of the subtropics, and the yellow clay of the temperate latitudes).
The enormous mass of facts which can be used in this way as fossil evidences of climate shows in an astonishing manner that in the past, in most regions of the earth, an entirely different climate prevailed from that of to-day. One especially striking example will now be given.
In Spitsbergen, which to-day with the severest polar climate lies under land-ice, forests of a greater variety of species of trees than are now to be found in Central Europe were still rustling in the Lower Tertiary. Not only were firs, pines and yews in existence, but also limes, beeches, poplars, elms, oaks, maples, ivy, sloes, hazel, hawthorn, guelder rose, ash, even such warmth-loving plants as water-lilies, walnut, swamp-cypress (Taxodium), immense sequoias, planes, chestnuts, ginkgo, magnolia, and the grape-vine. Therefore a climate must have prevailed in Spitsbergen similar to that of France to-day, and its average annual temperature must have been 20° C. higher than at present. And if we go further back into the earth’s history we find indications of a still greater warmth. In the Jurassic and lower Cretaceous sago-palms, which nowadays only occur in the tropics, ginkgo (only a solitary species to-day in China and South Japan), and tree-ferns flourished amongst others. Finally, in the Lower Carboniferous we find in Spitsbergen the tree-like Calamites, Lepidodendra, tree-ferns; in short, the same flora as that of the great coal-deposits of the Upper Carboniferous of Europe, which, in the judgment of those best qualified to form an opinion, was tropical. Therefore the climate of Spitsbergen must have been at that period about 30° C. higher than to-day.
This enormous variation of climate from a tropical
