CHAPTER XVIII.

FORMER GLACIAL EPOCHS; GEOLOGICAL EVIDENCE OF.

Cambrian Conglomerate of Islay and North-west of Scotland.—Ice-action in Ayrshire and Wigtownshire during Silurian Period.—Silurian Limestones in Arctic Regions.—Professor Ramsay on Ice-action during Old Red Sandstone Period.—Warm Climate in Arctic Regions during Old Red Sandstone Period.—Professor Geikie and Mr. James Geikie on a Glacial Conglomerate of Lower Carboniferous Age.—Professor Haughton and Professor Dawson on Evidence of Ice-action during Coal Period.—Mr. W. T. Blanford on Glaciation in India during Carboniferous Period.—Carboniferous Formations of Arctic Regions.—Professor Ramsay on Permian Glaciers.—Permian Conglomerate in Arran.—Professor Hull on Boulder Clay of Permian Age.—Permian Boulder Clay of Natal.—Oolitic Boulder Conglomerate in Sutherlandshire.—Warm Climate in North Greenland during Oolitic Period.—Mr. Godwin-Austen on Ice-action during Cretaceous Period.—Glacial Conglomerates of Eocene Age in the Alps.—M. Gastaldi on the Ice-transported Limestone Blocks of the Superga.—Professor Heer on the Climate of North Greenland during Miocene Period.

CAMBRIAN PERIOD.

_Island of Islay._—Good evidence of ice-action has been observed by Mr. James Thomson, F.G.S.,[154] in strata which he believes to be of Cambrian age. At Port Askaig, Island of Islay, below a precipitous cliff of quartzite 70 feet in height, there is a mass of arenaceous talcose schist containing fragments of granite, some angular, but most of them rounded, and of all sizes, from mere particles to large boulders. As there is no granite in the island from which these boulders could have been derived, he justly infers that they must have been transported by the agency of ice. The probability of his conclusion is strengthened by the almost total absence of stratification in the deposit in question.

_North-west of Scotland._—Mr. J. Geikie tells me that much of the Cambrian conglomerate in the north-west of Scotland strongly reminds him of the coarse shingle beds (Alpine diluvium) which so often crowd the old glacial valleys of Switzerland and Northern Italy. In many places the stones of the Cambrian conglomerate have a subangular, blunted shape, like those of the re-arranged moraine débris of Alpine countries.

SILURIAN PERIOD.

_Wigtownshire._—The possibility of glacial action so far back as the Silurian age has been suggested. In beds of slate and shales in Wigtownshire of Lower Silurian age Mr. J. Carrick Moore found beds of conglomerate of a remarkable character. The fragments generally vary from the size of one inch to a foot in diameter, but in some of the beds, boulders of 3, 4, and even 5 feet in diameter occur. There are no rocks in the neighbourhood from which any of these fragments could have been derived. The matrix of this conglomerate is sometimes a green trappean-looking sandstone of exceeding toughness, and sometimes an indurated sandstone indistinguishable from many common varieties of greywacke.[155]

_Ayrshire._—Mr. James Geikie states that in Glenapp, and near Dalmellington, he found embedded in Lower Silurian strata blocks and boulders from one foot to 5 feet in diameter of gneiss, syenite, granite, &c., none of which belong to rocks of those neighbourhoods.[156] Similar cases have been found in Galway, Ireland, and at Lisbellaw, south of Enniskillen.[157] In America, Professor Dawson describes Silurian conglomerates with boulders 2 feet in diameter.

_Arctic Regions._—The existence of warm inter-glacial periods during that age may be inferred from the fact that in the arctic regions we find widespread masses of Silurian limestones containing encrinites, corals, and mollusca, and other fossil remains, for an account of which see Professor Haughton’s geological account of the Arctic Archipelago appended to McClintock’s “Narrative of Arctic Discoveries.”[158]

OLD RED SANDSTONE.

