THE MANUFACTURE OF TELESCOPES. 



383 



property of resisting all decomposition by the action of 

 air. A council medal was awarded to him at the London 

 Exhibition. 



The other son of Guinand was introduced by M. Lere- 

 bours, of Paris, to M. Bontemps, who had devoted much 

 attention to the manufacture of glass generally, and par- 

 ticularly of such as is required for optical purposes. He 

 formed an association with Bontemps, which, however, 

 was not of long continuance. In 1828, they succeeded 

 in producing good flint-glass, and discs of from 12 to 14 

 inches. In 1848, M. Bontemps was induced to accept 

 the invitation of Messrs. Chance, Brothers & Co., of 

 Birmingham, England, to unite with them in the attempt 

 to improve the quality of glass. They have succeeded 

 in producing a disc in flint of 29 inches in diameter, 

 weighing 200 pounds, and of crown-glass up to 20 

 inches. The former disc was exhibited at the London 

 Exposition of 1851, and was found to be entirely free 

 from any striae, except a small portion near one of its 

 edges. A council medal was awarded to Messrs. Chance 

 for this disc. 



The following is a list of prices by Chance, Brothers 

 & Co., of Birmingham, for warranted first quality discs 

 of flint or crown-glass : 



inches diameter, 2 OOs. 



" " 27 



" " 2 15 



" " 3 15 



" " 5 00 



6 inches diameter, 

 64- " 



7 " " 



7 4s. 

 9 10 

 12 00 

 14 10 

 17 00 



