1879.] Capt. Abney. On Mapping the Solar Spectrum. 67 



January 8, 1880. 



THE PRESIDENT in the Chair. 



The Presents received were laid on the table and thanks ordered for 

 them. 



The Right Hon. Thomas George Baring, Lord Northbrook, v?hose 

 certificate had been suspended as required by the Statutes, was bal- 

 loted for and elected a Fellow of the Society. 



The Bakerian Lecture — "On the Photographic Method of 

 Mapping the Least Refrangible End of the Solar Spectrum 

 (with a Map of the Solar Spectrum from 7600 to 10750)" 

 — was then delivered by Captain W. DE W. Abney, R,E., 

 F.R.S. The following is an abstract: — 



The author refers to the sensitiveness of different forms of silver 

 salts when exposed to the action of the spectrum, and shows how 

 he has been able to prepare, by methods indicated, silver bromide 

 which absorbs the red and ultra-red rays, and which is sensitive to 

 these rays. 



In his paper he describes the apparatus employed by him in the 

 photography of the invisible least refrangible rays, both with a pris- 

 matic, and also with the diffraction apparatus. From photographs 

 taken with the latter, he has constructed a map extending from 

 X 7600 to X 10750, which he submits to the Society. He has also 

 compared Lamansky's prismatic thermograph and that of Sir J. 

 Herschel with his photograph of the prismatic spectrum. The 

 paper closes with some theoretical remarks on the silver compounds 

 employed. 



