388 HISTORY OF ASTRONOMY. 



5 inches. Highest magnifying power 400 times. Price, 

 with clock work and micrometer, $1050 ; without clock- 

 work and micrometer, $825. Several telescopes of this 

 size have been sold. 



No. 7 has a focal length of 5 feet, and an aperture of 

 4 inches. Highest magnifying power 250 times. Price 

 $225, without clock-work or micrometer. 



Mr. Fitz obtains his crown-glass from the manufactory 

 of Bontemps, of Birmingham, England; his flint-glass 

 he obtains from Paris. 



Several of these instruments have been subjected to a 

 very thorough trial before they were purchased. The in- 

 strument for the Chilian expedition was procured under 

 the following circumstances. Mr. Fitz volunteered to 

 make an object-glass from Gruinand's discs, of the same 

 dimensions as that of the High School observatory in 

 Philadelphia, which should be compared with that in- 

 strument, and, if pronounced equal to it, he should charge 

 for it only the cost of a similar lens at Munich. In 

 May, 1849, Professor Kendall, of the High School ob- 

 servatory, made trial of the Fitz object-glass upon the 

 moon, Jupiter, and several double stars; and, after 

 careful comparison with his Fraunhofer, declared him- 

 self unable to pronounce which was the better glass. 

 Several other competent judges assisted at the trial, and 

 concurred with Professor Kendall in his opinion. The 

 glass was therefore purchased by the government 

 according to the contract. Lieutenant Gilliss, after 

 thorough trial, pronounced this telescope perfectly 



