termined relatively to the sun. . . . In the brief time allotted it was not practicable to change the eye-piece and observe the star in question under a higher power. Its light was quite red, and, so far as my recollection of its appearance in the telescope will enable me to determine, I am of the opinion that it was situated beyond the sun. "In regard to the star B, which I consider to be the planet sought, there is no uncertainty whatever, beyond the unavoidable errors of the record as made. I consider the place given to be trustworthy.... I have further observations of contacts, and also some sketches of the corona made by members of my party, which I will send you in due season. Meanwhile, I doubt not that you will agree with me that the observations above detailed establish the existence of one new star in the vicinity of the sun, and point possibly to the existence of two." Professor Watson is now inclined to believe that both of the new objects seen by him are planets. Mr. Swift's observations were made at Denver. He says: "About one minute after totality I observed two stars, by estimation three degrees south west of the sun, pointing towards the sun, of about the fifth magnitude, or what I estimated at the time, as bright through the telescope as Polaris is to the naked eye. How much allowance ought to be made in estimating magnitudes so close to a totally eclipsed sun I do not know. I saw them three times, and attempted, at the last moment, to get another observation; but at the critical moment a little cloud passed over the sun, and I hastened to observe again the sun for the third contact and attending phenomena. At each of the observations, by careful comparison, they appeared exactly of the same magnitude, and both as red as Mars. I looked closely for twinkling, but they were as free from it as the planet Saturn. They both, at the time, seemed to my eye and mind to have a small round disk about like the planet Uranus. Whether the disks were imaginary or real I cannot tell, but every time I saw them (the stars) the disks attracted my attention." Professor Pliny E. Chase writes to the Smithsonian Institution that "Gaillot's orbit for Watson's second intra-Mercurial planet represents his tenth subsidence-node [ Jupiter (2n-1)], and gives the ninth verification to his harmonic prediction. Gaillot 0.1803; Chase 0.1826." THE PLANETS AND SATELLITES. Mercury. The principal observations of Mercury are spoken of under the heading Transits of Mercury. Venus.-M. Boutigny has called the attention of the French Academy to the fact that Varro (31 B.C.) spoke of changes in the diameter, color, figure, and path of Venus. The passage referred to is quoted in a work of St. Augustine. Venus has been observed during the last year with the 26inch Washington equatorial. No markings on the disk were seen, but the illumination of the dark hemisphere was frequently noted by several observers. Mars. From the recent discussion by Professor Hall of his observations of the satellites of Mars, we extract the following: "The planes of the orbits of both satellites are very nearly coincident with the equator of Mars. The elements of these orbits are determined with tolerable accuracy, excepting the periodic times, for an accurate determination of which we must wait until the satellites have been observed in another opposition. The times that have now been found will serve to carry forward an ephemeris to 1879. In the orbit of Deimos, the value of the eccentricity being small, the position of the line of apsides is of course uncertain. This eccentricity is so small that circular elements of this satellite may be considered as sufficient for the observations. In the case of Phobos, the eccentricity of its orbit has, I think, a real existence. It will be noticed that in the comparison of the observations of Phobos with the assumed circular elements, every comparison of distance confirms the existence of an eccentricity. It is true that the observations of this satellite were always difficult on account of its closeness to the planet, and also because of the brightness of the planet; and it may be suspected that some systematic error has influenced the result. Such an error would indeed have more influence on the eccentricity of the orbit of the inner satellite than on that of the outer one. But the resulting eccentricity is too large, I think, to be explained in this manner, and I conclude that the orbit of Phobos is really eccentric." The mass of Mars can be determined from the motion of these satellites. "Expressing the mass of the planet in the common unit, we have, from the above values of the elements, the following results: "These results agree so nearly within the limits of their probable errors that I have taken the mean by weights as the final result from the Washington observations. In this way we have The recent report of Professor Pickering, Director of Harvard College Observatory, states that it has been decided to devote the large refractor chiefly to photometry. In this way a field is taken up which has too long been unoccupied. Besides a great number of photometric observations on double stars, asteroids, and satellites of the outer planets, the satellites of Mars have been studied. Assuming the albedo, or intrinsic reflecting power of these bodies, to be the same as that of Mars, it is concluded