Dr Fyfe on the Comparative Value of Oil and Coal Gas. 175 
On the Quantity of Gas obtained from Coal. 
The quantity of gas to be got from coal varies according 
to the coal employed, and the manner in which it is treated ; the 
quality also depends on the mode of applying the heat. Taking 
it for granted that the most advantageous method of decomposing 
it is followed, the quantity from the different kinds of coal varies. 
In stating the proportions, therefore, we can come only at an 
average conclusion. 
Mr Peckston, in his work on Coal-gas, states, that a chaldron 
of Newcastle Walsend coal will yield 10,000 feet, supposing it 
decomposed under the most advantageous circumstances ; 2 cwt. 
will, therefore, yield about 750 feet. 
At Edinburgh, 2 cwt. of parrot-coal yield on an average 860 
feet of gas *. 
According to Mr Neilson, engineer, Glasgow, 2 cwt. of Les- 
mahago coal will produce 1080 cubic feet of gas, allowing 4J to 
each pound, Mr llussell of London has stated the quantity 
from Newcastle coal to be the same, 4j feet per pound. Mr 
Dewy, in a late paper in the Annals of Philosophy, asserts, that, 
at Liverpool, Mr King considers it good economy to procure 
7000 feet from a ton of Wigan Orral-ccal, making it only 700 
feet from 2 cwt., a very little more than 3 feet per pound. He 
has stated also, that, at Glasgow, 1200 feet are procured from 
2 cwt. of cannel-coal, which is considerably above that mentioned 
by Mr Neilson. From these various statements, the general con- 
clusion has been drawn, that 2 cwt. of good coal ought to yield 
about 1000 feet of gas. 
With respect to the quantity to be got from oil, this must of 
course also depend on the nature of the oil, and the manner of 
decomposing it. Mr Ricardo mentions, that, from repeated trials, 
in various oil-gas establishments, it has been ascertained that 1 
gallon produces 100 cubic feet. From the experiments of Mr 
Brande and Mr Faraday, it appears that the same quantity af- 
fords from 100 to 110 feet. In some instances I have known 
it amount to about 120, but in these cases it was not good, the 
additional quantity having been derived from substances put 
* The gas yielded by this coal is found to be of superior quality to that from 
the other kinds submitted to trial. 
