CHAPTER II.

CURRENTS OF THE OCEAN.

" ... seas that sweep The three-decker's oaken mast."

TENNYSON.

The ocean is a scene of unceasing agitation; "its vast surface rises and falls," to use the image suggested by Schleiden, "as if it were gifted with a gentle power of respiration; its movements, gentle or powerful, slow or rapid, are all determined by differences of temperature."

Heat increases its volume and changes the specific gravity of the water, which is dilated or condensed in proportion to the change of temperature. In proportion as it cools, water increases in density, and descends into the depths until it reaches a constant temperature of four degrees twenty-five minutes Cent. below zero, which it preserves in all latitudes at the depth of a thousand yards, according to M. D'Urville.

If the water continues to cool, and reaches zero, it becomes lighter than it was at four degrees twenty-five minutes Cent., and ascends in a state of congelation--a process which, by an admirable provision of nature, can only take place at the surface. So long as the temperature is above four degrees twenty-five minutes, water is light, and ascends to the surface, while colder water sinks to the bottom. Below four degrees twenty-five minutes the process is reversed; the first phenomenon is always in force under the Equator, the second near the Poles. The evaporation, which is in continual operation in warm seas, forming vast rain-clouds at the expense of the sea, is compensated by unceasing currents of colder water flowing from the Poles. This evaporation has a direct influence, moreover, on the density of sea water, and is pointed out by Dr. Maury as a remarkable instance of the compensations by which the oceanic waters are governed: "According to Rodgers' observations," he says, "the average specific gravity of sea water on the parallels of thirty-four degrees north and south, at a mean temperature of sixty-four degrees, is just what it ought to be, according to saline and thermal laws; but its specific gravity, when taken from the Equator at a mean temperature of eighty-one degrees, is much greater than, according to the same laws, it ought to be--the observed difference being ·0015, whereas it ought to be ·0025. Let us inquire," he adds, "what makes the equatorial waters so much heavier than they ought to be.

"The anomaly occurs in the trade-wind region, and is best developed between the parallel of forty degrees in the North Atlantic and the Equator, where the water grows warmer, but not proportionally lighter. The water sucked up by the trade-winds is fresh water, and the salt it contained, being left behind, is just sufficient to counteract by its weight the effect of thermal dilatation upon the specific gravity of water between the parallels of thirty-four degrees north and south. The thirsting of the trade-winds for vapour is so balanced as to produce perfect compensation, and a more beautiful instance than we have here stumbled upon is not, it appears to me, to be found in the mechanism of the universe."

The oceanic currents are due to a great number of causes: the duration and force of the winds, for instance; the rise and fall of tides all over the globe; the variations in the density of the waters, according to its temperature, and the evaporating powers of the atmosphere; the depth and degree of saltness to which we have already alluded; finally, to the variations of barometric pressure.

The currents which furrow the ocean present a striking contrast with the immobility of the neighbouring waters; they form rivers of a determinate breadth, whose banks are formed by the water in repose, and whose course is often made quite perceptible by the vrachs and other aquatic plants which follow in their train.

In order to comprehend the origin of these _pelagic rivers_, it is necessary to consider the laws which govern the atmospheric currents, in particular the _trade-winds_. "Hence," says Maury, "in studying the system of oceanic circulation, we set out with the very simple assumption, that from whatever part of the ocean a current is found to run, to that same part a current of equal volume is bound to return; for on this principle is based the whole system of currents and counter currents." The differences of temperature between equinoctial and polar countries generate two opposing currents, the upper one proceeding from the Equator to the Poles, the lower one directed from the Poles towards the Equator. On reaching the Equator, the cold current of air from the Poles is warmed and rarefied, and ascends to the upper beds of the atmosphere, whence it is again led to its point of departure; there it is again cooled, and returns with the lower current towards the tropical regions. But the rotatory movement of the earth modifies the direction of these atmospheric currents. The movement by which it is carried from west to east being almost nothing at the Poles, but inconceivably rapid under the Equator, it follows that the cold air, in proportion as it advances towards the Tropics, ought to incline a little towards the west. This is just what takes place with these counter currents. The _north-east trade-winds_, which prevail in the northern hemisphere, move in a sort of spiral curve, turning to the west as they rush from the Poles to the Equator, and in the opposite direction as they move from the Equator towards the Poles; the immediate cause of this motion being the rotation of the earth on its axis. "The earth," says Dr. Maury, "moves from west to east. Now, if we imagine a particle of atmosphere at the North Pole, where it is _at rest_, to be put in motion in a straight line towards the Equator, we can easily see how this particle of air, coming from the very axis of diurnal rotation, where it did not partake of the diurnal motion, would, in consequence of its own _vis inertiæ_, find as it travelled south that the earth was slipping from under it, as it were, and it would appear to be coming from the north-east and going towards the south-west; in other words, it would be a north-east wind."

In the same manner, the upper currents of air, which proceed towards the Poles with equatorial rapidity, ought to outstrip the atmospheric beds, which are gifted with much smaller rapidity of motion towards the Poles, and turn them towards the east in consequence. These are the south-west and north-west counter trade-winds, which, passing above the _north_ and _south-east trades_, often sweep the surface of the sea in the latitudes of the Temperate zone. The two _trades_ are separated by a belt more or less broad, where the friction experienced at the surface of the sea neutralizes their impulse towards the west; in general, the current of air there is an ascending current. This belt, which does not exactly correspond with the Equator, is called the _Zone of Calms_, where atmospheric tempests frequently occur, and the winds make the entire tour of the compass, which has acquired for them the name of _tornadoes_.

The trade-winds, whose movement towards the west is retarded by the friction which the waves of the ocean oppose to them, communicate to these waves, by a sort of reaction, a tendency towards the west, or, to speak more exactly, towards the south-west in the northern hemisphere, and towards the north-west in the opposite hemisphere. The currents on the surface of the water which result from this reaction, reunite under the Equator, and form the _grand equinoctial_ current which impels the waters of the east towards the west. This movement is stronger at the edges than in the middle of the current, because the force which produces it acts there with more energy: it results from this, that the currents bifurcate more readily when any obstacle presents itself to its movement. In the Atlantic Ocean, bifurcation takes place a little to the south of the Equator; the southern branch descends along the coast of Brazil, and probably returns by reascending along the west coast of Africa. The northern branch follows the coast of Brazil and Guiana, enters the Sea of the Antilles, and directs its course, reinforced by the current which reaches it from the north-east, into the Bay of Honduras, traverses the Yucatan Channel, and enters the Gulf of Mexico, whence it debouches by the Florida Channel, under the name of the _Gulf Stream_. Of this oceanic marvel Dr. Maury observes that "there is a river in the bosom of the ocean; in the several droughts it never fails, and in the mightiest floods it never overflows; its banks and its bottom are of cold water, while its current is of warm; it takes its rise in the Gulf of Mexico, and empties itself into the Arctic Seas. This mighty river is the Gulf Stream. In no other part of the world is there such a majestic flow of water; its current is more rapid than the Amazon, more impetuous than the Mississippi, and its volume is more than a thousand times greater. Its waters, as far as the Carolina coast, are of indigo blue; they are so distinctly indicated that their line of junction can be marked by the eye." Such is Dr. Maury's description of this powerful current of warm water, which traverses the Atlantic Ocean, and influences in no slight manner the climate of Northern Europe, and especially our own shores.

