmospheric refraction, by which the apparent positions of the heavenly bodies, or of distant terrestrial objects, are made to differ from the true direction; and to determine accurately the amount of refraction we should know the temperature of the successive strata of air intervening between the observer and the object. In determining heights by means of the barometer, or any other instrument for measuring the pressure of the air, it is equally necessary for accuracy to know the variations of temperature in the space between the higher and the lower station.

Three different opinions have prevailed among physicists as to the law, or supposed law, of the rate of variation of temperature in ascending from the sea-level. The simplest supposition, and the most convenient in practice, is that the fall of temperature is directly proportional to the height, and this has been adopted in several physical treatises. In English works the rate has been stated at a fall of 1° Fahr. for 300 feet of ascent, and by French writers the not quite equivalent rate of 1° C. for 170 metres has been adopted. The formula proposed by Laplace for the determination of heights from barometric observations, which has been very generally adopted by travellers and men of science, implicitly assumes that the rate of decrease of temperature is more rapid as we ascend to the higher regions than it is near the sea-level, and this opinion was explicitly affirmed by Biot in his memoirs on atmospheric refraction. A third hypothesis may be said to have originated when, in 1862, Mr. Glaisher made his report of the results of the famous balloon ascents effected by him and Mr. Coxwell,[50] and among others exhibited a table showing the average decline of temperature corresponding to each successive thousand feet increase of elevation from the sea-level to a height of 29,000 English feet.

As Mr. Glaisher’s tables showed a gradual decline in the rate of fall of temperature with increasing height, they clearly did not accord with the ordinary assumption of an uniform rate, and still less with the hypothesis of Laplace and Biot. In February, 1864, Count Paul de St. Robert, of Turin, communicated to the _Philosophical Magazine_ a short paper, in which he showed the incompatibility of Mr. Glaisher’s results with the ordinary formulæ for the reduction of barometric observations, and proposed a new formula based on a law of decrement of heat based upon Mr. Glaisher’s tables. In the following June, M. de St. Robert published in the same journal a further paper, in which, still accepting Mr. Glaisher’s results as accurate, he investigated the subject in a masterly manner, as well with reference to the measurement of heights, as in its connection with the determination of the amount of atmospheric refraction. The formula proposed by M. de St. Robert, and the tables subsequently published by him for its adaptation to use, appearing to be at once the most accurate and the most convenient, have been adopted by myself and by many other travellers;[51] but it is evident that their value depends on the correctness of the results, above referred to, deduced by Mr. Glaisher, and their conformity with observation in mountain countries.

Before we inquire into the conclusions to be drawn from observation, it may be well to point out how incomplete is our knowledge of the physical agencies which regulate the distribution of temperature in the atmosphere.

The primary source of temperature is solar radiation, and its effect at any given point on the earth’s surface depends on the absolute amount of heating power in the sun’s rays, irrespective of absorption, commonly designated the _solar constant_, and on the proportion of heat which is lost by absorption in passing through the atmosphere. The temperature of the air at any point will, in the first place, depend on the amount of solar radiation and of heat radiated from terrestrial objects directly absorbed, and next on the heating of the strata near the surface by convection. The amount of heat received from the sun, directly or indirectly, varies of course with the sun’s declination at the time, and the length of the day at the place of observation. When the sun is below the horizon the air loses heat by radiation, and still more, in the strata near the surface, by convection to surfaces cooled by radiation.

It was until lately believed that the experiments of Herschel and Pouillet had given an approximate measure of the absolute intensity of solar radiation, and that the proportion absorbed by the atmosphere at the sea-level at a vertical incidence might be estimated at about one-fourth of the whole. It is not too much to say that the recent researches of Mr. Langley, especially those detailed in his _Report of the Mount Whitney expedition_,[52] have completely revolutionized this department of physics. It now appears that the true value of the solar constant is not much less than twice as great as the previous estimate, and that rather more than one-third is absorbed by the atmosphere before reaching the sea-level. Mr. Langley has further proved that the absorptive action of the atmosphere varies with the wave-length of the rays, and that, omitting the “cold bands” which correspond to the dark bands in the visible spectrum, it diminishes as the wave-length increases. It further appears highly probable that the larger part of the absorptive action of the atmosphere is due to the aqueous vapour, the carbonic acid gas, and the minute floating particles of solid matter, which are present in variable proportions. Allowing for the probable extension of our knowledge by further research, it is yet evident that, even if we had not to take into account the further elements of the problem next to be specified, the distribution of heat in the atmosphere, as dependent on solar radiation, is a question of extreme complexity.

The action of winds has an important effect in modifying the temperature of the air. It is not possible to draw a distinct line between the great air-currents, which affect large areas, and slight breezes, depending on local causes, and limited to the lower strata of the atmosphere; but in relation to the present subject it is necessary to distinguish between them. There is a general circulation in the aërial envelope covering the earth, caused by unequal heating of different parts of the surface. Heated air rises in the equatorial zone, and its place is filled by currents from the temperate and subtropical zones. The heated air from the equator flows at first as an upper current towards the poles, but as it gradually loses its high temperature, it becomes mixed with the currents setting from the poles towards the equator, causing the atmospheric disturbances and variable winds characteristic of the cooler temperate zones. As a rule, bodies of air of different temperatures do not very quickly mix, but tend to arrange themselves in layers or strata in which masses of unequal temperature are superposed. It is obvious that in such a condition, where a layer of colder air lies between two having a higher temperature, the whole cannot be in a state of equilibrium. But in nature we constantly find that equilibrium is never attained. There is a continual tendency towards equilibrium, along with fresh disturbances which alter the conditions.

As Professor Stokes remarks in a letter on this subject with which he favoured me, “to know the temperature of the successive strata as we ascend in a balloon, we should know the biographies of the different strata.” Those which are now superposed may have been hundreds of miles apart twenty-four hours before. It follows that without a knowledge of the course and velocity of the higher currents existing in the atmosphere, we cannot expect to learn the vertical distribution of temperature.

Apart from the effects of the great movements of the air, there is another effect of air-currents to be considered, which tends especially to modify the temperature found at or near the earth’s surface. The heating of the surface by day, and the cooling by night, determine the existence of local currents of ascending or descending air. In rising, the air encounters diminished pressure, and therefore expands, and in so doing overcomes resistance. The molecular work involved in dilatation is performed at the expense of the other form of molecular work which we call heat. In other words, the air in ascending loses heat. It is found that the amount of decrement of temperature due to the ascent of a body of air is nearly exactly 1° C. for 100 metres. As a general rule, ascending currents arise from the surfaces exposed to the sun during the day, and must largely contribute to produce the rapid decrement of heat which is found in the lower strata near the surface, as compared with the rate of change in the higher regions; but it will be obvious that the amount of effect produced by this cause is subject to continual variation from changes in local conditions. The nature of the soil, the extent and character of the vegetation, the form of the surface, are all elements which modify the amount of disturbance in the equilibrium of the surrounding atmosphere. As above remarked, in discussing the climate of Western Peru, prevailing winds which impinge upon a range of mountains may indirectly affect the temperature of the higher region by mechanically forcing masses of air to rise along the slopes, and ultimately, by expansion, to be cooled much below the temperature which they possessed when they originally flowed against the slopes.

One of the most important agencies affecting the distribution of temperature in the atmosphere arises from the presence of aqueous vapour. In its invisible condition it affects the absorptive power of the air on the solar rays, and, when condensed in the form of cloud, it acts as a screen, intercepting most of the calorific rays which would otherwise reach the earth. But it is especially through the large amount of heat consumed in converting water into vapour, and set free when vapour returns to the fluid state, that the temperature of the air is largely modified. When we consider that in converting a given volume--say, one cubic metre--of water into vapour, enough heat is consumed to lower about 1,650,000 cubic metres of air by 1° C. in temperature, and that the same amount of heat is liberated when the vapour so produced returns to the liquid state, we perceive how powerfully the ordinary processes of evaporation and condensation must affect the temperature of the air.

It is needless to analyze further the several agencies which, sometimes co-operating, and sometimes in mutual opposition, determine the vertical distribution of temperature in the atmosphere. It is but too obvious that no approach to uniformity can be expected, and it might even be anticipated that any approximation to a regular law of distribution that should be found under one set of conditions--as, for instance, in serene weather by day--would be altogether inapplicable under different conditions, such as exist in stormy weather, or by night.

The need for practical application of some empirical rule, or law, of vertical distribution has made it necessary to appeal to the results of observation, and for this object the only existing materials are to be found in the records of balloon ascents, and in the observations made on high mountains. In balloon ascents the temperature at any considerable height is free from the disturbances caused by the vicinity of the earth’s surface, and the results might be expected to contribute to the more accurate determination of the amount of atmospheric refraction. For the measurement of heights by the barometer, it would appear safer to rely on such information as may be gleaned from mountain observations.

Of balloon ascents by far the most important are those achieved in 1862 by Messrs. Glaisher and Coxwell, to which I have referred in a preceding page. Mr. Glaisher has given in his report a full record of the actual observations made in the course of his eight ascents, and has explained the processes by which he constructed the successive tables, from which he deduced as the final result a continuous decline (unbroken save in a single instance) in the rate of decrement of temperature found in passing through each successive zone of 1000 feet, in ascending from the sea-level to a height of 29,000 English feet.

I am not aware that the processes employed by Mr. Glaisher in obtaining these results have ever been subjected to such close scrutiny as their importance demands, and as I have found on careful examination that his results are not borne out by the actual observations, I am forced to express my dissent from his conclusions. The admiration due to the courage, skill, and perseverance displayed by Mr. Glaisher throughout these memorable ascents will not be lessened if we should find it necessary to modify the inferences which he has drawn from them.

The full discussion of Mr. Glaisher’s observations involves an inconvenient amount of detail, and such readers as may be disposed to enter more fully into the subject I must refer to an article in the _London, Edinburgh, and Dublin Philosophical Magazine_.

The general conclusions to which I have arrived from the observations made under a clear or partially clear sky is, that the average results show a rapid fall of temperature in the zone extending to about 5000 feet, or 1500 metres, above the earth’s surface, and that, within that limit, the rate of fall diminishes as the height increases. Above the height specified the observations prove that in each ascent the balloon passed through successive strata of air whose temperature varied in a completely irregular manner, the fall of temperature being sometimes very rapid for an ascent of a few hundred feet, and sometimes very slight in a much longer interval. In each of the higher ascents we even find instances in which the thermometer rose in ascending from a lower to a higher station, reversing the ordinary progression. These alternations occurred at various heights from 5000 to 25,000 or 26,000 feet above the sea-level.[53] It seems to me very doubtful whether any safe conclusions can be drawn from averages deduced from separate series of observations so discordant, but, in any case, I may confidently assert that the results of actual observations do not bear out the conclusions deduced by Mr. Glaisher.

I desire further to point out that these balloon ascents were all executed by day, in summer, and in weather as serene as can ordinarily be found in our climate. If they did authorize us to derive from them an empirical law regulating the vertical distribution of temperature, this might, at the best, serve to approximate to the true amount of atmospheric refraction found by day in geodetical observations, but would be no guide to the conditions obtaining by night, which are those important to the astronomer.

Mr. Glaisher has not failed to notice the great difference shown by the observations made when the sky was overclouded as compared with those under a clear or partially clear sky, and has given a table showing that the mean results up to a height of 4000 feet above the sea show a nearly uniform decline of 1° Fahr. for each 244 feet at ascent. The numerical results of observations made under, or amidst, cloud appear to me of no practical value, as they depend upon conditions which are subject to constant variation.

If it be true that observations in balloon ascents, which are free from the disturbances caused by the vicinity of the earth’s surface, have hitherto failed to lead to any general results indicating a normal rate of decrease of temperature with increasing elevation, it could scarcely be hoped that observations on mountains should contribute farther to enlighten us. From what has been already said, it is apparent that the fact that the place of observation is close to the surface causes disturbances the nature and amount of which must vary with each particular spot, and with the season and the condition of the atmosphere at the moment of observation.

The intensity of solar radiation increases rapidly with increasing elevation,[54] so that when the sky is clear surfaces exposed to the sun are heated much above the normal temperature. Owing to its slight absorptive power the free atmosphere is little affected; but the strata nearest the surface are heated by convection, while a contrary effect follows when the surface is no longer exposed to the sun, and radiates freely to the sky.

The air in mountain countries is rarely at rest. Even when there is no sensible breeze, the unequal heating of the surface causes ascending and descending currents, which lose or gain heat by expansion or contraction. More commonly winds are experienced which, by impinging on the inclined surfaces, force bodies of air to higher elevations, and thereby directly cause a fall of temperature.

