125 
Application of the Gas from Coal. 
exactness with which the business of this mill is conducted, 
afforded as excellent an opportunity of making the compara- 
tive trials I had in view, as is perhaps likely to be ever obtained 
in general practice. And the experiments being made upon 
so large a scale, and for a considerable period of time, may, I 
think, be assumed as a sufficiently accurate standard for de- 
termining the advantages to be expected from the use of the 
gas lights under favourable circumstances. 
It is not my intention, in the present Paper, to enter into a 
particular description of the apparatus employed for producing 
the gas ; but I may observe generally, that the coal is distilled 
in large iron retorts, which during the winter season are kept 
constantly at work, except during the intervals of charging ; 
and that the gas, as it rises from them, is conveyed by iron 
pipes into large reservoirs, or gazometers, where it is washed 
and purified, previous to its being conveyed through other pipes, 
called mains, to the mill. These mains branch off into a variety 
of ramifications (forming a total length of several miles), 
and diminish in size, as the quantity of gas required to be 
passed through them becomes less. The burners, where the 
gas is consumed, are connected with the above mains, by short 
tubes, each of which is furnished with a cock to regulate the 
admission of the gas to each burner, and to shut it totally off 
when requisite. This latter operation may likewise be instan- 
taneously performed, throughout the whole of the burners in 
each room, by turning a cock, with which each main is pro- 
vided, near its entrance into the room. 
The burners are of two kinds : the one is upon the prin- 
ciple of the Argand lamp, and resembles it in appearance ; 
the other is a small curved tube with a conical end, having 
