OF HIGH REFRAN GIBILITT UPON GASEOUS MATTER. 
365 
The cell was again introduced, and after three minutes again withdrawn. The particles 
had increased considerably. Seven minutes’ action rendered them sufficiently numerous 
to be visible in the blue light. After ten minutes the coarse cloud was very plainly seen. 
The action was continued with white light after the removal of the blue liquid ; it was 
scarcely more energetic than that produced by the blue rays. 
Nitrite of butyl 1 inch. 
Hydrochloric acid 15 inches. 
Examined for a moment by white light the tube was optically empty. After ten mi- 
nutes’ exposure to the dark rays the tube was again examined by the white beam ; it 
was still optically empty. The blue liquid was then introduced, and in a J of a minute 
a long streak of cloud had formed. In 2 \ minutes a dense cloud had formed throughout 
the entire tube. An exceedingly delicate blue light, and at some parts a deep violet, 
was scattered by this cloud. After five minutes’ exposure to the blue rays an intensely 
white cloud had formed, which completely filled the tube. The action here was very 
fine. 
Bisulphide of carbon ... 8 inches. 
Nitric acid 8 inches. 
The tube was optically empty when the opaque solution was introduced ; but after 
ten minutes’ exposure to the calorific rays a faint blue tinge was observed, when the 
opaque solution was removed*. The experiment was abandoned, and the mixed vapour 
and acid were again introduced. At the beginning the tube was optically empty ; after 
ten minutes’ exposure to the calorific rays it was also empty. In two minutes after the 
introduction of the blue cell, a cloud became visible ; it quickly increased, and after four 
minutes extended throughout the tube. After ten minutes’ action a dense whitish-blue 
cloud filled the entire tube. The experiment was repeated twice with the bisulphide, 
with substantially the same result. 
These experiments are quite conclusive as to the inability of the calorific rays to pro- 
duce actinic clouds ; they are the product of the more refrangible rays of the spectrum. 
* It is sometimes difficult to get the bisulphide into the tube without this blue tinge. It is certainly due to 
some impurity. With care it can he caused to disappear wholly. 
3 C 
MDCCCLXX. 
