THE MANUFACTURE OP TELESCOPES. 385 



tablishment on his own account. He makes large discs 

 both of flint and crown-glass of the very best quality 

 fbr telescopes. 



While experiments, made in this country with Ameri- 

 can glass, have generally proved failures, experiments 

 with the aid of foreign glass have been more success- 

 ful. Three artists have specially distinguished them- 

 selves in the manufacture of refracting telescopes, viz., 

 Mr. Henry Fitz, of New York ; Mr. Alvan Clarke, of 

 Boston ; and Mr. Charles A. Spencer, of Canastota, New 

 York. 



TELESCOPES BY HENRY FITZ, OF NEW YORK. 



Mr. Fitz's first telescope was a Cassegrain reflector of 

 six inches aperture, and three feet focal length, which 

 was constructed in 1838. In 1844 he saw the fine 

 Munich telescope of the Philadelphia High School 

 observatory, and determined to attempt the construction 

 of an achromatic. In this he succeeded by first making 

 a lens of three inches aperture, and afterward one of 

 3f inches, being the largest piece of flint glass he could 

 obtain. The quality of both of these lenses was im- 

 paired by veins, as the concave lens was of quite 

 ordinary table-ware glass ; still, they compared so favor- 

 ably with good Munich telescopes, that Mr. Fitz im- 

 mediately commenced one of six inches aperture. This 

 was also filled with striae, excepting in the convex lens, 

 which (like the first two) was made of French mirror 

 plate. This telescope was examined by the late S. C. 



