"Its gravity is only three-eighths of the earth's gravity, thus everything upon Mars would weigh proportionately lighter than on the earth, and the amount of labour required to do such work as digging or lifting would be lessened. There would, for the same reason, be greater ease of movement in walking, jumping, or running, and large bulky animals like our elephants could move with almost the same ease and freedom as our goats. "Theoretically, we should expect to find the atmosphere upon Mars very much thinner than our atmosphere, and actual observation proves this to be the case. We are able to see details on the surface of Mars with very much greater distinctness than would be the case if its atmosphere were as dense as ours. Moreover, clouds are comparatively rarely seen; and the majority that are observed present more the appearance of clouds of sand than rain clouds. Usually, also, they float very much higher above the planet's surface than our clouds are above the earth's surface; ten miles high is quite an ordinary altitude, and some have been estimated as quite thirty miles above the planet. "Many theorists have attempted to prove that, owing to the planet's distance from the sun, and the thinness of its atmosphere, the temperature of Mars must be very low, probably below freezing-point even at the equator. Dr. Alfred Russel Wallace has gone further than this, and suggests that the temperature must be eighty degrees Centigrade below freezing-point; that there is no water or water vapour on the planet; and that it is quite impossible for life to exist there! "However, as the result of delicate bolometric experiments, careful calculations, and consideration of conditions affecting the result which have not previously received so much attention, Professor Very has arrived at a different opinion; and actual observation has shown that there is very little indication of frost outside the frigid zones. Even in the polar regions it is at times evidently warmer than at the earth's poles, because during the spring and summer the snow-caps upon Mars not only melt more rapidly, but melt to a much greater extent than our polar caps do. In 1894 the southern polar snow-cap of Mars was observed almost continuously during the melting period, and it was actually observed to dwindle and dwindle until it had entirely disappeared. It is rather strange to think that we know more about the snow-caps of that far-distant world than we do about those on our own earth. "Owing to the lesser gravity on Mars the snow and ice which forms the caps would certainly be lighter and less closely compacted than the snow and ice upon our earth; but it is quite clear that it could not melt to any extent unless the temperature remained above freezing-point for a considerable length of time.