and deposited upon it in fine crystals; and as the influx of air is constant and all-pervading, a never-ceasing supply of frost is going on all the time. In consequence of the larger quantity of moisture, the process is still more marked and regular at the south pole. The explanation of the glaciation of the northern part of our temperate zone during the ice age, still unfound, is a matter of great importance, for the present topography of the land was brought out and the organic life of the whole earth was modified by it; and it is the general opinion that the solution of the problem is to be found, if it is found, by the study of the polar regions.
In the period immediately preceding the ice age the polar regions were not covered with ice, but had a rich growth of plants, reaching up even to the glaciers of their mountains, and plants were represented in them which are now known only in warmer countries. This was a very noteworthy time in the history of the earth. Organic life, in the continents at least, was in its greatest extension, and, I believe, specificism and diversity. The forests also were more luxuriant than now. And this was the time when man originated. Upon this came the ice age, during which man was scattered over the whole world, and organic beings were divided according to their capacity to resist the cold into the three great classes of arctic, temperate, and tropical life—a division which probably existed too during the earlier period, but then only locally, as on mountain ranges. The study of the organic life of the poles is therefore of the greatest importance for the understanding of the history of the organic life of our planet; and the more so because the arctic region has always been an important station for the distribution of organisms. The plants and animals of the south polar lands, on the contrary, and of the pointed southern continental terminations have never shown any permanent community with one another. This peculiar feature of the southern continents appeared very early.
Knowledge concerning the origin and spread of peoples may likewise receive valuable contributions from polar research. That is shown by the Eskimos and their wonderful adaptation to that nature which is so destructive to civilized peoples. In this we have a clear demonstration of the maxim which is one of the most important if not the most important law of all organic and human life: that what is to be permanent can be brought about only by gradual, extremely slow formation; never by sudden, immediate transition, or by sharp, violent breach. It is the same in the mental life. It is impossible to create anything new and enduring by simply casting the old away. Only what has connection has permanence. This maxim may be called the funda-
