Chemical Force in the Spectrum. 29 
carbonic acid. The curve of the production of chlorophyl, the 
curve of the destruction of chlorophyl, the curve of the visible 
absorption of chlorophyl, and the curve of the decomposition 
of carbonic acid, are not all necessarily coincident. ‘To con- 
found them together, as is too frequently done, is to be led to 
incorrect conclusions. 
Two different methods may be resorted to for determining 
the rays which accomplish the decomposition of carbonic acid. 
Ist, The place of maximum evolution of oxygen gas in the 
Spectrum may be determined. 2d, the place in which young 
etiolated plants turn green. 
I resorted to both these methods, and obtained from them 
the same results. The rays which decompose carbonic acid are 
portion of green on the other. Though the form of experimen- 
tation does not admit a close reference to the fixed lines, I think 
The two absorptive media, potassium bichromate, and 
cupro-ammonium sulphate, so often and so usefully employed 
In actino-chemical researches, corroborate this conclusion. 
Plants cannot decompose carbonic acid, nor can they turn green 
in rays that have passed through a solution of the latter salt. 
€y accomplish both those results in rays that have passed 
through the former. 
€ decomposition of carbonic acid, and the production of 
chlorophyl by the less refrangible rays of the spectrum, afford 
thus a striking illustration that chemical changes may be brought 
about by other than the so-called chemical rays. 
4th.— Case of the Colors of F lowers. 
The production and destruction of vegetable colors by the 
agency of light has of course long been a matter of common 
observation. Little has, however, been done in the special ex- 
Ae of the facts, and that little for the most part by 
ersche 
We have only to examine his memoir in the Philosophical 
Transactions (part II, 1842), to be satisfied that nearly every 
radiation can produce effects. Thus the yellow stain im 
by the Corchorus Japonica to paper is whitened by the green, 
blue, indigo and violet rays. e rose-red of the Zen weeks 
