Tak ea aia 
Experiments on the Gas from Coal. 397 
gradual diminution took place, as the process 
advanced, in the combustibility of the gas, 
as determined by its requiring less and less 
oxygen for saturation. A great variety was 
ascertained to exist in the quality of the gas 
from different kinds of coal; that from 
Wigan cannel, holding the highest rank in 
illuminating power, and that from the stone 
coalof South Wales, the lowest. 
Since the period when the second of these 
papers was published, the use of artificial 
gases, as a source of light, has been rapidly 
increasing’ in‘ this, and, I believe, in other 
countries, and promises to attain an extent 
and importance, sufficient to justify any ‘la- 
bour that may tend, however remotely, to its 
improved application. It has frequently 
happened, of late years, that I have been 
requested’ by the proprietors of large manu- 
factories lighted by gas in this neighbourhood, 
to give an opinion on practical points, res- 
pecting some of which I felt myself incom- 
petent ‘to decide, from’ the want of the ne- 
cessary data. It isto supply these data, that 
I have once more returned to the investiga- 
tion of the subject. The objeets,. which I 
have had it.in. view: to determine by the fol- 
lowing course of experiments, are; whether, 
on the large scale of manufacture, there is a 