_North of England._—According to Professor Ramsay and some other geologists the brecciated, subangular conglomerates and boulder beds of the Old Red Sandstone of Scotland and the North of England are of glacial origin. When these conglomerates and the recent boulder clay come together it is difficult to draw the line of demarcation between them.

Professor Ramsay observed some very remarkable facts in connection with the Old Red Sandstone conglomerates of Kirkby Lonsdale, and Sedburgh, in Westmoreland and Yorkshire. I shall give the results of his observations in his own words.

“The result is, that we have found many stones and blocks distinctly scratched, and on others the ghosts of scratches nearly obliterated by age and chemical action, probably aided by pressure at a time when these rocks were buried under thousands of feet of carboniferous strata. In some cases, however, the markings were probably produced within the body of the rock itself by pressure, accompanied by disturbance of the strata; but in others the longitudinal and cross striations convey the idea of glacial action. The shapes of the stones of these conglomerates, many of which are from 2 to 3 feet long, their flattened sides and subangular edges, together with the confused manner in which they are often arranged (like stones in the drift), have long been enough to convince me of their ice-borne character; and the scratched specimens, when properly investigated, may possibly convince others.”[159]

_Isle of Man._—The conglomerate of the Old Red Sandstone in the Isle of Man has been compared by Mr. Cumming to “a consolidated ancient boulder clay.” And he remarks, “Was it so that those strange trilobitic-looking fishes of that era had to endure the buffeting of ice-waves, and to struggle amidst the wreck of ice-floes and the crush of bergs?”[160]

_Australia._—A conglomerate similar to that of Scotland has been found in Victoria, Australia, by Mr. Selwyn, at several localities. Along the Wild Duck Creek, near Heathcote, and also near the Mia-Mia, Spring Plains, Redesdale, localities in the Colony of Victoria, where it was examined by Messrs. Taylor and Etheridge, Junior, this conglomerate consists of a mixture of granite pebbles and boulders of various colours and textures, porphyries, indurated sandstone, quartz, and a peculiar flint-coloured rock in a matrix of bluish-grey very hard mud-cement.[161] Rocks similar to the pebbles and blocks composing the conglomerate do not occur in the immediate neighbourhood; and from the curious mixture of large and small angular and water-worn fragments it was conjectured that it might possibly be of glacial origin. Scratched stones were not observed, although a careful examination was made. From similar mud-pebble beds on the Lerderderg River, Victoria, Mr. P. Daintree obtained a few pebbles grooved after the manner of ice-scratched blocks.[162]

And the existence of a warm condition of climate during the Old Red Sandstone period is evidenced by the fossiliferous limestones of England, Russia, and America. On the banks of the Athabasca River, Rupert-Land, Sir John Richardson found beds of limestone containing _Producti_, _Spiriferi_, an _Orthis_ resembling _O. resupinata_, _Terebratula reticularis_,[163] and a _Pleurotomaria_, which, in the opinion of the late Dr. Woodward, who examined the specimens, are characteristic of Devonian rocks of Devonshire.

CARBONIFEROUS PERIOD.

_France._—It is now a good many years since Mr. Godwin-Austen directed attention to what he considered evidence of ice-action during the coal period. This geologist found in the carboniferous strata of France large angular blocks which he could not account for without inferring the former action of ice. “Whether from local elevation,” he says, “or from climatic conditions, there are certain appearances over the whole which imply that at one time the temperature must have been very low, as glacier-action can alone account for the presence of the large angular blocks which occur in the lowest detrital beds of many of the southern coal-basins.”[164]

_Scotland._—In Scotland great beds of conglomerate are met with in various parts, which are now considered by Professor Geikie, Mr. James Geikie, and other officers of the Geological Survey who have had opportunities of examining them, to be of glacial origin. “They are,” says Mr. James Geikie, “quite unstratified, and the stones often show that peculiar blunted form which is so characteristic of glacial work.”[165] Many of the stones found by Professor Geikie, several of which I have had an opportunity of seeing, are well striated.

