408 Mr. Henry’s Experiments on 
original bulk of the gas.* This fact evidently implies that the 
expansion ceased only in consequence of the entire destruction 
of the matter, whose decomposition afforded the light inflam- 
mable air, and this substance could not be carbon, because Dr. 
Austin admits that a large portion, and I have shewn that the 
whole of it, still remains unaltered. 
If the dilatation of the carbonated hydrogenous gas arose from 
the decomposition of water, the effect should cease when this fluid 
is previously abstracted. To ascertain whether this consequence 
would really follow, I exposed a portion of the gas, for several 
days before electrization, to dry caustic alkali. On attempting 
its expansion, I found that it could not be carried beyond one- 
sixth the original bulk of the gas. By 160 very strong explo- 
sions it attained this small degree of dilatation, but 80 more 
produced not the least effect ; though the former number would 
have been amply sufficient to have dilated the gas, in its ordi- 
nary state, to more than twice its original volume. A drop or 
two of water being admitted to this portion of gas, the expan- 
sion went on as usual ; and I may here observe, that when a 
little water gained admission into the tube along with the gas, 
in any experiment, which often happened before I had acquired 
sufficient expertness in transferring the air from water to mer- 
cury, the dilatation went on with remarkable rapidity. 
* “ After the inflammable air has been expanded to about double its original bulk,” 
says Dr. Austin, “ I do not find that it increases further by continuing the shocks. 
“ Conceiving that the progress of the decomposition was impeded by the mixture of the 
“ other airs with the heavy inflammable, I passed the spark through a mixture of the 
“ heavy inflammable air and light inflammable; but the expansion succeeded nearly as 
“ well as when the heavy inflammable was electrified alone.” Phil. Trans. Vol. LXXX. 
