About Polar Glaciation &c.

Abstract

Summary Evaporation and condensation, atmospheric and oceanic circulation are caused by unequal local temperatures. Rivers and land-glaciers alike result from atmospheric circulation, and from local condensation, and they flow for the same reasons at different rates. The existing Arctic current is part of ocean circulation, caused by unequal polar and equatorial temperatures. That current is a conspicuous fact. It is far larger and more powerful than any existing river or ice flow on land. It is more than three thousand miles long, and it is very broad; it moves vast fragments of the largest existing land-glaciers, and great sheets of thick polar sea-ice, at great speed. It lowers the perpetual snow-limit where it flows, and it there modifies climate and all that depends on climate. Within an area equal to that of India, in Greenland it increases local condensation, and snow-flake's, and snow-falls, and ice flows and rivers; and so it increases local denudation on shore while it works on the shallows. Ice rafts in the ocean-stream carry drift southwards; and the water which drags these loaded rafts over shallows and makes them drop boulders, also rolls and packs mud and shingle and builds a delta in the sea. This kind of polar “glaciation” and deposition of “drift,” caused directly and indirectly by one of the northern polar currents, cannot be denied. The agent is a true cause at work; and the work ought to be like that which I saw in Russia in 1873. Where a sedimentary rock exists there water has been; and the drift-plains of Russia are spread upon sedimentary series little disturbed. That part of the earth's crust has been up and down many times without breaking much. If glacial periods, due to astronomical or other causes, have in fact increased evaporation and condensation, ice-flows, and rivers to any given extent, then polar currents must have gained power during these periods, because movements in air and ocean result from unequal local temperatures, on which also depend the local growth of ice on land.