In 1851 Professor Haughton brought forward at the Geological Society of Dublin, a case of angular fragments of granite occurring in the carboniferous limestone of the county of Dublin; and he explained the phenomena by the supposition of the transporting power of ice.

_North America._—In one of the North American coal-fields Professor Newberry found a boulder of quartzite 17 inches by 12 inches, imbedded in a seam of coal. Similar facts have also been recorded both in the United States, and in Nova Scotia. Professor Dawson describes what he calls a gigantic esker of Carboniferous age, on the outside of which large travelled boulders were deposited, probably by drift-ice; while in the swamps within, the coal flora flourished.[166]

_India._—Mr. W. T. Blanford, of the Geological Survey of India, states that in beds considered to be of Carboniferous age are found large boulders, some of them as much as 15 feet in diameter. The bed in which these occur is a fine silt, and he refers the deposition of the boulders to ice-action. Within the last three years his views have received singular confirmation in another part of India, where beds of limestone were found striated below certain overlying strata. The probability that these appearances are due, as Mr. Blanford says, to the action of ice, is strengthened by the consideration that about five degrees farther to the north of the district in question rises the cold and high table-land of Thibet, which during a glacial epoch would undoubtedly be covered with ice that might well descend over the plains of India.[167]

_Arctic Regions._—A glacial epoch during the Carboniferous age may be indirectly inferred from the probable existence of warm inter-glacial periods, as indicated by the limestones with fossil remains found in arctic regions.

That an equable condition of climate extended to near the north pole is proved by the fact that in the arctic regions vast masses of carboniferous limestone, having all the characters of the mountain limestone of England, have been found. “These limestones,” says Mr. Isbister, “are most extensively developed in the north-east extremity of the continent, where they occupy the greater part of the coast-line, from the north side of the Kotzebue Sound to within a few miles of Point Barrow, and form the chief constituent of the lofty and conspicuous headlands of Cape Thomson, Cape Lisburn, and Cape Sabine.”[168] Limestone of the same age occurs extensively along the Mackenzie River. The following fossils have been found in these limestones:—_Terebratula resupinata_,[169] _Lithostrotion basaltiforme_, _Cyathophyllum dianthum_, _C. flexuosum_, _Turbinolia mitrata_, _Productus Martini_,[170] _Dentalium Sarcinula_, _Spiriferi_, _Orthidæ_, and encrinital fragments in the greatest abundance.

Among the fossils brought home from Depôt Point, Albert Land, by Sir E. Belcher, Mr. Salter found the following, belonging to the Carboniferous period:—_Fusulina hyperborea_, _Stylastrea inconferta_, _Zaphrentis ovibos_, _Clisiophyllum tumulus_, _Syringopora (Aulopora)_, _Fenestella Arctica_, _Spirifera Keilhavii_, _Productus cora_, _P. semireticulatus_.[171]

Coal-beds of Carboniferous age are extensively developed in arctic regions. The fuel is of a highly bituminous character, resembling, says Professor Haughton, the gas coals of Scotland. The occurrence of coal in such high latitudes indicates beyond doubt that a mild and temperate condition of climate must, during some part of the Carboniferous age, have prevailed up to the very pole.

“In the coal of Jameson’s Land, on the east side of Greenland, lying in latitude 71°, and in that of Melville Island, in latitude 75° N., Professor Jameson found plants resembling fossils of the coal-fields of Britain.”[172]

PERMIAN PERIOD.

