1028 Transactions of the American Institute. 

 December 3, 1867. 

 Mr. H. J. Newton in the chair; 0. G. Mason, Secretary. 



Miuutes of the last meeting were read and approved. 



Prof. Tillman read a letter received from Professor Joy. 



The committee appointed at the last meeting to try experiments 

 with Mr. B. F. Gage's negative process, reported progress. 



Mr. Anthony laid before the Section a very fine series of photo- 

 graphs, made by Adam Salomon, of Paris. 



Mr. Newton explained a method by which he had produced a 

 similar effect of illumination, by using a vignette arrangement 

 between the back lens of the camera and the sensitized plate. 

 Others suggested the use of reflectors for the local effects of light. 

 Then followed quite an animated discussion upon the means for 

 producing similar results. 



Mr. Boyle exhibited and explained the working of a sub-marine 

 telescope, which might be used for examining the bed of the ocean, 

 or rivers; or by simple modification the same objective could be 

 used for photographing objects under water. 



Mr. Boyle also exhibited one of his ratio lenses, constructed by 

 Mr. Alvin Clark, of Cambridge, Mass., and explained its construc- 

 tion, and gave a history of its manufacture and date of invention, 

 which he fixes in the year 1861. He exhibited two prints from 

 negatives made by his lens in September, 1863. 



Mr, Boyle stated that the Zentmayer lens was identical in its con- 

 struction, though not achromatised. 



Mr. Newton exhibited dry plate negatives made by using tinc- 

 ture of opium and sugar of milk. 



Tincture made as follows: 



30 ounces water, 16 ounces alcohol. 



25 ounces tinct. opium, 21 ounces opium, 



li ounces sugar of milk. 



This he used to flow over the plate, after removing all free 

 tiitrate by washing or chlorising. Exposure in the camera about 

 ouble the time required for a wet plate. Develop with iron. 

 The Section then adjourned to the first Tuesday in January. 