The Gulf Stream thus described by the American _savant_ issues from the Florida Channel, with a breadth of thirty-four miles, and a depth of two thousand two hundred feet, moving at the rate of four and a half miles per hour. The temperature of the water in the vicinity is about thirty degrees Cent. From the American coast the current takes a north-east direction towards Spitzbergen, its velocity and volume diminishing as it expands in breadth. Towards the forty-third degree of latitude it forms two branches, one of which strikes the coast of Ireland and of Norway, whither it frequently transports seeds of tropical origin: it also warms the frozen waters of the glacial sea. The other branch, inclining towards the south, not far from the Azores, visits the coast of Africa, whence it returns to the Antilles. Throughout this vast circuit may be seen all sorts of plants and driftwood, with waifs and strays of every description borne on the bosom of the ocean. "Midway the Atlantic, in the triangular space between the Azores, Canaries, and Cape de Verd Islands, is the great Sargasso Sea, covering an area equal in extent to the Mississippi Valley: it is so thickly matted over with the Gulf Weed (_Sargassum bacciferum_), that the speed of vessels passing through it is actually retarded, and to the companions of Columbus it seemed to mark the limits of navigation; they became alarmed. To the eye at a little distance it seemed sufficiently substantial to walk upon." These moving vegetable masses, always green, which tail off to a steady breeze, serving as an anemometer to the mariner, afford an asylum to multitudes of mollusks and crustaceans.

The Gulf Stream plays a grand part in the Atlantic system. It carries the tepid water of the equinoctial regions into the high latitudes; beyond the fortieth parallel the temperature is sixteen degrees Cent. Urged by the south-west winds which predominate in that zone, its tepid waters mix with those of the Northern Sea, softening the rigour of the climate in these regions. To the south of the great bank of Newfoundland, the warm current, in vast volume rushing from the Florida Straits, meets the cold currents descending from the Arctic Circle through Baffin's Bay and the Sea of Greenland, running with equal velocity towards the south. A portion of these waters reascend towards the Pole along the western coast of Greenland. It is to this conflict of the polar and equatorial waters, that the formation of the banks of Newfoundland is ascribed. Each of these great currents having unceasingly deposited the débris carried in its bosom, the bank has been thus formed bit by bit in the concourse of ages.

The difference of temperature between the Gulf Stream and the waters it traverses gives birth inevitably to tempests and _cyclones_. In 1780 a terrible storm ravaged the Antilles, in which twenty thousand persons perished. The ocean quitted its bed and inundated whole cities; the trunks of trees, mingled with other débris, were tossed into the air. Numerous catastrophes of this kind have earned for the Gulf Stream the title of the King of the Tempests. In consequence of the numerous nautical documents which have been placed at the command of the National Observatory of Washington, and the admirable use made of them by the late Naval Secretary and his assistants, the directions and range of these cyclones engendered by the Gulf Stream may be foreseen, and their most dangerous ravages turned aside. As an example of the utility of Dr. Maury's labours in settling the direction of storms in the traject of the Gulf Stream, we quote a well-known instance: In the month of December, 1859, the American packet _San Francisco_ was employed as a transport to convey a regiment to California. It was overtaken by one of these sudden storms, which placed the ship and its freight in a most dangerous position. A single wave, which swept the deck, tore out the masts, stopped the engines, and washed overboard a hundred and twenty-nine persons, officers and soldiers. From that moment the unfortunate steamer floated upon the waters, a waif abandoned to the fury of the wind. The day after the disaster the _San Francisco_ was seen in this desperate situation by a ship which reached New York, although unable to assist her. Another ship met her some days after, but, like the other, could render no assistance. When the report reached New York, two steamers were despatched to her assistance; but in what direction were they to go? what part of the ocean were they to explore? The luminaries of Washington Observatory were appealed to! Having consulted his charts as to the direction and limits of the Gulf Stream at that period of the year, Dr. Maury traced on a chart the spot to which the disabled steamer was likely to be driven by the current, and the course to be taken by the vessels sent to her assistance. The crew and passengers of the _San Francisco_ were saved before their arrival. Three ships, which had seen their distressing situation, had been able to reach them, and the steamers sent to their assistance only arrived to witness the safety of the passengers and crew. But the point where the steamer foundered shortly after they were transferred to the rescuing ships was precisely that indicated by Dr. Maury. If the ships sent to their assistance had reached in time, the triumph of SCIENCE would have been complete.

The equinoctial currents of the Pacific are very imperfectly known. It is believed, however, that they traverse the Great Ocean in its whole length, and bifurcate opposite the Asiatic coast, where the weakest branch bends northward until it encounters the polar current from Behring's Straits, when it returns along the Mexican coast. The larger branch inclines towards the south, passing round Australia, where it is met by one or many counter currents coming from the Indian Ocean--of the complicated and dangerous nature of which both Cook and La Peyrouse speak.

The cold waters from the Antarctic Pole are carried towards the Equator by three great oceanic rivers. The first bifurcates in forty-five degrees; one portion goes round Cape Horn; the other--Humboldt's current--ascends the Chilian and Peruvian coasts up to the Equator, ameliorating the rainless climate as it goes, and making it delightful. A second great current takes the direction of the African coast, and is divided at the Cape, ascending both the east and west coasts of Africa. On either side of the warm current which escapes from the intertropical parts of the Indian Ocean, but especially along the Australian coast, a polar current wends its way from the Antarctic regions, carrying supplies of cold water to modify the climate and restore the equilibrium in that part of the world. This cold current turns at first towards the west, then towards the south in the direction of Madagascar; more to the south still it is driven back by the polar current from Cape Horn. It is thus that the warm waters from the Bay of Bengal, pressed by the Indian polar current, circulate between Africa and Australia, one lateral branch of the current sweeping along the south coast of this vast continent.

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The monsoons which reign in the Indian Ocean tend still more to complicate the currents, already sufficiently intricate and confused. But it is not intended at present to occupy the reader's attention further with these questions of intricate currents.

We have already spoken of a submarine current which appears to carry the waters of the Mediterranean into the Atlantic Ocean. Its existence is in some respects established by calculations which prove that the quantity of salt water supplied by the upper current through the Straits of Gibraltar is equal to seventy-two cubic miles per annum, while the quantity of fresh water brought down by the rivers is equal to six, and the quantity lost by evaporation to twelve cubic miles per annum. This would leave an annual excess of sixty-six cubic miles, if the equilibrium was not re-established by an under current flowing into the Atlantic. This hypothesis would appear to have been confirmed by a very curious fact.

