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sides of the central building are wings 28 feet by 19 ; the 

 east wing being appropriated to the meridian circle, and 

 the west wing being appropriated for the apartments of 

 the astronomer. The cost of the entire building has been 

 about $7000. 



The meridian circle was made by Pistor and Martins, 

 of Berlin. It has a telescope of eight feet focal length, 

 and has two graduated circles of three feet diameter, each 

 of which is read by four microscopes. There are also 

 two small circles, with levels near the eye-piece for set- 

 ting the instrument to the proper altitude. The eight 

 microscopes are illuminated by two stationary lamps, 

 which stand on the brass columns which support the 

 counterpoises. The illumination of the wires can be so 

 regulated as to present either a bright field with dark 

 Jines, or a dark field with bright lines. Two collimators 

 are mounted on the north and south of the meridian circle, 

 and there are conveniences for observing stars, as well as 

 the nadir point, by reflection from a basin of mercury. 

 The circle, with the collimators, cost $3300, and this sum 

 was contributed by H. N. Walker, Esq., of Detroit. The 

 clock was made by M. Tiede, of Berlin. It has a pen- 

 dulum with a steel and zinc compensation, and cost $300. 



The great equatorial telescope was made by Mr. Fitz, 

 of New York. The object-glass has a clear aperture of 

 twelve and a half inches, and a focal length of seventeen 

 feet. It has seven negative and six positive eye-pieces, 

 the highest magnifying power being 1200. The circles 

 are each twenty inches in diameter, the hour circle read- 