All these causes of disturbance are complicated by the action of aqueous vapour, which, in most mountain countries, is supplied from the surface, as well as borne upwards by ascending currents. Besides the effect of raising the temperature where condensation takes place, and lowering it where clouds are dissolved in strata of dry air, the amount of aqueous vapour present at a given place affects the intensity of solar radiation, and the consequent amount of heating of the surface.

In spite of these obstacles to the attainment of accurate numerical results from which to infer the distribution of temperature in the atmosphere, we are yet, for the larger part of the earth, forced to rely on mountain observations as the only available source from which any indications of a law of distribution can be gleaned. Balloon observations have hitherto, so far as I know, been confined to a few places in Europe; and, even if the results were more conclusive than they have hitherto been, we should not be entitled to infer that they held good for all parts of the earth. In countries where the course of the seasons is more uniform, and the direction and force of the winds less inconstant, it might be expected that the distribution of temperature would exhibit some nearer approach to uniformity; and the possibility of making observations at mountain stations by night might enable us to form some conjecture as to a condition of the atmosphere very different from that which obtains when the influence of the sun is present.

It cannot be said that the observations hitherto made on mountains have done as much as they might do, if properly conducted, to contribute to our knowledge; but a few leading facts may be derived from them, and it is worth while to point them out.

The most important of these is, perhaps, the influence of plateaux of elevated land in raising the temperature of the adjacent air. This is established by observation in all parts of the world, and it would appear that the rapid fall of temperature in the strata near the surface which is found at or near the level of the sea, is equally marked when we ascend from a plateau to an isolated summit. Both these conclusions, however, apply only to observations made in the summer of temperate regions, or in the warmer parts of the earth. Apart from this effect of a relatively heated surface which appears to extend above the surface to a height of about 1500 metres, or, in round numbers, 5000 English feet, mountain observations give but slight confirmation to the belief that the rate of decrease of temperature, in normal conditions of the atmosphere, diminishes as the elevation increases.

In endeavouring to use the available materials one difficulty arises from the fact that, in comparing the temperature of the upper with the lower stations, observers have rarely been supplied with simultaneous observations at the lower station, or that, when these have been available, the distance has been so great that the results throw little light on the probable condition of a vertical column of air near the higher station. In parts of the world where the daily range of temperature near the coast is very slight, we may with small risk of error use the mean temperature of the season at the lower station as the element of comparison, and, in places near the equator, the mean annual temperature. For this reason, observations in the Andes of Ecuador, Peru, and Bolivia present great advantages, and I think it may be useful to discuss the results so far as they are now available.

It is scarcely necessary to examine critically the results of the earlier explorations. Humboldt has given in the “Recueil des Observations Astronomiques,” etc., and in the “Memoires de la Société d’Arcueil,” vol. iii. p. 579, and elsewhere, the observations made by himself in Mexico, Colombia, and Peru, and also those of Caldas and Boussingault, and has derived from them a table which, with more or less modification, has been adopted in many physical treatises. It exhibits the mean differences of temperature found in successive zones differing in height by 500 toises, the interval corresponding to 974·6 metres, or very nearly 3000 English feet.

----------+-----------------+------------------+-------------------- Height in |Mean temperature.|Number of metres |Number of metres toises. | |corresponding to a|corresponding to a | |fall of 1°C. from |fall of 1°C. between | |the sea-level. |successive zones of | | |500 toises. ----------+-----------------+------------------+-------------------- Sea-level | 27·5 | -- | -- 500 | 21·8 | 171 | 171 1000 | 18·4 | 216 | 287 1500 | 14·3 | 221 | 238 2000 | 7·0 | 190 | 133 2500 | 1·5 | 187 | 177 ----------+-----------------+------------------+--------------------

The first remark to be made about this table is that the observations on which it is founded are not properly comparable, being partly single observations made during an ascent, and partly the mean of numerous observations made at certain places, such as Mexico, Quito, etc. It may further be remarked that many of the heights determined by Humboldt have been considerably modified by the results obtained by more recent travellers, and cannot now be regarded as correct. The influence of plateaux is, however, very apparent, as nearly all the observations from which the estimated temperatures for 1000 and 1500 toises were derived were made at places situated on open elevated valleys or plateaux. At the utmost, the results can be regarded merely as rough approximations to the truth.

By far the most important available observations in the Andes are those of Mr. Whymper, made during his remarkable explorations in 1880; but, unfortunately, the details have not yet been given to the world, and, in endeavouring to make use of them, I have been forced to content myself with the brief summary published in the _Proceedings of the Royal Geographical Society_ for 1881. Mr. Whymper was able to secure a register of the temperatures observed at Guayaquil during his stay in Ecuador, which will doubtless be published along with the record of his own observations; but it does not appear that he was able to obtain observations at Quito during his ascents to the higher peaks; and it seems that, in comparing the temperatures for the purpose of reducing his barometrical observations, he was forced to assume for Quito a mean temperature of 57·9 Fahr., or 14·4 C., obtained from a series of thermometric observations made during his stay at that place. There is reason to believe that the daily range of the thermometer at Quito is very moderate; and at the equator the differences of season are comparatively slight; nevertheless, the absence of simultaneous observations at that place diminishes the value of the results shown in the following table, in which Mr. Whymper’s results are reduced to metrical measure.

I have adopted the heights determined by Mr. Whymper as those deserving most confidence. They agree very well with those published by MM. Reiss and Stubel, so that the limits of error from this cause are inconsiderable. I have also adopted the height assigned to Quito--9350 feet, or 2848 metres. Where Mr. Whymper remained long enough on any summit to observe notable variations in the reading of the thermometer, I have taken the mean of the observed temperatures; but I have entered separately the results of the ascents of Chimborazo, one being made in January, the other in July, and in a separate line I have entered the mean results of the two.

In the following table I have entered in the first column the names of the peaks ascended by Mr. Whymper; in the second, the height of each as given by him; in the third, the observed temperature in degrees Centigrade; in the fourth, the difference between the observed temperature and 27° C.--that assumed for Guayaquil; in the fifth, the average number of metres corresponding to a fall of 1° C. in rising from the sea-level to the higher station; in the sixth, the difference between the observed temperatures and that assumed for Quito--14·4°; and in the seventh, the average number of metres corresponding to a fall of 1° C. in rising from Quito to the higher station. It is obvious that the more rapid the fall the less will be the number in columns 5 and 7.

Key: A: Name of Mountain. B: Height above sea-level. C: Observed temperature. D: Difference of temperature at sea-level. E: Average number of metres for fall of 1° C. from sea-level. F: Difference of temperature at Quito. G: Average number of metres for fall of 1° C. from Quito.

---+---------------------+------+--------+-------+-------+-------+------ | A | B | C | D | E | F | G ---+---------------------+------+--------+-------+-------+-------+------ 1 | Chimborazo (Jan.) | 6253 | -6·1 | 33·1 | 189 | 20·5 | 166 2 | Chimborazo (July) | 6253 | -8·06 | 35·06 | 178 | 22·46 | 151 3 | Mean of (1) and (2) | 6253 | -7·08 | 34·08 | 183·5 | 21·48 | 158·5 4 | Cotopaxi | 5959 | -8·4 | 35·4 | 168 | 22·8 | 136·5 5 | Antisana | 5870 | +11·1 | 15·9 | 369 | 3·3 | 916 6 | Cayambe | 5852 | +2·5 | 24·5 | 239 | 11·9 | 252 7 | Cahihuairazo | 5035 | +4·44 | 22·56 | 223 | 9·96 | 220 8 | Cotocachi | 4965 | +2·2 | 24·8 | 202 | 12·2 | 173·5 9 | Pichincha | 4851 | +7·77 | 19·23 | 255 | 6·63 | 302 10 | Corazon | 4837 | +4·44 | 22·56 | 214 | 9·96 | 200 11 | Sara Urcu | 4718 | +10·0 | 17·00 | 284 | 4·4 | 425 ---+---------------------+------+--------+-------+-------+-------+------

It will at once be seen that the temperatures observed on Antisana, Pichincha, and Sara Urcu were altogether exceptional, probably due to rapid condensation of vapour; and these may best be excluded from any discussion of the general results. The temperatures noted in the second ascent of Chimborazo were probably below the mean, or at least below the mean for the hours at which most of the other observations were made. But, as opinions may differ on that point, I have also given below the results of comparison with the mean for the two ascents of Chimborazo. For a similar reason I regard the figures for Cotopaxi, where Mr. Whymper remained for twenty-six hours on the summit, as giving too low a temperature, while that observed on Cayambe is certainly too high. The mean result for these two summits is probably a near approximation to the average for that height.

In attempting to draw conclusions from the above table, we must first remark that, in consequence of its position on a plateau, the temperature of Quito is considerably higher than it would probably be if the higher peaks descended with an uniform slope to the sea-level. The difference between the means for that place and Guayaquil is only 12·6° C.; whereas, on the supposition of an uniform decrease in ascending from the sea-level, it should be 14·2°, and still greater if we supposed that the rate of fall of temperature gradually diminishes as the elevation increases. Omitting altogether the results for numbers 5, 9, and 11 in the above table, we perceive that the observations fall into three groups: (1) those for Chimborazo, at 6253 metres; (2) those for Cotopaxi and Cayambe, with a mean height of 5905 metres; (3) those for Cahihuairazo, Cotocachi, and Corazon, whose mean height is 4950 metres. To these it may be well to compare the mean of the results for the entire series, and also the rate of decrease between the sea-level and Quito. I shall designate observations included hereunder by numbers corresponding to the lines in the preceding table. The number of metres of ascent corresponding to a fall of 1° C. gives the most convenient measure of the rate of decrease.

Key: A: Mean height. B: Difference of temperature at sea-level. C: Metres for fall of 1° C. from sea-level. D: Difference of temperature at Quito. E: Metres for fall of 1° C. from Quito.

------------------------------+--------+-------+-------+-------+------ | A | B | C | D | E ------------------------------+--------+-------+-------+-------+------ Quito | 2848 | 12·6 | 226 | 0 | 0 Mean of 1, 4, 6, 7, 8, and 10 | 5483·5 | 27·19 | 201·5 | 14·59 | 180·6 ” 3, 4, 6, 7, 8, and 10 | 5483·5 | 27·35 | 200·5 | 14·75 | 178·7 ” 7, 8, and 10 | 4946 | 23·37 | 212 | 10·77 | 195 ” 4 and 6 | 5905 | 29·95 | 197 | 17·35 | 176 ------------------------------+--------+-------+-------+-------+------

We see from this table that, in ascending from the coast to the highest peaks of Ecuador, the average fall of the thermometer was, in round numbers, 1° C. for every 200 metres of ascent, while in ascending from the sea-level to the plateau of Quito the fall was proportionately less, being at the rate of 1° C. for 226 metres. On the other hand, the fall of temperature was more rapid in ascending from Quito to the higher peaks. On an average of all the ascents, we may reckon the rate of 1° for 180 metres. But it is remarkable that, taking the average of the three peaks which rise about 2000 metres above the level of Quito, the temperature fell only at the rate of 1° for 195 metres, while in ascending to peaks higher by nearly 1000 metres, the rate of fall was 1° for 176 metres, and if we take the still higher summit of Chimborazo we may reckon the rate of fall at about 1° for 160 metres.

The apparent increase in the rate of decline of temperature in the higher region is still more clearly shown if we compare the mean of the three peaks whose average height is 4946 metres, with that of the two whose average height is 5905. For a difference in the mean height of 959 metres, we find an average fall of 6·58° C., or a fall of 1° for 145 metres. Taking the first ascent of Chimborazo as giving the most probable results, we find that between this peak and the mean of the three lower summits, with a difference in height of 1307 metres, the difference of temperature is 9·73°, or a fall of 1° for 134 metres. Again, comparing Chimborazo with the mean of Cotopaxi and Cayambe, we find, for a difference of height of 348 metres, a difference of temperature of 3·15°, or a fall of 1° for 110 metres.

I am fully aware that these observations are not numerous enough to lead to any safe general conclusions; the comparatively high temperatures found at the height of about 5000 metres may be due to exceptional local conditions, such, for instance, as the ordinary formation of clouds at about that level; but, so far as they go, the observations tend to negative the supposition that in the tropics the rate of decrease of temperature diminishes as we ascend to the higher regions of the atmosphere.

MM. Reiss and Stubel made numerous observations in the Andes of Ecuador and Peru, during a prolonged visit to that region. Lists of heights obtained by reduction from their observations have appeared in various German scientific periodicals, and more fully in the _American Journal of Science_, vol. ii. pp. 268, 269; but, so far as I can ascertain, the record of their observations of the barometer and thermometer has never been given to the world.

