o02 Telescopes — Life of Fraunhofer. 



Letter from Dr. Oliver. 



TO THE EDITOR. 



Dear Sir — I have recently been favored with an answer 

 to a letter which I had addressed to that eminent artist Lere- 

 bours, of Paris,* which makes me regret that Yale College 

 should have sent to London for an achromatic telescope.! 

 Nothing can more fully evince the great superiority of the 

 telescopes of Lerebours, than this consideration, that while 

 the English thirty inch telescope has an aperture of two 

 inches diameter, and magnifies seventy five or eighty times ; 

 the best thirty two inch achromatic of the above eminent 

 artist, has an aperture of four inches, and magnifies three 

 hundred times.f The reported excellence of his instru- 

 ments does not rest on the artist's word, but on the report of 

 a committee of the National Institute, composed of M. 

 Arago and several other astronomers of the first rank among 

 the philosophers in Europe. The telescope made for the 

 Royal Observatory of Paris, had an aperture of nine inches, 

 and cost three thousand dollars. He has made one since of 

 nine inches aperture, and which magnifies from nine hun- 

 dred to a thousand times, according as the atmosphere is 

 more or less favorable for the application of a great power. 

 You will recollect that Fraunhofer's great telescope made 

 for the observatory of Dorpat, magnified with its greatest 

 power, only seven hundred times. M. Lerebours informs me 

 that he is now engaged in making a telescope of twelve 

 inches aperture, which he expects to finish this year. M. 

 Tully wrote to me, that a disc of flint glass of seven inches 

 diameter was out of the question, as a piece of glass of this 

 size could not be obtained either at Paris or Munich, since 

 the death of Guinand senior. But I am informed by Lere- 

 bours, that the glass-house in which he is interested, in com- 

 pany with the son of Guinand, now make discs of twelve 

 and fourteen inches in diameter. There are also, two very 

 good artists besides, that make good flint-glass for telescopes. 



* Dated Paris, Dec. 12, 1828. 



1 Dr. Oliver alludes to a telescope presented to Yale College, by a private 

 individual, of whom more particular mention may be made when the instrument 

 arrives, which we trust will shortly be the fact, and we indulge the hope that 

 it may prove that the British artist, Mr. Dollond, is not far behind his conti- 

 nental brethren. — Editor. 



X Tne price of such an instrument is eight hundred dollars, and several of 

 them are placed in the Royal observatory of Paris. 



