On the Manufacture of Optical Glass. [1829. 



always evinced to assist in the advancement of science; and 

 the readiness with which the application was granted, showed 

 that no mistaken notion had been formed in this respect. As 

 a member of both bodies, I felt much anxiety that the investi- 

 gation should be successful. A room and furnaces were built 

 at the Royal Institution in September 1827, and an assistant 

 was engaged, Sergeant Anderson of the Royal Artillery, whose 

 steady and intelligent care has been of the greatest service to 

 me in the experiments that have been proceeding constantly 

 from that time to the present. At first, the inquiry was pur- 

 sued principally as related to flint and ground glass ; but in 

 September 1828 it was directed exclusively to the preparation 

 and perfection of peculiar heavy and fusible glasses, from which 

 time to the present continual progress has been made. 



I have thought it right to give this brief explanatory state- 

 ment of the manner in which it has happened to become my 

 duty, on the present occasion, to give an account of what has 

 been done in the improvement of glass for optical purposes by 

 the Committee of the Royal Society, working at the Royal In- 

 stitution. I would willingly have deferred this account until 

 the inquiry were more complete than at present ; for though 

 glass has been made, and telescopes manufactured, yet I have 

 no doubt that much more of improvement will be effected. It 

 may be said that a long time has elapsed since the experiments 

 were first instituted ; and that if anything could be done, it 

 should have been effected in so long a period. But be it re- 

 membered, that it is not a mere analysis, or even the develop- 

 ment of philosophical reasoning, that is required : it is the 

 solution of difficulties, which, as in the cases of Guinand and 

 Fraunhofer, required many years of a practical life to effect, if 

 it was ever effected. It is the foundation and development of 

 a manufacturing process, not in principle only, but through all 

 the difficulties of practice, until it is competent to give constant 

 success : and I may be allowed to plead the acknowledged dif- 

 ficulty and importance of the subject as a reason, both why it 

 may not yet have obtained perfection, and why it should still 

 be pursued. 



My wish, however, to delay the account of the researches 

 until I could have carried the experiments further, is overcome 

 by the conviction that much more time must be expected to 