_England._—From the researches of Professor Ramsay in the Permian breccias, we have every reason to believe that during a part of the Permian age our country was probably covered with glaciers reaching to the sea. These brecciated stones, he states, are mostly angular or subangular, with flattened sides and but very slightly rounded at the edges, and are imbedded in a deep red marly paste. At Abberley Hill some of the masses are from 2 to 3 feet in diameter, and in one of the quarries, near the base of Woodbury Hill, Professor Ramsay saw one 2 feet in diameter. Another was observed at Woodbury Rock, 4 feet long, 3 feet broad, and 1½ feet thick. The boulders were found in South Staffordshire, Enville, in Abberley and Malvern Hills, and other places. “They seem,” he says, “to have been derived from the conglomerate and green, grey, and purple Cambrian grits of the Longmynd, and from the Silurian quartz-rocks, slates, felstones, felspathic ashes, greenstones, and Upper Caradoc rocks of the country between the Longmynd and Chirbury. But then,” he continues, “the south end of the Malvern Hills is from forty to fifty miles, the Abberleys from twenty-five to thirty-five miles, Enville from twenty to thirty miles, and South Staffordshire from thirty-five to forty miles distant from that country.”[173]

It is physically impossible, Professor Ramsay remarks, that these blocks could have been transported to such distances by any other agency than that of ice. Had they been transported by water, supposing such a thing possible, they would have been rounded and water-worn, whereas many of these stones are flat slabs, and most of them have their edges but little rounded. And besides many of them are highly polished, and others grooved and finely striated, exactly like those of the ancient glaciers of Scotland and Wales. Some of these specimens are to be seen in the Museum of Practical Geology, Jermyn Street.

_Scotland._—In the Island of Arran, Mr. E. A. Wunsch and Mr. James Thomson found a bed of conglomerate which they considered of Permian age, and probably of glacial origin. This conglomerate enclosed angular fragments of various schistose, volcanic, and limestone rocks, and contained carboniferous fossils.

_Ireland._—At Armagh, Ireland, Professor Hull found boulder beds of Permian age, containing pebbles and boulders, sometimes 2 feet in diameter. Some of the boulders must have been transported from a region lying about 30 miles to the north-west of the locality in which they now occur. It is difficult to conceive, says Professor Hull, how rock fragments of such a size could have been carried to their present position by any other agency than that of floating ice. This boulder-bed is overlaid by a recent bed of boulder clay. Professor Ramsay, who also examined the section, agrees with Professor Hull that the bed is of Permian age, and unquestionably of ice-formation.[174]

Professor Ramsay feels convinced that the same conclusions which he has drawn in regard to the Permian breccia of England will probably yet be found to hold good in regard to much of that of North Germany.[175] And there appears to be some ground for concluding that the cold of that period even reached to India.[176]

_South Africa._—An ancient boulder clay, supposed to be either of Permian or Jurassic age, has been extensively found in Natal, South Africa. This deposit, discovered by Dr. Sutherland, the Surveyor-General of the colony, is thus described by Dr. Mann:—

“The deposit itself consists of a greyish-blue argillaceous matrix, containing fragments of granite, gneiss, graphite, quartzite, greenstone, and clay-slate. These imbedded fragments are of various size, from the minute dimensions of sand-grains up to vast blocks measuring 6 feet across, and weighing from 5 to 10 tons. They are smoothed, as if they had been subject to a certain amount of attrition in a muddy sediment; but they are not rounded like boulders that have been subjected to sea-breakers. The fracture of the rock is not conchoidal, and there is manifest, in its substance, a rude disposition towards wavy stratification.”

“Dr. Sutherland inclines to think that the transport of vast massive blocks of several tons’ weight, the scoring of the subjacent surfaces of sandstone, and the simultaneous deposition of minute sand-grains and large boulders in the same matrix, all point to one agency as the only one which can be rationally admitted to account satisfactorily for the presence of this remarkable formation in the situations in which it is found. He believes that the boulder-bearing clay of Natal is of analogous nature to the great Scandinavian drift, to which it is certainly intimately allied in intrinsic mineralogical character; that it is virtually a vast moraine of olden time; and that ice, in some form or other, has had to do with its formation, at least so far as the deposition of the imbedded fragments in the amorphous matrix are concerned.”[177]

In the discussion which followed the reading of Dr. Sutherland’s paper, Professor Ramsay pointed out that in the Natal beds enormous blocks of rock occurred, which were 60 or 80 miles from their original home, and still remained angular; and there was a difficulty in accounting for the phenomena on any other hypothesis than that suggested.

