RECENT IMPROVEMENTS IN THE 



vouring to meet them. A strong desire, however, was excited, 

 that some more efficient means of improvement should be 

 adopted, which the increasing devotion to Astronomy among 

 us, manifested by the institution and prosperity of the Astro- 

 nomical Society of London, had undoubtedly been mainly in- 

 strumental in producing. Accordingly, in 1824, the President 

 (then Sir H. Davy) and Council of the Royal Society, to 

 which body the public interests of science are in a manner com- 

 mitted by the nation, appointed a Committee for the improve- 

 ment of glass for optical purposes, consisting of Fellows of the 

 Royal Society, and of members of the Board of Longitude, an 

 official body afterwards dissolved by Government. Experiments 

 were accordingly made under the direction of this Committee, 

 and as it soon appeared that they would require to be pursued 

 unremittingly for a long period, in the following year a S Lib- 

 Committee was appointed, to whom the direct superintendance 

 and performance of experiments were entrusted. This Com- 

 mittee consisted of Mr. Herschel, the son of the late astrono- 

 mer of that name ; Mr. Dollond ; and Mr. Faraday, the Di- 

 rector of the Laboratory of the Royal Institution, whose duty 

 it became to investigate particularly the chemical part of the 

 inquiry ; for which, certainly, no chemist in this country, and 

 perhaps no one in Europe, could be more adequate. Early 

 in 1829, Mr. Herschel retired from the Committee, when 

 about proceeding to the Continent. The requisite chemical 

 experiments were conducted entirely by Mr. Faraday; and 

 since the month of September, 1827, at that scientific esta- 

 blishment, the Royal Institution, which has been distinguished, 

 successively, by the discoveries, or important researches, of 

 Sir H. Davy, and Mr. Brande, and of late years by those of 

 Mr. Faraday himself. In order to convey an adequate idea of 

 the improvements in the manufacture of glass for optical pur- 

 poses which have been effected by the Sub-Committee I have 

 named, and so far as the direct application of chemistry is 

 concerned by the knowledge, the skill, and the ingenuity in 

 the arrangement and combination of instruments and age*nts, 

 of Mr. Faraday, I shall briefly describe those characters of 

 ordinary glass, which interfere with its successful application to 

 the more delicate purposes of optical and astronomical science. 

 The general properties of transparency, hardness, and a 

 certain degree of refractive and dispersive power, which ren- 

 der glass so valuable as an optical agent, are easily obtained ; 

 but there is one condition, essential in all delicate cases of its 

 application, which is not so readily fulfilled: to obtain, namely, 

 a perfectly homogeneous composition and structure. Although 

 every part of the glass may in itself be as good as possible, 



