Astronomy. 245 



leaving unexplained the origin of the variety, has long appeared 

 to the writer to account for much in the history of a variation 

 that is ordinarily attributed to outside conditions or natural 

 selection. J. 1). D. 



[V. Astronomy. 



1. Transactions of the Astronomical Observatory of Tate 

 University i Vol. I, Part II. — Dr. Asaph Hall, Jr., has spent the 

 larger part of four years 1 labor in the determination, by use of the 

 Vale heliometer, of the orbit of Titan and the mass of Saturn, 

 and in this publication are given his observations, and their 

 reduction. The work has been done under the general direction of 

 Dr. Elkin, who has charge of the instrument. There has been an 

 uncertainty of about jfo part in previous, determinations of 

 Saturn's mass, and the importance of this element in the theory 

 of the planets made it very desirable that there be a new determi- 

 nation. Dr. Hall finds the mass 1 3500-5^: 1*44, a result substan- 

 tially agreeing with that of H. Struve, and with that of Bessel 

 when the proper correction has been applied to Bessel's scale- 

 values. Prof. Hall, from observations with the Washington re- 

 fractor, had found by different methods four different values of the 

 mass, three of which were decidedly larger than the one found by 

 the Yale heliometer. 



•2. The Algol System. — Dr. Vogel, from his observations of 

 the motions of Algol in the line of sight, finds {Astron. JVachr., 

 No. 2947) that the star before the minimum has at quadrature a 

 velocity of + 5*3 miles (German) toward the earth, and after the 

 minimum a velocity of — 6-2 miles. This gives a mean motion 

 of the system — 0*5 miles, and an orbital motion of 5*7. Com- 

 bining these with the observed laws of change of brightness and 

 assuming that there are two bodies one brighter than the other 

 moving in circular orbits about their center of gravity, he offers, 

 the following provisional scheme of the system. 



Diameter of principal star = 230,000 miles (German). 



" companion star — 180,000 " " 



Distance of the centers =700,000 " " 



Orbital velocity of companion star = 12 " " 



Masses, (assuming equal density) = ^ and § of sun's mass. 



3. Hotation of Mercury. — Prof. Schiaparelli announces in 

 the Astronomische Nachrichten an interesting determination of the 

 period of rotation of Mercury. This planet he finds behaves 

 toward the sun as the moon does toward the earth, its periods of 

 rotation on its axis and revolution in its orbit about the sun being 

 equal to each other. 



OBITUARY. 



Chester Smith Lyman. — Prof. Lyman, Professor of Astron- 

 omy and Physics in the Sheffield Scientific School of Yale Uni- 

 versity, died on the 29th of January, at the age of seventy-six. 

 He was graduated at Yale College in 1837, and at the Theological 

 School of the University in 1840. His health failing and unfitting 



