ASTRONOMY. 39 



been connected with solar physics, though studies for the prepara- 

 tion of an apparatus for eliminating personal equation in transit 

 observations have occupied some time. 



In solar physics, work is being done here now on the comparison 

 of the heat of the sun with terrestrial sources, on the distribution 

 of radiant energy in the spectrum, and on the change of wave-lengths 

 of light from the different parts of the sun caused by rotation the 

 latter in connection with an appropriation from the Bache Fund 

 all in active progress. Besides these, other investigations in the 

 same field are in progress. 



The routine work for time-determinations has also always been 

 carried on. Besides its work of research, this observatory has been, 

 since 1870, the supplier of time to a large number of railroads, of 

 which it is the official standard, and since to cities. The automatic 

 signals from its mean-time clock have thus been transmitted from 

 Pittsburgh to New York for the past seven years, and during the 

 latter part of that time as for west as Chicago, and over about 6000 

 miles of main and branch railway lines daily, as well as to the city of 

 Pittsburgh, etc. ; and observations and computations for the control 

 of these are made daily. 



4th. The work of the coming year, it is anticipated, will be in 

 solar physics very largely, and will, it is hoped, be made to include, 

 for the first time, systematic solar photography. Pending the intro- 

 duction of this, the usual daily studies of the solar surface will be 

 continued, accompanied (as at present) with a daily drawing on a 

 scale of 8 inches to the solar diameter, made by projection, and an 

 enlarged drawing of any part of interest, made with the micrometer 

 and polarizing eye-piece. A daily spectroscopic review of the solar 

 limb will be made also, and most of the subjects already mentioned 

 will be continued. 



5th. The incompletion of work now in hand, and the desire to 

 make a thorough presentation of it, have limited the publications of 

 the past year. Three communications to scientific journals, describ- 

 ing results recently obtained here, have been made by the director 

 in the Comptes Rendus des Seances de V Academie des Sciences for May, 

 1877, and in The American Journal of Science and Arts for July and 

 August, 1877. 



Harvard College Observatory, Cambridge, Mass. 



Professor E. C. Pickering, Director. 



First. The observers and computers at present constantly employ- 

 ed at the observatory building are : 



Edward C. Pickering, S.B., Phillips Professor of Astronomy and 

 Director of the Observatory. 



William A. Rogers, A.M., Assistant Professor of Astronomy. 



