44 ASTRONOMICAL OBSERVATIONS 



and a half feet high, having a fiat roof covered with tin. In its centre is a pier 

 of fine sand-stone. Its top is twenty-seven inches by thirteen, and rises twenty- 

 four inches above the floor. It has a slope of one inch to the foot, and descends 

 about six feet below the surface of the earth . It is entirely detached from the 

 building, and the floor is no where in contact with it. The openings for the 

 transit are fifteen inches wide ; the side openings being closed by solid wooden 

 shutters, and a single trap-door covers the entire top. This covering is such 

 as effectually to exclude the most violent rain. The transit commands an 

 unobstructed meridian from ninety degrees zenith distance on the south, to 

 eighty-nine degrees on the north. 



The central room of the observatory is occupied by the equatorial, and is 

 fourteen feet square upon the inside. In its centre is raised a circular plat- 

 form, ten feet in diameter and four feet high, upon whose circumference rest 

 twelve small cherry columns, which help to sustain the dome. The dome is a 

 hemisphere of nine feet internal diameter. It rests upon ten wheels of lignum 

 vitee, five inches in diameter, placed equidistant from each other, running in a 

 grooved channel, and set in a wooden ring, consisting of five arcs, joined by 

 hinges, to allow greater freedom of motion to the wheels. The dome has an 

 opening fifteen inches wide, reaching from the base to eight inches past the 

 zenith, closed by three doors, the top one closing last, and the joints being so 

 secured as effectuallv to exclude the rain. The whole is covered with tin, and 

 a single person can readily revolve it by hand. The top of the equatorial pin 

 is twenty inches by thirty, and rises three feet six inches above the platform. 

 Its slope is one inch to the foot, and it descends six feet below the surface of 

 the ground. It is of the same material with the transit pier, and, like that, is 

 also entirely detached from the building. 



The right hand room in the above figure, which is the west room, contains 

 no instruments, but is provided with a stove, and serves as a convenient ante- 

 room. 



The instruments of the observatory are a transit circle, an equatorial tele- 

 scope, and a clock. The transit circle was made by Simms, of London, in 

 1837. It has a telescope of thirty inches focal length, with a very superior 

 object glass, whose clear aperture is 2.7 inches. This is supported by broad 

 cones, forming an axis of eighteen inches in length. The pivots are of steel, 

 and rest on brass y's. It is supported by a heavy cast iron frame, which rests 



