OF ARTS AND SCIENCES. 165 



sand dollars, was not only in itself of the greatest importance, 

 but had been still more useful from having been tendered at 

 the earliest stage of the enterprise, and when its success was 

 uncertain. He further stated, that, although the instrument 

 had been but for a very short time in operation, its perform- 

 ance was such as to warrant the belief, that it fully came 

 up to the conditions of the order under which its manufac- 

 ture was undertaken by Messrs. Merz and Mahler, — which 

 were, that it should be as good as any instrument of its class 

 in the world. 



Mr. Everett then read the following letter from Mr. Bond, 

 the Director, furnishing some information in detail as to the 

 performance of the instrument in reference to test objects. 



" Observatory at Cambridge^ 26 July^ 1847. 

 " Dear Sir : — 



" I take great pleasure in complying with the request you made, 

 during your last visit to the Observatory, that I should prepare 

 for you a brief account of the large refracting telescope which has 

 recently been placed within its walls. 



" The construction of this instrument was intrusted to the eminent 

 opticians and mechanicians, Messrs. Merz and Mahler, of Munich, in 

 Bavaria, the successors of the celebrated Frauenhofer. By the terms of 

 the contract, they bound themselves to make for us a telescope equal 

 in dimensions to the one at Pulkova, and of the best quality they were 

 able to produce. We received the object-glass of this telescope in 

 November, 1846. The tube and machinery arrived on the 11th of 

 last month. We had prepared for the support of this instrument a 

 stone pier, composed of massive blocks of granite, resting on a bed of 

 hydraulic cement, made with coarse gravel, which forms a mass 

 almost as solid as the stone itself. The substratum is fine gravel 

 mixed with sand. The diameter of the pier is twenty feet at the base, 

 and ten feet at the top. In form it is the frustum of a cone, and is 

 surmounted by a single block of granite, two feet in thickness and ten 

 feet in diameter, weighing fourteen tons. On this rests the stone ped 

 estal, eleven feet high, weighing about nine tons, to which are attach 

 ed the bed-plate of the hour-axis and framework of the telescope 

 Five hundred tons of granite were employed in constructing this pier 



" The hour-circle of the instrument is eighteen inches in diameter 

 and reads by two verniers to single seconds of time in right ascension 



