262 HISTORY OF ASTRONOMY. 



FRIENDS' OBSERVATORY, PHILADELPHIA. 



This observatory is situated in the city of Philadelphia, 

 about 400 feet east of Independence Hall. It was built 

 in 1846, and has a revolving dome fifteen feet in 

 diameter. In the center is the stand for the equatorial, 

 which rests on the walls of the building, unconnected 

 with the floor of the observatory. The principal instru- 

 ment is a refracting telescope of five inches aperture, and 

 seven feet focal length, made by Henry Fitz, of New 

 York, and mounted equatorially after the manner of 

 Fraunhofer, by William J. Young, of Philadelphia. The 

 hour circle is nine inches in diameter, and the declination 

 circle twelve inches. 



A twenty -inch transit instrument is permanently placed 

 on a pier built on the wall of the building. A clock, 

 with a mercurial pendulum, made by J. L. Gropengiesser, 

 of Philadelphia, is placed on a pier adjoining the transit 

 instrument. The observatory has also a portable refract- 

 ing telescope of three inches aperture, and forty-two 

 inches focal length, made by Chevalier, of Paris, and a 

 comet-seeker of three inches aperture, mounted on a 

 tripod, made by Henry Fitz, of New York. 



Since the establishment of this observatory, occulta- 

 tions, eclipses, etc., have been regularly observed by the 

 director, Mr. Miers Fisher Longstreth, who has recently 

 distinguished himself by his successful labors in the 

 construction of new Luiiar Tables. 



