The Herschel Effect is a regression of the latent photographic image under the influence of long wave-length radiation. Although we have observed no studies concerning the effect of temperature upon the rate of the Herschel Effect, extensive and seemingly conflicting reports exist concerning the effect of temperature upon the rate of formation of density by ordinary exposures.
Abney a in I884 found that heating a plate with a hot iron increased the sensitivity to light many fold. Lumiere 2 found that exposures of 300 to 400 times as long were required at liquid air temperatures to produce the same densities as exposures at room temperatui'es. Precht and Scheller ~ found small variation in sensitivity between -320 C. and 9 oΒ°. Daleziki 4 found a temperature coefficient of I.o5 between 7 Β° and 64 Β°. Zimmern ' ~ found a small increase in sensitivity between 20 Β° and 80 Β° . I(ing, 6 on the other hand, found a 50 per cent. increase in sensitivit3~ between 7 Β°0 F. and o Β° F.
Wallace ; found that the effect of temperature upon the sensitivity was dependent upon the intensity of the exposing radiation. Webb s in I935 verified these findings of Wallace.
The first portion of this paper deals with the effect of temperature upon the rate of the Herschel Effect.
Different strips of a rectangular sheet of chloride paper (Co;nvira 5) parallel to the shorter dimension were given