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We take from La Nature the annexed engraving of the planet Mars and its second satellite, as the same appeared through the great telescope at the observatory of Paris, at 10:15 P.M., on August 37 last. The first satellite moves around the planet in 15 hours, at an average distance of 9,000 miles; the second completes its course in thirty hours, and is distant about 15,000 miles. Both bodies are very small, and their observation requires powerful instruments. Judging, however, by its brilliancy, the diameter of the sec-1 ond satellite is estimated at only some 30 miles. Future observation of their motion will lead to the exact determination of the elements of their orbit, and will show whether the revolution is relatively direct, as in the case of the moons of Jupiter and Saturn, or relatively inverse, as in the case of the satellites of Uranus and Nep-tune. It will also lead to more exact data relative to the mass of Mars. In a former article on the dis covery of these bodies, we noted the fact that while most astronomers did not regard it even as probable that Mars might have satellites, others had admitted the possibility, and had predicated their admission on certain physical characteristics of the planet itself. Lea Momies has recently published an extract S from a work by Bron, a French astronomer, entitled "Celestial Physics," and printed in 1867. wherein the author says: "Mars is distinguished from the seven other planets by its satellite, which no one has ever seen, although it exists, because Mars has thrown out jets of burning matter, to which are due, first, its rotary movement, and, second, the existence of two recesses which appear to be movable spots. It appears, incontestably, that these spots are due I to light reflected in different degrees by the slopes of these recesses, which are constantly being differently exposed to I the sun and to the earth."