Mr. Stow, in his paper on the Karoo beds, has expressed a similar opinion regarding the glacial character of the formation.[178]

But we have in the Karoo beds evidence not only of glaciation, but of a much warmer condition of things than presently exists in that latitude. This is shown from the fact that the shells of the _Trigona_-beds indicate a tropical or subtropical condition of climate.

_Arctic Regions._—The evidence which we have of the existence of a warm climate during the Permian period is equally conclusive. The close resemblance of the _flora_ of the Permian period to that of Carboniferous times evidently points to the former prevalence of a warm and equable climate. And the existence of the magnesian limestone in high latitudes seems to indicate that during at least a part of the Permian period, just as during the accumulation of the carboniferous limestone, a warm sea must have obtained in those latitudes.

OOLITIC PERIOD.

_North of Scotland._—There is not wanting evidence of something like the action of ice during the Oolitic period.[179]

In the North of Scotland Mr. James Geikie says there is a coarse boulder conglomerate associated with the Jurassic strata in the east of Sutherland, the possibly glacial origin of which long ago suggested itself to Professor Ramsay and other observers. Mr. Judd believes the boulders to have been floated down by ice from the Highland mountains at the time the Jurassic strata were being accumulated.

_North Greenland._—During the Oolitic period a warm condition of climate extended to North Greenland. For example, in Prince Patrick’s Island, at Wilkie Point, in lat. 76° 20′ N., and long. 117° 20′ W., Oolitic rocks containing an ammonite (_Ammonites McClintocki_, Haughton), like _A. concavus_ and other shells of Oolitic species, were found by Captain McClintock.[180] In Katmai Bay, near Behring’s Straits, the following Oolitic fossils were discovered—_Ammonites Wasnessenskii_, _A. biplex_, _Belemnites paxillosus_, and _Unio liassinus_.[181] Captain McClintock found at Point Wilkie, in Prince Patrick’s Island, lat. 76° 20′, a bone of _Ichthyosaurus_, and Sir E. Belcher found in Exmouth Island, lat. 76° 16′ N., and long. 96° W., at an elevation of 570 feet above the level of the sea, bones which were examined by Professor Owen, and pronounced to be those of the same animal.[182] Mr. Salter remarks that at the time that these fossils were deposited, “a condition of climate something like that of our own shores was prevailing in latitudes not far short of 80° N.”[183] And Mr. Jukes says that during the Oolitic period, “in latitudes where now sea and land are bound in ice and snow throughout the year, there formerly flourished animals and plants similar to those living in our own province at that time. The questions thus raised,” continues Mr. Jukes, “as to the climate of the globe when cephalopods and reptiles such as we should expect to find only in warm or temperate seas, could live in such high latitudes, are not easy to answer.”[184] And Professor Haughton remarks, that he thinks it highly improbable that any change in the position of land and water could ever have produced a temperature in the sea at 76° north latitude which would allow of the existence of ammonites, especially species so like those that lived at the same time in the tropical warm seas of the South of England and France at the close of the Liassic, and commencement of the Lower Oolitic period.[185]

The great abundance of the limestone and coal of the Oolitic system shows also the warm and equable condition of the climate which must have then prevailed.

CRETACEOUS PERIOD.

