(9 ) 



destroy the latent image of the blue and violet ones. At the same 

 time a change in the degree of colour sensitiveness was ascertained. 

 This was confirmed by Claudet l ), H. W. Vogel 2 ), W. Abney 3 ), 

 P. Villard 4 ) and R. W. Wood 5 ). E. Englisch fl ), H. W. Vogel and 

 W. Abney, however, considered this phenomenon to be solarization. 

 An experiment published by P. Villard clearly shows that in the 

 case of very advanced exposures the critical exposure does not appear 

 any more, and the whole phenomenon coalesces with solarization. 

 The highest sensitiveness of the plate is manifested towards red, the 

 lowest to green. 



Warnerke 7 ) observed Herschel's effect in images obtained by print- 

 ing, and P. Villard, R. W. Wood, R. Luther and W. A. Uschkoff 8 ) 

 with Röntgeii rays in the case of primary exposure. At the same 

 time they demonstrated that the phenomenon did not appear if these 

 exposures were reversed. 



J. Sterry 9 ) communicated another variety, viz. that certain kinds 

 of chemical fog can be neutralized by weak light. 



Some time ago one of my friends showed me a few camera 

 exposures on Eastman films 10 ), which I recognized as the phenomenon 

 observed by J. Sterry. They had been exposed once, but had been 

 in the camera for about 3 years without any precautions having 

 been taken except that light had been prevented from reaching them. 

 Consequently in this case the diffused exposure had been replaced 

 by a chemical process of analysis, which had acted similarly, and 

 had been exercised upon the silver bromide by the vapours given 

 off by the celluloid, which had been diffused in the silver bromide 

 gelatine. 



Fig. 5 is an outdoor subject; it had a short exposure and shows 

 various abnormalities. Nearly the whole copy is polarized, with the 

 exception of the sky near a, where the critical exposure had been 

 exceeded. The dogs in the foreground, reflecting the greatest amount 

 of light there, show the beginning of the formation of a normal copy, 



i) Annal. d. Ghimie et de Phys. 1848; 3e série; T. XXII. 



2) H. W. Vogel. Handb. d Phot. 1890J; Bd. 1; S. 221. 



*) Phot. Archiv. 1881 ; S. 120. 



*) Soc. d'encourag. pour Flndustrie nation. Extr. d. Bulletin; Nov. 1899. 



5 ) Astrophys. Journ. 1903; Vol. XVII; p. 361. 



6) J. M. Eder. Jahrb. f. Phot. u. Bepr. 1902; S. 73. 

 7j Phot. Arch. 1881; S. 120. 



8 ) Phys. Zeitschr. 1903; S. 866. 



<J ) This paper I only know from a resumé in J. M. Eder. Jahrb. f. Phot. u. 

 Repr. 1903; S. 425. 



10 ) The lens of the camera was a slow aplanat, and was used with full opening 

 for the interior; for the outdoor exposure it was stopped down. 



