ASTRONOMICAL OBSERVATORIES. 239 



the top, and upon it rests the equatorial telescope, made 

 by Simms, of London, which was received in 1849. The 

 object-glass has a focal length of 80 inches, and an 

 aperture of nearly 5 inches, with powers, from 25 to 408. 

 The hour circle is 16 inches in diameter, and reads to 

 one second of time ; the declination circle is 20 inches 

 in diameter, and reads to five seconds of arc. The -in- 

 strument is supplied with clock-work, by which a celestial 

 object may be kept continually in the field of view. This 

 instrument cost $2000. 



The east and west rooms, which contain the meridian 

 instruments, have meridian openings two feet wide 

 through the roofs, and down the north and south walls 

 to within two feet of the ground. In the west room is 

 mounted, on sand-stone piers, a transit instrument, made 

 by Ertel and Son, of Munich, which was received in 

 1844. The object-glass is four and a half inches clear 

 aperture and 76 inches focal length. It has a reversing 

 stand, by which the Instrument can be reversed in a 

 minute and a half. This instrument cost $1180, be- 

 sides the expenses of transporting it from Munich. There 

 is also in this room* a good sidereal clock by Molineux, 

 of London. 



In the east room is mounted on two massive piers a 

 45 inch meridian circle, made, in 1845, by William 

 Simms, of London, with a telescope five feet long, and a 

 4 inch object-glass. The circle is graduated to five 

 minutes, and there are four micrometers fixed to the 

 eastern pier, reading to one second of arc. When the in- 



