A pound of water thus vaporized at the equator has absorbed one thousand times the quantity of heat which [1. "The Great Ice Age," p. 98.] {p. 60} would raise a pound of the liquid one degree in temperature. . . . It is perfectly manifest that by weakening the sun's action, either through a defect of emission or by the steeping of the entire solar system in space of a low temperature, _we should be cutting off the glaciers at their source_."[1] Mr. Croll says: "Heat, to produce _evaporation_, is just as essential to the accumulation of snow and ice as cold to produce condensation."[2] Sir John Lubbock says: "Paradoxical as it may appear, the primary cause of the Glacial epoch may be, after all, _an elevation of the temperature in the tropics_, causing a greater amount of evaporation in the equatorial regions, and consequently a greater supply of the raw material of snow in the temperate regions during the winter months."[3] So necessary did it appear that heat must have come from some source to vaporize all this vast quantity of water, that one gentleman, Professor Frankland,[4] suggested that the ocean must have been rendered hot by the internal fires of the earth, and thus the water was sent up in clouds to fall in ice and snow; but Sir John Lubbock disposes of this theory by showing that the fauna of the seas during the Glacial period possessed an Arctic character. We can not conceive of Greenland shells and fish and animals thriving in an ocean nearly at the boiling-point. A writer in "The Popular Science Monthly"[5] says: "These evidences of vast accumulations of ice and snow on the borders of the Atlantic have led some theorists [1. "Heat considered as a Mode of Motion," p. 192. 2. "Climate and Time," p. 74. 3. "Prehistoric Times," p. 401. 4. "Philosophical Magazine," 1864, p. 328. 5. July, 1876, p. 288.] {p. 61} to suppose that the Ice period was attended, if not in part caused, by a far more abundant evaporation from the surface of the Atlantic than takes place at present; and it has even been conjectured that submarine volcanoes in the tropics might have loaded the atmosphere with an unusual amount of moisture. This speculation seems to me, however, both improbable and superfluous; improbable, because no traces of any such cataclysm have been discovered, and it is more than doubtful whether the generation of steam in the tropics, however large the quantity, would produce glaciation of the polar regions. The ascent of steam and heated air loaded with vapor to the altitude of refrigeration would, as it seems to me, result in the rapid radiation of the heat into space, and the local precipitation of unusual quantities of rain; and the effect of such a catastrophe would be slowly propagated and feebly felt in the Arctic and Antarctic regions.