THE PHOTOGRAPHIC IMAGE. 379 



1834, and tlie following year he succeeded in imprinting the camera 

 picture on paper coated with the chloride. In January, 1839, some of 

 his "photogenic drawings" — the first " silver prints" ever obtained — 

 were exhibited in this Institution by Michael Faraday. In the same 

 month he communicated his first paper on a photographic process to the 

 lloyal Society, and in the following month he read a second paper 

 before the same society, giving the method of preparing the sensitive 

 paper and of fixing the prints. The outcome of this work was the 

 "Calotype" or Talbotype process, which was sufficiently perfected for 

 portraiture by 1840, and which was fully described in a paper commu- 

 nicated to the Royal Society in 1841. The following year Fox Talbot 

 received the Rumford medal for his "' discoveries and improvements in 

 photography."* 



Herschel's process consisted in coating a glass plate with silver chlo- 

 ride by subsidence. The details of the method, from Herschel's own 

 notes, have been published by his son, Prof. Alexander Herschel.t 

 By this means, the old 40-foot reflecting telescope at Slough was pho- 

 tographed in 1839. By the kindness of Professor Herschel, and with 

 the sanction of the Science and Art Department, Herschel's original 

 photographs have been sent here for your inspection. The process of 

 coating a plate by allowing a precipitate to settle on it in a uniform 

 film is however impracticable, and was not further developed by its 

 illustrious discoverer. We must credit him however as being the first 

 to use glass as a substratum. Herschel further discovered the im- 

 portant fact that while the chloride was very insensitive alone, its sen- 

 sitiveness was greatly increased by washing it with a solution of silver 

 nitrate. It is to Herschel also that we are indebted for the use of 

 sodium thiosulphate as a fixing agent, as well as for many other dis- 

 coveries in connection with photography which are common matters of 

 history. 



Admitting the impracticability of the method of subsidence for pro- 

 ducing a sensitive film, it is interesting to trace the subsequent devel- 

 opment of the processes inaugurated about the year 1839. The first of 

 photographic methods — the bitumen process of Niepce — survives at 

 the present time, and is the basis of some of the most important of 

 modern i)hoto-mechanical printing processes. [Specimens illustrating 

 photo-etching from Messrs. Waterlow «& Sous exhibited.] The Daguer- 

 reotype process is now obsolete. As it left the hands of its inventor 

 It was unsuited for portraiture on account of the long exposure re- 

 quired. It is evident moreover that a picture on an opaque metallic 

 plate is incapable of re-production by printing through, so that in this 

 respect the Talbotype possessed distinct advantages. This is one of 

 the most important points in Fox Talbot's contributions to photogra- 



* For these and other details relating to Fox Talbot's work, necessarily excluded 

 for want of time, I am indebted to his son, Mr. C. H. Talbot, of Lacock Abbey. 

 \ Photog. Journ. and Trans. Photog. Soc. June 15, lo7'2., 



