204 M. C. Lea—Influence of Color upon Reduction by Light. 
The first series was tried with short exposures to violet and 
to white light only. In this case the mauveine appeared to 
give a slight increase of sensitiveness, but as this extended 
equally to white and to violet, no conclusion as to influence on 
specific rays could be drawn. The aniline green, blue and 
rosaniline diminished the general sensitiveness a re: the 
eee a oa deal, and the aurine nearly destroye 
influence of the entire spectrum the following 
serail were oben: 
Red and orange rays. Mauveine same as plain uranium salt; 
other colors less sensitive. 
Yellow. Bescon same as plain uranium salt; other colors 
sensitive 
Green hd blue. All the colors less sensitive. 
Violet. Mauveine same as plain uranium salt; all the rest less 
sensitive. 
These effects are evidently not capable of being reduced to 
any general law 
Silver Chloride. 
A number of experiments led to the following results : 
Coralline increased the sensitiveness to all the rays, but 
especially to blue and violet, in which the increase is very 
eaahiline Heras the sensitiveness to blue and violet, but 
diminished all the é 
Aniline blue ditsinistied sensitiveness to green, increased it 
to yellow, and was without effect on 
Aurine diminished sensitiveness to all. 
Mauveine and aniline green were without effect. 
Litmus reddened by acetic acid strongly increased the sensi- 
tiveness to the yen and violet, and somewhat diminished it to 
the red and ora 
Here we Rive re red colors increasing the sensitiveness to 
the blue and violet. But one, coralline, increases the sensitive- 
ness at the red end also, whe reas red litmus and rosaniline 
diminish the sensitiveness at the red end. 
Silver Iodide. 
The one of the action ot light to be investigated 1 in the 
