REPORTS OF AMERICAN OBSERVATORIES. 543 



II. Instruments: 



(a) Meridian citric : Makers, Troughton & Simms (glasses by Alyan 

 Clark & Sons); diameter of circles, 36 inches; divided to 5'; each cir- 

 cle read by 4 microscopes to 0.1". Aperture of objective, 8£ inches; 

 for observations of the sun, aperture employed, 8^ inches; magnifying 

 power ordinarily employed, 300 to 350 diameters. 



(a') East transit circle, by Troughton & Simms ; diameter of circles, 

 48 inches; divided to 5'; each circle read by 4 microscopes to 0".2. 

 Aperture of objective, 4^ inches. 



(b) Meridian transit instruments : Maker, Herbst, of Pulkowa; aper- 

 ture, 2| inches; magnifying power, up to 200 diameters. 



(b') Large photometer, mounted in the meridian, for comparing im- 

 ages of stars during transit. 



(c) Equatorial instruments : Maker, Merz ; aperture of objective, 15 

 inches ; magnifying powers of eyepieces, 100 to 2000. 



(c') West equatorial, by Alvan Clark & Sons ; aperture, 5J inches. 



(d) Spectroscopes : Three, described iu Vol. VIII of the Annals of the 

 Observatory. 



(e) Photometers and other subsidiary apparatus : One Zollner photo- 

 meter, and several photometers of other kinds. 



(/) Chronographs: Two spring governors, by W. Bond & Son; one 

 small barrel chronograph. 



(g) Clocks : Mean time ; maker, Bond, 394 : sidereal ; makers, Fkod- 

 sham, 1327 ; Bond, 312. 



(h) Chronometers: Sidereal; makers, Frodsham, 3451; Bond, 23G; 

 thermometric chronometer, Frodsham, 3424. 



(/) Miscellaneous ; Comet-seeker and other small telescopes and appa- 

 ratus. 



III. Observations during the past year: 

 From September 1, 1878, to September 1, 1879. 



(a) Completion of observation of stars to the ninth magnitude, inclu- 

 sive, in zone 50° to 55°; completion of observations of bright stars not 

 recently well determined; commencement of observations of absolute 

 places of important stars; observations for clock error, for use of time 

 service (signals sent every two seconds to many points in and near 

 Boston). 



(b) Observations for clock error, as above. 



(b') Photometric comparisons of stars visible to the naked eye ; the 

 observing list includes about 4,000 stars. 



(c) («') Photometric observations of satellites of superior planets; pho- 

 tometric observations of the eclipses of Jupiter's satellites; commence- 

 ment of spectroscopic and photometric observations of selected nebulae; 

 observations of comets and asteroids. 



IV. Work proposed for the coming year (1879-'80) : 

 Continuation of observations now in progress. 



