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tionable practical importance originated in apparently useless inquiries.

The phenomena and distribution of Arctic ice are subjects worthy of investigation. It does not answer our purpose to detail the numerous observations made by Arctic voyagers. These observations indicate that the icebergs and ice-fields are loosened every summer, and sent drifting southward. These masses accumulate most where there is most land, and by their melting they transfer the cold of higher latitudes to these more southern lands, and thus reduce their mean temperature. This has the effect of throwing the zone of greatest cold towards the south, especially where the lands advance far north. Observations upon the thickness of ice found each winter or each year at several localities would enable us to define the zone of greatest cold, and also infer from the thickness of the ice whether the regions around the Pole are warmer than in about 75° N. What are the regions of perennial ice ? for that there are such regions seems clear from the occurrence of sea ice in sheets formed of annual layers. These regions may be the true sources of the cold currents of the sea ; while the warm currents have a temperature of 40° or 45° F., and flowing from the north, may arise from the area where the sea is freed every year from ice by the

INTRODUCTORY CHAPTER.

summer heat. This is a conjecture, but, probably, as good a one as that advanced by some, that the Gulf Stream flows right across the Pole, that is, by Spitzbergen, and out again through Smith Sound and Behring Strait. The ice presses against the northern coasts, and where the passages to the south are narrow, blocks them up with ice. On either view the evidence is in favour of a continuous sea across the Pole; for if the Gulf Stream flows across the polar area there must be sea, and where the water is not perceptibly cooled, probably open sea. The idea seems, however, to be preposterous. On the other hand the outflow of warm water in all directions from the Pole involves a large and open sea around the Pole.

In zoology and botany something has been done, but there is much more to do. The facts to be discovered cannot fail to have an important influence on all theories connected with their present and past distribution. This has been well shown in the case of botany by Dr. Hooker, whose remarks we quote. He referred to the existing flora of Greenland as being one of the most poverty-stricken in the globe, and yet possessed of unusual interest. “It consists of some 300 kinds of flowering plants (besides a very large number of mosses, algæ, lichens, &c.), and presented the following peculiarities :-(1.) The flowering plants were, almost without exception, natives of the Scandinavian peninsula. (2.) There was in the Greenland flora scarcely any admixture of American types, which, nevertheless, were found on the opposite coast of Labrador and the Polar Islands. (3.) A considerable proportion of the common Greenland plants were nowhere found in Labrador and the Polar Islands ; nor, indeed, elsewhere in the New World. (4.) The parts of Greenland south of the Arctic circle, though warmer than those north of it, and presenting a coast 400 miles long, contained scarcely any plants not found to the north of that circle. (5.) A considerable number of Scandinavian plants, which are not natives of Greenland, are nevertheless natives of Labrador and the Polar Islands. (6.) Certain Greenland and Scandinavian plants, which are nowhere found in the Polar plains, Labrador, or Canada, reappear at considerable elevations on the White, and the Alleghany, and other mountains of the United States. No other flora known to naturalists presents such a remarkable combination of peculiar features as this, and the only solution hitherto offered is not yet fully accepted. It is that the Scandinavian flora (which had been shown by himself to be one of the oldest on the globe,) did, during the warm period preceding the glacial—a period warmer than the present- extend in force over

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the Polar regions, including Greenland, the Polar American Islands, and probably much now-submerged land in places connected or lying between Greenland and Scandinavia, at which time Greenland no doubt presented a much richer Scandinavian flora than it now does. On the accession of the glacial period this flora would be driven slowly southward, down to the extremity of the Greenland peninsula in its longitude, and down to the latitude of the Alleghanies and the White Mountains in their longitudes. The effect in Greenland would be to leave there only the more Arctic forms of vegetation unchanged in habits or features, the rest being, as it were, driven into the sea. But the effect on the American continent would be to bring the Scandinavian flora into competition with an American flora that preoccupied the lands into which it was driven. On the decline of the glacial epoch, Greenland, being a peninsula, would be repeopled with plants only by the northward migration of the purely Scandinavian species, that had previously been driven into its southern extremity ; and the result would be a uniform Scandinavian flora throughout its length, and this an Arctic one from north to south. But in America a very different state of things would supervene; the Scandinavian plants would not only migrate north, but ascend the Alleghanies, White Mountains, &c.; and the result would be, that, on the one hand, many Scandinavian plants which had been driven out of Greenland, but were preserved in the United States, would reappear on the Polar Islands and Labrador, accompanied with sundry American mountain types; and, on the other, that a few Greenland Scandinavian types which had been lost in the struggle with the American types during their northward migration, and which hence do not reappear in Labrador and the Polar Islands, might well be preserved in the Alleghanies and White Mountains. And, lastly, that a number of Scandinavian plants which had changed their form or habit during the migration in America in conflict with the American types, would appear in the Polar Islands as American varieties or representative species of Scandinavian plants. Whether or not his be a true hypothesis, it embraces all the facts; and botanists look anxiously to further explorations in the northern parts of Greenland for more light on the subject, and especially for evidence of rising or sinking of the land, and for evidence of ancient connection between Greenland and Scandinavia ; for observations on the temperature, direction, and depth of transporting currents in these seas, and on the habits of the ruminant migrating animals that may have influenced the dis

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