that the diameters are for Deimos (outer satellite) about 6 miles, and for Phobos (inner) about 6.5 miles. Following are some previous values of the mass of Mars which are interesting for comparison with Professor Hall's results: Laplace assumed the mass of Mars to be 1848082 Delambre reduced this estimate to 20 Burckhardt, 543 in 1816, diminished this still further to 680337. By Hansen and Olufsen, of Sweden, in their solar tables, the estimate is 2000. Leverrier got 94790. The spectrum of Mars has been photographed by Dr. Huggins. Professor Hall, of Washington, made, during the last opposition of Mars, a large number of measures (thirty-two nights) of the position of the south polar spot of Mars. From all of these he finds for the angle of position of this spot for 1877, September 17.0 G. M. T., 166° 22', and for the same epoch the radius of the small circle described by the spot is 5° 11'. The various determinations of the south polar dis tance of the spot are: Herschel (1783), 8° 8'; Bessel (1830), 8° 6'; Mädler (1837), 12° 0'; Secchi (1857), 17° 42'; Linsser (1862), 20° 0'; Kaiser (1862), 4° 16'; Hall (1877), 5° 11'. A similar work has been done by Professor Schiaparelli at Milan, and he finds for 1877, September 27.0, 26° 15', Hall's result for this epoch being 5° 18'. Professor Hall's observations were of the angle of position of the spot, while Schiaparelli made his own by placing the micrometer wire tangent to the limb of the planet at the middle of the spot. A series of the same kind (as yet unpublished) was made at the Dudley Observatory by Professor Boss. Jupiter. The conclusions of Mr. Neison upon the atmosphere of Jupiter are that it may be regarded as certain that it is physically impossible for Jupiter to have an atmosphere of great depth, unless the temperature of the planet be supposed to be many million times hotter than a white heat, or unless the atmosphere is constituted of some substance unknown to us, and widely different from substances familiar to us. Saturn. In the Astronomische Nachrichten, Mr. Marth continues his very complete ephemeris of the five inner satellites of Saturn. He notes the desirability of observations of the conjunctions of Mimas with the ends of the ring, but has overlooked the fact that no satisfactory observations of these phenomena have ever been made. From his own observations at Malta, and the experience at Washington, it is even doubtful if they ever can be made. It may be worth while to note in this place the times of sidereal revolution of the five inner satellites adopted by Marth. They are, Mimas, 0 d. 22 h. 37 m. 8.26 s.; Enceladus, 1 d. 8 h. 53 m. 6.86 s.; Tethys, 1 d. 21 h. 18 m. 25.96 s.; Dione, 2 d. 17 h. 41 m. 9.33 s.; Rhea, 4 d. 12 h. 25 m. 11.87 s. M. Tisserand continues in the Comptes Rendus his researches on the system of Saturn, and has published the motions of the perisaturnium of each of the five inner satellites. For Mimas this motion is 349° per annum. Tisserand further shows how the mass of the ring itself may be determined, as well as the oblateness of the ball. For this, continued observations of Mimas and Titan are necessary. "The appearance of the ring of Saturn was carefully observed at Washington during the whole opposition, and it was followed until February 11, 1878. The disappearance of the ring occurred about February 6. tion of the major axis of the ring was observed on thirty-six nights by Professor Hall, and on twenty-two nights by Professor Holden. Although at the time of the disappearance of the ring the planet was too near the sun for good observations, yet the whole of these observations indicate that Bessel's elements of the ring are very nearly correct." Professor Hall, of Washington, has an investigation of the outline of the shadow of a planet projected on any plane-first, for the case where the luminous and opaque bodies are both spherical; and, second, where the opaque body is supposed to be an ellipsoid of revolution. The conclusion is that, even in the case of Saturn, which has the most eccentric figure of any of the planets, the outline of the geometric shadow on the plane of the ring is sensibly a right line. The apparent convexity of the bounding line of this shadow towards the centre of Saturn has then to be explained from conditions other than geometrical. M. Souillart, known by his researches on the theory of Jupiter's satellites, has a paper in the Astronomische Nachrichten on the shape of the shadow of a planet, and comes to essentially the same conclusions as previously given by Professor Hall in the same journal. M. Tisserand, of Toulouse, who has lately occupied himself with the system of Saturn, has an important note in Comptes Rendus on the nature of the ring. Laplace proved in 1787 that even if observation did not show that the ring of Saturn was composed of two or more concentric rings, the theory of gravitation would require this. Tisserand, as the result of the re-examination of the problem, comes to the conclusion that a continuous ring of the dimensions of the real ring cannot exist in equilibrium. Hence it is divided. In fact, the ring of Saturn has been seen (by Bond, De la Rue, Dawes, etc.) divided into numerous fine concentric rings, just as this condition requires. Uranus and Neptune.-The satellites of these planets are followed at the Naval Observatory, Washington. B 2 |