Royal Society. 373 



We have little doubt that the cultivators of science in Europe will 

 be greatly gratified by the evidence this Journal affords of the activity 

 of the scientific men in India ; and that the work itself will prove 

 highly valuable to them, adding, as it does so materially, to our stock 

 of knowledge, more especially as regards that most interesting portion 

 of the world. 



LXV. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



1832. A PAPER was read, entitled "On some Properties of 



Nov. 15. — <£*- Numbers in Geometrical Progression." By Charles 

 Blacklewar, Esq. B.A. Communicated by J. G. Children, Esq. Sec. 

 R.S. 



Nov. 22. — A paper was read, entitled "Account of an Improve- 

 ment in the Machine for producing Engravings of Medals, Busts, &c. 

 directly from the Objects themselves, in which the Distortions hitherto 

 attending such Representations are entirely obviated." By Mr. Bate. 

 Communicated by J. G. Children, Esq. Sec. R.S.* 



A paper was also read, entitled " An Account of the Construction 

 of a fluid refracting Telescope of eight inches aperture and eight feet 

 nine inches in length, made for the Royal Society by George Dollond, 

 Esq. F.R.S." By Peter Barlow, Esq. F.R.S. 



The author has, in former papers read to this Society, pointed out 

 the great variety of cases included under the general formulae relating 

 to the operation of fluid refracting telescopes, and stated the difficulty 

 of selecting, independently of experiment, the particular case which 

 was likely to produce the best result. This subject is pursued in the 

 present paper j and the principles and calculations stated at length 

 which the author has applied in the construction of the telescope 

 which the Council of the Royal Society directed should be made by 

 Mr. Dollond, under the superintendence of the author, in order to 

 put these principles to the test of experiment, and to decide the ques- 

 tion of the expediency of proceeding in the construction of a similar 

 telescope of much larger dimensions. When the experimental tele- 

 scope was completed, it was found that its performance agreed in every 

 respect with the computed results, as well in focal distance as in 

 chromatic and spherical aberration. The arrangement of the lenses 

 was such, that the corrections are all of them made in the transmis- 

 sion of the light through the fluid, and by the fluid only. The author 

 abstains from offering any remarks on the performance of this tele- 

 scope, leaving it to those whom the Council of the Royal Society 

 may appoint, to decide upon its merits. He concludes by expressing 

 his obligations to Mr. Dollond, for the readiness with which he com- 

 plied with all the suggestions of the author, and for the accuracy 

 with which he has executed every part of the instrument. 



A notice of this improvement, by Mr. Bate, will be found in our last 



number, p. 288.— Edit. 



