20 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



normal direction of the curvature of the bounding-line of 

 the shadow, it being now convex towards the ball, instead 

 of concave. The abnormal figure of this shadow has often 

 been noticed, and is corroborated by many independent ob- 

 servers. In particular the drawing of the shadow by M. 

 Trouvelot, October, 1874, is undoubtedly correct, as other 

 drawings made at the same time by other observers give 

 the same appearance. 



Todd, of Washington, has prepared a continuation of 

 Damoiseau's tables of the satellites of Jupiter, which ex- 

 tends to 1900. This has been printed by the American 

 Ephemeris in a quarto of forty pages, and will be sent to 

 any astronomer having a copy of Damoiseau. The errata 

 in Damoiseau's tables found by Hind, Kendall, and Todd, 

 respectively occupy nearly throe quarto pages. The British 

 Nautical Almanac for 1881 contains tables with a similar 

 object by Professor J. C. Adams. 



An outer satellite of Mars was observed by Professor 

 Asaph Hall, U.S.N., at the United States Naval Observa- 

 tory, on the night of the 11th of August, 1877. Cloudy 

 weather prevented the certain recognition of its true char- 

 acter at that time. On August 16 it was again observed, 

 and its motion was established by observation extending 

 through an interval of two hours, during which the planet 

 moved over thirty seconds of arc. 



An inner satellite was first observed on the night of 

 August 17, also by Professor Hall. Both were discovered 

 with the 26-inch telescope made by Alvan Clark and Sons. 



On Saturday, August 19, the discoveries were telegraphed 

 to Alvan Clark and Sons, Cambridgeport, Massachusetts, in 

 order that, if the weather should be cloudy at Washington, 

 they might confirm the existence of the satellites with the 

 2G-inch telescope of Mr. M'Cormick, which is in their hands. 



These discoveries were confirmed by Professor Pickering 

 and his assistants, at Cambridge, Massachusetts, with the 

 15-inch telescope, and by the Messrs. Clark, at Cambridge- 

 port, with a 12-inch glass. 



On August 19 the discoveries were communicated to the 

 Smithsonian Institution, by which they were announced to 

 the American and European observatories. The period of 

 the outer satellite is about 30 li. 18 m. ; of the inner,*? h. 35 m. 



