\ 
418 Hxperimenis on the Gas from Coal. 
gas; or, if all be collected, to reserve dif- 
ferent portions apart from each other, and to 
apply them to appropriate uses. Thus, when 
coal gas is conveyed in portable gazometers 
to adistance, (as is now practised by Mr. Lee 
in supplying his house two miles from the 
manufactory*) it will be important to select - 
that. gas, which in a given volume has the 
highest illuminating power, and which there- 
fore requires vessels of the smallest capacity 
_foritsconveyance. Having, I hope, furnished 
documents for solving questions of this sort, 
I shall proceed to describe in what manner 
the facts were ascertained. 
Method of Analysis. 
1. Determination of the proportions of car- 
bonic acid and sulphuretted hydrogen gases in 
coal gas. In experiments formerly made 
* A small carriage upon springs conveys two square 
close gazometers made of wrought iron plates, and each 
containing 50 cubic feet of perfectly purified gas, equiva- 
lent together to about 6lb. of tallow. Each gazometer 
weighs about 160 pounds ; and has a valve at the bottom, 
which is opened by the upright main pipe, the moment the 
gazometer is immersed in the pit. The strength of one 
man is found to be sufficient for the labour of removing the 
gazometer from the carriage to its place. 
