536 EEPORTS OF AMERICAN OBSERVATORIES. 



II. Instruments: 



(b) Meridian transit instruments : Makers, Troughton & Simms ; 

 aperture, 4 inches ; magnifying power, 150 diameters. 



(c) Equatorial instruments: Makers, Fitz, reworked by Clark; 

 aperture of objective, 13 inebes ; magnifying powers of eye-pieces, 50 to 

 1,200 ; equatorial carries a 12-incb flat mirror by Clark at south end of 

 its polar axis : also, position filar micrometer, polarizing solar eye-piece ; 

 apparatus for projecting solar image ; eigbt otber subsidiary pieces. 



(d) Spectroscopes : One employing large Eutherfurd grating ; one 

 with small grating; one 2-prism spectroscope ; apparatus for using large 

 equatorial as collimator, etc. 



(e) Photometers and other subsidiary apparatus ; A variety of ther- 

 mopiles, used in connection with a Thompson reflecting galvanometer ; 

 large Bunsen pbotometer ; small portable heliostat, etc. 



(/) Chronographs: One of Bond's pattern, built by LIamblet. 



(g) Clocks : Mean time ; two by Howard, both break-circuit : sidereal ; 

 one by Frodsham, break-circuit. 



(h) Chronometers : Meantime; one by Frodsham : sidereal; one Frod- 

 sham, break-circuit. 



(i) 2liscellaneous : One reflecting telescope of 6^-inch aperture, spe- 

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

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

 investigations in heat and light. 



Electric appliances for the distribution of ej^ct time, automatically 

 and continuously to points outside the observatory. 



III. Observations during the past year: 

 From September, 1878, to September, 1879. 



(b) Nightly observations of from 3 to 6 stars for time determinations; 

 observations to determine the longitude of Ebensburg, Pa. 



(c) Daily map of solar surface, drawn by projection on a scale of 8 inches 

 to diameter ; enlarged drawings of any spots ; measurements by thermo- 

 piles of heat of solar image; study of protuberances, and other work 

 with attached spectroscopes. 



(d) Studies of the lower end of the spectrum ; mapping of lines in the 

 extreme red, etc. 



(i) Comparison of solar heat with that of the Bessemer converter; 

 the distribution of exact time to cities, railroads, corporations, or indi- 

 viduals. 



IV. Work proposed for the coming year, 1879-80: 

 Systematic observation of sun as heretofore; continuance of researches 



now in progress, chiefly in solar physics; measurement of heat of diffrac- 

 tipn spectrum by tasimeter, etc. ; the continuance and extension of the 

 " time-service." 



