Experiments on the Gas. from Coal. 399. 
On the ¢ Quality of the Gas, at different stages 
of -the Distillation. : 
The gas; which I first submitted to experi-- 
ment, was obtained from Wigan cannel coal, 
a substance preferred in this neighbourhood 
as affording aériform products, which, both, 
by their quantity and quality, more than com-: 
pensate its higher price.* _ The retorts are 
charged while red hot with this substance, and 
indeed are never suffered, during the whole of 
the winter season, to fall below the tempera- 
ture of ignition. 'The gas was collected in a. 
bladder furnished with a stop-cock, which. 
was fixed into an opening in the pipe be- 
tween the retort and the tar-pit. It was 
taken at this place, in order to avoid contact 
with water, and admixture ‘with any at- 
mospherical air, that might accidentally’ re- 
main in the gazometer. Wishing to examine 
the gas in a perfectly recent state, and find- 
ing’it impossible to make the necessary ex- 
periments with sufficient accuracy in a shorter 
interval, [ was obliged to be satisfied with 
procuring it every other hour. In this place, 
* Abouta shilling per ewt. of 112lb. or 133d. delivered 
in Manchester, ; 
