ed VF rr 
89 
Mr. Thomas Bergin read the following communication 
from Dr. Thomas Woods of Parsonstown, on a new photo- 
graphic process, which he calls the Catalysotype. Mr. Ber- 
gin also read two letters from H. Fox Talbot, Esq. (M. P.) 
to Dr. Woods, and his answer. 
While investigating the property that sugar possesses, in 
some instances, of preventing precipitation, I noticed that 
when syrup of ioduret of iron was mixed in certain proportions 
with solution of nitrate of silver, the precipitate was very 
quickly blackened when exposed to the light, and I thought 
that, if properly used, it might be employed with advantage 
as a photographic agent. If not entirely without profit, it 
would hardly repay the trouble of reading the history of all 
the experiments I tried in order to prove whether or not this 
idea were correct, for there were many difficulties to be over- 
come, and unexpected hindrances to be surmounted, before I 
could be certain of success. However, the results at which I 
have arrived make me hope that my trouble has not been 
thrown away, and that a photographic process has been dis- 
covered, which is more manageable, and more satisfactory, 
than any which has before been used; and I think that the 
pictures produced by it are more minutely and delicately 
brought out, and the time for their production at least not 
longer than is required by any other method. 
To enter very minutely into the particulars, or to explain 
the rationale of the process would be too tedious; however, 
it is so simple, that those who will feel any pleasure in trying 
it will, Iam sure, easily succeed, and to attempt any expla- 
nation of its theory would, in the present state of our know- 
ledge of light, be advancing a mere hypothesis; I will, therefore, 
only state generally the method in which the. paper is pre- 
pared, and then briefly giving my reasons for such parts of 
the process as are not at first sight obvious, will thereby 
enable the experimenter to be guarded against the failures that 
these precautions are intended to overcome, 
VOL. Ill. H 
