for ManufaBur'ing Cajl Iron. 2i 



reaching from top to bottom, into which the burning fuel 

 is introduced. This is immediately covered by fmall pieces 

 of coal beat hard into the aperture : thefe reprefs the kin- 

 dling fire from afcending, and oblige it to feek a paffage by 

 creeping along the bottom, which is moft expofed to air. In 

 this progrefs the fire of each vent meets, and, when united, 

 rife gradually, and burft forth on all fides at once. 



If the coal contains pyrites, the combuftion is allowed to 

 continue a confiderable time after thedifappearance of fmoke; 

 the fulphur then becomes difengaged, and part of it is found 

 in flowers upon the furface of the heap. If the coal is free 

 from this hurtful mixture, the fire is covered up in a fhort 

 time after the fmoke difappears; beginning at the foun- 

 dation, and proceeding gradually to the top. 



The length of time neceflary to produce good coaks de- 

 pends upon the nature of the coal to be coaked, and the ftate 

 of the weather. In 50, 60 to 70 hours the fire is generally 

 completely covered over with the afhes of char formerly 

 made : the coaks, thus entirely fecluded from air, foon cool, 

 and in 12 or 14 days may be drawn and wheeled to the 

 furnace. 



It is with pit-coal, in a great meafure, as with wood, in 

 the procefs of charring. Coals do not always afford a weight 

 of coaks in proportion to the quantity of carbon in the coal. 

 It depends more upon the capability of the coal to refill the 

 wafte occafioned by combuftion, fupported by external air, 

 than upon the real quantity of carbon inherent in the coal ; 

 as may be feen by comparing the lofs of weight which coals 

 undergo in the large way, and the refults obtained from the 

 fame coals, by burning them unexpofed to external air in 

 the fmall way. 



The lofs fuftained in coaking coals fit for the purpofe of 

 manufacturing, or melting iron, is found to be nearly as 

 follows ; 



4240 pounds of free coals - - yield 700 lbs. coaks, lofs 1540 lbs. 

 JU4Q - . of fplint andfree coal mict - L'40 lbs. coaks, loi's 1400 lbs. 



C 3 *Z40 



