Mars

Fourth planet in order of distance from the sun, 141,500,000 m.; diameter 4,230 m.; ma .107 that of the earth; period of revolution about sun 686.95 days; time of revolution about axis 24h. 37m. 22.72s. There are two satellites, Phobos and Deimos, discovered by Hall at Washington 1877. At opposition Mars may approach the earth within 35,500,000 m. The conditions for telescopic examination of the surface are then especially favorable. The planet appears to resemble the earth in many important respects; the inclination of the equator to the plane of the orbit, 24° 50', is nearly the same as that of the earth, producing a similar succe ion of seasons. There is an atmosphere of considerable extent. The markings on the surface are of four kinds; (a) bright spots about the poles, believed to be snow and ice; (b) dark greenish patches of irregular outline, supposed to be water; (c) bright portions, probably land; (d) long thin lines, running sometimes for great distances in directions nearly straight, first seen by Schiaparelli 1877. The latter are called canals, although the explanation of their true nature has puzzled astronomers not a little. They are generally a umed to be water-courses. They seem to be unlike anything on the earth, especially if it be true, as stated by a number of observers, that many of them are double. There is not the slightest reason for supposing them to be artificial. IMG:content-1258.png:[blocks in formation] 1849-53, and to Italy from 1861; author of Lectures on the English Language , 1861, its Origin and History , 1862, and Man and Nature , 1864-74.