Towards the end of the seventeenth century, a Dutch brig, pursued by the French corsair _Phoenix_, was overhauled between Tangier and Tarifa, and seemed to be sunk by a single broadside; but, in place of foundering and going down, the brig, being freighted with a cargo of oil and alcohol, floated between the two currents, and, drifting towards the west, finally ran aground, after two or three days, in the neighbourhood of Tangier, more than twelve miles from the spot where she had disappeared under the waves. She had therefore traversed that distance, drawn by the action of the under current in a direction opposite to that of the surface current. This ascertained fact, added to some recent experiments, lend their support to the opinion which admits of the existence of an outward current through the Straits of Gibraltar. Dr. Maury quotes an extract from the "log" of Lieutenant Temple, of the United States Navy, bearing the same inference. At noon on the 8th of March, 1855, the ship _Levant_ stood into Almeria Bay, where many ships were waiting for a chance to get westwards. Here he was told that at least a thousand sail were waiting between the bay and Gibraltar, "some of them having got as far as Malaga only to be swept back again. Indeed," he adds, "no vessel had been able to get out into the Atlantic for three months past." Supposing this current to run no faster than two knots an hour, and assuming its depth to be four hundred feet only, and its width seven miles, and that it contained the average proportion of solid matter, estimated at one-thirtieth, it appears that salt enough to make eighty-eight cubic miles of solid matter were carried into the Mediterranean in those ninety days. "Now," continues Dr. Maury, "unless there were some escape for all this solid matter which has been running into the sea, not for ninety days, but for ages, it is very clear that the Mediterranean would long ere this have been a vat of strong brine, or a bed of cubic crystals."

For the same reason, Dr. Maury considers it certain that there is an under current to the south of Cape Horn, which carries into the Pacific Ocean the overflowings of the Atlantic. In fact, the Atlantic is fed unceasingly by the Great American rivers, while the Pacific receives no important affluent, but ought to be, and is, subjected to enormous losses, in consequence of the evaporation continually taking place at the surface.

TIDES.

Tides are periodical movements produced by the attraction of the sun and moon. This action, which influences the whole mass of the earth, is made manifest by the swelling movement of the waters. The attractive force exercised by the moon is three times that of the sun, in consequence of its approximation to the earth, as compared to the greater luminary.

In order to comprehend the theory of tides, we shall first consider the _lunar_ influences, putting aside for a moment the _solar_ action.

The attraction which the moon exercises upon any point on the earth's surface is in the inverse ratio of the square of its distance. If we draw a straight line from the moon passing through the centre of the earth, this line will meet the surface of the waters at two points diametrically opposite to each other--namely, Z and N (Fig. 5); one of these points would be to the moon its _zenith_, the other its _nadir_. The point of the sea which has the moon in the zenith--namely, that above which the moon is perfectly perpendicular--will be nearest to the planet, and will consequently be more strongly attractive to the centre of the earth, while the points diametrically opposite to which the moon is the _nadir_ will be more distant, and consequently less strongly attracted by that luminary. It follows that the waters situated directly under the moon will be attracted towards it, and form an accumulation or swelling at that point; the waters at the antipodes being less strongly attracted to the moon than to the centre of the earth, will form also a secondary swelling on the surface of the sea, thus forming a double tide, accumulating at the point nearest the moon and at its antipodes. At the intermediate points of the circumference of the globe, where the waters are not subjected to the direct attraction of the moon, the sea is at low water, as represented in Fig. 5.

The earth, in its movement of rotation, presents, in the course of twenty-four hours, every meridian on its surface to the lunar attraction; consequently, each point in its turn, and at intervals of six hours, is either under the moon, or ninety degrees removed from it: it follows, that in the space of a lunar day--that is to say, in the time which passes between two successive passages of the moon on the same meridian--the oceanic waters will be at high and low tide twice in the month on every point of the surface of the globe. But this result of attraction is not exercised instantaneously. The moon has passed from the meridian of the spot before the waters have attained their greatest height; the flux reaches its maximum about three hours after the moon has culminated; and the watery mountain follows the moon all round the globe, from east to west, about three hours in its rear.

It is obvious, however, that the great inequalities of the bottom of the sea; the existence of continents; the slopes of the coast, more or less steep; the different breadths of channels and straits; finally, the winds, the pelagic currents, and a crowd of local circumstances,--must materially modify the course of the tides. Nor is the moon the only celestial body which influences the rise and fall of the waters of the sea. We have already said that the sun asserts an influence on the waves. It is true that, in consequence of its great distance, this only amounts to a thirty-eight-hundredth part of that of the earth's satellite. The inequality which exists between the solar and lunar days--the latter exceeding the first by fifty-four minutes--has also the effect of adding to or subtracting from this force alternately. When the sun and moon are in _conjunction_ (Fig. 6), or in opposition, that is to say, placed upon the same right line, their attraction on the sea is combined, and a _spring_ tide is produced. This happens at the period of the _syzygies_--the period of new and full moon. At the period of the _quadrature_, or the first and last quarters, the solar action, being opposed to that of lunar attraction, tends to produce a sensibly weaker tide.

These effects are never produced instantaneously; but, the impulse once given, it will continue to influence the tides for two or three days, the highest and lowest tides being nearly in the proportion of 138 to 63, or of 7 to 3. The highest tides occur at the _equinoxes_, when the moon is in perigee; the lowest at the _solstices_, when it is in apogee. In our ports, and along the coast, the water rises twice in twenty-four hours, when it is said to be high water; when it retires, it is low water: they are respectively the _flux_ and _reflux_ of the waves.

The tide is retarded every day about fifty minutes, the lunar day being twenty-four hours fifty minutes of mean time. If, for instance, it is high water to-day at two o'clock in the morning, that of the next day will take place at fifty minutes past two. Low water does not occur, however, at the half of the intermediate time; the flux is more rapid than the reflux: thus at Havre, Boulogne, and at corresponding places on this side of the Channel, it takes two hours and eight minutes more in retiring; at Brest, the difference is only sixteen minutes more than the flux. The daily retardation of high water by the passage of the moon in the meridian, at the equinoxes, is a constant quantity for the same locality, which can be determined by direct observation.

The height of the tide varies in the different regions of the globe, according to local circumstances. The eastern coast of Asia and the western coast of Europe are exposed to extremely high tides; while in the South Sea Islands, where they are very regular, they scarcely reach the height of twenty inches. On the western coast of South America, the tides rarely reach three yards; on the western coast of India they reach the height of six or seven; and in the Gulf of Cambay it ranges from five to six fathoms. This great difference makes itself felt in our own and adjoining countries: thus, the tide, which at Cherbourg is seven and eight yards high, attains the height of fourteen yards at Saint Malo, while it reaches the height of ten yards at Swansea, at the mouth of the Bristol Channel, increasing to double that height at Chepstow, higher up the river. In general, the tide is higher at the bottom of a gulf than at its mouth.

* * * * *

The highest tide which is known occurs in the Bay of Fundy, which opens up to the south of the isthmus uniting Nova Scotia and New Brunswick. There the tide reaches forty, fifty, and even sixty feet, while it only attains the height of seven or eight in the bay to the north of the same isthmus. It is related that a ship was cast ashore upon a rock during the night, so high, that at daybreak the crew found themselves and their ship suspended in mid-air far above the water!

In the Mediterranean, which only communicates with the ocean by a narrow channel, the phenomenon of tides is scarcely felt, and from this cause--that the moon acts at the same time upon its whole surface, which are not sufficiently abundant to increase the swelling mass of waters formed by the moon's attraction; consequently, the swelling remains scarcely perceptible. This is the reason why neither the Black Sea or White Sea presents a tide, and the Mediterranean a very inconsiderable one. Nevertheless, at Alexandria the tide rises twenty inches, and at Venice this height is increased to about six feet and a half. Lake Michigan is slightly affected by the lunar attraction.