In “Copernicus,” vol. iii. p. 193, _et seq._, Mr. Ralph Copeland has published a summary of the results of a series of meteorological observations made by him at various stations on the line of railway connecting Mollendo on the Pacific coast with Puno in Bolivia, near the lake of Titicaca, and also at La Paz and at Tacna. Two series of observations were made at Vincocaya, the summit station of the railway, 4377 metres above the sea. All the other stations are either on elevated plateaux, or on open slopes inclining gently towards the coast. The temperatures are partly derived from numerous observations and partly by taking the mean of the maxima and minima, with corrections for each station, the reasons for which are assigned by Mr. Copeland. In most of these I am inclined to concur, but there are two from which I am forced to dissent. In reducing Mr. Copeland’s tables to metrical measure, I have therefore ventured to make some corrections, which do not, however, much alter the results.

I give below the heights above the sea, in metres, with the corrected mean temperature for each place, and the dates for each set of observations.

-----------------+--------------+-------+----------------+------------ | | | | Mean Places. | Latitude. |Height.| Dates of |temperature, | | | observation. | corrected. -----------------+--------------+-------+----------------+------------ Mollendo | 17° 2′ 54″ | 20 | July 2 | 16·7° C. Tacna | 18° 1′ 21″ | 560 | July 7-10 | 14·2° Arequipa Hotel | 16° 25′ 20″ | 2346 | Feb. 2-8 | 16·2° Arequipa railway | | | | station | ---- | 2300 | June 29-30 | 9·0° Vincocaya, I. | 15° 53′ 56″ | 4377 |Feb. 28-March 4 | 2·83° Vincocaya, II. | ---- | -- | June 6-27 | -2·2° Puno, I. | 15° 50′ 2″ | 3840 |March 20-April 4| 9·2° Puno, II. | ---- | -- |April 15-June 2 | 7·8° La Paz | 16° 27′ 0″ | 3645 | Feb. 12-25 | 10·7° -----------------+--------------+-------+----------------+------------

Without entering into minute details, or discussing the small corrections for changes in the sun’s declination to be allowed for latitude and for the dates of observation, we perceive that on the western slope of the Cordillera the rate of decrease of temperature in this region is much below the ordinary average. Estimating the mean temperature of Mollendo at 22° at the beginning of February, we find between Mollendo and Arequipa a difference of 5·8° C., or a fall in summer of 1° for an ascent of 401 metres; while in mid-winter we obtain a difference of 7·7°, showing that an ascent of 364 metres is necessary to cause a fall of 1°. This abnormal condition is, no doubt, mainly due to the exceptionally low temperature of the coast-zone. Between Arequipa and Vincocaya we may reckon the fall of temperature on the 1st of March at 14·2° for an ascent of 2031 metres, giving the proportion of 1° to 143 metres; but in winter the decrease is less rapid, as we have at the end of June a difference of about 11·5° for an ascent of 2077 metres, or about 181 metres for a fall of 1°.

A remarkable contrast is shown when we compare the temperature at Vincocaya with that of places on the plateau surrounding the great lake of Titicaca. From Mr. Copeland’s observations we may estimate the mean annual temperature of Vincocaya at 1° C., that of Puno at 8·5°, and that of La Paz at 8·8°. These figures would give a mean difference of 7·5° for a difference in height of 537 metres between Vincocaya and Puno, or a decrease of 1° for 72 metres. Between Vincocaya and La Paz we have a difference of 7·8° for a difference in height of 732 metres, or a fall of 1° for 94 metres. The mean of the two comparisons gives a fall of 1° for 83 metres, or about twice as rapid a change as the average of the comparison between Arequipa and Vincocaya. I am not disposed to attribute this remarkable difference of atmospheric conditions exclusively to the influence of plateaux in raising the mean temperature.

In my own slight experience in the Peruvian Andes, in ascending from Chicla, at about 3700 metres, to Casapalta, at about 4200 metres, I observed so complete and rapid a change in the character and aspect of the vegetation as to satisfy me that the difference in the annual mean temperature must be even greater than that observed by Mr. Copeland for a somewhat greater difference of height between Vincocaya and Puno. It may be that, in this comparatively dry region of the Andes, the higher stations receive more frequent, though not copious, falls of rain or snow, the evaporation of which maintains a constant low temperature in the surface and the surrounding air.

In comparing observations in Peru, Bolivia, or Chili with those made in the Andes of Ecuador, it must not be forgotten that the climatal conditions are essentially different. Owing to the fact that in the latter the range of the Andes is much narrower, and on one side the main valleys descend in a nearly due easterly direction, the hot, vapour-laden, easterly winds reach the plateaux still charged with moisture, and at all seasons rain is frequent and abundant. Farther south, the winds from the Atlantic have deposited the greater part of their moisture before they arrive at the western side of the main range, and the annual rainfall must be comparatively trifling.

I have sought in vain in the records of mountain observations in other parts of the world for materials from which any probable inference may be drawn as to a law regulating the ratio of decrease of temperature with increasing height above the sea-level. There is reason to admit that isolated peaks of no great height show a more rapid decrease as compared with the plain than do considerable mountain masses. Of mountains exceeding the height of 3000 metres in the tropics, the most rapid rate of decrease is that recorded for Pangerango in Java, being 1° for 178·5 metres.

The greater mountain masses in or near the tropics show nearly the same rate of decrement, by comparison with the sea-level, that I have been led to infer from the observations in Ecuador. The average rate for the Himalayas is about 1° for 194 metres of ascent, and for the less lofty peaks of Mexico Humboldt’s observations show a decrease of 1° for 188 metres. The great irregularities due to local conditions make it impossible to derive any positive conclusions as to the comparative rate of decrease in successive zones of elevation.

In Europe and North America comparisons between the temperatures at mountain summits and the sea-level give rates of decrease varying between 1° for 160 metres, and 1° for 170 metres; but it must be remarked that the averages are mainly founded on observations made in summer, and it is certain that the rate of decrease is much slower in winter. Where the difference of height is not very great, it not uncommonly happens that in winter the phenomenon is reversed, and that we experience an increase of temperature in ascending above the plain. The same result on a small scale may often be remarked on clear cold nights, when the temperature rises for a distance of some hundred feet in ascending isolated eminences, the effect being due to the cooling effect of radiation from the surface.

It seems most probable that in the winter of the temperate and polar zones the distribution of temperature in the atmosphere is subject to conditions widely different from those prevailing in summer; and, if that be true, we should have intermediate conditions in the spring and autumn; so that even if we could arrive at comparatively accurate results for one season of the year, these would not be applicable at other periods.

The general result to which I have arrived is that to ascertain the distribution of temperature in the atmosphere in successive zones of elevation is a problem of extreme complexity, towards which the existing materials do not furnish even an approximate solution. I hold, however, that it ought to be possible to obtain much more definite knowledge than we now possess by means of properly conducted observations in various parts of the world.

Foremost of these I would suggest the importance of well-conducted balloon ascents within the tropics. In selecting stations for such ascents we are somewhat restricted by local considerations, especially the extension of forests in many regions, such as the greater part of tropical Brazil. In British India there would be no difficulty in selecting suitable stations, and there would be additional value in comparing the results obtained from ascents in Bengal, and in the very different climate of the North-west Provinces. Elsewhere in the tropics we might expect valuable results from ascents in Queensland, and from the _llanos_ of Venezuela. It seems not impossible that, with a considerably smaller outlay, useful results may hereafter be obtained by means of improved self-recording instruments sent up in captive balloons; but in most countries such a record would be liable to interruption owing to storms.

The next desideratum is to obtain for a series of years simultaneous observations at successive stations, at vertical intervals of 500 or 600 metres, situated on the flanks and at the summits of high mountains to be chosen for the purpose. Some of these might with advantage be chosen on islands, and among these the following may be suggested:--the Peak of Teneriffe, Mauna Kea in the Sandwich Islands, Fusiyama in Japan, the Piton de Neige in the island of Réunion, and Etna in Sicily. It would add much to the value of these observations if in each case there were a double series of stations, one series being on the windward, the other on the leeward side of the mountain. It would also be important to obtain observations at similar series of stations in continental regions, removed from the immediate influence of the sea. Pike’s Peak in Colorado, which already possesses an observing station at the summit, and Mount Whitney in California, which Mr. Langley has selected as eminently suited for an observatory, both offer many advantages for the desired purpose. Another desirable station might easily be found in the Caucasus, or in Armenia, and one or more could be selected on the southern declivity of the Himalayas. In South America, where railways have been carried to such great heights, it may be hoped that regular observations may at some future time be secured at the successive railway stations. It would be worthy of the enlightened governments of Chili and Argentaria to make a commencement, by providing for such a series being obtained at the stations on the railway now in course of construction over the Uspallata Pass.

For the realization of most of these desires, as well as many others affecting the progress of human knowledge, and the general welfare of our race, we must be content to await the advent of a happier era, when the fruits of industry, and the efforts of rulers, shall no longer be mainly devoted to the maintenance and development of the arts of destruction.

While awaiting such additional knowledge as may hereafter be obtained, it is necessary in the mean time to form some provisional hypothesis on which to base the formulæ for determining the difference of heights of two stations, by barometric observations, and for ascertaining the amount of atmospheric refraction; and the subject might with advantage be discussed at a congress of scientific men. I have no authority to decide on a question of such difficulty, nor do I pretend to be thoroughly versed in the somewhat voluminous literature of the subject. I may remark, however, that in one of the fullest and most elaborate works by recent writers, Dr. Rühlmann[55] has proposed a formula for the reduction of barometric observations which implicitly assumes that the rate of decrement of temperature in ascending mountains is uniform, inasmuch as he takes the mean of the temperatures observed at the higher and lower stations as the value of the mean temperature of the column of air between the two stations. It would appear that his adoption of the hypothesis of an uniform rate of decrease is merely due to the apparent impossibility of discovering a more satisfactory hypothesis. Following on a line of inquiry first suggested by the late M. Plantamour and M. Charles Martins, Dr. Rühlmann has analyzed a series of two-hourly observations of temperature made during six years at the hospice of the Great St. Bernard and at the Geneva Observatory. Treating the mean temperature of the column of air between the levels of those places as the unknown quantity, and neglecting, as unimportant, the corrections for the tension of aqueous vapour and for gravity, he has deduced the “true temperature,” as he styles it, of the intermediate column from the equation of condition between the pressures, the heights, and the temperatures of the two stations, for the average of the two-hourly periods of observation for each month. He has shown that, while on the average of the entire year the mean “true temperature” of the intermediate column of air agrees pretty well with the mean of the yearly observations at the two extreme stations, the means for the separate hours and those for the separate months usually differ widely from the so-called “true temperatures” for the corresponding periods.

From this investigation Dr. Rühlmann has shown that during the warm hours of the day, and the summer months, the “true mean temperature” is lower than the mean of the observed temperatures at the two extreme stations, while at night, and during winter, it exceeds that mean to a rather greater extent. It may be objected that the cause of the apparent discrepancy lies in the fact that, in thermometric observations, we obtain, not the true temperature of the surrounding air, but that of the thermometer, and that, however carefully screened, the thermometer cannot be completely freed from the effects of radiation to and from surrounding objects. This remark applies especially to the observations at the St. Bernard, which lies at a considerable distance from Geneva, and where the temperature is unduly depressed by surrounding masses of snow. I do not, however, attach much importance to these sources of error; and I have no doubt that under the most favourable conditions the discrepancy shown by Rühlmann will be found to a greater or less extent, but I differ from that writer in the inference that he has drawn from the facts.

If I have not misunderstood his remarks, Dr. Rühlmann concludes that the true temperature of the successive strata of air in the zone between the base and the summit of a mountain is but slightly affected by the diurnal changes that are exhibited in the range of the thermometer, and to a moderate extent only by the changes of season as shown by the range of the monthly means. He has not adverted to the fact that the differences disclosed in his tables may be the result of changes in the rate of decrement of temperature in ascending from the lower to the higher station. He shows that, on the mean of the July observations, the mean temperature of the air between the levels of Geneva and the St. Bernard is lower than the mean difference of the temperatures observed at those places by 1·57° C. But this is not inconsistent with the supposition that the thermometers have recorded the true air temperature at each station, but that the rate of decrement of temperature in ascending, at that season, diminishes rapidly in the successive vertical zones. In the same manner the fact that the true mean temperature in January is higher than the mean of the observed thermometers by 1·83° C., might be accounted for by supposing that in winter the rate of decrement is smaller in the lower strata, and increases in ascending above the surface. It is equally true that, in both cases, the facts may be consistent with such an irregular distribution of the atmosphere in successive layers, or strata, of very unequal temperature as was apparent in most of Mr. Glaisher’s balloon ascents. What is completely proved is that it is only under exceptional conditions that the hypothesis of an uniform rate of decrement of temperature, directly proportional to height above the sea-level, is approximately correct for observations in the temperate zone, where there is a considerable diurnal and annual range of the thermometer.

