THE MANUFACTURE OF TELESCOPES. 



separating power, the glass is competent to divide a sixth- 

 magnitude star composed of two equal stars, whose central 

 distance is 0".6." 



Mr. William Lassell, of Liverpool, in a letter to the 

 author, dated July, 1855, says of this telescope : " The 

 optical efforts of Mr. Clark have greatly astonished me. 

 I have had an opportunity of observing with his tele- 

 scope, purchased by Mr. Dawes, and I consider it, so far 

 as I can judge, unsurpassed if not unequaled" 



Mr. Dawes paid $930 for this telescope, and had it fitted 

 to his Munich equatorial stand. 



4. A telescope of 7| inches aperture and a .focal dis- 

 tance of 101 inches, sold to Amherst College. This tele- 

 scope has a pendulum driving clock with Bond's spring- 

 governor, and is so arranged with a sector clamping upon 

 the polar axis, that its motion is remarkably equable and 

 firm. The circles are 12 inches in diameter; the right 

 ascension circle reading by verniers to two seconds of 

 time, the declination circle to SO* of arc. The price of 

 this telescope was $1800. 



5. A telescope of 7j inches aperture, sold to Williams 

 College for $900. The equatorial mounting was made by 

 Phelps and Gurley. 



6. A telescope of 6 inches aperture was ordered by 

 Baron de Rottenburg, for subscribers in Kingston, Canada 

 West. This telescope had a plain equatorial mounting 

 and was furnished for $850. 



The following is a list of the double stars which Mr. 



