Miscellanies. I75 



this circumstance, engaged me to make some experiments upon your pre- 

 paration, in order to vary its application to the researches in which I am 

 occupied. First, I wished to know whether the change of color was in 

 any degree mfluenced by the paper itself; T therefore spread the sub- 

 stance on a piece of white unglazed porcelain instead of paper taking 

 care to operate by night, and drying it each time at the fire, as you say I 

 thus obtamed a dry solid coating upon the porcelain, which I shut up hi 

 a dark place untd the morning. In the morning I took it out, and found 

 It of a pale sulphur yellow color: I then presented it to the daylight at 

 an open wmdow looking north; the weather was then very cloudy- yet 

 no sooner had I so presented it than already it was turned careen ' and 

 soon afterwards it became black. I then wished to know w'hether the 

 preparation would succeed equally well if not dried at the fire; I there- 

 fore, m a darkened room, mixed the aqueous solution of bromide of po- 

 tassium with that of nitrate of silver ; a precipitate fell, which I spread 

 pn a porcelam plate and left it to dry in the dark : the next day I wrapped 



It in several folds of paper, and brought it into another room to show it to 

 a friend ; but having taken off the covers in a dark corner of the room 

 m order to exhibit the original color, pale lemon yellow, instantly we saw 

 Its tmt become green, and I had hardly time to present it to a window 

 opening to the north before its color had passed to dark olive green after 

 which It almost immediately became nearly black. I do not think it pos- 

 sible to find any substance more sensitive to light." Had M. Da^uerre 

 or M. Niepce published their experiments at the commencemenr, Mr. 

 Talbot would have appeared merely as an improver of a foreign discovery. 

 We must notice here that, by possibility, this art may not be altogether 

 unknown to jugglers in India. It is many years since an offer was made, 

 m our presence, by one of them, to show any gentleman his portrait taken 

 by a single look alone. The master of the house, however, deemincr the 

 proposal an insult on the credulity of the comp; 

 science to be instantly expelled with the rattan. 



II. Photographic processes, ly Andrew Fyfe*M. D., F. R. S. E., ^-c. 



Photography may be divided into three parts: the preparation of 

 the paper, — taking the impressions, — and preserving them. 



1. Methods of preparing the Paper- 



Though paper besmeared with solution of lunar caustic is darkened 

 by exposure to light, it is by no means sensitive; other methods hare 

 therefore been recommended for preparing it for photographic purpo- 

 ses. That originally given by Mr. Talbot is to soak it first in a weak 



man 



• Read before Soc. of Arts Edinb. Mar. and Apr, 1839. From the New Edinb. 

 Phil. Jour. April to July, 1839. 



