THE MANUFACTURE OF TELESCOPES. 377 



ture, with four eye-pieces, magnifying from 40 to 300 

 times. 



These telescopes are of the Herschelian form, and have 

 received medals from the American Institute of New 

 York, and the Franklin Institute of Philadelphia, after a 

 most thorough and severe examination. With a tele- 

 scope of the second size, the double stars, 51 Librae, 

 and Bootis, the components of which are distant from 

 each other but little more than one second, have been 

 easily separated, and Saturn's ring seen double nearly 

 throughout its visible portion. Mr. Holcomb has sold 

 five telescopes of his first size, and as many of the 

 second, with a much larger number of the smaller 

 sizes. 



KEFEACTING TELESCOPES. 



The experiments which have been made in this 

 country in the manufacture of refracting telescopes, may 

 be divided into two classes : namely those which have 

 employed American glass, and those which have em- 

 ployed foreign glass. 



Several telescopes of small dimensions have been made 

 of American glass, which have performed quite satisfac- 

 torily; but the attempts to make large telescopes with 

 American glass, so far as the results have been laid be- 

 fore the public, have invariably proved failures. At 

 several establishments in this country, glass is manufac- 

 tured which answers perfectly all the ordinary purposes 

 of the arts, and for transparency, compares well with 