_Croydon._—A large block of crystalline rock resembling granite was found imbedded in a pit, on the side of the old London and Brighton road near Purley, about two miles south of Croydon. Mr. Godwin-Austen has shown conclusively that it must have been transported there by means of floating ice. This boulder was associated with loose sea-sand, coarse shingle, and a smaller boulder weighing twenty or twenty-five pounds, and all water-worn. These had all sunk together without separating. Hence they must have been firmly held together, both during the time that they were being floated away, and also whilst sinking to the bottom of the cretaceous sea. Mr. Godwin-Austen supposes the whole to have been carried away frozen to the bottom of a mass of ground-ice. When the ice from melting became unable to float the mass attached to it, the whole would then sink to the bottom together.[186]

_Dover._—While the workmen were employed in cutting the tunnel on the London, Chatham, and Dover Railway, between Lydden Hill and Shepherdswell, a few miles from Dover, they came upon a mass of coal imbedded in chalk, at a depth of 180 feet. It was about 4 feet square, and from 4 to 10 inches thick. The coal was friable and highly bituminous. It resembled some of the Wealden or Jurassic coal, and was unlike the true coal of the coal-measures. The specific gravity of the coal precluded the supposition that it could have floated away of itself into the cretaceous sea. “Considering its friability,” says Mr. Godwin-Austen, “I do not think that the agency of a floating tree could have been engaged in its transport; but, looking at its flat, angular form, it seems to me that its history may agree with what I have already suggested with reference to the boulder in the chalk at Croydon. We may suppose that during the Cretaceous period some bituminous beds of the preceding Oolitic period lay so as to be covered with water near the sea-margin, or along some river-bank, and from which portions could be carried off by ice, and so drifted away, until the ice was no longer able to support its load.”[187]

Mr. Godwin-Austen then mentions a number of other cases of blocks being found in the chalk. In regard to those cases he appropriately remarks that, as the cases where the occurrence of such blocks has been observed are likely to be far less numerous than those which have escaped observation, or failed to have been recorded, and as the chalk exposed in pits and quarries bears only a most trifling proportion to the whole horizontal extent of the formation, we have no grounds to conclude that the above are exceptional cases.

Boulders have also been found in the cretaceous strata of the Alps by Escher von der Linth.[188]

The existence of warm periods during the Cretaceous age is plainly shown by the character of the flora and fauna of that age. The fact that chalk is of organic origin implies that the climate must have been warm and genial, and otherwise favourable to animal life. This is further manifested by such plants as _Cycas_ and _Zamia_, which betoken a warm climate, and by the corals and huge sauroid reptiles which then inhabited our waters.

It is, in fact, the tropical character of the fauna of that period which induced Sir Charles Lyell to reject Mr. Godwin-Austen’s idea that the boulders found in the chalk had been transported by floating ice. Such a supposition, implying a cold climate, “is,” Sir Charles says, “inconsistent with the luxuriant growth of large chambered univalves, numerous corals, and many fish, and other fossils of tropical forms.”

The recent discovery of the Cretaceous formation in Greenland shows that during that period a mild and temperate condition of climate must have prevailed in that continent up to high latitudes. “This formation in Greenland,” says Dr. Robert Brown, “has only been recently separated from the Miocene formation, with which it is associated and was supposed to be a part of. It is, as far as we yet know, only found in the vicinity of Kome or Koke, near the shores of Omenak Fjord, in about 70° north latitude, though traces have been found elsewhere on Disco, &c. The fossils hitherto brought to Europe have been very few, and consist of plants which are now preserved in the Stockholm and Copenhagen Museums. From these there seems little doubt that the age assigned to this limited deposit (so far as we yet know) by the celebrated palæontologist, Professor Oswald Heer, of Zurich, is the correct one.”[189] Dr. Brown gives a list of the Cretaceous flora found in Greenland.

EOCENE PERIOD.

