Photograpeical Section Proceedings. 1095 



of pyrogalic acid in alcohol, one-fourth drachm. He placed the 

 exposed plate in a mixture of the first thi-ee, and after allowing it to 

 reujain a short time he mixes the pyrogalic acid solution with it, in 

 a graduated glass, and flows the whole over the plate until all details 

 of the image are visible, then ^vashes the plate in pure w^ater, and 

 flows with a solution consisting of water, eight ounces ; proto-sulph- 

 ate of iron, one-half an ounce ; citric acid, one-eighth of an ounce ; 

 a fifteen grain solution of nitrate of silver, and as much of this solu- 

 tion as may be found necessary to render the image suiiiciently 

 intense. 



Mr. C. W. Hull called attention to the use of sulphuric acid for 

 drying tannin plates, as recommended by Mr. Gary Lea of Phila- 

 delphia. Several members discussed the propriety of drying plates 

 by such means, and the probable action of the acid upon the film, 

 some members believing that it would be rendered less sensitive. 



Prof. S. D. Tillman read an article upon vitrified India rubber or 

 leather collodion. 



Mr. A. J. Drummond stated that he had made a similar substance 

 by adding a small quantity of castor oil to the India rubber transfer- 

 ring solution used in the carbon process of Mr. Swan. In .answer to 

 . a question by the chairman, Mr. Drummond said that the " blister- 

 ing " in carbon prints might be avoided: by first soaking the prints 

 in cold water with the face down, by whicli the air between the film 

 and paper was brought through the paper, and could be. removed 

 by passing the fingere over the surface while under water. 



The section then adjourned to the first Tuesday in October next. 



October 6, 1868. 



Vice-President Charles A. Jot, in the chair. Oscak G. Hason, Secretary. 



Mr. H. J. Xewton, chairman of the, committee . appointed to 

 experiment with the alkaline process, introduced by Mr. McLochlan, 

 reported progress. He had rendered his negative -bath alkaline by 

 adding ammonia and cyanide of potash ; he then exposed the solu- 

 tion to sunlight six weeks, and, upon trial, found it in most excellent 

 condition for work. Some of the results produced .were laid before 

 the section, accompanied by a sample of the sensitizing bath and 

 test proper, for the purpose of showing more clearly its condition. 



Mr. S. A. Thoujas remarked that he had rendered his. bath alka- 



