ASTRONOMICAL OBSERVATORIES . 24:3 



ing rises three stories in height. The pier is built of 

 stone, and is grouted from its foundation on the rock to 

 the top. The equatorial room is 25 feet square, and is 

 surmounted by a roof so arranged that it may be entirely 

 removed during the time of observations. 



The object-glass of the telescope has an aperture of 12 

 inches, and a focal length of 17 feet. The hour circle is 

 16 inches in diameter, and reads by two verniers to two 

 seconds. The declination circle is 26 inches in diameter, 

 and divided on silver to five minutes, reading by verniers 

 to four seconds. The instrument has five common eye- 

 pieces and nine micrometrical, with powers varying from 

 100 to 1400. It is furnished with clock-work, by which 

 a star is kept steadily in the field of view of the tele- 

 scope. 



Through the liberality of Dr. Bache, the superintendent 

 of the United States Coast Survey, this observatory has 

 been furnished with a five feet transit instrument ; and a 

 new sidereal clock has recently been received. 



Professor Mitchell has hitherto devoted much of his 

 time to the measurement of Struve's double stars south 

 of the equator. A number of interesting discoveries have 

 been made in the course of this review. Stars which 

 Struve marked as oblong, have been divided and meas- 

 ured ; others marked doubk, have been again subdivided 

 and found to be triple ; while a comparison of the recent 

 measures of distance and position with the measurements 

 of Struve, has demonstrated the physical connection of 

 the components of many of these stars. 