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Professor Whewell has prepared maps, in which the course of the tidal wave is traced in every country of the globe. We see here that it traverses the Atlantic, from the fiftieth degree of south latitude up to the fiftieth parallel north, at the rate of five hundred and sixty miles an hour. But the rapidity with which it proceeds is least in shallow water. In the North Sea it travels at the rate of a hundred and eighty miles. The tidal wave which proceeds round the coast of Scotland traverses the German Ocean and meets in St. George's Channel, between England and Ireland, where the conflict between the two opposing waves presents some very complicated phenomena.

The winds, again, exercise a great influence on the height of the tides. When the impulse of the wind is added to that of the attracting planet, the normal height of the wave is considerably increased. If the wind is contrary, the flux of the tide is almost annihilated. This happens in the Gulf of Vera Cruz, where the tide is only perceptible once in three days, when the wind blows with violence. An analogous phenomenon is observable on the coast of Tasmania.

The rising tide sometimes strikes the shore with a continuous and incredible force. This violent shock is called the _surf_. The swell then forms a billow, which expands to half a mile. The surf increases as it approaches the coast, when it sometimes attains the height of six or seven yards, forming an overhanging mountain of water, which gradually sinks as it rolls over itself. But this motion is not in reality progressive--it transports no floating body. The surf is very strong at the Isle of Fogo, one of the Cape de Verd Islands in the Indian Ocean, and at Sumatra, where the surf renders it dangerous and sometimes impossible to land on the coast. Fig. 7 represents the effects of the surf at Point du Raz, on the coast of Brittany. The winds adding their influence to these causes, give birth on the surface of the sea to waves or billows, which increase rapidly, rising in foaming mountains, rolling, bounding, and breaking one against the other. "In one moment," says Malte Brun, "the waves seem to carry sea-goddesses on its breast, which seem to revel amid plays and dances; in the next instant, a tempest rising out of them, seems to be animated by its fury. They seem to swell with passion, and we think we see in them marine monsters which are prepared for war. A strong, constant, and equal wind produces long swelling billows, which, rising on the same line, advance with a uniform movement, one after the other, precipitating themselves upon the coast. Sometimes these billows are suspended by the wind or arrested by some current, thus forming, as it were, a liquid wall. In this position, unhappy is the daring navigator who is subjected to its fury." The highest waves are those which prevail in the offing off the Cape of Good Hope at the period of high tide, under the influence of a strong north-west wind, which has traversed the South Atlantic, pressing its waters towards the Cape. "The billows there lift themselves up in long ridges," says Dr. Maury, "with deep hollows between them. They run high and fast, tossing their white caps aloft in the air, looking like the green hills of a rolling prairie capped with snow, and chasing each other in sport. Still, their march is stately, and their roll majestic. The scenery among them is grand. Many an Australian-bound trader, after doubling the Cape, finds herself followed for weeks at a time by these magnificent rolling swells, furiously driven and lashed by the "brave west winds." These billows are said to attain the height of thirty, and even forty feet; but no very exact measurement of the height of waves is recorded. One of these mountain waves placed between two ships conceals each of them from the other--an effect which is partially represented in Fig. 8. In rounding Cape Horn, waves are encountered from twenty to thirty feet high; but in the Channel they rarely exceed the height of nine or ten feet, except when they come in contact with some powerful resisting obstacle. Thus, when billows are dashed violently against the Eddystone Lighthouse, the spray goes right over the building, which stands a hundred and thirty feet above the sea, and falls in torrents on the roof. After the storm of Barbadoes in 1780, some old guns were found on the shore, which had been thrown up from the bottom of the sea by the force of the tempests.

If the waves, in their reflux, meet with obstacles, whirlpools and whirlwinds are the result--the former the terror of navigators. Such are the whirlpools known in the Straits of Messina, between the rocks of Charybdis and Scylla, celebrated as the terror of ancient mariners, and which were sung by Homer, Ovid, and Virgil:--

"Scylla latus dextrum, lævum irrequieta Charybdis, Infestat; vorat hæc raptis revomitque carinas. ... Incidit in Scyllam, cupiens vitare Charybdim."

These rocks are better understood, and less redoubted in our days. At Charybdis, there is a foaming whirlpool; at Scylla, the waves dash against the low wall of rock which forms the promontory, scarcely noticed by the navigator of our days.

Another celebrated whirlpool is that of Euripus, near the Island of Euboea; another is known in the Gulf of Bothnia. But perhaps the best known rocky danger is the Maelström, whose waters have a gyratory movement, producing a whirlpool at certain states of the tide, the result of opposing currents, which change every six hours, and which, from its power and magnitude, is capable of attracting and engulfing ships to their destruction, although chiefly dangerous to smaller craft.

To the combined effects of tides and whirlpools may also be attributed the hurricanes, so dreaded by navigators, which so frequently visit the Mauritius and other parts of the Indian Ocean. In periods of the utmost calms, when there is scarcely a breath to ruffle the air, these shores are sometimes visited by immense waves, accompanied by whirlwinds, which seem capable of blowing the ships out of the water, seizing them by the keel, whirling them round on an axis, and finally capsizing them. "At the period of the changing monsoon, the winds, breaking loose from their controlling forces, seem to rage with a fury capable of breaking up the very fountains of the deep."

The hurricanes of the Atlantic occur in the months of August and September, while the south-west monsoon of Africa and the southeast monsoon of the West Indies are at their height; the agents of the one drawing the north-east trade-winds into the interior of Mexico and Texas, the other drawing them into the interior of Africa, greatly disturbing the equilibrium of the atmosphere.

THE POLAR SEAS.

The extreme columns of the known world are Mount Parry, situated at eight degrees from the North Pole, and Mount Ross, twelve degrees from the South Pole. Beyond these limits our maps are mute; a blank space marks each extremity of the terrestrial axis. Will man ever succeed in passing these icy barriers? Will he ever justify the prediction of the poet Seneca, who tells us that "the time will come in the distant future when Ocean will relax her hold on the world, when the immense earth will be open, when Tethys will appear amid new orbs, and where Thule (Iceland) shall no longer be the extreme limit of the earth?"

"Venient annis Sæcula seris quibus oceanus Vincula rerum laxet et ingens Pateat tellus, Tethysque novos Detegat orbes, nec sit terris Ultime Thule."

_Medea._

No one can say. Every step we have taken in order to approach the Pole has been dearly purchased; and it is not without reason that navigators have named the south point of Greenland, Cape Farewell. Of the number of expeditions, for the most part English, which have been fitted out, at the cost of nearly a million sterling, to explore the Frozen Ocean, one-twentieth have had for their mission to ascertain the fate of the lamented Sir John Franklin.

The first navigator who penetrated to Arctic polar regions was Sebastian Cabot, who in 1498 sought a north-west passage from Europe to China and the Indies. Considering the date, and the state of navigation at that period, this was perhaps the boldest attempt on record. Scandinavian traditions attribute similar undertakings to the son of the King Rodian, who lived in the seventh century; to Osher, the Norwegian, in 873; and to the Princes Harold and Magnus, in 1150.

Sebastian Cabot reached as high as Hudson's Bay, but a mutiny of his sailors forced him to retrace his steps. In 1500, Gaspard de Cortereal discovered Labrador; in 1553, Sir Hugh Willoughby Nova Zembla; and Chancellor the White Sea, about the same time. Davis visited in 1585 the west coast of Greenland, and two years later he discovered the strait which bears his name. In 1596 Barentz discovered Spitzbergen, which was again seen by Hendrich Hudson, who sailed up to and beyond the eighty-second parallel. Three years later Hudson gave his name to the great Labrador Bay, but he could get no farther. His crew also revolted, and he was left in the ship's launch with his son, seven sailors, and the carpenter, who remained faithful. Thus perished one of our greatest navigators.

