Litchfield enquirer., 1878-10-24
THE SATELLITES OF MARS.

| One of the most interesting astronomical publications of the present. century-fruitful as it has been in books of this kind-has just
 been issued from the government printing office at Washington. The Observations and Orbits of the Satellites of Mars, i" in forty-six quarto
 pages, by Professor Asaph Hall, contains the account of his discovery of these little bodies, the observations of them by himself and by all others who were SO fortunate as to possess telescopes of sufficient power to show them, the times of their revolutions, their distances from the planet, and estimates of their mag nitude. In fact the book contains all the in- formation concerning these wonderful mem-
 bers of our solar system that can be had until the fiery planet again whirls into position for further observations, which will occur in Nov enber, 1879. At that time Mars will not be SO near the Earth as it was in August, 1877, but it's altitude, or distance from the horizon,
 will be considerably greater; circumstance which will probably quite balance it's greater distance from us, by afording better and more easy vision. 9s
 The last favorable opposition of Mars, previ- | ous to 1877, was in 1862. At that time, as the event has shown, there were several telescopes in existence capable of reaching the satellites, and of making famous those who had them in charge but as the idea had taken possession OI dSITOuOILcI6 tI1bG p1duCG lSt0 uO no search was made for them, so far as is known, except by one observer. This was D'Arrest, director at the time of the observa- tory of Copenhagen. He died in 1875 his re- cords showing that he had looked carefully for satellites, and failed to find any This search was generally accepted as ending the matter, and was almost enough to discourage Profes- sor Hall but remembering the power and ex- cellence of the Washington glass, there seemed to be a little hope left. Herschel, in 1783, had search for satellites round Mars, but, powerful as his telescopes were, none of them could reach the objects of his search, so min- nte have they proved to be.
 l Professor Hall began his search early in Au- gust, as soon as the planet had reached posi- l tion that would render the detection of a satel- lite easy. On the night of the 11th of August, l having gradually brought his search closer and closer to the brilliant disc of Mars at half-past | two o'clock he found faint object following the planet, which proved to be the outer moon. | He had hardly time to secure an observation when fog from the Potomac river stopped the work. Not until the 10th did pleasant weather return. We can imagine the anxiety with which he watched the clouds that for four nights consistently hung over the observatory, | refusing him the opportunity of solving the 1 problem that nasty look had presented. When | it cleared up the object was not seen but on the 18th it was found on the other side of the planet. This settled the question as to it's be- ing satellite. On the r, while waiting and watching for it's re-appearance, he discovered the inner moon. The observations of that and the following night put the character of both | beyond doubt, and their discovery was an- nounced by Admiral Rogers Still, for sever- al days, Professor Hall says, the inner satellite was puzzle. It would appear on bothsides of the planet during the same night, and at first | he thought there were two or three inner moons, since it seemed altogether improbable that satellite should revolve around it's | primary in less time than that in which the primary revolves upon it's axis. Further watch | ing, however, showed this to be really the case he found that the inner moon made its revolution around Mars in less than one-third of Martial day! Nothing like this is known | to exist in the solar system.
 Observations of the inner moon were con- tinued until October f5; and of the outer moon l until October 31. Sufficient data were obtain l ed for fixing with considerable accuracy the l times of their revolutions and their distances | from their primary.
 The outer moon revolves in thirty hours, l seventeen minutes and fifty-fOur seconds, at a distance from the centre of Mars of fourteen l thousand five hundred miles; the inner per- forms its revolution in seven hours, thirty nine | minutes and fifteen seconds, at a distance of only fifty-eight hundred miles from the centre of the planet On account of his rapid motion and it's nearness to the planet, the satellite will present very singular appearance to an inhabitant of Mars. A day with that planet has very nearly the same length as ours; so that while all other celestial bodies, including the outer satellite, will appear as they do tous, rising in the east and setting in the west, this inner moon will rise in the west and set in the east, twice in every Martial day-meeting and passing the outer moon, with 30 rapid amotion as to be easily seen and measured by the eye, like the minute-hand of an immense clock. In regard to the size of these objects Prof. l lessor Hall scarcely ventures an opinion, not going beyond the indefinite statement that they are very small. They are exceeding diff ficult to observe, and in nearly every telescope which showed them, the planet had to be hid behind a bar fixed in the eye-piece so as to re- lieve the eye from it's glare, before they could be seen. The only way in which their could be guessed at, was by making estimates of their brightness. In this many observations, were desirable, and Professor Hall has collect ed accounts from all who were able to see them. Besides the Washington observer, with the twenty-six inch glass made by Alvan Clark, the satellites were seen at Cambridge, by Mir. Leonard Waldo, with the fifteen-inch
 
 Struve, with glass of the same size and by the same maker, Merz of Berlin; at Glasgow, Missouri, by Professor Pritchett, with atwelve- and-a- quarter inch Clark glass at Hastings on the Hudson, by Dr. Draper, with his twelve inch Clark glass; at Eaton Rise, England, by Mir. A. Common, with an eighteen-inch silver ed glass reflector; at Sherrington, IraIepd, by Mir. Wentworth Erck, with a seven-ahd a half inch Clark glass (the smallest instrument which showed them); at Oxford, England, by Professor Prichard, with the telescope of the Oxford observatory. which is, believe, of ten inches aperture; at Greenwich, England, with the twelve-inch glass by Merz; at Paris, with the largest telescope in the observatory, about fifteen inches aperture; by Professor Watson of Ann Aarbor, Michigan, with the telescope of twelve-and-a half inches belong: ing to the University; at Chicago, by Mir. 5: w. Burnham, with the eighteen and -a-half inch Clark glass of the Dearborn observatory; at Albany, by Professor Boss, with the thir- teen-inch glass of the Dudley observatory; at Cambridge, by Alvan Clark, with a glass like that at Washington, and by Hartford observ- CT with at Clark telescope of nine and -one- third inches aperture. Thus it will be seen that while all the telescopes in the world were pointed at Mars, and eager eyes were gazing in each for glimpse of the little moons, con- siderably less than score. of the instruments were perfect enough to show them. Only one reflector accomplished the feat and of the re- tractors, it appears that nearly all the good observations were made by means of those that came from the hands of Alvan Clark.
 These. observers agreed pretty we'll that the light of each of the satellites was about equal to that of star of the eleventh or twelfth magnitude; and photometric determinations of their size give the result that the diameters are somewhere between six and fourteen miles. The inner one is undoubtedly the large, all the observers agreeing in this opinion but it is doubtful if either exceeds ten miles in diamet- CT! The discovery of a large number of aste- roids within a few years many of which must be as small as these satellites, prevents our very great surprise at learning how minute they are; but when we consider the brief peri ods of their revolution, especially that of the inner one, as most astonishing picture of celes- tial mechanics is presented to our view. We have noticed the singular apparent motion of