13G Professor Baphael Meldola [^lay 16, 



Faraday. In the same month he communicated his first paper on a 

 photographic process to the Koyal Society, and in the following 

 month he read a second paper before the same society, giving tlie 

 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 communicated to the Eoyal Society in 

 1841. The following year Fox Talbot received the Eumford Medal 

 for his " discoveries and improvements in photography." * 



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

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

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

 By this means the old 40-foot telescope at Slough was photographed 

 in 1839. By the kindness of Prof. 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 illus- 

 trious 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 

 sensitiveness 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 discoveries in connection with photography, which are common 

 matters of history. 



Admitting the impracticability of the method of subsidence for 

 producing a sensitive film, it is interesting to trace the subsequent 

 development 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 j)hoto-mechanical j)riuting processes. [Specimens 

 illustrating photo-etching from Messrs. Waterlowand Sons exhibited.] 

 The Daguerreotype process is now obsolete. As it left the hands of 

 its inventor it was unsuited for portraiture, on account of the long 

 exposure required. It is evident, moreover, that a picture on an 

 opaque metallic plate is incapable of reproduction 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 photography. He was the first to produce 

 a transparent paper negative from which any number of positives 

 could be obtained by printing through. The silver print of modern 

 times is the lineal descendant of the Talbotype print. After forty 



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

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

 Abbey. 



t * rhotog. Journ, and Trans. Fhotog. Soc.,' June 15, 1S72. 