_Switzerland._—In a coarse conglomerate belonging to the “_flysch_” of Switzerland, an Eocene formation, there are found certain immense blocks, some of which consist of a variety of granite which is not known to occur _in situ_ in any part of the Alps. Some of the blocks are 10 feet and upwards in length, and one at Halekeren, at the Lake of Thun, is 105 feet in length, 90 feet in breadth, and 45 feet in height. Similar blocks are found in the Apennines. These unmistakably indicate the presence of glaciers or floating ice. This conclusion is further borne out by the fact that the “_flysch_” is destitute of organic remains. But the hypothesis that these huge masses were transported to their present sites by glaciers or floating ice has been always objected to, says Sir Charles Lyell, “on the ground that the Eocene strata of Nummulitic age in Switzerland, as well as in other parts of Europe, contain genera of fossil plants and animals characteristic of a warm climate. And it has been particularly remarked,” he continues, “by M. Desor that the strata most nearly associated with the ‘_flysch_’ in the Alps are rich in echinoderms of the _Spatangus_ family which have a decided tropical aspect.”[190]

But according to the theory of Secular Changes of Climate, the very fact that the “_flysch_” is immediately associated with beds indicating a warm or even tropical condition of climate, is one of the strongest proofs which could be adduced in favour of its glacial character, for the more severe a cold period of a glacial epoch is, the warmer will be the periods which immediately precede and succeed. These crocodiles, tortoises, and tropical flora probably belong to a warm Eocene inter-glacial period.

MIOCENE PERIOD.

_Italy._—We have strong evidence in favour of the opinion that a glacial epoch existed during the Miocene period. It has been shown by M. Gastaldi, that during that age Alpine glaciers extended to the sea-level.

Near Turin there is a series of hills, rising about 500 or 600 feet above the valleys, composed of beds of Miocene sandstone, marl, and gravel, and loose conglomerate. These beds have been carefully examined and described by M. Gastaldi.[191] The hill of the Luperga has been particularly noticed by him. Many of the stones in these beds are striated in a manner similar to those found in the true till or boulder clay of this country. But what is most remarkable is the fact that large erratic blocks of limestone, many of them from 10 to 15 feet in diameter, are found in abundance in these beds. It has been shown by Gastaldi that these blocks have all been derived from the outer ridge of the Alps on the Italian side, namely, from the range extending from Ivrea to the Lago Maggiore, and consequently they must have travelled from twenty to eighty miles. So abundant are these large blocks, that extensive quarries have been opened in the hills for the sake of procuring them. These facts prove not only the existence of glaciers on the Alps during the Miocene period, but of glaciers extending to the sea and breaking up into icebergs; the stratification of the beds amongst which the blocks occur sufficiently indicating aqueous action and the former presence of the sea.

That the glaciers of the Southern Alps actually reached to the sea, and sent their icebergs adrift over what are now the sunny plains of Northern Italy, is sufficient proof that during the cold period of Miocene times the climate must have been very severe. Indeed, it may well have been as severe as, if not even more excessive than, the intensest severity of climate experienced during the last great glacial epoch.

_Greenland._—Of the existence of warm conditions during Miocene times, geology affords us abundant evidence. I shall quote the opinion of Sir Charles Lyell on this point:—

“We know,” says Sir Charles, “that Greenland was not always covered with snow and ice; for when we examine the tertiary strata of Disco Island (of the Upper Miocene period), we discover there a multitude of fossil plants which demonstrate that, like many other parts of the arctic regions, it formerly enjoyed a mild and genial climate. Among the fossils brought from that island, lat. 70° N., Professor Heer has recognised _Sequoia Landsdorfii_, a coniferous species which flourished throughout a great part of Europe in the Miocene period. The same plant has been found fossil by Sir John Richardson within the Arctic Circle, far to the west on the Mackenzie River, near the entrance of Bear River; also by some Danish naturalists in Iceland, to the east. The Icelandic surturband or lignite, of this age, has also yielded a rich harvest of plants, more than thirty-one of them, according to Steenstrup and Heer, in a good state of preservation, and no less than fifteen specifically identical with Miocene plants of Europe. Thirteen of the number are arborescent; and amongst others is a tulip-tree (_Liriodendron_), with its fruit and characteristic leaves, a plane (_Platanus_), a walnut, and a vine, affording unmistakable evidence of a climate in the parallel of the Arctic Circle which precludes the supposition of glaciers then existing in the neighbourhood, still less any general crust of continental ice like that of Greenland.”[192]

At a meeting of the British Association, held at Nottingham in August 1866, Professor Heer read a valuable paper on the “Miocene Flora of North Greenland.” In this paper some remarkable conclusions as to the probable temperature of Greenland during the Miocene period were given.

