ASTRONOMICAL OBSERVATORIES. 275 



MR, CAMPBELL'S OBSERYATORT, NEW YORK. 



This observatory is built on the top of Mr. Campbell's 

 dwelling-house in New York city, in Sixteenth-street, 

 near the Fifth Avenue, and Was completed in 1852. The. 

 house is 30 feet wide and four stories high. The hall is 

 10 feet wide, and the partition wall which separates the 

 hall from the rest of the house is of brick, and extends to 

 the roof. This and the adjoining gable were raised so as 

 to make another story over that part of the house, and a 

 room was thus obtained 10 feet wide and 35 feet long. 

 Twelve feet at one end are appropriated for the dome and 

 telescope. The observatory is furred off so as to make 

 an octagon of 12 feet in diameter ; and at the height of 5 

 feet, the octagon is changed into a circle to support the 

 wooden curb- which constitutes the bed-plate of the dome. 

 Upon the bed-plate is placed a circular rail, 12 feet in 

 diameter on the inside, 3 inches wide, and having a raised 

 bead upon the upper surface. 



The dome is 12 feet in diameter, the base being a coun- 

 terpart of the curb, which constitutes the bed-plate. The 

 aperture for the telescope is 15 inches wide, and extends 

 a little beyond the zenith. It is closed with a sliding 

 door, which is made so that it may slip over the zenith to 

 the opposite side of the dome, and this motion is effected 

 by turning a crank. The dome revolves upon seven 

 wheels of four inches diameter, in which grooves are 

 turned to correspond with the bead on the iron rail. The 

 shaft of one of these wheels, is made long enough to re- 



