324 L. Gaffield on the action of Sunlight on Glass. 
better pictures under a newly glazed skylight, than under one 
which had long been exposed to sunlight. The cause of 
1D- 
s of 
Various manufacturers which may be offered them. The “ 
Loe glasses of light green, or bluish white color are the bes 
or photographers, and when I say pure glasses, I mean _ 
most free from oxyd of iron or manganese, but especially of t 
latter, which, I th: I 
which I have observed. Mr. J. W. Osborne, of New York, 
phy 
vee T believe your researches will prove of much practical ” 
portance, and I wish the glass manufacturers could be got to ae 
oe ous attention to the subject. It takes but a very slight img 
portionately, With the best of glass, the loss from reflectio 
5 and Spi stg is considerable. is may be fearfully inoreased 
hy the color, and if that undergoes a continual change for #® 