My own impression, as the result of such study as I have been able to give to the subject, is that, in the present state of our knowledge, the reduction of barometric observations for the height of mountains made by day, and in summer, in temperate latitudes, may best be effected by the formula proposed by M. de St. Robert; while for observations made at other seasons, and in the tropics, I should prefer the formula proposed by Mr. Rühlmann.

Before closing these remarks, I may refer to an ingenious suggestion made by M. de St. Robert in a paper published in the journal _Les Mondes_ in Paris, in 1864, the substance of which is to be found in the _Atti dell’ Academia delle Scienze di Torino_ for 1866, p. 193. Impressed with the difficulty of approximating in practice to a correct knowledge of the distribution of temperature in the air between the summit of a mountain and a lower station, the author sought to escape from it by seeking a phenomenon, susceptible of observation, which should give a direct measure of the mean density of the air in the space between the two stations. He pointed out that the velocity of sound supplies such a measure, and that, given the barometric pressures at the higher and lower stations, the angle of elevation of the former, measured by a theodolite and corrected for refraction, and the exact time required for sound to traverse the interval between them, the height is given with a near approximation to accuracy by a simple formula. The error arising from air currents, which increase or diminish the velocity of transmission, would be readily eliminated by discharging a fire-arm simultaneously at both stations, observing the interval between the light reaching the eye and the report becoming audible, and taking the mean of the intervals observed at both stations.

M. de St. Robert does not disguise the practical difficulty of measuring the time interval with the requisite accuracy, but he thinks that it may be obtained within a fifth of a second. The error in the result is inversely proportionate to the time required to traverse the distance, and where the stations are as distant as is compatible with the sound being audible, its amount for an error of a fifth of a second is inconsiderable.

This suggestion has not received the attention which it seems to deserve. It possesses the advantage that the observations may readily be repeated with little trouble or cost, and that the risk of error may be much diminished by taking the mean of the observed intervals of time. A comparison between observations between stations whose height is known, made under different conditions, by day and night, and in different states of weather, might, I think, contribute to diminish our ignorance as to the variable conditions of the atmosphere at different heights above the surface.

APPENDIX B.

REMARKS ON MR. CROLL’S THEORY OF SECULAR CHANGES OF THE EARTH’S CLIMATE.

Most scientific readers are familiar with the theory respecting the influence of changes in the eccentricity of the earth’s orbit on the climate of the globe, which has been sustained with remarkable ability by Mr. James Croll. The views originally advanced in various scientific periodicals were presented to the public in a connected form in the volume entitled “Climate and Time,” wherein the author has brought a wide knowledge of the principles of physics, and of the whole field of geological science, to the support of his theory. Even those who have not given especial attention to the subject are also acquainted with the conclusions which Sir Charles Lyell drew from the discussion of Mr. Croll’s arguments, and which are contained in the thirteenth chapter of the tenth edition of his “Principles of Geology,” and also with the more recent examination of the subject which is to be found in Mr. Alfred Wallace’s important work, “Island Life.”

I need not say that a theory so important in its bearing on some of the most obscure problems of geology has been discussed, in more or less detail, by many other writers. To most of the objections presented to his theory, Mr. Croll has replied with his usual ability; and I believe that at present the prevailing tendency among geologists is towards a partial acceptance of his views, subject to the limitations assigned by Mr. Wallace. The latter author holds, in common with Sir Charles Lyell, that geographical causes, arising from the varying distribution of land and sea, have mainly controlled the distribution of temperature over the earth’s surface; but he is disposed to go farther than Lyell in admitting the influence of periods of high eccentricity in causing those great accumulations of snow and ice which were requisite to produce the phenomena of a glacial period, whenever a sufficient area of elevated land in high latitudes coincided with the period of high eccentricity.

It would probably be of little avail, even if I were to undertake the task, that I should attempt any thorough discussion of this vast and difficult problem; and it would certainly require far more space than can here be given to it. I may, however, venture to make a few remarks upon some points which have not, to the best of my knowledge, been much noticed in the discussion.

In reading Mr. Croll’s work, which charmed many an hour during the voyage to and from South America, I found it very difficult to discover any flaw in the chain of close reasoning by which he supports his conclusions. Most of the facts on which he relies are warranted by observation, and have been accepted as well established by writers of the highest authority; and his inferences as to the results of altered conditions appeared to be in strict conformity with admitted physical principles. Nevertheless, when I reflected on the anomalies which are found at the present time in respect to the climate of many spots in the world, and the complexity of the causes which determine its actual condition, I felt a doubt whether, in his attempt to trace the result of possible changes, Mr. Croll may not have overlooked some of the elements of the problem.

Let me briefly state the leading propositions of Mr. Croll’s theory in order to make intelligible the succeeding remarks.

Estimating approximately the mean distance of the earth from the sun at ninety-one and a half millions of miles, and the eccentricity[56] of the sun’s place in the orbit at one and a half million, it follows that at one period of the year, which happens to be about the winter solstice of the northern hemisphere, the earth receives from the sun a quantity of heat greater than that which reaches it in the opposite part of its orbit, in the proportion of 93^2 to 90^2, or about as 1000 to 936. Midsummer of the southern hemisphere is the season when the earth is nearest to the sun; the winter of the southern and the summer of the northern hemisphere occur when the earth is farthest from the source of heat. The conclusion seems inevitable--the southern hemisphere must have hotter summers and colder winters than our hemisphere, where the heat of summer is tempered by the greater distance, and the cold of winter mitigated by the comparative nearness, of the sun.

The next point to be considered is the effect of ocean-currents, and especially of the Gulf-stream, in modifying the climatal conditions of some parts of the earth. Following in the track of the late Captain Maury and Principal Forbes, Mr. Croll has especially insisted on the importance of the great current which, issuing from the Gulf of Mexico, and flowing northward between Florida and the Bahamas, extends across the Atlantic towards the western shores of Europe. He calculates that by this current alone an amount of heat equal to that received on the entire surface of the earth in a zone thirty-two miles in breadth on each side of the equator is carried from the tropics to the cooler regions of the northern hemisphere. Mr. Croll has, I think, victoriously replied to several of the objections opposed to this portion of his argument. His estimate of the volume of water transferred by the Gulf-stream from the tropics to the northern part of the Atlantic, which he reckons at the annual amount of about 166,000 cubic miles, is, I think, in no degree exaggerated; and I also think that he is warranted in estimating the mean initial temperature at about 65° Fahr. I am, however, persuaded that in assuming 40° Fahr. as the temperature to which, on an average, this vast body of water is reduced before it returns to the equatorial zone, Mr. Croll has gone beyond the probable limit. A large part of the stream is diverted eastward about the latitude of the Azores, and is never cooled much below 55° Fahr. before the waters enter the return current on the eastern side of the Atlantic basin; and I believe that, if we allow the water of the Gulf-stream to undergo an average loss of temperature of 20° Fahr., we shall be more likely to exaggerate than to underrate the amount of cooling.

In insisting on the importance of the Gulf-stream in modifying the climate of Europe and the adjacent parts of the arctic zone, Mr. Croll agrees with many preceding writers; but, so far as I know, he was the first to suggest that in consequence of the greater persistency of the south-east trade-winds, which ordinarily extend up to, and, at some seasons, even north of, the equator, the warm waters of the Northern Atlantic derive a large share of the heat which is carried to the temperate and arctic zones from the southern hemisphere. Applying the same reasoning to the currents of the Pacific Ocean, Mr. Croll arrives at the general conclusion (“Climate and Time,” p. 94) that “the amount of heat transferred from the southern hemisphere to the northern is equal to all the heat falling within fifty-two miles on each side of the equator.”

I do not believe that the facts on which Mr. Croll bases this essential portion of his theory are sufficiently established. With regard to the Atlantic, I have expressed in the text (p. 344) an opinion, derived from conversations with practical seamen, that in the Atlantic the trade-winds of the northern are stronger than those of the southern hemisphere. That opinion, I am disposed, on further examination, to regard as incorrect. I believe that the north-east trade-winds often blow with greater force; but, taking the average of the entire year, I now think there can be no doubt that the south-east trade-winds extend over a wider area in the equatorial zone. However this may be, our knowledge of the currents of the Atlantic does not, I think, authorize us to conclude that the portion of heated water carried from the southern to the northern hemisphere is nearly so large as Mr. Croll has estimated. If the heat of the Gulf-stream were mainly supplied, as Mr. Croll contends, from that source, there should be a marked difference in the volume and temperature of the current, between the season when the north-east trade-winds approach the equator and that in which the south-east trades prevail to the north of the line, for which there is no evidence.

As regards the currents and winds of the Pacific, in spite of one considerable exception, to which I shall further allude, I think that the balance of evidence points to a greater prevalence of the south-east trade-winds, and to the probable transference of some portion of the equatorial waters from the southern to the northern hemisphere.

For the present discussion it is best to accept Mr. Croll’s estimate, and to compare the amount of heat which he supposes to be transferred from one hemisphere to the other with the total amount which is received annually from the sun on each hemisphere. For this purpose I have taken the known areas of the torrid, temperate, and frigid zones respectively, and, following Mr. Croll, I have adopted Mr. Meech’s estimate of the average amount of heat, per unit of surface, received from the sun in each zone, irrespective of absorption by the atmosphere. To estimate the proportion of heat which actually reaches the surface, I have adopted Pouillet’s measure of the proportion of solar radiation cut off at vertical incidence, which is 24 per cent. I assume 28 per cent. to be the average loss in the torrid zone, 50 per cent. in the temperate zone, and 75 per cent. in the frigid zone.[57] The resulting figures, showing the proportional amount of heat annually received on the surface of each zone, and on the entire hemisphere, are as follows:--

Torrid zone 3370 Temperate zone 2304 Frigid zone 112 ---- Whole hemisphere 5786

Calculating, on the same basis, the amount received on a zone one mile wide at the equator, allowing a loss of 25 per cent. from atmospheric absorption, and multiplying the result by 104, I obtain the number 233·1 or rather more than one twenty-fifth part of the entire heat annually received from the sun by each hemisphere.

To trace the results of such a transfer of heat from one hemisphere to the other, I shall adopt a mode of reasoning, sanctioned by the great authority of Sir John Herschel, to which Mr. Croll frequently resorts. It is by solar heat that the surface of the earth is raised above the temperature of space, which is assumed to be 239 degrees below the zero of Fahrenheit’s scale. Adopting Ferrel’s estimate, I take the mean temperature of the northern hemisphere at 59·5° Fahr., or 298½ degrees above the temperature of space. To maintain this temperature, it receives one-half of the amount of solar radiation which reaches the earth, and in addition, on Mr. Croll’s hypothesis, one twenty-fifth part of that which reaches the southern hemisphere. It follows that the heat available to raise the southern hemisphere above the temperature of space stands to that which is received by the northern hemisphere in the ratio of 24:26, and that the mean temperature of the southern hemisphere should be 298·5 × 12/13, or 275·5° above the temperature of space; so that, in ordinary language, the mean temperature of the southern hemisphere should be 36·5° Fahr. If the fact corresponded with this result of theory, it would not be necessary to invoke increased eccentricity of the earth’s orbit to account for the extreme cold of one hemisphere, seeing that the actual conditions would suffice to completely alter their relative temperatures.

It occurs to me, however, that, on further consideration, Mr. Croll would reduce his estimate of the volume of heated water transferred from the southern to the northern hemisphere; but even if that estimate were reduced by one-half, we ought to find in the southern hemisphere a mean temperature of 47·8° Fahr., or nearly 12 degrees lower than that of our hemisphere.

We have already seen that, so far as climate depends on the relative position of the earth and the sun, we ought to find in the southern hemisphere climates of a more extreme character, with hotter summers and colder winters, than those to which we are accustomed. If it be true that through the agency of ocean-currents a considerable amount of heat is transferred to the northern hemisphere, that circumstance might serve to account for the fact that the summers of the southern are not generally hotter than those of the northern hemisphere; but it would, at the same time, tend to aggravate the severity of the southern winters.

At the time of the publication of Mr. Croll’s earlier memoirs, there existed a general belief that the southern hemisphere was in fact notably cooler than our portion of the globe, and he naturally referred to the supposed fact as harmonizing with the general conclusions drawn by him from theory. But, imperfect as our knowledge of the southern hemisphere still is, a good deal of information has been obtained of late years. The only stations south of the fiftieth degree of latitude from which we possess continuous observations are those mentioned in the text (p. 273); but we also know with sufficient accuracy the climates of two widely separated islands lying about 50° south; and from these we derive results widely different from those to which we were led by theoretical considerations. The following table gives approximately the mean temperatures, on Fahrenheit’s scale, for the year and for the hottest and coldest months of the places referred to in the southern hemisphere, and the means for corresponding latitudes in the northern hemisphere:--

Key: A: S. latitude. B: Temperature of January. C: Temperature of July. D: Mean of year. E: N. hemisphere. July. F: N. hemisphere. January. G: N. hemisphere. Yearly mean.

