From 4 pecks or 1 bushel of coals, weighing 69lbs. for which we now pay (1809) 1s. we produce 4¾ pecks of coke and ½ peck of coal not carbonised remains in the distilling pot, which together with the coke weighs 58lbs. 6 oz. value at 1s. per bushel 0 1 4 we procure 6lbs. 4 oz. of tar which we use as pith--it saves us 0 1 0 ---------- 0 2 4 Deduct for coal 0 1 0 ---------- Profit on coke and tar 0 1 0 ---------- The gas yielded by the 4 pecks of coals in the pot, make 42 brilliant lights, which burn 7 hours. To keep 42 tallow candles which were formerly used in the manufactory burning for the same time, required 7lbs. which at 1s. per lb. cost 0 7 0 To this, add profits on coke and tar 0 1 0 ---------- Gained out of every bushel of coal 0 8 0 ---------- “The gas-burners made use of in our manufactory produce jets of flame, which in our business, where much soldering with the blow-pipe must be done, have a decided superiority over Argand’s lamps. We are not nice concerning the quality of the gas--a great part of it is burned from the gasometer, without allowing it to purify itself in the gasometer, because our gasometer is not large enough to store up the whole quantity of gas we want for use.” THEORY OF THE PRODUCTION OF GAS-LIGHT, AND DESCRIPTION OF A PORTABLE APPARATUS FOR EXHIBITING, IN THE SMALL WAY, THE GENERAL NATURE OF THIS SPECIES OF LIGHT.