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tion of the principal star in a direction nearly north and south. Professor Young, of Dartmouth College, was requested to examine it with his splendid refractor, and reported that he suspected that it was double, but could not be certain. During the summer of 1874, Mr. Burnham with his sixinch telescope, Mr. Newcomb with his great twenty-six-inch refractor at Washington, and Baron Dembowski, at Florence, with a nine-inch telescope, all nearly simultaneously were able to see that the principal star was double, and to measure the relative positions. We have, therefore, in this case a star which to the naked eye appears of the fourth magnitude, resolved by fine telescopes and sharp eyes into four stars, of the fourth, sixth, seventh, and eighth magnitudes respectively. The last-named and most distinguished observer of double stars says that “this is one of the finest multiple stars known.” There are others of the same kind, but none presenting the same striking assemblage of brilliant objects within such narrow bounds.-Burnham on Nu Scorpii.

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HERSCHIEL'S CATALOGUE OF DOUBLE STARS. It is well known to astronomers that Sir John Herschel in his later years engaged himself in collecting, arranging, and revising the previous literary and scientific labors of his life. His general catalogue of all nebulæ discovered up to 1863 was published in the Transactions of the Royal Society of London for the following year. His arrangement of all the double stars observed by his father, Sir William Herschel, was published by the Royal Astronomical Society. The last great work undertaken by him was that of collecting in one catalogue all the trustworthy observations of multiple and double stars which had been recorded up to the date of the undertaking. This catalogue, containing over 10,000 stars, together with a synoptical history of all the known observations of about two fifths of them, was completed at the time of the death of Sir John Herschel. It was bequeathed to the Royal Astronomical Society, at whose expense it has been recently published. This important work will be welcomed heartily by those astronomers and amateurs interested in double-star observations. It unfortunately does not contain any indication of the magnitudes and distances of the double stars of which it treats, but, by giving the positions in right ascension and north polar distance of every known double star, it becomes a valuable aid to those who may be searching for new ones, or to those who wish to add to our present knowledge of these interesting subjects of observation. Mem, of Roy. Astr. Soc., XL.

ORBIT OF A DOUBLE STAR.

The double star, 70, Ophiuchi, which consists of a bright yellow star of the 4; magnitude, and a rose-colored star of the sixth magnitude, was first observed by Sir William Herschel in 1779, and has since formed a favorite subject of observation for observers in both hemispheres. Some computations based on these observations have lately been made by Flammarion, in order to determine the apparent orbit and, if possible, the true orbit of this sidereal system. Flammarion's results are practically identical with those of Klinkerfues, as deduced a number of years ago. Flammarion, assuming the parallax as determined by Krüger, concludes the distance of these stars from the earth to be 1,400,000 times that of the sun, and the actual distance of the two stars from each other to be somewhat less than the distance of Neptune from the sun. The relative movement of the stars is, according to Klein, 1.65 that of Neptune and the sun. The two stars have, however, a common movement through space, which is three and a half times as great as their orbital velocities about each other.—19 C, VIII., 46. THE ORBIT OF THE DOUBLE STAR

MU BOOTIS.” Among the theses published by the University of Kasan, in Russia, is an investigation into the orbit of the double star Mu Bootis, by Venogradski. Observations of this star have been made since 1782, when it was first observed by the elder Herschel; and its orbit has been investigated once previously by Wilson, but the computations of Venogradski take precedence, inasmuch as he has had access to very accurate and long-continued observations of Otto Struve and Dembowski. During the past ninety years the smaller star has described nearly one half of its orbit about the larger one; and the mutual distance has diminished from one and a half seconds to less than half a second. According to the present computation, the periodic time of these stars is about

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one hundred and eighty-two years; the inclination of the orbit being 47.5 degrees, and its eccentricity 0.5. The probable errors of the measurements of the distance of the stars is scarcely one tenth of a second. According to the ephemeris published at the conclusion of the work of Venogradski, the relative movement of these stars is at present at its maximum.-Journal of the Imperial University at Kasan, XLI., 311.

SPECTRA OF THE FAINT STARS.