The Island of Jan Mayen was discovered in 1611; the channel which Baffin took for a bay, and which bears his name, was discovered in 1616. Behring discovered, in his first voyage in 1727, the strait which separates Siberia from America; he sailed through it in 1741, but his ship was stranded, and he himself died of scorbutic disease.

In the year 1771 the Polar Sea was discovered by Hearne, a fur merchant; it was explored long after by Mackenzie.

From the year 1810, when Sir John Ross, Franklin, and Parry turned their attention to the Arctic regions, these expeditions to the Polar Seas rapidly succeeded each other. In 1827 Parry reached the eighty-second degree of north latitude; and in 1845 Sir John Franklin, with the ships _Erebus_ and _Terror_, and their crews, departed on their last voyage, from which neither he nor his companions ever returned. There is now no doubt that they perished miserably, after having discovered the north-west passage, which Captain M'Clure also discovered, coming from the opposite direction, in 1850. In 1855 the expedition of Dr. Elisha Kane found the sea open from the Pole.

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The Antarctic Pole had in the meantime attracted the attention of navigators. In 1772 the Dutch captain, Kerguelen, discovered an island which he took for a continent. In 1774 Captain Cook explored these regions up to the seventy-first degree of latitude. James Weddell, in a small whaler, sailed past this parallel in 1823. Biscoe discovered Enderby's Land in 1831. The _Zelée_ and _Astrolabe_, under the command of Captain Dumont D'Urville, of the French Marine, and the American expedition, under Captain Wilkes, reached the same region in 1838. The former discovered Adelia's Land. Finally, in 1841, Sir James Clark Ross, nephew of Sir John Ross, with the _Erebus_ and _Terror_, penetrated up to the seventy-eighth degree south latitude. Here he discovered the volcanic islands which he named after his ships, and, farther to the south, a new continent or land, which he called Victoria's Land.

While these efforts were being made to penetrate the ice which surrounds the Antarctic Pole, a region having little which could attract human enterprise, the interests of commerce seemed to call for obstinate and persevering attempts to penetrate to the Arctic Pole. In spite of these numerous expeditions, however, which extend over two centuries, the regions round the North Pole are far from being known to geographers. The fogs and snows which almost always cover them were the source of many errors made by the earlier navigators. In his first voyage, made in 1818, Sir John Ross was led to think that Lancaster Sound was closed by a chain of mountains, which he called the Croker Mountains; but in the following year Captain Parry, in command of two ships, the _Hecla_ and _Griper_, discovered that this was an error. This celebrated navigator discovered Barrow's Straits, Wellington Channel, and Prince Regent Inlet; Cornwallis, Sir Byam Martin, and Melville Islands, to which the name of Parry's Archipelago has been given. In this short voyage he gathered more new results than were obtained by his successors during the next forty years. He was the first to traverse these seas. Upon Sir Byam Martin Island he has described the ruins of some ancient habitations of the Esquimaux. He passed the winter on Melville Island. In order to attain his chosen anchorage in Winter's Bay, he was compelled to saw a passage in the ice of a league in length, which involved the labour of three days; but scarcely were they moored in their chosen harbour than the thermometer fell to eighteen degrees below zero. They carried ashore the ship's boats, the cables, the sails, and log-books. The masts were struck to the maintop; the rest of the rigging served to form a roof, sloping to the gunwale, with a thick covering of sail-cloth, which formed an admirable shelter from the wind and snow. Numberless precautions were taken against cold and wet under the decks. Stoves and other contrivances maintained a supportable degree of temperature. In each dormitory a false ceiling of impermeable cloth interposed to prevent the collection of moisture on the wooden walls of the ship. The crew were divided into companies, each company being under the charge of an officer, charged with the daily inspection of their clothes and cleanliness--an essential protection against scurvy. As a measure of precaution, Captain Parry reduced by one-third the ordinary ration of bread; beer and wine were substituted for spirits; and citron and lemon drinks were served out daily to the sailors. Game was sometimes substituted to vary a repast worthy of Spartans. As a remedy against _ennui_, a theatre was fitted up and comedies acted, for which occasions Parry himself composed a vaudeville, entitled "The North-west Passage; or, the End of the Voyage." During this long night of eighty-four days, the thermometer in the saloons marked 28°, and outside 35° below zero, and for a few minutes actually reached 47°. Some of the sailors had their members frozen, from which they never quite recovered. One day the hut which served as an observatory was discovered to be on fire. A sailor who saved one of the precious instruments lost his hands in the effort; they were completely frost-bitten in the attempt.

Nevertheless, the month of June arrived, and with it the opportunity of making excursions in the neighbourhood. It was found that, in Melville Island, the earth was carpeted with moss and herbage, with saxifrages and poppies. Hares, reindeer, the musk-ox, northern geese, plovers, white wolves and foxes, roamed around their haunts, disputing their booty with the crew. Captain Parry could not risk a second winter in this terrible region. He returned home as soon as the thaw left the passage open.

In 1821, Captain Parry undertook a second voyage with the _Fury_ and _Hecla_. He visited Hudson's Bay and Fox's Channel. In his third voyage, undertaken in 1824, he was surprised by the frost in Prince Regent's Channel, and was constrained to pass the winter there. The _Fury_ was dismantled, and, being found unfit for service, Captain Parry was obliged to abandon her and return to England.

Accompanied by Sir James Ross, Parry again put to sea in the _Hecla_, in April, 1826. On his third voyage, on leaving Table Island on the north of Spitzbergen, Parry placed his crew in the two training ships, _Enterprise_ and _Endeavour_; the first under his own command, the second under orders of Sir James Ross. Sometimes they sailed, sometimes hauled through the crust of the ice; sometimes the ice, which pierced their shoes, showed itself bristling with points, intersected into valleys and little hills, which it was difficult to scale. In spite of the courage and energy of their crews, the two ships scarcely advanced four miles a day, while the drifting of the ice towards the south led them imperceptibly towards their point of departure. They reached latitude eighty-two degrees forty-five minutes fifteen seconds, however, and this was the extreme point which they attained.

In the month of May, 1829, Sir John Ross, accompanied by his nephew, James Clark Ross, again turned towards the Polar Seas. He entered Prince Regent's Channel, and there he found the _Fury_, which had been dismantled and abandoned by Parry, in these regions, eight years before. The provisions, which the old ship still contained, were quite a providential resource to Ross's crews. The distinguished navigator explored the Boothian Peninsula, and passed four years consecutively in Port Felix, without being able to disengage his vessel, the _Victory_. This gave him ample leisure to become familiar with the Esquimaux. Sir John Ross, in his account of this long sojourn in polar countries, has recorded many conversations with the natives, which our space does not permit us to quote. From this terrible position he was extricated, and emerged with his crew from this icy prison, when all hope of his return had been abandoned. After being exposed to a thousand dangers, Ross and his crew were at last observed by a whaling ship, which received them on board, after many efforts to attract attention. On learning that the ship which had saved them was the _Isabella_, formerly commanded by Captain Ross, he made himself known. "But Captain Ross has been dead two years," was the reply.

