296 Astronomical Society. 



science, a competent mathematician, an admirable mechanist, 

 and a man of a truly philoso})hical and scientific turn of mind. 



Raised by his extraordinary talents from the lowest station 

 in a manufacturing establisliment, to the direction of the opti- 

 cal department of the business in which he originally laboured 

 as an ordinary workman, he applied the whole power of his 

 mind to the perfection of the refracting telescope. Easily 

 mastering the refinements of its theory, he saw with regret 

 that they were for the most part unavaihible in practice for 

 want of precise knowledge of the optical properties of the mate- 

 rials used. This he set about to remedy ; and by a series of 

 admirable experiments (of which it is impossible in a report of 

 this nature to give any idea) succeeded in giving to optical de- 

 terminations the precision of astronomical observations, sur- 

 passing in this respect all that had gone before him, except 

 perhaps his great pi'edecessor Newton. He had, it is true, 

 advantages in these researches (such as neither Newton nor 

 any other experimenter has ever possessed) in a command of 

 apparatus limited only by his own inventive powers. It was 

 in the course of these researches that he was led to the impor- 

 tant discovery of the dark lines which occur in the solar spec- 

 trum. In this, indeed, he was in some degree anticipated by 

 an illustrious countryman of our own, to whose powers uni- 

 versal science bears grateful testimony. But it is certain that he 

 had no knowledge of the facts thus previously ascertained, and 

 that he pushed his discovery to a point very far beyond them: 

 being aided in so doing by possessing the happy secret of ma- 

 nufacturing flint glass of perfect homogeneity. Whether he ori- 

 ginally invented this process, or procured it from another, this 

 is not the occasion to pronounce ; but at least his own distinct 

 assertion that he brought it to its final state of perfection, and 

 to a certainty of manipulation by his personal investigations, 

 ought not to be doubted. Nor did he suffer the secret to lie 

 idle or useless, — his telescopes are scattered over Europe; and 

 his last splendid performance has already demonstrated, by 

 the results it has afforded, his claims to unbounded admiration 

 as an artist. The mechanism employed in the working of his 

 glasses, his mode of centering and adjusting them, and every 

 other part of his processes (the fabrication of his glass only 

 excepted) has been witnessed by more than one member of 

 this Society. It bore the stamp of all his works — simplicity, 

 regularity, and incomparable neatness and precision. 



Of his other valuable experiments and discoveries in physi- 

 cal optics, connected with the interferences of the rays of light, 

 (in all of which, though pushed far in advance of the actual 



state 



