ASTRONOMY. 41 



of the ninth magnitude, or brighter, belonging to the northern hemi- 

 sphere ; secondly, in observing the stars contained in a list drawn 

 up to facilitate astronomical work of various kinds ; thirdly, in ob- 

 serving Mars during the period of its opposition, with suitable com- 

 parison stars, and also some comparison stars for use by Mr. D. Gill 

 in his observations of asteroids at Ascension Island. 



Meteorological observations have been regularly made. 



Special observations for clock-error are regularly made, to main- 

 tain the accuracy of the clock-signals transmitted to various points 

 in this part of the country, for the purpose of supplying the com- 

 munity with a trustworthy standard of time. 



Fourth. The work of the coming year will be a continuation of 

 that just described, with the exception of the observations connected 

 with the recent opposition of Mars. The stars of a list drawn up 

 by the Coast Survey will also be observed at the request of that 

 institution. 



Fifth. The eighth volume of the Annals of the observatory was pub- 

 lished in November, 1876 ; the tenth volume in the spring of 1877. 



L. Trouvelot's Physical Observatory, Cambridge, Mass. 



Observer, L. Trouvelot, occasionally assisted by Geo. H. Trouvelot. 



Principal Instruments. 1st. Equatorial Refractor, by Merz, 6 inches 

 aperture, 8^- feet focal length. 



2d. Rutherford's Diffraction-plate Spectroscope, by Alvan Clark 

 axd Sons. 



3d. Apparatus for Photographing the Sun-spots. 



The observatory was built early in 1875, and observations begun 

 March 15 of the same year. 



During the years 1875, 1870, and 1877, close attention was given 

 to the Sun, Moon, Planets, Clusters, Nebula?, Double Stars, Meteors, 

 Zodiacal Light, and the Auroral phenomena. From March 15, 1875, 

 to November 30, 1877, the following observations w T ere made : 



Total of observations, 2159 ; drawings, 571 ; of diagrams, 121 