--------------------------+-------+-----+-----+-----+-----+-----+----- | A | B | C | D | E | F | G --------------------------+-------+-----+-----+-----+-----+-----+----- Kerguelen Land |49° 17’|44·3°|35·3°|39·6°|63·3°|22·0°|42·9° Auckland Island |50° 30’|50·2°|35·6°|44·6°|62·3 |19·0°|41·1° Falklands (Stanley) I.[58]|51° 41’|49·6°|36·5°|43·0°|61·6°|17·1°|39·8° Falklands II. |52° 5’ |55·9°|37·4°|47·3°|61·3°|16·4°|39·3° Falklands, mean of I. | | | | | | | and II. | |52·7°|37·0°|45·1°|61·5°|16·7°|39·6° Punta Arenas |53° 25’|51·4°|34·7°|43·0°|60·6°|14·2°|37·7° Ushuaia[59] |54° 53’|53·2°|31·8°|41·9°|59·6°|12·0°|36·2° --------------------------+-------+-----+-----+-----+-----+-----+-----

If we compare the mean results of these five stations with those for corresponding latitudes in the northern hemisphere, we find that the summers are cooler and the winters very much milder, and that in the latitudes between 50° and 55° the mean annual temperature is notably higher. In Kerguelen Land alone the mean annual temperature is lower than the normal for the same latitude north of the equator; but that island is evidently exposed to exceptional conditions.

The differences between the mean results given above are shown by the following table, in which the signs show the excess or deficiency of the southern as compared with the northern hemisphere:--

Warmest month. Coldest month. Annual mean. -11·1° Fahr. +18·1° Fahr. +4·2° Fahr.

Dr. Hann has carefully discussed the question as to the comparative mean temperatures of the two hemispheres in a paper published in the proceedings of the Vienna Academy, the substance of which is given in his _Klimatologie_, pp. 89, _et seq._; and it is difficult to refuse assent to his conclusion that so far as the available evidence goes, it shows that the mean temperature of both hemispheres is equal.

I find, then, that the same train of reasoning by which Mr. Croll has sought to explain the occurrence of glacial periods by changes in the eccentricity of the earth’s orbit, and the precession of the equinoxes, leads us to conclusions respecting the climatal condition of the different parts of the earth, at the present amount of eccentricity, which are altogether opposed to the results of observation; and I am driven to the conclusion that the causes which he has adduced have not the predominant influence which he has attributed to them, and that there must be other agencies to which he has not assigned their due importance, but which are adequate to counteract the efficiency of those which, as observation proves, fail to achieve the effects anticipated from them.

I am far from pretending to be able to analyze completely the complex agencies which, by their mutual action, determine the climate of different parts of the earth, but I may briefly refer to two of them. Foremost of these is the relative distribution of land and sea, for a due appreciation of which we are indebted to the great work of Sir Charles Lyell. It is unnecessary here to discuss how far his view of the probable amount of change in past geological epochs may, in the present state of our knowledge, be subject to limitation. Mr. Wallace, who is the most strenuous supporter of the modern doctrine of the permanence of the present continents and ocean basins, recognizes the theoretical correctness of Lyell’s views, and admits that changes of level great enough to cause profound modifications of climate have actually occurred. Notwithstanding recent objections, it appears to me that Darwin’s hypothesis as to the subsidence of a great tract in the Southern Pacific is that which best accounts for the existence of the countless coral islands in that region; nor is the probability of a nearly continuous barrier of volcanic islands across the Atlantic to be completely dismissed. That such changes would have largely affected the climate of the earth cannot, I think, be doubted.

If I may venture to express my own view on this difficult subject, I must say that, although it has not been overlooked by the able men who have discussed it, the paramount importance of aqueous vapour as an agent for modifying climate has not yet been fully recognized. Mr. Croll has constantly discussed the phenomena of ocean-currents, as if their chief function were to affect climate by heating or cooling the surrounding air, which is thence diffused over the land surfaces, and he has devoted little attention to the effects of evaporation from the sea, and the subsequent condensation in some other region of the vapour produced. When we remember that as much heat is consumed in the conversion of one cubic mile of water into vapour as would raise the temperature of nearly ninety-seven cubic miles of water by 10° Fahr., we get some measure of the vast power of vapour as a vehicle of heat. Admitting, as I am disposed to do, that 166,000 cubic miles of water are annually conveyed northward by the Gulf-stream, and suffer an average loss of 20° Fahr. before returning to the torrid zone, I must point out that the entire heat requisite to maintain this great volume of water at the higher temperature would be consumed in the conversion of 3433 cubic miles of water into vapour. In point of fact, I believe that more than one-half of the quantity specified is expended in evaporation, and that the cooling of the waters of the Gulf-stream is mainly due to this agency. To follow the vapour thus produced, to ascertain where it is condensed, and where the heat disengaged in the act of condensation becomes available to raise the temperature of the air, is a task which is beyond our present resources; but it is one which must be performed before we can reason with any confidence as to the ultimate distribution of the heat carried by the Gulf-stream or any other ocean-current. Whatever part of the vapour produced by evaporation from the Gulf-stream goes to supply the rainfall of Western Europe, or to form snow in the arctic regions, acts as a vehicle to transfer heat from the tropics to the temperate and frigid zones. But it is more than probable that a large part of the vapour in question is carried back to the torrid zone, and that some of it is even restored to the southern hemisphere. The south-eastern branch of the Gulf-stream flows, at least partially, into the area of the north-east trade-winds. These winds reach the lower region as cold and very dry winds. As they advance towards the equator, and are gradually warmed, their capacity for aqueous vapour constantly increases, and there can be no doubt that in both hemispheres the trade-winds bear with them a large share of the vapour which goes to supply the heavy rainfall of the tropics.

In the Pacific region we have direct evidence to this effect, in the fact that in Hawaii, and elsewhere, the side of the islands exposed to the trade-winds is that of heavy rainfall, and is generally covered with forest. No sufficient data exist for estimating the amount of vapour thus carried back to the tropics from high latitudes on both sides of the equator, nor the amount of heat set free by its condensation; but we may form some conception of its probable amount by considering that at the moderate estimate of a mean annual rainfall of seventy-two inches for the portion of the globe between the tropics, this amounts to a yearly fall of 88,737 cubic miles, and that we can scarcely reckon the share of this great volume of water supplied by evaporation from the same part of the globe at more than one-half. Still less is it possible to calculate the amount of vapour annually transferred from the northern to the southern hemisphere, which goes to neutralize the apparent effect of the diversion of portions of the equatorial waters to the north side of the line. In the Atlantic basin it is probable that the larger part of the rainfall in the region including and surrounding the Gulf of Mexico and the Caribbean Sea is supplied by vapour carried from the temperate zone by the north-east trade-winds. There is some reason to believe that a portion of the rainfall of the great basin of the Amazons, south of the line, is also supplied from the same source. Several travellers report that during the rainy season the prevailing winds are from the west and north-west, the latter being especially predominant at Iquitos, about 4° S. latitude, and 1600 miles from the mouth of the river.

In tropical Australia the rainy season falls during the prevalence of the north-west monsoon, and we cannot doubt that this is mainly supplied by vapour carried from the northern hemisphere. Another region wherein the same phenomenon is exhibited on a large scale is the central portion of Polynesia, extending from the Feejee to the Society Islands over a space of at least twenty degrees of longitude. Over that wide area, as far as about twenty degrees south of the line, the regular south-east trade-wind prevails only in the winter of the southern hemisphere, while during the rest of the year, especially in summer, north and north-east winds have the predominance. Taking the mean of three stations in the Feejee Islands, of which the returns are given by Dr. Hann, I find in round numbers the very large amount of 150 inches for the mean annual rainfall, of which 105 fall during the seven months from October to April, while the five colder months from May to September supply only forty-five inches of rain. There can be little doubt that the larger part of the 105 inches falling during the warm season is derived from the northern hemisphere.

I by no means seek to account fully for the apparent contradiction between the results of theory, as developed by Dr. Croll, and the actual distribution of heat over the earth as proved by observation; but I venture to think that I have shown reason to doubt the possibility of drawing absolute conclusions as to the results of astronomical changes until we shall have fuller knowledge than we now possess of all the agencies that regulate climates.

Before concluding these remarks, I will notice one other branch of the argument in regard to which I am unable to concur with Mr. Croll. As we have seen, the essential point in his theory as to the _modus operandi_ of changes of eccentricity, and the relative position of the poles, on the distribution of temperature, is that the currents of the equatorial zone are driven towards the pole which has the summer in aphelion, and that the cause of this shifting of the currents depends on the greater strength of the trade-winds in the hemisphere which has the winter in aphelion; the strength of the trade-winds in turn depending on the amount of difference of temperature between the equatorial and the colder zones. Taking the surface of the earth generally, the trade-winds of the southern are probably stronger than those of the northern hemisphere, and, if it were true that the south temperate and frigid zones were colder than those of the other hemisphere, it would be allowable to argue that the greater difference of temperature as compared with the equatorial zone was the cause of the greater strength of the trade-winds. But we now certainly know that the southern hemisphere between latitudes 45° and 55° is considerably warmer than the corresponding zone of the northern hemisphere, and we have good grounds for believing that the mean temperature of the whole hemisphere south of latitude 45° is higher, and certainly not lower, than that of the same portion of the northern hemisphere. We are therefore not justified in explaining the greater strength of the southern trade-winds by a greater inequality of temperature between the equator and the pole.

In my opinion the cause of this predominance of the southern trade-winds is to be sought in the fact that the southern is mainly a water hemisphere, while the northern is in great part a land hemisphere. In the south, the great currents of the atmosphere flow with scarcely any interruption, except that caused by Australia, where, in fact, the trade-winds are irregular, and lose their force. In the northern hemisphere the various winds originating in the unequal heating of the land surface interfere with the normal force of the trade-winds, and weaken their effect.

In connection with this branch of the subject, I may remark that the belief in the greater cold of the southern hemisphere mainly rests on the fact that all the land hitherto seen in high latitudes has been mountainous, and is covered by great accumulations of snow and ice. But this does not in itself justify the conclusion that the mean temperature is extremely low. It is true that the fogs which ordinarily rest on a snow-covered surface much diminish the effect of solar radiation during the summer in high latitudes, but this is compensated by the great amount of heat liberated in the condensation of vapour. The only part of the earth which is now believed to be covered with an ice-sheet is Greenland, but the mean of the observations in that country shows a temperature higher by at least 10° Fahr. than that of Northern Asia, where the amount of snowfall is very slight, and rapidly disappears during the short arctic summer. If there be, as some persons believe, a large tract of continental land surrounding the south pole, I should expect to find that the great accumulations of snow and ice are confined to the coast regions. In that case the mean temperature of the region within the antarctic circle would probably be lower than it would be in the supposition, which appears to me more probable, that the lands hitherto seen belong to scattered mountainous islands. If, from any combination of causes, one pole of the earth has ever been brought to a mean temperature much lower than that now experienced, I should expect to find that the phenomena of glaciation would be exhibited towards the equatorial limit of the cold zone, rather than in the portions near the pole. The formation of land-ice depends on the condensation of vapour, and before air-currents could reach the centre of an area of extreme cold the contained vapour would have been condensed. This consideration alone suffices, to my mind, to make the supposition of a polar ice-cap in the highest degree improbable.

Mr. Wallace (“Island Life,” p. 142) cites, as conclusive evidence of the effect of winter in aphelion in producing glaciation, the facts, to which attention was first directed by Darwin, as to the depression of the line of perpetual snow, and the consequent extension of great glaciers, on the west coast of Southern Chili. I have adverted to this subject in the text (p. 229), and I may further remark that if winter in aphelion be the cause of the depression of the snow-line in latitude 41° S., it can scarcely fail to produce some similar effect in latitude 34° S. Yet we find on the southern limit the snow-line much lower, and at the northern much higher, than it has ever been observed in corresponding latitudes in the northern hemisphere, the line being depressed by more than 8000 feet within a distance of only seven degrees of latitude. The explanation, as I have ventured to maintain, is altogether to be found in the extraordinary rainfall of Southern Chili; and to the same cause we must attribute the fact that, in spite of the greater distance of the sun, the winter temperature is higher than in most places in corresponding latitudes in the northern hemisphere. At Ancud in Chiloe, in latitude 41° 46′, the temperature of the coldest month is lower by less than three and a half degrees of Fahrenheit than it is at Coimbra in Portugal, one and a half degree nearer the equator, in the region which receives the full warming effect of the Gulf-stream.

