ASTRONOMY. 5 1 



the Coast Survey, a list of the bright stars whose places have not re- 

 cently been accurately determined ; and, thirdly, in the determination 

 of the observer's scale of magnitudes, by comparing the effects of 

 different apertures upon estimates of brightness. 



Time-signals are sent every two seconds to many places in Boston 

 and its vicinity. The time thus furnished is in use by the principal 

 railroads of New England, and by many important towns. A time- 

 ball is also dropped in Boston every day at noon by an electric sig- 

 nal from the Cambridge clock. 



Photographs of the transit of Mercury were taken in co-operation 

 with the U. S. Naval Observatory. Observations have been made 

 to determine the coefficient of atmospheric absorption at different 

 times. Meteorological observations have been regularly made. 



4th. The work done with the Equatorials during the coming year 

 will largely depend upon the results of experiments now in progress 

 with new forms of photometric and micrometric apparatus. The 

 observations of Jupiter" s satellites will be continued, and probably 

 much attention will be directed to the opposition of Mars in 1879. 



The principal work of the Meridian Circle will be the determina- 

 tion of the absolute positions of a number of standard stars. 



5th. The second part of Vol. IV. of the Annals of the Observatory, 

 and also Vol. IX., as well as the " Director's Annual Report for 1877," 

 have been published during the past year. 



Cambridge, Mass. : Physical Observatory of L. Trouvelot, Esq. 



During the year 1878,- the sun has been observed daily as usual, 

 with the Telescope and Spectroscope ; 230 observations were made, 

 and one drawing of a group of sun-spots and 12 of solar protuber- 

 ances were 'obtained. Besides, the total eclipse of the sun of July 

 29 was observed, under the auspices of the U. S. Naval Observatory, 

 at Creston, Wyoming Territory, and a drawing of the corona made. 



During the last twelve months the surface of the sun has been 

 still more quiet than it was in 1877, only 22 groups of spots or single 

 spots having been observed, most of them very small ; the only group 

 of importance having appeared towards the end of May. The facuke 

 and the veiled spots have also been of very rare occurrence, while 

 the pores were fewer and the granulations not so crowded. The sun 

 has been observed without any spots on 130 days. The total num- 

 ber of spotless days must have been greater, as two mouths of obser- 

 vations were lost on account of the eclipse expedition. In general 

 the chromosphere has been very shallow, especially in the equatorial 

 regions, and the protuberances comparatively few in number and dim. 



The series of observations on the planet Mars, begun last year, has 

 been continued as late as May 2 when the planet was too near the 



