S9B Proceedings of the Society of Arts. 



tbe light has not been strong, and the iodine not completely loosened, 

 the mercurial coating is less dense. On putting the plate into the hypo- 

 sulphite, the iodine is washed off, and there arc then exposed two distinct 

 metallic surfaces, a silver and a mercurial one ; which, reflecting the light 

 differently, brings out the image. That this is really the nature of the 

 action, Dr Fyfe considered to be proved from the results of the experi- 

 ments detailed by him, by which he shewed that representations similar 

 to Daguerreotype can be procured by placing on one of the^polished plates 

 of silver without iodine, any object, such as a profile on paper, moistening 

 the paper to make it adhere to the silver, and then mercurialising as re- 

 commended by Daguerre. In this case the mercury adheres to the me- 

 tallic surface exposed, and when the paper is removed, the highly polished 

 silver covered by it, is left resplendent, and thus gives the dark profile on 

 the white ground. Specimens of this kind were exhibited. Similar effects 

 are produced by exposing other plates, such as tinned iron, glass, and 

 many others. If, when silver is used, the temperature to which the mer- 

 cury is subjected be raised to about 400, the mercury adheres firmly to 

 the silver, and accordingly the image is not apt to be rubbed off as in 

 Daguerreotype — Experimentalillustrations were exhibited. Thanks voted. 

 Dr Fyfe was requested to give in writing a short account of his interesting 

 experiments. 



4. The large model of Mr Ponton's Galvanic Telegraph was exhibited, 

 and the principles of its construction explained, previous to its being de- 

 posited in the Society's Museum. (682.) Thanks voted. 



The following Candidates were admitted as Ordinary Mem- 

 bers, viz. : — 



1. Mr George Potts, cabinet-maker, 14 Scotland Street ; 2. Thomas 

 Thomson, Esq. W. S., 25 Melville Street ; 3. Alexander Fleming, Esq. 

 W. S., 2 South Charlotte Street. 



A Committee was appointed on the subject of the Ventilation of the Hall. 



2dth January, 1840.— David Maclagan, M.D., F.R.S.E., 

 Vice-President, in the chair. The following communications 

 were made : — 



1. Essay on Life Assurance, Part III. being, — On what constitute the 

 Profits of a Mutual Assurance Society. By Edward Sang, Esq. Actuary, 

 6 North St David Street, M.S.A. (67G.) 



2. Description of a process for multiplying Photographic Drawings. 

 JSy Mr C. Galpin, 1 Lowther Arcade, London. Specimens were exhibit- 

 ed. (680.) Referred to a Committee. 



3. A Map of England and Wales, for the use of the Blind. By John 

 Alston, Esq. of Rosemount, Honorary Treasurer to the Institution for the 

 Blind, Glasgow, Hon. M.S.A. (G84.) Referred to a Committee. 



4. Donation. — The Transactions of the London Electrical Society. 

 Part I. Comprising Papers read during 1837. Presented by Mr E, M. 



