l£ On the Materials ufc.T 



manner that no greater a portion of it may undergo corn 1 -- 

 ouftion than is neceflary to produce that effect.. Hence the 

 neceffity for guarding againft too free an accefs of air during 

 the procefs. As foon as the operation is ended, which may 

 laft for 10 or 14 days, the whole is more clofely covered up, 

 and kept fo till fuch time as the char is deemed fufficiently 

 cool to be fit for drawing : it is then feparated from the 

 earth, and carried away in bags or in waggons. Thofe 

 pieces of wood not fufficiently charred arc by the Workmen 

 called brands, and are commonly ufed for fuel to the next fire. 



The loi's of weight i.i charring wood is inconceivably 

 great. In the large way it is almolf. impofhble to afcertain 

 it to any degree of exatlnefs. The qualities of wood are fo 

 various, and the tendency which fome have beyond others 

 of parting with their juices, even when expofed to the fame 

 temperature, render it at belt but a matter of dubiety. I 

 mall however infert a few which I have charred in the 

 fmall wav, and the refults obtained from them ; before 

 weighing they were all expofed to the fame temperature for 

 a confiderablc time, and thoroughly dried. 



It is however worthy of remark, that the produce in 

 charcoal in the fmall way, does not give an invariable 

 ttandard whereby to judge of that obtained on a large fcale, 

 where ignition is caufed by the ad million of external air 

 into contact with the wood. In the large way the quantity 

 of char afforded will depend more upon the hardriefs and 

 cooipaftnefe of the texture of wood, and the (kill of the 

 workman, than on the quantity of carbon it contains. In 

 the following tables I have fimply cxprefled the exiftence of 

 the alkaline principle, in the various afiies obtained from the 

 combuftion of I pound of wood avoirdupoife weight: this 

 may be of ufe to thole who with to make experiments upon 

 the formation of pot-afh. It will alfo be obferved,. that there 

 are fome woods that yield a much larger proportion of 

 carbon than oak : thefe, however, are either too fcarce or 

 too valuable to be applied to the manufacturing of iron in 

 this country. 



- tabu: 