I should have expressed myself ill in the preceding pages if I should be supposed to deny that, in his writings on this subject, Mr. Croll has made an important contribution to the physics of geology. He has, in my humble opinion, been the first to recognize the full importance of one of the agencies which, under possible conditions, may have profoundly affected the climate of the globe during past epochs, although I do not believe that, in the present state of our knowledge, we can safely draw those positive inferences at which he has arrived. Even those who are unable to accept any portion of his theory as to the causes of past changes of climate must feel indebted to his writings for numerous valuable suggestions, and for the removal of many popular opinions which his acute criticism has shown to be untenable.

INDEX.

A

_Acacia Cavenia_, 157

Aconcagua, 192

---- valley, vegetation of, 195

_Adesmia_, 182

Agassiz, Professor Alexander, 342

Ajulla, Promontory of, 51

Albatross, 215

Alligators, 41

Alpine zone in Andes, 91

Amancais, 71

Amatapi, Sierra, 52

Ancud, 145

Andean Flora, Alpine zone, 104

----, divisions of the, 104

----, European genera common to, 101

Andean railways, 63

Andes, 49

----, Alpine zone in, 91

----, cactoid plant in, 92

----, Chilian, view of, 183

----, climate of Peruvian, 99

----, _Compositæ_ in, 102

----, cosmopolitan weeds in, 101

Aneroid barometers, 353, 354

Angol, 213

Antarctic beech, 256

---- Flora, range of, 219

_Anthopterus Wardii_, 34

Anticosti, 273

Apoquinto, baths of, 188

Araucanian Indians, 212

----, language of, 213

_Araucaria Brasiliensis_, 311

Argentaria, climate of, 300

----, emigration to, 298, 299

----, forests of, 295

----, progress of agriculture, 298

----, frontier of Chili and, 258

Arica, vegetation of, 121

_Armeria maritima_, var. _andina_, 263

Artichoke, wild, 168

Atacama, desert of, 124, 131

Atlantic, colour of, 7

----, summer temperature of, 362

----, temperature of, 5

----, winds of, 345

_Ayacucho_ steamship, 118

Azores, 5

B

_Baccharis_, 157

Bahia Blanca, 298, 357, 358

Bahia de Todos Santos, 346

_Baillonia spartioides_, 202

Balmacedo, Don F., 191

Banda Oriental, 281

----, vegetation of, 293

Barbadoes, absence of venomous snakes in, 14

----, black population of, 11

---- harbour police, 9

---- planters, 13

----, productiveness of, 8

Barometer, high, 4

----, tables for, 4

Beagle Channel, 273

Belem, Tower of, 363

_Berberis buxifolia_, 263

---- _empetrifolia_, 263

---- _ilicifolia_, 263

Berberry, 225

Bentos, Fray, 287

Bio-Bio river, 213

Black-fish, 7

Blue Mountains, Jamaica, 17

_Bombax pubescens_, 328

Borya Bay, 241

Bossi, Signor Bartolomeo, 281

Botafogo, 322

Bove, Lieutenant, 252

Bramble in Chili, 150

Brazil, ancient mountains of, 317

----, coffee-planting in, 341

----, geology of, 313, 314

----, glacial deposits in, 342

----, rainfall in coast region of, 334

Brazilian physicians, their fees, 340

Bridges, suspension, in the Andes, 85

Buenaventura, 32

Buenos Ayres, 293-295, 299

C

Cabo Blanco, 43

---- San Lorenzo, 37

---- Santa Elena, 38

Cachapoal river, 178

Cactoid plant in Andes, 92

Caldera, 133

Callao, 61

----, quarantine at, 57

Canary Islands, 362

Cape Froward, 243

---- Parinas, 44

---- pigeon (_Daption capensis_), 214

---- Pillar, 238

---- Verde Islands, 359

Capricorn, Tropic of, 132

Cardoon, 164

Casapalta, 91

Catamarans, 352

_Cathartes atratus_, 112

Caudivilla, 109

Cauquenes, Morro de, 182

----, town of, 169

Cauquenes Baths, 172

----, railway to, 163

Celery, wild, 221

_Cereus Quisco_, 151, 176

Cerro de Pasco, 72

---- del Roble, 151

Chacao, Canal de, 216

Chagres river, 22

Chañeral, 133

Channels of Patagonia, 222, 223

Chicla, hotel at, 80

----, scenery at, 84

----, vegetation of, 98

Chili and Argentaria, frontier of, 258

---- and Peru, naval war of, 58

----, bramble in, 150

----, Central, flora of, 141

---- ----, climate of, 143-145

---- ----, rainfall in, 144

----, European plants in, 164

----, physical geography of, 170

----, Southern, glaciers of, 229

---- ----, rainfall of, 229

Chilian elections, cumulative vote, 191

---- mines, 161

_Chiliotrichium amelloides_, 234

Chiloe, island of, 215

Chimborazo, 38

Chonos Archipelago, 216

Chosica, 73

_Chuquiraga spinosa_, 91

Churches in Lima, 62

_Chusquea_, 152

Cigars, Guayaquil, 41

Cinnamon tree, 10

Claraz, M. Georges, 357, 358

Clarence Island, 243

Climate, effects of tropical, 39

_Cnicus lanceolatus_, 164

Cobeja, 131

Coffee-planting in Brazil, 341

_Colletia spinosa_, 177

Colomba, 214

Colon, 21, 22, 27

Commercial travellers, German, 309

_Compositæ_ in Andes, 102

Concepcion del Uruguay, 288

Condor, 87, 93

Condors, captive, 185

Copiapò, 133

----, Rio de, 133

Coquimbo, vegetation of, 136, 138

Corbett, Mr., 328

Cordillera de la Costa, 218

Cordillera Grande, of Goyaz, 315

Cordillera Pelada, 218, 219

Cordillera in Peru, 49

Corrientes, 294, 300

Cosmos Line, German steamers of, 205

Cousiño, Madame, 207

Crab, red, 227

Croll, Dr. James, 271

----, remarks on his theory of secular changes of climate, 393

_Cryptocarya Peumus_, 160

Cuyabà, 279, 310

D

Dandelion (_Taraxacum lævigatum_), 263

_Daption capensis_, 214

Darwin, Mount, 267, 270

Dawson Island, 245

_Desfontainea spinosa_, 225

Desolation, Land of, 235, 241

_Diomedea exulans_, 215

---- _fuliginosa_, 215

_Don_, Royal Mail steamer, 2

_Doterel_, wreck of the, 267

_Drimys Winteri_, 147

Drummond-Hay, Mr., 148

Dungeness, 271

_Duvaua dependens_, 293

E

Earthquake-waves, 122

_Eccremocarpus scaber_, 199

Ecuador, 36, 40

Eden harbour, 224

Education, Chilian zeal for, 265

Elections, Chilian, cumulative vote, 191

_Encelia canescens_, 134

Engler, Dr., 34, 106

English Narrows, 223

English the _lingua franca_ of America, 88

Ensenada, 302

Entrerios, 288

Equator, cold current near, 356

----, path of the sun, 37

Equatorial rains, 352

---- vegetation, 33

_Erodium cicutarium_, 165

_Escallonia_, 181

Espiritu Santo, Cape, 271

_Eucalyptus globulus_, 160, 292

Evergreen beech (_Fagus betuloides_), 225

Existence, struggle for, 330

Eyre Sound, 228

F

_Fagus betuloides_, 225

---- _obliqua_, 151

Falkland Islands, 247, 273

Fayrer, Sir Joseph, 349

Fenton, Dr., 250, 262, 269

Fernando Noronha, 354, 355

Feuillée, Father, 184

Flint, Mr., 153

Flowering plants, origin of, 318

Flying-fish, 5

---- of Pacific, 53

Fogs on Peruvian coast, 54

_Francoa sonchifolia_, 210

French, Dr., 289, 291

Fruit-sellers, migratory, 42

Fuegians, 233, 242, 260, 261

G

Gallinazo, 87

----, scavenger bird, 112

_Galvesia limensis_, 45

Gillies, Captain, 344

Glacial deposits in Brazil, 342

Glaciers in South Patagonia, 239

---- of Southern Chili, 229

Glaziou, Dr., 324

_Gleichenia_, 226, 311

_Glyptodon_, 358

Gongo Seco, 316

Gordontown, Jamaica, 18

----, cool climate of, 19

Graham, Mr. J. R., 67

Granite, disintegration of, 315

Grisebach, 34, 145

Gualtro, 168

Guanacos, 131, 253

Guano Islands, 53

Guayaquil cigars, 41

Guayaquil, city of, 40, 41

----, Gulf of, 38, 40

Guayas river, 38, 41, 42

_Gynopleura linearifolia_, 157

H

Hale Cove, 220

Hann, Dr. Julius, 144, 305, 349

Hanover Island, 236

Hayti, island of, 15

----, cannibalism in, 16

Haze, opacity of, 158

Heights above sea-level, fall of temperature in ascending to, 369

Henderson’s Inlet, 231

Hess, Mr., 163

_Hippeastrum equestre_, 19

Hopedale, in Labrador, 273

Huanillos, 127

Humboldt current, 50

Humming-birds, 209

_Hura crepitans_, 10

_Hymenophylla_, 226

I

_Iberia_ steamship, 269

Ice-axe, 226

Ice, floating, 228

Illiluk, 274

Immigrant plants, Darwin’s view of, 166

----, checks on their extension, 167

Indians, Araucanian, 212

----, Patagonian, 260

Iquique, 121

----, sea-fight at, 127

Isla de Santa Maria, 211

_Islay_ steamship, 29

Itamariti, Falls of, 329

J

Jamaica, 16

----, black population of, 20

----, vegetation of, 18

Jacmel harbour, 15

K

_Kageneckia oblonga_, 175

Kingston, Jamaica, 16

L

_Lapageria rosea_, 209

La Plata, estuary of, 277, 283

Las Condes, 163

La Serena, 136, 145

Lavapie Promontory, 211

Liais, M., 342

_Libocedrus_, 235

Lichens, 221

Lima, 61

----, a dinner-party at, 108

----, ancient beaches near, 113

----, meteorological observations at, 99

_Liriodendron_, 344

Lisbon, Rock of, 363

Llaillai, 150

Llama in Peru, 95

Loa river, 127

_Lobelia gigantea_, 184

_Lobelia tupa_, 184

----, poisonous species of, 76

Lobos de tierra, 53

---- de afuera, 53

_Lomaria magellanica_, 226

Lombardi, Signor M., 109

Lombardy poplar, 160

_Loranthus_, 176, 202

Lord Nelson Strait, 236

Lota, coal deposits of, 207

----, parque of, 208

Lynch, Don Patricio, 67

----, his administration, 68

M

Maceio, 347

Magellan, Straits of, 238, 239, 367

----, forests in the, 240

----, variable climate in, 240, 254

Maipo river, 134

Maldonado, 304

_Malesherbiaceæ_, 157

Mango tree, 10

Mapocho river, 157

Markham, Captain Albert, 135

_Marrubium vulgare_, 138

Matto Grosso, 279

Matucana, San Juan de, 76

Mayne Channel, 237

_Maytenus magellanica_, 263

Meiggs, Mr., 65

Mejillones, 132

Memory, lapses of, 26

Mendoza, 300

Mercator’s projection, 30

Messier’s Channel, 220, 231

Mist, clearing of, 333

_Mitraria coccinea_, 225

Molina, 175

Mollendo, 119

----, a bad port, 120

Monkeys, domesticated, 332

Monson, Mr., 280

Montaña of Eastern Peru, 97

Monte Video, 277, 279

Morro de Cauquenes, 182

Mountain-sickness, 81

_Mulinum_, 189

_Mutisia_, 177

_Mutisiaceæ_, 102

_Myzodendron punctulatum_, 256

N

Napp, Mr. Richard, 300

Nation, Mr. W., 70, 108

Naval war of Chili and Peru, 58

New Granada, 32

_Nicotiana glauca_, 360

Nikolaiewsk, 273

North Atlantic, trade-wind of, 361

Northern hemisphere, temperature of, 273, 274

O

O’Higgins, General, 154

Olfactory nerve, fugitive impressions, 190

_Oreodoxa regia_, 324

Organ Mountains, 325

Oroya railway, 64

----, spiral tunnel of, 79

----, viaducts of, 74

Ostrich, South American, 261

_Oxalis lobata_, 146

P

Pacific coast-steamers, 31

Pacific, colour of water of, 31

----, first view of, 25

----, flying-fish of, 53

----, high seas in Southern, 211

---- steamer, delay of, 269

Paisandu, 288, 289

Palms, avenue of, 323

Panama, 21

---- Bay, birds in, 29

---- Grand Hotel, 27

---- railway, 25

---- ship-canal, 23

----, vegetation of, 24

Paraguay river-steamers, 279

Paranà, 317

----, basin of the, 312

---- river, 284

Paranagua, Bay of, 308

Paranahyba, 313

---- valley, 320

Parasites and climbers, 330

Patagonia, 300

---- Channels, scenery of, 222, 227

----, vegetation of, 225, 235

----, women of, 253

Patagonian coast, winter climate, 276

Patagonian Indians, 260

Payta, climate and vegetation of, 45

Peckett Harbour, 262, 270

Pedro, Dom, Emperor of Brazil, 337

Pelicans, black, 59

Peñas, Gulf of, 218

Pernambuco, 351

_Pernettya_, 225

Peru, 44

---- and Chili, naval war of, 58

----, climate of Northern, 47

----, future of, 117

Peruvian coast, fogs on, 54

----, low temperature of, 55

---- sugar-plantation, 110

Pessimism, 365, 366

Petrel, giant, 215

