632 REPORTS OF ASTRONOMICAL OBSERVATORIES. 



Chicago, Cooh County^ Illinois, 

 Dearborn Observatory. 



Longitude from Washington, 42°^ 14^09 W. 



Latitude, 41° 50' 1" N. 



Directors : T. H. Safford, 1865 ; 

 G. W. Hough, 1875. 



Annexed to the University. Founded by subscription in 1822. In 

 1SG4 it came into iiossession of an equatorial of 18^ inches (0™.47) ajier- 

 ture, made by Alvan Clark, with the assistance of which S. W. 

 BURNHAM has made a close and most interesting study of many double 

 stars. 



Instruments : 



{a) Meridian circle: makers, Eepsold & Son; diameter of circle, 40 

 inches; divided to 2'; read by 4 microscopes to 0".l; aperture of object- 

 ive, 6 inches; for observations of the sun, aperture employed, 3 inches. 



(c) Equatorial instrument : makers, Alvan Clark & Sons ; aperture 

 of objective, 18^ inches ; magnifying powers of eyepieces, positive, 120, 

 190, 287, 385, 900; negative, 135, 225, 450, 900. 



(/) Chronograph: G.W. Hough; cylinder recording. 



{g) GlocJcs: one mean time; makers, Howard & Co.; Graham escape- 

 ment, mercury pendulum : one sidereal : makers, Charles Gortner & 

 Co., London; Graham escapement, mercury pendulum. 



(h) Chronometer: sidereal; makers. Bond & Son. 



(i) Miscellaneous: signal mean time clock for transmitting time sig- 

 nals. 



Observations during the past year (from January, 1880, to 

 March ], 1881): 



{a) Eepsold meridian circle. Observations for "Time." 



(c) Micrometer observations of the satellites of Uranus. Micrometer 

 observations on the planet Jupiter. (1) Great red spot; longitude, lat- 

 itude, length, breadth, &c. (2) Equatorial white spots ; longitude, lat- 

 itude, length. (3) Miscellaneous spots; longitude, latitude, length. 

 (4) Position and magnitude of the equatorial belt. (5) Position and 

 magnitude of the faint belts. (6) Physical observations. Comet obser- 

 vations for positions. Miscellaneous work. 



Work proposed for the coming year (1881): 



Satellites of Uranus. 



Jupiter continued. 



Miscellaneous. 



Principal publications of the observatory during the 

 YEAR 1880: 

 G. W. Hough, Eeport of the Director. Pamphlet. 



Satellites of Uranus. Astron. Nachr. 

 Eed spot on Jupiter. Astr. Eegister. 

 Observing seat for the equatorial. Monthly Notices. 



