Page:Is Mars habitable - Wallace 1907.djvu/17

 CHAPTER III. PAGE


 * No permanent water on Mars—Rarely any clouds and no rain—Snow-caps the only source of water—No mountains, hills, or valleys on Mars—Two-thirds of the surface a desert—Water from the snow-caps too scanty to supply the canals—Miss Clerke's views as to the water-supply—Description of some of the chief canals—Mr. Lowell on the purpose of the canals—Remarks on the same—Mr. Lowell on relation of canals to oases and snow-caps —Critical remarks on the same.

CHAPTER IV.


 * Water and air essential for animal life—Atmosphere of Mars assumed to be like ours—Blue tint near melting snow the only evidence of water—Fallacy of this argument—Dr. Johnstone Stoney's proof that water-vapour cannot exist on Mars—Spectroscope gives no evidence of water.

CHAPTER V.


 * Problem of terrestrial temperature—Ice under recent lava—Tropical oceans ice-cold at bottom—Earth's surface-heat all from the sun—Absolute zero of temperature—Complex problem of planetary temperatures