392 Experiments on the Gas from Coal. 
By the first train of experiments, I en- 
deavoured to derive, from a careful analysis 
of the compound combustible gases, a mea- 
sure of their illuminating power, admitting 
of more exact appreciation, than the optical 
method of a comparison of shadows. The 
one, which I was led to propose as the most 
accurate, and which I still think entitled to 
preference, was the determination of the 
quantities of oxygen gas consumed, and of 
carbonic acid formed, by the combustion of 
equal measures of the different inflammable 
gases; that gas having the greatest illuminat- 
ing power, which, in a given volume, conden- 
ses the largest quantity of oxygen. The aver- 
age results of a great variety of experiments 
were comprized in the following table. 
Kinds of gas. Oxygen gas required Carbonic acid 
to saturate 100 produced, ~ 
measures, 
Pure hydrogen............ 50 
Gas from moist charcoal 60 .......--.sceeesereee OD 
WOOd (Oak)...6. D4 ccessereseeveereeeee OO 
dried peat...... GB ...ceccssvecsveees 43 
cannel coal ...170 ..ssscsseeeseeeeesee 100 
Jamp-oil........190 ...... seecees deveese 124 
WAX. cescceereee RPO sseessveeseces mere 
Olefiant 2aS....cssese00es2Bd seccesereeesecereeel 79 
In the same essay, I maintained an opinion, 
which, on the most mature consideration, I 
see no reason to change; that the great va- 
