1026 Transactions of the American Institute. 



gave the course of the current in its passage from the cloud to the 

 earth, and a view of the East river, and a portion of the city of 

 Brooklyn beyond, and tops of several buildings in New York. 



Prof. Tillman read a paper upon the phenomenon actinescence 

 discovered by Gary Lee, of Philadelphia. 



Mr. Rutherfurd made remarks upon the terms "floresence," 

 "phosphorescence," and "actinism," and the actinic force of the 

 spectrum rays, and the phenomenon of developing tannin plates 

 long after exposure. 



Mr. Hull made some interesting remarks upon the keeping 

 quality of dry plates after exposure to light. 



Prof. Rood spoke of the very short duration of the visible action 

 of phosphorescence, it generally being only the fraction of one 

 second, though, under one or two conditions, it lasts several hours. 



Mr. Chapman stated that the keeping qualities of tannin plates 

 seemed to depend in a great measure upon the strength of the 

 tannin solution used in their preparation. The strong solution 

 produced plates of better keeping qualities. 



Mr. Hull chose weak tannin, as, by its use, he was able to pro- 

 duce greater harmony of effect. 



Mr. Newton read a paper upon the keeping of sensitized albu- 

 men paper. 



The Secretary laid before the Section two dozen stereographs 

 of Green Mountain scenery, donated hj Mr. A. F. Stiles, of Bur- 

 lington, Vermont. 



The Section then adjourned, to meet on the second Monday in 

 November. 



November 11, 1867. 

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



IVIinutes of the last meeting Avcre read and approved. 



Mr. Hull laid before the Section a series of prints from negatives 

 made by the Zantmyre lens, and globe lens, showing the relative 

 field and illumination of the lenses. He also read a letter from 

 Mr. B. F. Gage, of St. Johusbury, Vt., accompanied by a cabinet 

 photograph and ambrotj^pe, showing the peculiarities of the pro- 

 cess which formed the subject matter of his communication to the 

 Section. 



