Such, in very brief form, is the celebrated theory of Mars as an inhabited world. It certainly captivates the imagination, and if we believe it to represent the facts, we cannot but watch with the deepest sympathy this gallant struggle of an intellectual race to preserve its planet from the effects of advancing age and death. We may, indeed, wonder whether our own humanity, confronted by such a calamity, could be counted on to meet the emergency with equal stoutness of heart and inexhaustibleness of resource. Up to the present time we certainly have shown no capacity to confront Nature toe to toe, and to seize her by the shoulders and turn her round when she refuses to go our way. If we could get into wireless telephonic communication with the Martians we might learn from their own lips the secret of their more than “Roman recovery.” XIV The Riddle of the Asteroids Between the orbits of Mars and Jupiter revolves the most remarkable system of little bodies with which we are acquainted—the Asteroids, or Minor Planets. Some six hundred are now known, and they may actually number thousands. They form virtually a ring about the sun. The most striking general fact about them is that they occupy the place in the sky which should be occupied, according to Bode’s Law, by a single large planet. This fact, as we shall see, has led to the invention of one of the most extraordinary theories in astronomy—_viz.,_ that of the explosion of a world! Bode’s Law, so-called, is only an empiric formula, but until the discovery of Neptune it accorded so well with the distances of the planets that astronomers were disposed to look upon it as really representing some underlying principle of planetary distribution. They were puzzled by the absence of a planet in the space between Mars and Jupiter, where the “law” demanded that there should be one, and an association of astronomers was formed to search for it. There was a decided sensation when, in 1801, Piazzi, of Palermo, announced that he had found a little planet which apparently occupied the place in the system which belonged to the missing body. He named it Ceres, and it was the first of the Asteroids. The next year Olbers, of Bremen, while looking for Ceres with his telescope, stumbled upon another small planet which he named Pallas. Immediately he was inspired with the idea that these two planets were fragments of a larger one which had formerly occupied the vacant place in the planetary ranks, and he predicted that others would be found by searching in the neighborhood of the intersection of the orbits of the two already discovered. This bold prediction was brilliantly fulfilled by the finding of two more—Juno in 1804, and Vesta in 1807. Olbers would seem to have been led to the invention of his hypothesis of a planetary explosion by the faith which astronomers at that time had in Bode’s Law. They appear to have thought that several planets revolving in the gap where the “law”