ASTRONOMICAL OBSERVATORIES. 261 



the Dorpat telescope, by Messrs. Gregg and Rupp, of 

 New York. The hour circle is eighteen inches in 

 diameter, and the declination circle eleven inches. The 

 telescope has four eye-pieces, the highest magnifying 600 

 times. The price of this instrument, including clock- 

 work and micrometer, was $2,200. The telescope rests 

 upon a brick column, surmounted by a revolving dome 

 of twelve feet diameter. 



Connected with this observatory is a small building- 

 containing a transit instrument by Simms, belonging to 

 Columbia College. The telescope has an aperture of 

 nearly three inches, and a focal length of four feet. It is 

 mounted upon two stone columns, resting upon a solid 

 foundation of sandstone. An opening in the roof affords 

 a view of about 160 degrees of the meridian. In a small 

 wing of this building is a stone column, upon which is 

 placed an altitude and azimuth instrument by Simms, 

 also belonging to Columbia College. The horizontal and 

 vertical circles are each fifteen inches in diameter, 

 graduated to five minutes, and reading by two micro- 

 scopes to one second of arc. The telescope has an aper- 

 ture of two inches, and a focal length of twenty-four 

 inches. 



During the summer of 1848, this observatory was 

 employed by the Coast Survey as a station for determin- 

 ing the difference of longitude between Cambridge and 

 New York by means of the electric telegraph. 