Upwards of sixty different species brought from Atanekerdluk, a place on the Waigat opposite Disco, in lat. 70° N., have been examined by him.

A steep hill rises on the coast to a height of 1,080 feet, and at this level the fossil plants are found. Large quantities of wood in a fossilized or carbonized condition lie about. Captain Inglefield observed one trunk thicker than a man’s body standing upright. The leaves, however, are the most important portion of the deposit. The rock in which they are found is a sparry iron ore, which turns reddish brown on exposure to the weather. In this rock the leaves are found, in places packed closely together, and many of them are in a very perfect condition. They give us a most valuable insight into the nature of the vegetation which formed this primeval forest.

He arrives at the following conclusions:—

1. _The fossilized plants of Atanekerdluk cannot have been drifted from any great distance. They must have grown on the spot where they were found._

This is shown—

(_a_) By the fact that Captain Inglefield and Dr. Ruik observed trunks of trees standing upright.

(_b_) By the great abundance of the leaves, and the perfect state of preservation in which they are found.

(_c_) By the fact that we find in the stone both fruits and seeds of the trees whose leaves are also found there.

(_d_) By the occurrence of insect remains along with the leaves.

2. _The flora of Atanekerdluk is Miocene._

3. _The flora is rich in species._

4. _The flora proves without a doubt that North Greenland, in the Miocene epoch, had a climate much warmer than its present one. The difference must be at least_ 29° F.

Professor Heer discusses at considerable length this proposition. He says that the evidence from Greenland gives a final answer to those who objected to the conclusions as to the Miocene climate of Europe drawn by him on a former occasion. It is quite impossible that the trees found at Atanekerdluk could ever have flourished there if the temperature were not far higher than it is at present. This is clear from many of the species, of which we find the nearest living representative 10° or even 20° of latitude to the south of the locality in question.

The trees of Atanekerdluk were not, he says, all at the extreme northern limit of their range, for in the Miocene flora of Spitzbergen, lat. 78° N., we find the beech, plane, hazelnut, and some other species identical with those from Greenland, and we may conclude, he thinks, that the firs and poplars which we meet at Atanekerdluk and Bell Sound, Spitzbergen, must have reached up to the North Pole if land existed there in the tertiary period.

“The hills of fossilized wood,” he adds, “found by McClure and his companions in Banks’s Land (lat. 74° 27′ N.), are therefore discoveries which should not astonish us, they only confirm the evidence as to the original vegetation of the polar regions which we have derived from other sources.”

The _Sequoia landsdorfii_ is the most abundant of the trees of Atanekerdluk. The _Sequoia sempervirens_ is its present representative. This tree has its extreme northern limit about lat. 53° N. For its existence it requires a summer temperature of 59° or 61° F. Its fruit requires a temperature of 64° for ripening. The winter temperature must not fall below 34°, and that of the whole year must be at least 49°. The temperature of Atanekerdluk during the time that the Miocene flora grew could not have been under the above.[193]

Professor Heer concludes his paper as follows:—

“I think these facts are convincing, and the more so that they are not insulated, but confirmed by the evidence derivable from the Miocene flora of Iceland, Spitzbergen, and Northern Canada. These conclusions, too, are only links in the grand chain of evidence obtained from the examination of the Miocene flora of the whole of Europe. They prove to us that we could not by any re-arrangement of the relative positions of land and water produce for the northern hemisphere a climate which would explain the phenomena in a satisfactory manner. We must only admit that we are face to face with a problem, whose solution in all probability must be attempted, and, we doubt not, completed by the astronomer.”