vn. PHOTOGRAPHY. 237 



duced so as to ensure repeated impressions ; thirdly, corrections may be made 

 on the copper, which could not be made on the original plate, -worn by 

 repeated working. The cost of reproduction on copper by Erhard's process 

 is small, and may be estimated at about 3 to 5 centimes per square centi- 

 metre. 



1 . Album containing 36 maps and plans reproduced by this electro-chemical 

 process. 



2. 10 copper plates obtained by this process, the impressions from which 

 are shown in the album. 



946. Photoglyphic engravings, 1853. 



H. Fox Talbot, F.R.S. 



947. Silver prints of views in Knoll Park. 



School of Military Engineering, Chatham. 



947a. Proof by Papyrotype Process. 



School of Military Engineering, Chatham. 



947b. Specimens of Enlarging Process. 



School of Military Engineering, Chatham. 



948. Second Proof of Photographic Engraving, 



obtained by M. Fizeau, without retouching, in 1843, and printed 

 in greasy ink. M. Fizeau, Paris. 



949. Daguerreotype Proof, fixed by M. Fizeau's process 

 with chloride of gold, by Hubert, in 1840. M. Fizeau, Paris. 



949a. Daguerrean Print, obtained by the continuous action 

 of red rays, without mercury. M. E. Becqucrel. 



950. Photochromic Proofs (selection). M. Vidal, Paris. 



951. Early Talbotypes. 



The Council of King's College, London. 



95 la. Specimens of Enamel Process. Wm. Mayland. 



952. Table of Specimens of Historical Records of 

 Photography. French Photographic Society. 



952a. Application of Photography to Cartography. 



The Topographical Department of the Imperial Hussian 

 General Staff, St. Petersburg. 



In the application of the negative process, Rupell's drying system, with 

 tannin, has been employed. The positive prints are either black silver copies 

 or blue iron pictures : preference is given to the latter if the photograph is 

 to be traced over with Indian ink, and the photographical ground to be 

 removed afterwards by etching for the purpose of producing a clean drawing. 



1 . Reproductions of Central Asiatic surveys and maps. 



2. Copies of plates of survey sheets in European Russia. 



