250 



HISTORY OF ASTRONOMY. 



rods. A sidereal motion is given to the telescope by 

 clock-work, regulated by centrifugal balls, by -which 

 means a celestial object may be kept constantly in 

 the field of view. The cost of this instrument was 

 $19,842. 



CAMBRIDGE EQTTATOBIAL. 



The optical character of this instrument has given 

 entire satisfaction. The components of the star Gamma 

 Ooronse, which Struve, with the Pulkova refractor, pro- 