Petropolis, 326, 327, 335

----, hermit of, 331

----, winter climate of, 334

Peumo tree, 159, 175

Philippi, Dr., 154

----, Professor Federigo, 155, 219

Physicians, Brazilian, their fees, 340

Pierola, Dictator of Peru, 117

Pietrabona, Commander, 257

Pimento tree, 10

Pisagua, 123

----, white rocks at, 125

Pisco, 119

_Plantago maritima_, 263

_Pleroma arboreum_, 342

---- _granulosum_, 336

_Podocarpus nubigena_, 235

Poncho, 179

_Porliera hygrometrica_, 199

Port Famine, 245, 250

---- Gallant, 241

Potato, wild, in Andes, 93

Prado, General, 36

_Prosopis limensis_, 46

_Proustia Baccharoides_, 195

_Pteris aquilina_, 329

Puente Infernillo, 78

Puerto Bueno, 233

Punta Arenas, 145, 246, 273

_Puya_, 151

Q

Quadras in Santiago, 153

Quarantine at Callao, 57

---- at St. Vincent, 359

_Quaresma_, 336

Queen Adelaide Island, 236, 238

_Quillaja saponaria_, 175

Quillota, Valley of, 150

Quinta Normal at Santiago, 155

R

Railways, Andean, 63

----, Oroya, 64

----, spiral tunnel of, 79

----, viaducts of, 74

Rancagua, 168

Reed, Mr. Edwin, 204

Reilly, Mr., 210

Resguardo del Rio Colorado, 200

_Rhamses_, the, 205

_Rhea Darwinii_, habits of, 261

Rimac, valley of the, 71

----, ancient terraces in, 75

----, _Compositæ_ in, 76

----, effects of sea-breeze in, 98

Rio Claro, 171

---- Colorado, 276

---- Janeiro, Bay of, 321, 322, 325

---- Parahyba do Sul, 313

---- San Francisco, 314

Rocks, disintegration of, 115

----, ice-action on, 228

_Rumex acetosella_, 263

S

_Sagittaria Montevidensis_, 297

Saladeros, 287

_Salix Humboldtiana_, 77

Salta, 294

Salto, 291

_Sambucus Peruviana_, 101

Sampayo, Don Francisco, 257

San Bartolomé, 73

---- Cristobal, Cerro, 156

Sand-box tree (_Hura crepitans_), 10

Sandy Point, 246, 250

----, burnt forest at, 256

----, mutiny of convicts at, 251

----, the hotel at, 249

----, vegetation of, 255, 263

San Felipe, 192

Sanitary rules, neglect of, 87

San José, Promontory of, 276

---- volcano, 164

San Lorenzo, island of, 59

San Matias, Bay of, 276

San Paulo, 308-310

---- and Rio Janeiro railway, 312

----, railway from Santos to, 307, 308

San Ramon, Salto de, 190

Santa Clara, 72

Santa Cruz settlement, 246

Santa Lucia, Rock of, 162

Santa Rosa de los Andes, 193, 196

Santiago, 145, 153, 156, 161

----, railway to, 149

----, sunset at, 186

Santos, 305, 306

----, tropical vegetation at, 307

São João da Barra, 312

São Salvador, 346

Sarmiento Channel, 231

Sarmiento, Mount, 243, 244, 267, 270

Scavenger bird, 112

_Schinus molle_, 77

Sea-sickness, 217

Seaweed, bands of, 6

_Senecio_, the genus, 268

Serra da Mantiqueira, 313, 314

Serra do Mar, 308, 314

Shannon, Captain, 269

Simpson, Captain, 207

Sitka, 274

Smyth’s Channel, 231, 237

_Solanum mammosum_, 33

Soroche, mountain-sickness, 81

Soto, Don Olegario, 171

South America, tropical, origin of flora, 35

----, rainless zone of, 48

South Brazil, plateau of, flora, 311

South Patagonia, glaciers in, 239

Southern Atlantic, climate of, 305

Southern Cross, 7, 253

Southern hemisphere, temperature of, 272-274

Spanish-Americans, indolence of, 89

Species, groups of incomplete, 181

Staten Island, 252, 258

St. Antão Island, 359

Steamers, Pacific coast, 31

Straits of Magellan, 270

Sunstroke, causes of, 349, 350

Surco station, 75

Swinburne, Don Carlos, 154

T

Taforò, Dr., 191

_Tagus_ steamship, 344

Talca, 145

Taltal, 133

Tamar, Cape, 240

Tambo de Mora, 119

Tarapacà, 125

_Taraxacum lævigatum_, 263

Telephone, use of, in South America, 290

Tierra del Fuego, 245, 267

Tijuca, 338

----, giant tree near, 343

----, vegetation of, 341

_Tillandsia_, 307

Titicaca, Lake of, 63, 66

Tocantins river, 315

Tocopilla, 128, 133

----, scenery of the moon, 129

Trade wind, north-east, 6

Trescott, Mr., 60

Tres Montes, Cape, 218

Trinidad, Gulf of, 231

_Triumph_, the ship, 135

_Tropæolum tuberosum_, 78

Trumpet-flower (_Bignonia venusta_), 307, 311

Tucuman, 294

Tumaco, 36

Tumbez, 43

_Tupa Berterii_, 184

---- _secunda_, 184

Tupungato, the Peak of, 153

U

Ucayali river, English settler at, 96

Unalaschka, 274

Uruguay, climate of, 279

----, fossil remains in, 291

----, islands of the, 287

---- Republic of, chronic disorder, 282, 284, 285

Ushuaia, mission station at, 260

Ushuaja, 273

Uspallata Pass, 200

_Utricularia_, 33

V

Valdivia, 145

Valparaiso, 138, 145

----, danger of earthquakes at, 139

Vegetation, equatorial, 33

Verbena family, 201

Viaducts, Oroya railway, 74

Vicuña Mackenna, Don Benjamin, 158

Villages, remains of ancient Peruvian, 73

Viña del Mar, 149

Vincent, St., aspect of, 360

----, quarantine at, 359

Vinciguerra, Signor, 252

Virgenes, Cape, 271

Volcano de Chana, 219

W

Wellington Island, 222

Willsen, Captain, 205

Winter’s bark (_Drimys Winteri_), 147

Y

Yellow fever, treatment of, 339

NOTE ON THE MAP OF SOUTH AMERICA.

In the annexed map an attempt has been made to represent the probable course of the isothermal lines--lines denoting equal temperature--in the South American continent. The black lines indicate the mean temperature for the entire year; the red lines that for January, the hottest month; and the green lines that of July, the coldest month. The numbers placed over each line in corresponding colours indicate the temperature in degrees of the Centigrade scale. We possess a fair amount of information as to the meteorology of the coasts of the continent; but of the interior our knowledge is miserably deficient, and is nearly limited to several stations in Argentaria, and a few in the basin of the Amazons. As a result, the course of the isothermal lines in the interior is to a great extent conjectural. As in all similar maps, no account has been taken of the relief of the surface; when a line crosses a mountain range, the temperature indicated is that which would be found, as is assumed, if the height were reduced to the sea-level. No attempt has been made to show the variations of temperature with the season in the part of the continent near the equator. These are very slight, and depend mainly on local conditions, the mean temperature of the year varying from 25·5° to 28° C., or from about 78° to 82° Fahr.; the hottest seasons near the equator, apart from local conditions, being those of the equinoxes.

The chief interest of the map to the physical geographer arises from the remarkable effect of the southern, or Humboldt, current, in lowering the temperature of the western coast between the fifth and the fortieth degrees of south latitude. This is, of course, most apparent in the isothermal for January. It will be seen that at that season the temperature of Northern Peru is about the same as that of Buenos Ayres, lying thirty degrees farther from the equator. In mid-winter (July) the effect is far less apparent, and in the south of the continent the isotherms for that season nearly correspond with the parallels of latitude. The lines indicating mean annual temperature naturally assume a course intermediate between those for the extreme seasons.

PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES.

FOOTNOTES

[1] For a list of the plants collected here, see a paper in the _Journal of the Linnæan Society_, vol. xxii.

[2] Much cinchona bark, coming from the interior, was formerly shipped at Tumaco; but between horrible roads and the reckless waste of the forests through mismanagement, but little is now conveyed by this way.

[3] For a list of the species collected, see the _Journal of Linnæan Society_, vol. xxii.

[4] The abrupt change in the vegetation on this part of the American coast has been noticed by Humboldt, Weddell, and other scientific travellers. In a note to the French edition of Grisebach (“Vegetation du Globe,” traduit par P. de Tchihatcheff, ii. p. 615), M. André expresses the opinion that this, as well as some other cases of abrupt change in the vegetation observed by him in Colombia, are to be explained by the nature of the soil, which in the arid tracts is sandy or stony, and fails to retain moisture. Admitting that in certain cases this may afford a partial explanation of the facts, it is scarcely conceivable that the limit of the zone wherein little or no rain falls should exactly coincide with a change in the constitution of the soil, and I should be more disposed to admit a reversed order of causation, the porous and mobile superficial crust remaining in those tracts where, owing to deficient rainfall, there is no formation of vegetable mould, and no accumulation of the finer sediment forming a retentive clay.

[5] The only detailed account of the operations that I have seen is in a work entitled, “Histoire de la Guerre du Pacifique,” by Don Diego Barros Arana. Paris: 1881. It appears to be fairly accurate as to facts, but coloured by very decided Chilian sympathies.

[6] The heights given in the text are those of the railway stations.

[7] Of 138 genera of _Helianthoïdeæ_ 107 are exclusively confined to the American continent, 18 more are common to America and distant regions of the earth, one only is limited to tropical Asia, and two to tropical Africa, the remainder being scattered among remote islands--the Sandwich group, the Galapagos, Madagascar, and St. Helena.

[8] See note to page 184.

[9] In _Nature_ for September 14, 1882.

[10] The only accurate information that I have found respecting the climate of Lima is contained in a paper by Rouand y Paz Soldan, “Resumen de las Observaciones Meteorologicas hechas en Lima durante 1869,” quoted in the French translation of Grisebach’s “Vegetation du Globe.” Reduced to English measures, they give the following results:--

Mean temperature of four years 66·6° Fahr. ” ” January, 1869 74·3° ” ” ” July, 1869 57·6° ” Rainfall in the year 1869 13·4 inches. ” June, 1869 2·45 ” ” July, 1869 2·72 ” ” August, 1869 2·48 ” ” September, 1869 2·33 ” ” October, 1869 2·16 ” ” remaining seven months 1·24 ”

There is reason to think that the temperature for July, 1869, given above was exceptionally low, and although the months during which fogs prevail are abnormally cool for a place within 13° of the equator, I believe that the thermometer rarely falls below 60° Fahr.

[11] See Appendix A, On the Fall of Temperature in ascending to Heights above the Sea-level.

[12] It is a curious illustration of the utterly untrustworthy character of statements made by unscientific travellers to read the following passage in a book published by a recent traveller in South America, who visited Chicla in November, the beginning of summer. He declares that the fringe of green vegetation “dwindles and withers at a height of nine or ten thousand feet;... while on the upper grounds, where sometimes rain is plentiful, the air is too keen and cold for even the most dwarfish and stunted vegetation to thrive.”

[13] “Versuch einer Entwicklungsgeschichte der Pflanzenwelt.”

[14] The heights are certainly incorrect. The base of the hill of Amancaes is nearly seven hundred feet above sea-level, and Mr. Nation states that the two localities mentioned by Mr. Cruikshank are at about the same elevation.

