The moons of Mars are among the most curious finds of modern astronomy. When the ingenious Dr. Jonathan Swift, in editing the travels of Mr. Lemuel Gulliver, of Wapping, wrote that the astronomers of Laputa had discovered 'two lesser stars, or satellites, which revolve about Mars,' the suggestion was, no doubt, put in merely because some detail of their skill had to be given, and as well one unlikely thing as another. Probably no one would have been more surprised than the Dean of St. Patrick's, had he lived long enough, or cared sixpence about the matter, to hear that his bow drawn at a venture had hit the mark, and that Professor Asaph Hall had detected two satellites of Mars. The discovery was one of the first-fruits of the 26-inch Washington refractor, and was made in 1877, the year from which the new interest in Mars may be said to date. The two moons have been called Deimos and Phobos, or Fear and Panic, and are, in all probability, among the very tiniest bodies of our system, as their diameter can scarcely be greater than ten miles. Deimos revolves in an orbit which takes him thirty hours eighteen minutes to complete, at a distance of 14,600 miles from the centre of Mars. Phobos is much nearer the planet, his distance from its centre being 5,800, while from its surface he is distant only 3,700 miles. In consequence of this nearness, he can never be seen by an observer on Mars from any latitude higher than 69°, the bulge of the globe permanently shutting him out from view. His period of revolution is only seven hours thirty-nine minutes, so that to the Martian inhabitants, if there are any, the nearer of the planet's moons must appear to rise in the west and set in the east. By the combination of its own revolution and the opposite rotation of Mars it will take about eleven hours to cross the heavens; and during that period it will go through all its phases and half through a second display.