T. Gaffield on the action of Sunlight on Glass. 325 
worse, the state of things is exceedingly unpleasant. I was 
warned by a photographic friend in England, to take care of a 
_ certain kind of cheap French glass, made for glass rooms, which 
| turned yellow; but I had no notion that the evil was so general 
_ a you appear to have found it. The subject is of such vital 
importance to photographers, that I intend drawing the attention 
of that friend to what you have done.” 
Iam indebted to Mr. Osborne for bringing our researches to 
the notice of his friends at home and abroad, who have contrib- 
uted interesting articles and valuable information on the subject 
to the Philadelphia Photographer, (October, 1866,) the London 
Photographic News, (August 2, 1866,) the London Photographie 
Journal (Aug. 15, 1866,) and the Photographische Mittheilungen 
(Sept. 1866). : 
t may seem Sk that so long an experience in the window 
n why t ! 
ken lain wee replaced by those of the usual light greenish color 
ged glass. ° 
this point I have convinced many who had held contrary 
ve thus gath . 
colors, and of differing lengths of exposure from old windows. 
The oldest specimen was one of crown glass set in a chureh in 
Lexington, Massachusetts, in 1794, from which the windows were 
Temoved in 1846, and since used as covers for hot-beds. The 