[15] Two small Chilian wooden ships, the _Esmeralda_, of 850 tons, mounting eight guns, commanded by Arturo Prat, and the _Covadonga_, of 412 tons, with two guns, commanded by Condell, were engaged in the blockade of Iquique, when, on the 21st of May, 1879, they were attacked by the Peruvian ironclad _Independencia_, of 2004 tons, mounting 18 (chiefly heavy Armstrong) guns, commanded by J. G. Moore, and the monitor _Huascar_, of 1130 tons, mounting two 300-pounder Armstrong turret guns, besides two deck guns, under Miguel Grau, the most skilful and enterprising of the Peruvian commanders. The Chilian captains resolved on a desperate defence. After maintaining for two hours the fight against the _Huascar_, Arturo Prat resolved on the attempt to board his adversary. Bringing his ship alongside, he sprang on the deck of the _Huascar_; but the ships were separated at once, and two men only fell along with him, while the _Esmeralda_ went to the bottom with her crew of 180 men, of whom several were picked up by the boats of the _Huascar_. The _Independencia_, following the little _Covadonga_, ran on the rocks in the shallows south of Iquique, and became a total wreck; while the _Covadonga_, though shattered by her enemy’s guns, was able to reach Autofogasta. The heroism of the Chilian commanders saved their country, and at the critical moment changed the fortune of the war.

[16] In the preface to his “Florula Atacamensis,” Dr. Philippi, who has explored this region more thoroughly than any other traveller, states that on the range of coast hills between the Pan de Azucar (lat. 26° 8′ south) and Miguel Diaz (lat. 24° 36′) the fogs, called in Peru _garua_, or _garruga_, deposit during a great part of the year some moisture which occasionally takes the form of fine rain, such as is familiarly known to occur on the hills near Lima. He remarks as singular the fact that the same phenomenon is not observed on the coast north or south of those limits. From more recent observations, it would appear that this is not strictly true as regards the higher coast hills near Coquimbo, but it seems to hold as regards the tract of coast to the northward, between the neighbourhood of Taltal and that of Iquique, a distance of about four degrees of latitude. It may be that the coast hills are lower here than further south, and that as the desert region inland rises very gradually, and has a higher temperature inland than near the coast, the formation of fog is prevented. Whatever be the cause, the absence of fog would go far to account for the utter sterility of this region.

[17] The four species of _Encelia_ described in De Candolle’s “Prodromus” appear to me to be but slightly modified forms of a single species. Since the publication of that work, several other and quite distinct species have been ranked under the same generic name.

[18] While botanizing in the Tajo de Ronda, the singular cleft which cuts through the rocky hill on which the town is built, I was once for some time in positive danger. The boys, having espied me, assembled on the bridge that crosses the cleft, some three hundred feet above my head, and commenced a regular fire of stones, that drove me to take shelter under an overhanging rock until, being tired of the sport, they turned their attentions elsewhere.

[19] One of the difficulties felt by all students of geographical distribution arises from the imperfect or careless indications given both in books and in herbaria, and this is more felt in regard to South America than as to any other part of the world. A very large proportion of the earlier collections bear simply the label “Brazil,” forgetting that the area is as great as that of Europe. In other cases local names of places, not to be found on maps or in gazetteers, embarrass the student and weary his patience. It is mainly from Darwin that naturalists have learned that geographical distribution is the chief key to the past history of the earth.

[20] The last season of excessive rainfall was that of 1877. I have seen no complete returns, but it appears that the rain of that year commenced in Central Chili in February, a very rare phenomenon; that more than six inches of rain fell in April, of which, at Santiago, four inches fell in twenty-four hours. More heavy rain fell in May, and finally in July a succession of storms flooded large districts, destroying property and life, the fall for the month being more than fourteen inches at Valparaiso. Much interesting information respecting the climate of Chili will be found in a work by Don B. Vicuña Mackenna, “Ensayo Historico sobre el Clima de Chile” (Valparaiso: 1877), from which I have borrowed the above-mentioned particulars.

[21] I believe that in the column for rainfall at Punta Arenas, snow has not been taken into account.

[22] The recent untimely death of this valuable official is deplored by all classes in Chili.

[23] This is doubtless the summit described by Darwin under the name Campana de Quillota. He gives the height as 6400 feet above sea-level. The figures in the text are taken from the Chilian survey.

[24] The mapping of the Andean chain is a task of immense difficulty, and although the Chilian survey is the best that has yet been executed, it leaves much to be desired. Even in the small district which I was able to visit, I found several grave errors in Petermann’s map, reduced from the Chilian survey, which is, nevertheless, the best that has been published in Europe. One of the most serious is the omission of the Uspallata Pass, the most frequented of those leading from Central Chili to the Argentine territory, which is neither named nor correctly indicated by the tints adopted to mark the zones of elevation.

[25] “Origin of Species,” 3rd edit., p. 410.

[26] Molina, one of the most pernicious blunderers who have brought confusion into natural history, grouped together under the generic name _Peumus_ several Chilian plants having no natural connection with each other. Misled by his erroneous description, botanists have applied the name _peumus_ to a fragrant shrub, common about Valparaiso and elsewhere, which is known in the country by the name _boldu_.

[27] The Baths of Cauquenes are said to be 2523 feet above the sea; the _Morro_, by aneroid observation, is about 2000 feet higher.

[28] As happens with many other plants described by early botanists, there has been much confusion in regard to the species named by Linnæus _Lobelia Tupa_. The plant was first made known to Europeans by the excellent traveller, Father Feuillée, whose “Journal des Observations Physiques Mathématiques et Botaniques faites sur les côtes de l’Amérique meridionale, etc.,” published in 1714, is a book which may still be consulted with advantage. His descriptions of plants are usually careful and accurate, but the accompanying plates all ill-executed and often misleading. Linnæus, followed by Willdenow, refers to Feuillée’s work, but gives a very brief descriptive phrase which suits equally well Feuillée’s plant and several others subsequently discovered. Aiton, in the “Hortus Kewensis,” gives the name _Lobelia Tupa_ to a plant which is plentiful about Valparaiso, where I found it still in flower, the seeds of which were received at Kew about a century ago from Menzies. This is now generally known by the not very appropriate name _Tupa salicifolia_ of Don, but was first published by Sims in the _Botanical Magazine_, No. 1325, as _Lobelia gigantea_, which name it should now bear. The plant which I found near Cauquenes appears to be the _Tupa Berterii_ of Decaudolle, a rare species, apparently not known to the authors of the “Flora Chilena.” No doubt could have arisen as to the plant intended by Linnæus as _Lobelia Tupa_ if writers had referred to Feuillée’s full and accurate description. His account of the poisonous effects of the plant was probably derived from the Indians, and may be exaggerated. The whole plant, he says, is most poisonous, the mere smell causing vomiting, and any one touching his eyes after handling the leaves is seized with blindness. I may remark that the latter statement, which appears highly improbable, receives some confirmation from the observations of Mr. Nation, mentioned above in page 77. The plant which I saw in Peru, but failed to collect, is much smaller than most of the Chilian species, and has purple flowers, but is nearly allied in structure. It is probably the _Tupa secunda_ of Don. I gather from a passage in one of Mr. Philippi’s writings that the word _tupa_ in Araucanian signifies poison. We are yet, I believe, ignorant of the chemical nature of the poisonous principle contained in the plants of this group.

[29] The measurements of the height of the peak of Aconcagua vary considerably in amount, but I believe that the most reliable is that adopted by Petermann--6834 metres, or 22,422 English feet.

[30] The inconvenience of using a periphrasis for the name of so important a country may warrant my adoption of the obvious name Argentaria in place of Argentine territory, or Argentine Confederation, and I shall adhere to the shorter designation in the following pages.

[31] It is quite possible that the bird which I took for the black albatross was the giant petrel, common, according to Darwin, in these waters, and closely resembling an albatross.

[32] See an interesting paper in the _Journal of Botany_ for July, 1884.

[33] The estimates given by Pissis do not rest on accurate observations, and seem to me exaggerated. I should be inclined to reckon the difference of height of the snow-line between the extreme stations as nearer to two thousand than to three thousand feet.

[34] I am not aware that the concurrent conclusions as to the height of this mountain have been verified by accurate observations, but the height commonly given appears to be a close approximation to the truth.

[35] “Flora Antarctica,” vol. ii. p. 289.

[36] See Appendix B.

[37] It is unfortunate that the Spaniards who had the naming of so large a part of the American continent should have shown so little inventive faculty. When they did not adopt a native name for a river, they rarely got beyond Red River, Black River, or Big River, and wherever we turn we encounter a Rio Colorado, a Rio Negro, or a Rio Grande.

[38] The constant inconvenience of employing such cumbrous expressions as Argentine Confederation or Argentine territory for a state of such vast extent and such yearly increasing importance must be felt by every one who has occasion to speak or write about this region of America. I trust that I shall be forgiven if in this book, as well as elsewhere, I have taken the liberty of applying a single name, which has nothing about it so strange as that it should not long since have come into use.

[39] The Paranà, with its great tributary the Paraguay, drains an area of more than 1,100,000 square miles; the basin of the Uruguay is reckoned at 153,000 square miles.

[40] The term _provinces_, commonly applied to the federated States, is misleading, and should be laid aside.

[41] Much information respecting this country is to be found in a volume entitled, “The Argentine Republic,” published in 1876 for the Centenary Exhibition at Philadelphia. It contains a series of papers prepared by Mr. Richard Napp, assisted by several German men of science.

[42] Dr. Hann (“Klimatologie,” p. 657, _et seq._) has discussed the causes of the prevalent high barometric pressure on both coasts of temperate South America, and has shown that in winter the area of maximum pressure moves northward towards the Tropic of Capricorn.

[43] The species common here is allied to _T. stricta_, but is not, I think, identical.

[44] The best general account of the geology of Brazil that I have seen is contained in a short paper by Orville A. Derby, entitled, “Physical Geography and Geology of Brazil.” It was published in the _Rio News_, in December, 1884, and, through the kindness of Mr. Geikie, i have seen a reprint in the library of the School of Mines.

[45] _Proceedings of the Royal Geographical Society_ for 1879, p. 564.

[46] See his valuable work, “Climats, Géologie, Faune et Géographie Botanique du Bresil.”

[47] “Klimatologie,” p. 382.

[48] Darwin’s estimate of the height was one thousand feet, while Professor Moseley gives double that amount. I incline to think that the lower figure is nearer to the truth.

[49] I borrow this statement from the excellent “Lehrbuch der Klimatologie,” by Dr. Julius Hann. Stuttgart, 1883.

[50] See _Reports of the British Association for the Advancement of Science_ for 1882, pp. 451-453.

[51] It is remarkable that there is no reference to the investigations of M. de St. Robert, and the formula deduced from them, in the article on the “Barometrical Measurement of Heights,” in the new edition of the _Encyclopædia Britannica_.

[52] Published by the War Department, United States Army, _Professional Papers of the Signal Service_, No. xv.

[53] Air nearly saturated with vapour is lighter than air relatively dry; and hence it may happen that, when a current of moist air meets one relatively dry, it will flow over the latter if they are nearly at the same temperature, but if the drier current be much warmer, it may flow beneath it.

[54] On this subject see _Handbuch der Klimatologie_, by Julius Hann, pp. 141, _et seq._ See also Tables I. and II. in a report on thermometric observations in the Alps, by J. Ball, in _Reports of the British Association for the Advancement of Science_ for 1862, pp. 366-368.

[55] See “Die Barometrischen Höhenmessungen und ihre Bedeutung für die Physik der Atmosphäre,” Leipzig, 1870, by R. Rühlmann.

[56] I use the term “eccentricity” in the popular sense, to express the distance of the focus from the centre of the ellipse.

[57] Viewed in the light of Mr. Langley’s recent researches on solar radiation, all these numerical determinations are probably far from the truth; but the errors do not much affect the present argument.

[58] The observations at Stanley Harbour, which are those adopted by Dr. Hann (_Klimatologie_, p. 697), show temperatures notably lower than those recorded for a place in the islands lying farther south, which are given in the _Zeitschrift der Œsterreichischen Gesellschaft für Meteorologie_, vol. v. p. 369. The mean of the two is probably nearly correct.

[59] These figures are derived from the tables given in the _Anales de la Oficina Meteorologica Argentina_, by B. Gould, vol. iii. The figures show a considerable amount of annual variation. The monthly means of the six months from February to July, 1879, exceed those of the same period in 1878 by more than 2° Fahr.

Transcriber’s Notes

Punctuation, hyphenation, and spelling were made consistent when a predominant preference was found in this book; otherwise they were not changed.

Simple typographical errors were corrected; occasional unbalanced quotation marks retained.

Ambiguous hyphens at the ends of lines were retained.

Index not checked for proper alphabetization or correct page references.

Page 4: “30·40” was misprinted as “39·40”.