REPORTS OF ASTRONOMICAL OBSERVATORIES. G25 



piece; apparatus for projecting' solar iniajio; eight other subsidiary 

 pieces. 



{<!) Spectroscopes: one einphjyiiig hirge Rutuerfurd grating; one 

 with small grating; one 2-prisni s[)ectros('()pe ; apparatus Cor using large 

 equatorial as collimator, &c. 



(e) Photometers and other sxhsidiary apparafns : A variety of ther- 

 mopiles, used in connection with a TiI():\ifs(>n rctleeting galvanometer; 

 large Bunsen photometer; small portable heiiostat, &c. 



(/) Chronograph : oue of Boind's pattern, built by Hamblet. 



{g) Clocks: two mean time; by Howard, both break-circuit: one 

 sidereal ; by Frodsiiam, break-circuit. 



[h) Chronometers: one mean time; by Frodsham: one sidereal; 

 FiiODSHAM, break-circuit. 



(i) Miscellaneous: Oue rellecting telescope of 0^-incli aperture, spe- 

 cially used for obtaining au image projected any size without the em- 

 ployment of any enlarging lenses, and a number of subsidiary pieces 

 for investigations in heat aud light. Electric appliauces for the distri- 

 bution of exact time, automatically and continuously to points outside 

 the observatory. 



The work of research duriug the past year has lain chielly in meas- 

 urements of the distribution of energy in the spectrum of the sun. The 

 routine work of the time service has been continued. 



Work proposed for the coming year (1881): 



(1.) The redetermination of the solar constant. 



(2.) Eedetermination of the law of the distribution of energy in the 

 solar spectrum as it is observed after absorption by our terrestrial 

 atmosphere. 



(3.) Determination (for the first time) of the law of the absolute dis- 

 tribution of the solar energy, or in other words the construction of a 

 curve showing- the distribution of the solar energy as it would appear 

 to an observer stationed outside of the earth's atmosphere. 



Professor Langley is now absent with a large party prosecuting his 

 investigations on the solar constant, on one of the ligh mountains in 

 Southern i^evada. 



Amherst, Massachusetts. 



College Observatory. 



Longitude from Washington, 18"^ 4«.8 E. 



Latitude, 42° 22' 15".G K. 



Director : W. C. Esty. 



Founded in 1857 as an annex to the College. 



S. Mis. 31 40 



