ASTRONOMICAL PROGRESS IX 1896. 



like the others, rotates on an axis. Considering the 

 dilliculties of the undertaking, the close agreement 

 of the observations made by Prof. C. A. Young, of 

 Princeton, with the 23-inch refractor with those of 

 Dr. Barnard is somewhat remarkable. Following 

 are the comparisons : 



Polar. 

 3-1I4I1" 

 3-930" 



4-150" 



Young. 

 Barnard. 



As is true of Jupiter and Saturn, the rotational 

 period of Uranus, computed from his spheroidity, 

 must be short. 



Double Stars. Few new double stars have been 

 discovered since the last writing ; but still this 

 work goes bravely on, and sets of measures have 

 been made, at different observatories, of over 

 1,500 of these interesting stars, the orbits of 50 

 binaries have been computed, and the distances 

 apart of their components calculated, as well as 

 their periodic times. That of shortest period, 

 Kappa Pegasi = Burnham 989, is 11'4 years, with 

 distance 0'42". Next is Delta Equulei = 11-5 years, 

 while the period of Mu Bootes is 219, and that of 

 Castor one thousand years. Several photo-spectro- 

 scopic doubles have periods a thousand times shorter 

 than that of Kappa Pegasi. Dr. T. J. J. See has com- 

 puted new elements of the orbit of Burnham 416, 

 the place of which for 1900'0 is right ascension 17 h 

 12-l m ; declination south, 34 52'. It is a rapid 

 binary whose period he gives as 33-0 years. Between 

 the years 1896'5 and 1900-5 the orbital motion will 

 have amounted to 29. Their distance at the first 

 epoch was T43", and at the last it will be 1'72". Dr. 

 See, in his study of 70 Ophiuchi, has found, to his 

 great surprise, that the angle of position was 4 in 

 advance of the theoretical place, as compared with 

 Schur's ephemeris, which, though it was made with 

 extreme care, he (Dr. See) deemed necessary to re- 

 vise. After rigid comparison with the observations 

 of others, he found irregularity not only in angular 

 motion but also in distance, and, moreover, that 

 these irregularities were periodic, and so demanded 

 special investigation. The duplicity of this star 

 was ascertained by Sir William Herschel in 1779, 

 since which time the companion has achieved one 

 complete revolution and made considerable advance 

 on a second one. Much study has been bestowed 

 on this star, and many orbits have been computed 

 for it, which, in turn, have needed revision. The 

 companion has departed from every orbit hereto- 

 fore obtained. Dr. See's opinion is that this star, 

 70 Ophiuchi like Beta Auriga, and Zeta Ursa 

 Majoris is a triple star, the nearer component 

 being either too close to its primary to be optically 

 visible or, like the companion of Algol, a dark 

 though massive star. He finds unmistakable evi- 

 dence of retardation of motion of the companion 

 near apastron, though recently this has changed to 

 acceleration, and until this disturbing element is 

 ascertained no satisfactory orbit is possible. Prof. 

 Schur, in 1868, from 400 mean observations of 

 position angle, naturally concluded that the orbit 

 deduced by him would give for many years, if not 

 indefinitely, good places of the visible companion ; 

 yet the error in position angle already amounts to 

 5 degrees. Dr. See thinks that the unseen body 

 moves retrograde, in a sinuous curve about the 

 common center of gravity of the system, in nearly 

 forty years. The period of the visible components 

 seems to be between ninety and one hundred years. 

 He assumes the present position angle of the dark 

 star to be about 330. His interesting paper on this 

 binary may be found in the " Astronomical Jour- 

 nal " of Jan. 9, 1896. In the same publication of 

 June 29, 1896, Dr. See gives the results of his re- 

 searches on the orbits of 40 binary stars. 



Variable Stars. The interest in the quest for 

 variable stars shows no abatement, though but few 

 astronomers make a specialty of their discovery. 

 The number of stars now known to vary in bright- 

 ness is more than 8,500, and the list has so extended 

 as to suggest the idea that all the stars may, within 

 small limits, vary in brightness. The tabulation 

 and revision, the ascertainment of their periods and 

 their inequalities, has been a laborious task. A 

 very remarkable feature of these changeful stars 

 is the frequency with which they are found in star 

 clusters. 



In the Harvard College Circular, No. 2, Prof. 

 Pickering announces that Prof. Solon J. Bailey has 

 discovered, from examination of photographs ob- 

 tained by him of certain globular clusters, an ex- 

 traordinary number of variable stars. In the cluster 

 in the Hunting Dogs, Messier 3 (General Catalogue, 

 3636), 87 stars, from an examination of 15 photo- 

 graphic plates, were found variable. Attention is 

 called to the fact that a few of these variables have 

 short periods, of a half day or less. 



In No. 3 Prof. Bailey omits 14 suspected of vari- 

 ability which is not yet proved. For more particular 

 information on this subject, the reader is referred 

 to " Astronomische Nachrichten," Xos. 2986, 3223, 

 3321 and 3354. 



The Harvard College Circular, No. 7, contains a 

 list of 10 new variables confirmed at that observa- 

 tury by study of photographic plates. Changes in 

 the light of Col. Markwich's star in Sagittarius 

 is shown by 89 plates. A large number of observa- 

 tions have been made with the meridian photometer 

 to determine the light curve of stars of the Algol 

 type. S. Antlias has been regarded hitherto as be- 

 longing to this class, and is of interest from the 

 shortness of its period = 7 h 46'8 m , and, since it re- 

 tains its full brightness for less than half its time, 

 it is difficult to accept the hypothesis that the varia- 

 tion is caused by a dark eclipsing body. After 

 much study and many observations, it is thought 

 that this star is not of the Algol class, but, rather, like 

 Delta Cephei and Eta Aquilaj, belongs to the family 

 of variables of short period. Observations of Beta 

 Lynp show that two or more bodies are revolving 

 about each other. 



At this maximum much attention has been given 

 to Omicron Ceti (Mira) to ascertain, if possible, the 

 cause of the fitful fluctuations observed at the last 

 maximum of this wonderful variable. While its 

 light has alternately steadily increased and de- 

 creased, yet its maximum seemed not to have been 

 attained until sixty days after it was due, and its 

 brightness was 1*5 to 2 magnitudes less than usual. 

 These changes of light not only in many of the 

 variables, but also in their periods, raises a doubt 

 as to the correctness of our accepted theories re- 

 garding them, and leads us to wonder if radical 

 change is not necessary. 



That the periodic mutations of the light of Algol 

 are due to being eclipsed by a dark star, is doubtless 

 true ; but this theory seems hardly adequate to ac- 

 count for all the fluctuations of the majority of 

 variables. As a single instance of many that might 

 be cited, let us take Eta of the southern constella- 

 tion Argo. In 1677 it was of the" fourth magnitude ; 

 in 1751 it was of the second; in 1811 it was again 

 of the fourth ; and in 1837 and the seven years 

 subsequent it ranked as of first magnitude, out- 

 shining every star in the heavens save the dog star. 

 In 1859 it had faded to the third magnitude, and, 

 decreasing almost uniformly, in 1867 it had shrunk 

 to the sixth, while three years later it was invisible 

 to the naked eye. Its minimum was reached in 

 1886, when it was of the 7'6 magnitude. It is now 

 very slowly growing brighter. In thirty years this 

 wonderful star assumed seven different magnitudes ; 



