ASTRONOMICAL OBSERVATORIES. 219 



within about one foot of the floor, and is capped by a 

 slab of marble, eight inches thick, upon which the piers 

 of the transit circle stand. In . the direction of the meri- 

 dian of the transit is a clear opening, 26 inches wide, in 

 the roof and down the sides to within about two feet of 

 the floor. On each side of the transit circle a flexible gas 

 tube hangs from the ceiling. One light is used to illumi- 

 nate the wires of the transit, while the other is used in 

 reading the circle. 



The clock is attached to the western wall, near the 

 transit instrument, and is lighted by gas. 



Adjoining the observing room on the east, is a small 

 apartment which serves as a library and computing room. 

 This room is provided with a stove, for which reason the 

 two rooms do not communicate directly with each other, 

 but both open on the staircase leading from the fourth 

 story to the observatory. 



WEST POINT OBSERVATORY. 



The "West Point observatory was erected about the 

 same time with that at Philadelphia. In 1839, a large 

 building was erected for the accommodation of the library 

 and philosophical apparatus, with three towers for the re- 

 ception of astronomical instruments. The central tower 

 is surmounted by a traveling dome, 27 feet in diameter, 

 and about 17 feet high from the spring. It is pierced by 

 five window-openings near the curb, and an observing 

 slit, two feet wide, extending from a point four feet above 

 the floor to nearly two feet on the opposite side of the 