We need not repeat here the enthusiastic reception Captain Ross and his companions met with on their arrival in London.

During an excursion made by the nephew of the Commander (afterwards Sir James Clark Ross), he very closely approached the North Magnetic Pole. This was at eight o'clock on the morning of the 1st of June, 1831, on the west coast of Boothia. The dip of the magnetic needle was nearly vertical, being eighty-nine degrees fifty-nine seconds--one minute short of ninety degrees. The site was a low flat shore, rising into ridges from fifty to sixty feet high, and about a mile inland.

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Contrary to the judgment of many officers of experience in polar explorations, the last and most fatal of all the expeditions was undertaken by Sir John Franklin, with one hundred and thirty-seven picked officers and men, in the ships _Erebus_ and _Terror_. The adventurers left Sheerness on the 26th of May, 1846, the ships having been strengthened in every conceivable way, and found in everything calculated to secure the safety of the expedition. On the 22nd of July the ships were spoken by the whaler _Enterprise_, and, four days later, they were sighted by the _Prince of Wales_, of Hull, moored to an iceberg, waiting an opening to enter Lancaster Sound. There the veil dropped over the ships and their unhappy crews. In 1848, their fate began to excite a lively interest in the public mind. Expedition in search of them succeeded expedition, at immense cost, sent both by the English and American authorities, and by Lady Franklin herself, some of which penetrated the Polar Seas through Behring's Straits, while the majority took Baffin's Bay. In 1850, Captains Ommaney and Penny discovered, at the entrance of Wellington Channel, some vestiges of Franklin, which led to another expedition in 1857, which was got up by private enterprise, of which Captain M'Clintock had the command. Guided by the indications collected in the previous expedition, and intelligence gathered from the Esquimaux by Dr. Rae in his land expedition, Captain M'Clintock in the yacht _Fox_ discovered, on the 6th of May, 1859, upon the north point of King William's Land, a cairn or heap of stones. Several leaves of parchment, which were buried under the stones, bearing date the 28th of April, 1848, solved the fatal enigma. The first, dated the 24th of May, 1847, gave some details ending with "all well." The papers had been dug up twelve months later to record the death of Franklin, on the 11th of June, 1847. The survivors are supposed to have been on their way to the mouth of the River Back, but they must have sunk under the terrible hardships to which they were exposed, in addition to cold and hunger.

In September, 1859, Captain M'Clintock returned to England, bringing with him many relics of our lost countrymen, found in the theatre of their misfortunes.

It only remains to us to say a few words on the latest voyages undertaken in the Polar Seas. After the return of Captain M'Clintock, in 1850, Captain M'Clure, leaving Behring's Straits, discovered the north-west passage between Melville and Baring's Island, which passage had been sought for without success during so many ages. He saw the thermometer descend fifty degrees below zero. In the month of October, 1854, he returned to England, and at a subsequent period it was ascertained with certainty that, before his death, Franklin knew of the other passage which exists to the north of America, to the south of Victoria Land, and Wollaston.

The expedition of Dr. Kane entered Smith's Strait in 1853, and advanced towards the north upon sledges drawn by dogs; the mean temperature, which ranged between thirty degrees and forty degrees below zero, fell at last to fifty degrees. At eleven degrees from the Pole they found two Esquimaux villages, called Etah and Peterovik, then an immense glacier. A detachment, conducted by Lieutenant Morton, discovered, beyond the eightieth degree of latitude, an open channel inhabited by innumerable swarms of birds, consisting of swallows, ducks, and gulls, which delighted them by their shrill, piercing cries. Seals (_phoca_) enjoyed themselves on the floating ice. In ascending the banks, they met with flowering plants, such as _Lychnis_, _Hesperis_, &c. On the 24th of June, Morton hoisted the flag of the _Antarctic_, which had before this seen the ice of the South Pole, on Cape Independence, situated beyond eighty-one degrees. To the north stretched the open sea. On the left was the western bank of the Kennedy Channel, which seemed to terminate in a chain of mountains, the principal peak rising from nine thousand to ten thousand feet, which was named Mount Parry. The expedition returned towards the south, and reached the port of Uppernavick exhausted with hunger, where it was received on board an American ship. Dr. Kane, weakened by his sufferings, from which he never quite recovered, died in 1857.

We cannot conclude this rapid sketch of events connected with the expeditions to the Arctic Pole without noting a geological fact of great and singular interest. When opportunities have presented themselves of examining the rocks in the regions adjoining the North Pole, it has been found that great numbers belong to the coal measures. Such is the case in Melville Island and Prince Patrick's Island. Under the ice which covers the soil in these islands coal exists, with all the fossil vegetable débris which invariably accompany it. This shows that in the coal period of geology, the North Pole was covered with the rich and abundant vegetation whose remains constitute the coal-fields of the present day; and proves to demonstration that the temperature of these regions was, at one period of the earth's history, equal to that of equatorial countries of the present day. What a wonderful change in the temperature of these regions is thus indicated! It is, indeed, a strange contrast to find coal formations under the soil covered by the polar ice. Let us suppose that human industry should dream of establishing itself in these countries, and drawing from the earth the combustible so needed to make it habitable, thus furnishing the means of overcoming the rigorous climatic conditions of these inhospitable regions.

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The Antarctic Pole is probably surrounded by an icy canopy not less than two thousand five hundred miles in diameter; and numerous circumstances lead to the conclusion that the vast mass has diminished since 1774, when the region was visited by Captain Cook. The Antarctic region can only be approached during the summer, namely, in December, January, and February.

The first navigator who penetrated the Antarctic circle was the Dutch captain, Theodoric de Gheritk, whose vessel formed part of the squadron commanded by Simon de Cordes, destined for the East Indies. In January, 1600, a tempest having dispersed the squadron, Captain Gheritk was driven as far south as the sixty-fourth parallel, where he observed a coast which reminded him of Norway. It was mountainous, covered with snow, stretching from the coast to the Isles of Solomon. The report of Simon de Cordes was received with great incredulity, and the doubts raised were only dissipated when the New South Shetland Islands were definitely recognized. The idea of an Antarctic continent is, however, one of the oldest conceptions of speculative geography, and one which mariners and philosophers alike have found it most difficult to relinquish. The existence of a southern continent seemed to them to be the necessary counterpoise to the Arctic land. The _Terra Australis incognita_ is marked on all the maps of Mercator, round the South Pole, and when the Dutch officer, Kerguelen, discovered, in 1772, the island which bears his name, he quoted this idea of Mercator as the motive which suggested the voyage. In 1774, Captain Cook ventured up to and beyond the seventy-first degree of latitude under the one hundred and ninth degree west longitude. He traversed a hundred and eighty leagues, between the fiftieth degree and sixtieth degree of south latitude, without finding the land of which mariners had spoken: this led him to conclude that mountains of ice, or the great fog-banks of the region, had been mistaken for a continent. Nevertheless, Cook clung to the idea of the existence of a southern continent. "I firmly believe," he says, "that near the Pole there is land where most part of the ice is formed which is spread over the vast Southern Ocean. I cannot believe that the ice could extend itself so far if it had not land--and I venture to say land of considerable extent--to the south. I believe, nevertheless, that the greater part of this southern continent ought to lie within the Polar Circle, where the sea is so encumbered with ice as to be unapproachable. The danger run in surveying a coast in these unknown seas is so great, that I dare to say no one will venture to go farther than I have, and that the land that lies to the south will always remain unknown. The fogs are there too dense; the snowstorms and tempests too frequent; the cold too severe; all the dangers of navigation too numerous. The appearance of the coast is the most horrible that can be imagined. The country is condemned by nature to remain unvisited by the sun, and buried under eternal hoar frost. After this report, I believe that we shall hear no more of a southern continent." This description of these desolate regions, to which the great navigator might have applied the words of Pliny, "_Pars mundi a natura damnata et densa mersa caligine_," only excited the courage of his successors. In our days, several expeditions have been fitted out for the express survey of regions which may be characterised as the abode of cold, silence, and death. In 1833, a free passage opened itself into the Antarctic Sea. The Scottish whaling ship, commanded by James Weddell, entered the pack ice, and penetrated it in pursuit of seals; but having, by chance, found the sea open on his course, he forced his way up to seventy-four degrees south latitude, and under the thirty-fourth degree of longitude, but the season was too advanced, and he and his crew retraced their steps. The voyage of Captain Weddell caused a great sensation, and suggested the possibility of more serious expeditions. Twelve years later three great expeditions were fitted out: one, under Dumont D'Urville, of the French Marine; an American expedition, under Captain Wilkes, of the United States Navy; and an English expedition, under Sir James Clark Ross.

