362 ^ 
any effect in it. Portions of them were then mixed, 
with equal bulks of oxymuriatic gas, in glass tubes 
which were closely-stopped. At the end of 24 hours, 
the mixed gases were opened under water, when a 
great dimunition of volume took place ; and the re- 
sidual gas, after two or three transmissions through 
lime water, gave abundant evidence of the presence 
of carbonic acid gas. When the gaseous mixture, 
consisting of carburetted hydrogen and oxymuriatic 
acid gas, was exposed to the direct agency of the so- 
lar rays, a dense white cloud instantly appeared, 
which soon subsided. A diminution of the volume 
of gas was then immediately produced, and by the 
method already described, the presence of carbonic 
acid in the residual air was at once detected. This 
effect of the sun's rays in quickening the action of 
hydrogen and oxymuriatic gases was observed by 
M. M. Gay Lussac and Thenard * ; and also by Mr 
Daltonf. These results, therefore, sufficiently prove, 
that animal as well as vegetable substances undergo 
such spontaneous changes as enable them to yield 
their carbon to the gases which may surround them j 
and they shew likewise that the carbon, which thus 
unites with nitrogen or hydrogen gas, may be again 
separated by the superior affinity of oxygen J. 
* Mem. d'Arcneil, torn. ii. p. 349- 
t Chem. Phil. p. 300. 
I We were led to this method of experiment by witnessing, m 
the late experiments of Mr Murray on the nature of oxymuriatic 
acid gas, the facility with which the carburetted gases and oxy- 
muriatic gas act on each other at low temperatures in day light : 
and, by exposing the gaseous mixture to the direct rays of the 
