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DIAMOND FLUORESCENCE. - 
By Arruur L. Fouey. 
[Abstract.] 
Some three or four years since, I had occasion to cut a large number 
of photographic dry plates to smaller sizes. They were cut in the usual 
way with a diamond, and on the side of the plate opposite the film. In 
developing it was noticed that the film, to a breadth of a few millimeters 
along the edge of the plate, turned dark, as if exposed to light. 
Several possible explanations suggested themselves: 
1. The breaking of the glass might produce momentary fluorescence 
and a fogging of the film near the break. 
2. The breaking or tearing of the film might result in some sort of 
change in its character. 
3. The scratching of the diamond might set up mechanical disturb- 
ances or vibrations in the glass and these might affect the film. 
4. The friction between the diamond and the glass might cause a mo- 
mentary fluorescence along the line tracéd by the diamond, and the radia- 
tion might penetrate the glass and fog the film on the other side. 
A Yo MR 8 
The last is the true explanation. 
The first and second suggested explanations were thrown aside at 
once, for the dark line in the film was found to appear along the diamond- 
scratched line, whether the plate was broken or not. That the third 
explanation was not the true one was shown in several ways. The breadth 
and intensity of the dark lines did not appear to depend upon the depth 
of the cut or the rapidity with which it was made. The line was always 
of the same breadth on the same plate, but of different breadths on differ- 
ent plates. Moreover, the film always developed first on the side next the 
glass, which would not have been the case had the effect been due to any 
sort of strain or mechanical disturbance. The effect was noticeable on 
the most rapid plates only. Seed’s “Gilt Edge’ were used in most cases. 
