Clegg's j4pparatus for produchig Coal Gas, 139 



aiid the various gas establisbinentB which he has erected, proceeds 

 as follows : 



"^ Lii this wide field of practice, I have had the most favourable 

 opportunities of ascertaining the processes best calculated to pro- 

 duce, oeconomise and purify gas; and I am now happy to be able 

 to lay before the public a rlescription of an apparatus (for which 

 I have obtained a patent) that combines the advantages of ckco- 

 nomy, regularity, certainty of operation and neatness. And, by 

 the application of mechanical and chemical powers, the coal un- 

 dergoes in its distillation an entirely new arrangement of its prin- 

 ciples, owing to the rapid decomposition and uniformity of tem- 

 perature, so that the whole of the hydrogen combines with the 

 charcoal, constituting olefiant gas : thus is the illuminating power 

 increased with tlie quantity produced ; and when passed through 

 cream of lime, we have a gas equal in illuminating power to the 

 gas from common lamp oil *, and as free from sulphuretted hydro- 

 gen, with a difference of expense as 1 to 18, as stated page 143. 



" On any plan of preparing coal gas hitherto adopted, this 

 result has not been obtained. The coal having never been com- 

 pletely decomposed, a considerable quantity of combustible mat- 

 ter has been suffered to escape in the form of tar and ammonia- 

 eal liquor. Thus substances not only of little or no value, but 

 luch as were deemed nuisances inseparable from the preparation 

 gas, were produced in great abundance. To obviate these isi- 

 conveniences, which have in many instances prevented the intro- 

 duction of this invaluable discovery, I apply the coal in thin 

 strata; by which mode, I have found from repeated experiments 

 upon an extensive scale, that Newcastle Wall's End coal will 

 yield per chaldron 25,000 cubic feet of gas, of a very superior 

 quality; whereas upon the former plan, 10,000 cubic i'eet is the 

 utmost average quantity which has been obtained f. Besides, 

 as the matter which has usually escaped in the fortn of tar and 

 ammoniacal liquor is completely decomposed, not only an in- 

 creased quantity, but a very superior quality of gas is obtained. To 

 produce these effects, the strata of coal ou^ht not to exceed half 

 an inch in thickness, and must be introduced to a red heat, with- 

 out the retorts being exposed to a mass of fresh coal ; for tliix 

 lowers their temperature so much tliat several hours are requisite 

 to raise them to their proper degree of heal: hence so large a 

 proportion of tar-water and inferior gas is produced, besides llu' 

 Ios« of time and fuel. As the coal is introduced in small portiou* 



* See Dr. Henry's paper in the Literaiy and Pliilosopliical TrannactioiiK 

 of ^!anchc-stcT, vol. hi. Second Seiit's, or the I'hiiosoplueal Mii};a^ine lor 

 Auj^iist IBiy, and Accurn's last Treatise on Gas Li;,MUs, pp. 12!', l.iO. 



t The difference in the quantity of [;as pioduted by tlie two iuo^e(< of 

 operation bears the same proportiju, vrlutcer description of coal is used. 



by 



