Until lately it was believed that Mars possessed no moons. Two very small ones have, however, been lately found circling round him.[2] They have been named Deimos and Phobos, after the “sons of Mars” in Greek mythology. Deimos travels round Mars in thirty-nine hours, while Phobos performs the same journey in the astonishingly short period of seven hours and a half! [2] The discovery of the two moons is due to the agency of a woman. Professor Asaph Hall, of Washington City, was searching by the aid of the most powerful telescope which had yet been directed to Mars, and at the very moment when the planet was in the most favorable condition for observation. Having searched in vain during several evenings in August, 1877, he was about to give up, when Mrs. Hall begged him to search a little more. He did so, and on the night of the 11th he discovered the first of the satellites, and then on the 17th the second. [Illustration: MARS AND THE PATH OF ITS SATELLITES.] We have here, then, a system very different from that of the earth and moon. But the most curious point is the rapidity with which the inner satellite of Mars revolves round its planet. This revolution is performed in seven hours, thirty-nine minutes, fifteen seconds, although the world of Mars rotates on itself in twenty-four hours, thirty-seven minutes--that is to say, this moon turns much more quickly than the planet itself. This fact is inconsistent with all the ideas we have had up to the present on the law of formation of the celestial bodies. Thus, while the sun appears to revolve in the Martian sky in a slow journey of more than twenty-four hours, the inner moon performs its entire revolution in a third of a day. It follows that _it rises in the west_ and _it sets in the east_! It passes the second moon, eclipses it from time to time, and goes through all its phases in eleven hours, each quarter not lasting even three hours. What a singular world!