986 Transactions of the American Institute. 



rather passing it through, various colored media, thereby rendering 

 it better adapted to photographic purposes. He had produced a fine 

 printing quality of light, by flowing upon the back of the plate a 

 solution of gum sandarach in plain collodion. He advised the use of 

 five, ten or fifteen grains of the gum in each ounce of collodion, as 

 may be required by the various negatives under treatment. The 

 greater the quantity of gum used the more dense become film of 

 coating when dry. It did not become transparent like ordinary gum 

 varnish. The preparation was also very good for backing glass posi- 

 tives, serving as a substitute for ground glass. He also exhibited 

 prints made upon albumenized paper, which had been sensitized on 

 January twentieth last, and afterwards drawn through water saturated 

 with alum. The prints were made on the morning of April 2d T 

 and gave no signs of deterioration in the printing quality of the 

 paper. 



Mr. O. G. Mason exhibited photographs of skin-grafts, made at 

 Bellevue Hospital, and made remarks on the treatment of disease by 

 this process and the utility of photography in illustrating the history 

 of results obtained. 



Mr. H. D. Anthony called attention to the success of Mr. M. Carey 

 Lea, of Philadelphia, in producing very sensitive collodio-bromide 

 plates, and stated that Col. Stuart "Wortley had, by the use of nitrate 

 of uranium in collodio-bromide, produced plates more sensitive than 

 those by the ordinary wet process. The plates were washed with 

 water when about to be used, and exposed wet in the camera. They 

 w r ere developed with an alkaline developer, and strengthened with 

 the ordinary redeveloper of pyrogallic acid and silver. 



The Section then adjourned to the first Tuesday in May. 



