82 
Prof. Draper’s Experiments on the Light 
Bichromate of potassa. 
Chromate of potassa. 
Yellow hydrosulphuret of ammonia. 
Hydrosulphuret of lime. 
Muriate of iron. 
Chloride of gold. 
Chloride of platinum. 
It is to be remarked, that every one of these solutions is 
yellow, but I also found that a great many vegetable coloured 
infusions would in like manner absorb the chemical rays, 
especially those which have ^yellonx) tint. 
2. When I exposed pieces of paper covered with a layer 
of chloride of silver, to a beam which had passed through the 
red sulpho-cyanate of iron, the paper became of a brick-red 
colour; if to a beam which had passed through a solution of 
sulphate of copper and ammonia, it became of a blue brown; 
and lastly, on exposing a piece in a box which I shall pre- 
sently mention, for five days, to light which had been acted 
on by bichromate of potassa, it became perceptibly of a faint 
yellowish green. 
3. It is very probable, that there exist in the sunlight, rays 
having particular chemical powers. 
A beam which has passed through bichromate of potassa, 
does not appear to cause the union of a mixture of chlorine 
and hydrogen. I kept such a mixture for several hours in it, 
and could not perceive any change. 
But this same beam can nevertheless enable vegetable leaves 
to effect the decomposition of carbonic acid. I took a wooden 
box, about a cubic foot in dimensions, and having removed 
its bottom, replaced it with a pair of parallel plates of glass, 
so adjusted that there was an interstice between them of half 
an inch or thereabouts. Into the trough thus formed, I poured 
a solution of bichromate of potassa, or any other salt under 
trial, and the box being raised on one end, served as a closet 
in which bodies could be exposed to the action of beams that 
had passed through any given medium. 
In th is little chamber, its trough being filled with a solu- 
tion of the bichromate, I placed a mattrass containing water 
slightly impregnated with carbonic acid, and a few vegetable 
leaves ; after a little while, air bubbles were copiously given 
off; there had been placed, similarly in all respects, another 
mattrass in the direct rays of the sun, and when> a quantity 
of gas sufficient for analysis was evolved, it was found that 
carbonic acid had in both cases been decomposed, though, 
as might have been expected, in the latter more energetically. 
The result gave a mixture of carbonic acid, oxygen, and ni- 