Dumont D'Urville, who perished so miserably in the railway catastrophe at Versailles, in 1842, passed the Straits of Magellan on the 9th of January, 1838, having under his command the two corvettes _Astrolabe_ and _Zelée_. He expected to find it as Weddell had described, and that, after passing the first icy barrier, he should find an open sea before him. But he was soon compelled to renounce this hope. The floating icebergs became more and more closely packed and dangerous. The southern icebergs do not circulate in straits and channels already formed, like those of the North Pole, but in enormous detached blocks which hug the land. Sometimes in shallow water they form belts parallel to the base of the cliffs, intersected by a small number of sinuous narrow channels. These icy cliffs present a face more or less disintegrated as they approximate to the rocky shore. The blocks of ice form at first huge prisms, or tabular, regular masses of a whitish paste; but they get used up by degrees, and rounded off and separated under the action of the waves, which chafe them, and their colour becomes more and more limpid and bluish. They ascend freely towards the north, in spite of the winds and currents which carry them in the contrary direction. One year with another these floating icebergs accumulate with very striking differences, and it is only by a rare chance that they open up a free passage such as Captain Weddell had discovered. These floating islands of ice have been met with in thirty-five degrees south latitude, and even as high as Cape Horn.

The two French ships frequently found themselves shut up in the icebergs, which continued to press upon them, and driven before the north winds, until the south wind again dispersed their vast masses, enabling them to issue from their prison in health and safety. In some cases D'Urville found it necessary to force his ship through fields of ice by which he was surrounded and imprisoned, and to cut his way by force through the accumulating blocks, using the corvette as a sort of battering-ram. In 1838 he recognized, about fifty leagues from the South Orkney Isles, a coast, to which he gave the name of _Louis Philippe's_ and _Joinville's Land_. This coast is covered with enormous masses of ice, which seemed to rise to the height of two thousand six hundred feet. Ross discovered still more lofty peaks, such as Mount Penny and Mount Haddington, rising about seven thousand feet. The English navigator states that this land is only a great island. The crew of D'Urville's ship being sickly and overworked, he returned to the port of Chili, whence he again issued for the South Pole in the following January.

On this occasion his approach was made from a point diametrically opposite to the former. He very soon found himself in the middle of the ice. He discovered within the Antarctic Circle land, to which he gave the name of _Adelia's Land_. The long and lofty cliffs of this island or continent he describes as being surrounded by a belt of islands of ice at once numerous and threatening. D'Urville did not hesitate to navigate his corvettes through the middle of the band of enormous icebergs which seemed to guard the Pole and forbid his approach to it. For some moments his vessels were so surrounded that they had reason to fear, from moment to moment, some terrible shock, some irreparable disaster. In addition to this, the sea produces around these floating icebergs, eddies, which were not unlikely to draw on the ship to the destruction with which it was threatened at every instant. It was in passing at their base that D'Urville was able to judge of the height of these icy cliffs. "The walls of these blocks of ice," he says, "far exceed our masts and riggings in height; they overhang our ships, whose dimensions seem ridiculously curtailed. We seem to be traversing the narrow streets of some city of giants. At the foot of these gigantic monuments we perceive vast caverns hollowed by the waves, which are engulfed there with a crashing tumult. The sun darts his oblique rays upon the immense walls of ice as if it were crystal, presenting effects of light and shade truly magical and startling. From the summit of these mountains, numerous brooks, fed by the melting ice produced by the summer heat of a January sun in these regions, throw themselves in cascades into the icy sea.

"Occasionally these icebergs approach each other so as to conceal the land entirely, and we only perceive two walls of threatening ice, whose sonorous echoes send back the word of command of the officers. The corvette which followed the _Astrolabe_ appeared so small, and its masts so slender, that the ship's crew were seized with terror. For nearly an hour we only saw vertical walls of ice." Ultimately they reached a vast basin, formed on one side by the chain of floating islands which they had traversed, and on the other by high land rising three and four thousand feet, rugged and undulating on the surface, but clothed over all with an icy mantle, which was rendered dazzlingly imposing in its whiteness by the rays of the sun. The officers could only advance by the ship's boats through a labyrinth of icebergs up to a little islet lying opposite to the coast. They touched the land at this islet; the French flag was planted, possession was taken of the new continent, and, in proof of possession, some portions of rock were torn from the scarped and denuded cliffs. These rocks are composed of quartzite and gneiss. The southern continent, therefore, belongs to the primitive formation, while the northern region belongs in great part to the transition, or coal formation. According to the map of Adelia's Land, traced by D'Urville over an extent of thirty leagues of country, the region is one of death and desolation, without any trace of vegetation.

A little more to the north, the French navigator had a vague vision on the white lines of the horizon of another land, which he named _Côte Clarie_, or Coast Clear, the existence of which was soon confirmed by the American expedition under Commodore Wilkes. This officer has explored the southern land on a larger scale than any other navigator, but he suffered himself to be led into error by the dense fogs of the region, and has laid down coast lines on his map where Sir James Boss subsequently found only open sea--an error which has very unjustly thrown discredit on the whole expedition.

