170 On the acriform Compounds 
gravity and chemical properties, are occasioned by the tempera- 
ture at which it is produced. So far as my experience goes, no 
temperature short of ignition is sufficient for the decomposition 
of oil into permanent combustible gases; but the lower the heat 
that is employed, provided it be adequate to the effect, the hea- 
vier and more combustible is the gas, and the better suited to 
artificial illumination. 
From the experiments which I published in 1805, and which 
were made on a single specimen of oil gas, I was led to consider 
it as constituted of one volume of olefiant gas with seven volumes 
of mixed gases, of which the greatest part was ‘carburetted 
hydrogen. Mr. Dalton has since favoured me with a specimen 
of oil gas prepared by himself, which contained in 100 parts, 40 
of a gas condensable by chlorine; and it appears from the table 
that oil gas, manufactured on the large scale, may contain in 
100 parts, 38 parts of a gas similarly characterized*. It is not 
improbable indeed, that, by a temperature carefully regulated, the 
whole of the aériform fluids may be obtained from oil, of such 
quality as to be entirely condensable by chlorine; and from the 
great superiority of the light which such a gas would afford, and 
the reduction that might be effected in the capacity of the gaso- 
meters, the discovery of a mode of producing it in this state would 
be an important practical improvement. 
The inferences respecting the nature of the gas from oil, I re- 
serve till after the aceount of the experiments on coal gas, as the 
same remarks, with some slight modifications, will apply to both 
cases. 
Experiments on the Gas from Coal. 
The numerous experiments and observations on the gas from 
coal, which I have already published, appear to me to preclude 
the necessity of going much into the subject on this occasion. 
What I have lately had in view, has been to render the analysis 
of this gas more complete, by a careful examination of that por- 
tion of it which remains after the action of chlorine. The gas, 
submitted to these recent experinfents, was prepared from Wigan 
cannel, at the manufactory of Messrs. Philips and Lee. _ It was 
collected from an opening in a pipe between the retort and the 
tar-pit, generally about an hour after the commencement of 
the distillation, except in the instance of the gas No. 4, which 
was taken five hours, and No. 5, which was taken ten hours, 
* Since this paper was written, I have received from Mr. Phillips a se- 
cond specimen of gil gas prepared by Messrs. Taylor. It contains in every 
100 volumes, 42 or 43 parts of gas condensable by chlorine ; but in other 
respects very nearly agrees (making allowance for the greater proportion 
of that ingredient) with the gas described in the text. 
from 
