Here we have unquestionably a very clear prophecy, a rare quality in this kind of writing. The astronomico-philosophical romance of “Micromégas” has been considered as an imitation of Gulliver. Let us open the masterpiece of Swift himself, composed about 1720, and we read, word for word, in Chapter III of the “Voyage to Laputa:” “Certain astronomers ... spend the greatest part of their lives in observing the celestial bodies, which they do by the assistance of glasses far excelling ours in goodness. For this advantage hath enabled them to extend the discoveries much farther than our astronomers in Europe; for they have made a catalogue of ten thousand fixed stars, whereas the largest of ours do not contain above one-third part of that number. They have likewise discovered two lesser stars, or satellites, which revolve about Mars, whereof the innermost is distant from the center of the primary planet exactly three of his diameters, and the outermost five. The former revolves in the space of ten hours, and the latter in twenty-one and a half; so that the squares of their periodical times are very near in the same proportion with the cubes of their distance from the center of Mars, which evidently shows them to be governed by the same law of gravitation that influences the other heavenly bodies.” What are we to think of this double prediction of the two satellites of Mars? Indeed, the prophecies which have been made so much of in certain doctrinal arguments have not always been as clear, nor the coincidences so striking. However, it is evident that no one had ever seen these satellites before 1877, and that there was in this hit merely the capricious work of chance. We may even remark that both the English and French authors have only spoken ironically against the mathematicians, and that in 1610, Kepler, on receiving the news of the discovery of the satellites of Jupiter, wrote to his friend Wachenfals that “not only the existence of these satellites appeared to him probable, but that doubtless there might yet be found two to Mars, six or eight to Saturn, and perhaps one to Venus and Mercury.” We can not, assuredly, help noticing that reasoning from analogy is here found on the right road. However this may be, this discovery truly constitutes one of the most interesting facts of contemporary astronomy. Mars is not only much smaller than the earth, but a good deal less dense in his “make.” His material is only about three-quarters as heavy as an equal amount of the earth’s material. A very heavy man on earth would be a most light and active individual on Mars. Gold taken from earth to Mars would weigh there no more than tin weighs upon earth.