The English expedition entered this region on Christmas Day, 1840, which was passed by Ross in a strong gale, with constant snow or rain. Soon after, the first icebergs were seen, having flat tabular summits, in some instances two miles in circumference, bounded on all sides by perpendicular cliffs. On New Year's Day, 1841, the ships crossed the Antarctic Circle, and reached the edge of the pack ice, which they entered, after skirting it for several days. On the 5th, the pack was passed through, amid blinding snow and thick fog, which on clearing away revealed an open sea, and on the 11th of January land was seen directly ahead of the ships. A coast line rose in lofty snow-covered peaks at a great distance. On a nearer view, this coast is thus described: "It was a beautifully clear evening, and two magnificent ranges of mountains rose to elevations varying from seven thousand to ten thousand feet above the level of the sea." The glaciers which filled their intervening valleys, and which descended from near the mountain summits, projected in many places several miles into the sea, and terminated in lofty perpendicular cliffs. In a few places the rocks broke through their icy covering, by which alone we could be assured that lava formed the nucleus of this, to all appearance, enormous iceberg. This antarctic land was named Victoria Land, in honour of the Queen. It was coasted up to latitude seventy-eight degrees south, and near to this a magnificent volcanic mountain presented itself, rising twelve thousand feet above the level of the sea, which emitted flame and smoke in splendid profusion. The flanks of this gigantic mountain were clothed with snow almost to the mouth of the crater from which the flaming smoke issued. At a short distance, Ross discovered the cone of an extinct, or, at least, inactive volcano nearly as lofty. He gave to these two volcanoes the names of his vessels, _Erebus_ and _Terror_ (Fig. 9)--names perfectly in harmony with the surrounding desolation. The ice-covered cliffs rose about a hundred and ninety feet high, and appear to be about three hundred feet deep, soundings being found at about four hundred fathoms. In the distance, towards the south, a range of lofty mountains were observed, which Ross named _Mount Parry_, in honour of his old commander. When Ross retraced his steps, the expedition had advanced as far as the seventy-ninth degree of south latitude.

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It may be said of polar countries, that they form a transition state between land and sea, for water is always present, although in a solid state; the surface is always at a very low temperature; snow does not melt as it falls, and the sea is thus sometimes covered with a continuous sheet of frozen snow; sometimes with enormous floating blocks of ice which are driven by the currents. Meeting with these floating masses of ice is one of the dangers of polar navigation. Captain Scoresby has given a very detailed description of the different kinds of ice met with in the Arctic Seas. The ice-fields of this writer form extensive masses of solid water, of which the eye cannot trace the limits, some of them being thirty-five leagues in length and ten broad, with a thickness of seven to eight fathoms; but generally these ice-fields rise only four to six feet above the water, and reach from three to four fathoms beneath the surface. Scoresby has seen these ice-fields forming in the open sea. When the first crystals appear, the surface of the ocean is cold enough to prevent snow from melting as it falls. On the approach of congelation the surface solidifies, and seems as if covered with oil; small circles are formed, which press against each other, and are finally soldered together until they form a vast field of ice, the thickness of which increases from the lower surface.

The water produced from melted ice is perfectly fresh--the result of a well-known physical cause. When a saline solution like sea water is congealed by cold, pure water alone passes into the solid state, the saline solution becomes more concentrated, increases in density, and, sinking to the bottom, remains liquid. Blocks of ice, therefore, in the Polar Seas, are always available for domestic use. There are, however, salt blocks of ice, which are distinguished from fresh-water ice by their opaqueness and their dazzling white colour: this saltness is due to the sea water retained in its interstices. Scoresby amused himself sometimes by shaping lenses of ice, with which he is said to have set fire to gunpowder, much to the astonishment of his crew.

The ice-fields, which are formed in higher latitudes, are driven towards the south by winds and currents, but sooner or later the action of the waves breaks them up into fragments. The edges of the broken icebergs are thus often rising and continually changing: these asperities and protuberances are called _hummocks_ by English navigators; they give to the polar ice an odd, irregular appearance. Hummocks form themselves of the stray, broken icebergs which come in contact with each other at their edges, and thus form vast rafts, the pieces of which may exceed a hundred yards in length.

When these icebergs are separated by open spaces, through which vessels can be navigated, the pack ice is said to be open. But it often happens that mountains of ice occur partly submerged, where one edge is retained under the principal mass, while the other is above the water. Scoresby once passed over a _calf_, as English mariners call these icy mountains, but he trembled while he did so, dreading lest it should throw his vessel, himself, and crew into the air before he could pass it. The aspect of the ice-fields varies in a thousand ways. Here it is an incoherent chaos resembling some volcanic rocks, with crevices in all directions, bristling with unshapely blocks piled up at random; there it is a strongly-marked plain, an immense mosaic formed of vast blocks of ice of every age and thickness, the divisions of which are marked by long ridges of the most irregular forms; sometimes resembling walls composed of great rectangular blocks, sometimes resembling chains of hills, with great rounded summits.

In the spring, when a thaw sets in, and the fields begin to break up, the pieces of light ice which unite the great blocks into unique masses are the first to melt; the several blocks then separate, and the motion of the water soon disperses them, and the imprisoned ships find a free passage. But a day of calm is still sufficient to unite the dispersed masses, which oscillate and grind against each other with a strange noise, which sailors compare to the yelping of young dogs.

When a ship is shut up in one of these floating ice-fields, inexplicable changes sometimes occur in the vast incoherent aggregations. Vessels, which think themselves immovable, are found in a few hours to have completely reversed their positions. Two ships shut in at a short distance from each other were driven many leagues without being able to perceive any change in the surrounding ice. At other times ships are drawn with the floating ice-fields, like the white bears, who make long voyages at sea upon these monster vehicles. In 1777 the Dutch vessel, the _Wilhelmina_, was driven with some other whaling ships from eighty degrees north back to sixty-two degrees, in sight of the Iceland coast. During this terrible journey the ships were broken up one after the other. More than two hundred persons perished, and the remainder reached land with difficulty.

Lieutenant De Haven, navigating in search of Sir John Franklin, was caught in the ice in the middle of the channel in Wellington Strait. During the nine months which he remained in captivity, he drifted nearly thirteen hundred miles towards the south; and the ship _Resolute_, abandoned by Captain Kellet in an ice-field of immense extent, was drifted towards the south with this vast mass to a much greater distance.

Some curious speculations are hazarded by Dr. Maury, arising out of his investigations of winds and currents, facts being revealed which indicate the existence of a climate, mild by comparison, within the Antarctic Circle. These indications are a low barometer, a high degree of aerial rarefaction, and strong winds from the north. "The winds," he says, "were the first to whisper of this strange state of things, and to intimate to us that the Antarctic climates are in winter very unlike the Arctic for rigour and severity." The result of an immense mass of observation on the polar and equatorial winds reveals a marked difference in atmospherical movements north, as compared with the same movements south of the Equator; the equatorial winds of the northern hemisphere being only in excess between the tenth and thirteenth parallel, while those of the southern hemisphere are dominant over a zone of forty-five degrees, or from thirty-five degrees south to ten degrees north.

"The fact that the influence of the polar indraught upon the winds should extend from the Antarctic to the parallel of forty degrees south, while that from the Arctic is so feeble as scarcely to be felt in fifty degrees north, is indicative enough as to the difference in degree of aerial rarefaction over the two regions. The significance of the fact is enhanced by the consideration that the 'brave west winds,' which are bound to the place of greatest rarefaction, rush more violently and constantly along to their destination than do the counter-trades of the northern hemisphere. Why should these polar-bound winds differ so much in strength and prevalence, unless there be a much more abundant supply of caloric, and, consequently, a higher degree of rarefaction, at one pole than at the other?"

That this is the case is confirmed by all known barometrical observations, which are very much lower in the Antarctic than in the Arctic, and Dr. Maury thinks this is doubtless due to the excess in Antarctic regions of aqueous vapour and this latent heat.

"There is rarefaction in the Arctic regions. The winds show it, the barometer attests it, and the fact is consistent with the Russian theory of a Polynia in polar waters. Within the Antarctic Circle, on the contrary, the winds bring air which has come over the water for the distance of hundreds of leagues all around; consequently, a large portion of atmospheric air is driven away from the austral regions by the force of vapour."