332 Method of producing Heat, Light, and 
quired. The weight of the counterpoise will be most easily 
found by experiment. If it be too little, it will correct the 
evil in part but not entirely ; the bellows will therefore still 
gain some force as they fall. | If again the counterpoise be 
too great, the bellows will have most force when full, and 
will gradually lose force as they fall. In testimony 
whereof, &c. 
LIX. Method of producing Heat, Light, and various 
useful Articles, from Pit-Coal. By Mr. B. Coox, of 
Birmingham *, 
Sir, Hav: ING paid much attention to the procuring of 
gas and other products from pit-coal, I now beg leave to lay 
before the Society for the Encouragement of Arts, &c. the 
results of some of my experiments on pit-coal, and the 
methods of procuring the sundry articles of which I have 
sent samples, and a japanned waiter varnished therewith. 
The quantity of clear tar which may be produced from 
every hundred weight of coal is about four pounds, from 
which a liquor, or volatile oil, may be distilled, which’ an- 
swers the purposes of oi] of turpentine in japanning. Every 
gallon of tar will produce nearly two quarts of this oil by 
distillation, and a residuum will be lett nearly, if not quite 
equal, to the best asphaltum. [ have sent a waiter, or hand- 
board, japanned with varnish made from this residuum, 
and the volatile oil above mentioned, This dries sooner, 
and will be found to answer as well as the best oil of tur- 
pentine, a circumstance which will be of immense advan- 
tage to this country, as in the vicinity of Birmingham only, 
nearly ten thousand tons of pit-coal are coked or charred 
per week ; andali the tar hitherto been lost; but by my pro- 
cess, I dare venture to say, that from the various coal-works 
in this kingdom, more tar might be produced than would 
supply all our dock-vards, boat-builders, and other trades, 
with tar and pitch, “besides furnishing a substitute for all 
the oil of turpentine and. asphaltum used inthe kingdom, 
and improving the coke so as to make iron with less char- 
coal. 
I have sent a large specimen of the asphaltum, and three 
vial bottles containing as follows: 
No. 1.--A sample of the oil or spirit, being part of that 
* From Transactions of the Society for the Encouragement of Arts, Manuface 
tures, and Commerce, for 1810. The. Society voted their silver medal to 
Mr. B. Cook for this invention. : 
which 