Vogel states that for some time past he has been almost exclusively occupied with the spectroscopic investigation of faint stars. Among these are some that are distinguished by having spectra which are sharply defined at the violet side, but on the red side are broken up into gradually diminishing bands. These are generally red stars. By a somewhat careful study of these spectra it seems to him undoubted that their discontinuity is only apparent, being brought about by dark bands of absorption, which, as we must assume, are the consequence of the absorption of the rays of light by the atmospheres surrounding these stars. The only rational classification of star spectra is, according to him, into the following three classes: 1. Stars whose temperature is such that the metallic vapors contained in their atmospheres can exert only a very slight absorptive effect. 2. Stars whose atmospheres, as in the case of our sun, are distinguished by powerful absorption due to vaporized metals. 3. Stars whose temperature is so lowered that the materials which compose their atmospheres can combine together. In the latter class Vogel embraces both the third and fourth types of spectra established by Secchi.— Astronom. Nachrichten, LXXXIV.,

115.

ON THE SCINTILLATION OF THE STARS. Montigny has lately presented to the Royal Academy of Brussels a continuation of his researches on the scintillation of the stars. In this work he has studied not only the number of bands in the spectra of the stars, but also their growth, and especially the obscurity of the lines and zones which characterize the bands. Making use of the obserrations of Secchi, he thinks he has been able to show with considerable exactness the connection between the frequency of the scintillations and the characters of the spectra, having regard especially to the four types that have been proposed by Secchi. The comparison of bis own and Secchi's observations leads him to the conclusion that the stars which have been chosen as showing spectra typical of the first and second classes are also those which have the most frequent scintillations. The typical stars of the fourth class of spectra are those whose scintillation is the most feeble. Those stars of the first class which scintillate less than the typical stars are in general distinguished by having less numerous spectral lines. These conclusions he subsequently finds con-. firmed by the observations of Huggins and Miller. His essay concludes by a calculation of the actual differences between the lengths of the routes through the air of the components of the light of any star, and this leads him to a formula which is applicable to the calculation of the relative frequency of the scintillations of various stars at different zenith distances.--Bull, Roy. Acad. of Belgium, 1874, 300.

THE STRUCTURE OF SOLAR SPOTS,

The study of the solar spots has very wisely been made a matter of especial attention at the observatory of Allegheny City, Pennsylvania, and Professor Langley, the director of that institution, has the credit of having published the finest photographs and engravings that have ever yet illustrated the subject. From the very cautious wording of a recent communication from him, we gather that among the typical characteristics of the solar phenomena he has observed the following new points: 1. The filaments both of the penumbra and of the umbra are all disposed in curves, which partake of the spiral type, bearing witness to the existence of a force directed toward the centre of the spot; but it does not appear that a uniform direction of rotation prevails, since some of the filaments turn to the one, and some to the other direction, while some have a distinct double curvature. 2. The filaments grow progressively brighter toward their extremities, no matter whether they are long enough to reach from the photosphere to the edge of the penumbra, or whether they are shorter than this. 3. He finds the blackest part of the spot to be intrinsically very bright, and its reddish-brown

masses are by his telescope resolved into filaments analogous to the penumbral ones, being disposed in curves, and having brighter extremities, as if their ends curled upward. Lang. ley sees no evidence of crystalline forms, but judges rather that we seem to look down through increasing depths of transparent whirling vapor, visible objects growing fainter till lost to sight at an unknown depth below the surface. The striking forms seen in the solar atmosphere are, he thinks, most nearly typified by certain rare types of cirrus clouds in our own atmosphere. In very many spots Mr. Langley recognizes the movement of one stratum of solar atmosphere over another.—4 D, IX., 192.

AGREEMENT OF SECCHI'S VIEWS WITII PROFESSOR LANGLEY's.

The very beautiful solar drawings published in the American and Italian journals by Professor Langley, of Allegheny City, together with the announcement of the conclusions reached by him from his study of the solar spots, has called forth some remarks by Secchi, of Rome, in which the latter seems to claim a certain amount of priority in respect to the ideas of Langley, and to maintain that they agree with each other to a very considerable extent. This, however, can only be true in case Secchi relinquishes certain of his long-held theories, and it is, therefore, important to put on record his conversion to the views of Professor Langley.

WHITE LINES IN THE SOLAR SPECTRUM. Mr. Hennessy writes, from Massorie, to Professor Stokes, that he has observed in the solar spectrum certain white lines for whose existence he is unable to account. He can not think that these are due either to the instrument or to the latitude of the station. The white lines in question can not be described as absolutely white, yet they closely resemble threads of white frosted silk held in the sunlight. They are best seen about noon.—7 A, XLVIII., 305.

PHOTOGRAPHS OF STELLAR SPECTRA. Mr. Lockyer, in a recent lecture on spectrum photography, gives great prominence to the admirable labors of Messi's. Rutherford and Draper in New York City, stating that the latter gentleman has not only taken the most perfect photo

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