Professor Geikie on supposed causes of the glacial period, 76; change in the relative level of the land and sea during glacial and post-glacial times, 77; submergence of northern lands at close of ice age, 78; the main cause of the movement of water from the northern seas at the close of glacial age, 79; why the earth-movement hypothesis should be rejected, 79; glaciers of Europe and Alaska, 80; North Pacific currents, 81; why the Pacific waters are growing cool, 82; the lowering temperature of the northern seas, 83; the increase of cold in Europe and Asia, 84; falling temperature of the Andean region, 85; General Drayson’s astronomical discoveries for explaining the cause of ice periods, 87; why the Gulf Stream was always confined to the North Atlantic, 89; the improbability of the Indian Ocean currents entering the arctic seas, 90; why the increase of glaciers must continue while the Cape Horn channel maintains its present capacity, 91; comments on the coming ice age, 92; tropical zone the abode of man during ice age, 93; preservation of the tropical ocean fauna through the glacial period, 93. CHAPTER I. CAUSE OF COLD AND MILD PERIODS. It is now generally conceded by those who have given the subject much attention that the greater portion of North America above the latitude of 39° north to the shores of the Arctic Ocean has been furrowed and scoured by the action of ice. Vast traces of ancient glaciers are also found in Europe; for it is reported that ice-sheets have left unmistakable marks of having overrun the greater part of the lands lying between the arctic seas and the latitude of the Pyrenees. In Asia evidences of glacial action have been noticed from Northern Siberia to the mountains of Syria. The great glaciers of Himalaya have in times past attained gigantic proportions. In Northern China huge bowlders are found scattered over the valleys, and a long distance from the mountains. The southern hemisphere, in proportion to the extent of its land surface, shows ample traces of former ice action. From the latitude of 38° south to the southern extremity of the western continent there is said to be the clearest evidence of former glacial action in numerous bowlders scattered over the land.