We thus know that the present distribution of land and water greatly influences climate, more especially by affecting that of the ocean currents and of the winds, and by the different action of land as compared with water in the reception and radiation of heat. The present distribution of land gives a large predominance to the Arctic and sub-Arctic regions, as compared with the equatorial and with the Antarctic; and we might readily imagine other distributions that would give very different results. But this is not an imaginary case, for we can to some extent restore, on geological grounds, the ancient geography of large regions, and can show that it has been very different from that prevailing at present. We know also that, while the forms and positions of the great continents have been fixed from a very early date, they have experienced many great submergences and re-elevations, and that these have occurred in somewhat regular sequence, as evidenced by the cyclical alternations of organic limestones and earthy sediments in the successive great geological periods, each of which, as may be seen in any geological text-book, presents a dip of the continental plateaus, with subsequent elevation, as if the land was subject to a series of regular pulsations.[182]
[182] See "Acadian Geology"—Introduction to the Carboniferous System.
Finally, the Lyellian theory tends to abate the tendency to imagine portentous and impossible climatal changes; and it inclines geologists to give more attention to the connection of palæogeography with changes in the life history of the earth.
References:—"Acadian Geology," 1st ed., 1855; 4th ed., 1892. Icebergs of Belle-Isle, and Glaciers of Mont Blanc, Canadian Naturalist, 1865. "Notes on Pleistocene of Canada," Montreal, 1871. Papers at various dates in the Canadian Naturalist and Canadian Record of Science. "The Ice Age in Canada," Montreal, 1892. Canadian Pleistocene, London Geological Magazine, March, 1883. Flora of the Pleistocene, Dawson and Penhallow. Bulletin of Geological Society of America, vol. i., 1890, p. 311.
[THE DISTRIBUTION OF ANIMALS AND PLANTS AS RELATED TO GEOGRAPHICAL AND GEOLOGICAL CHANGES.]
DEDICATED TO THE MEMORY OF MY LATE FRIEND,
MR. GWYN JEFFRIES,
who so ably investigated the Distribution
of Oceanic Molluska,
more especially in the North Atlantic.