358 Ofi the Manvfaclure and 



form (threCj four, or five cords of wood making what is called 

 a pit), and covered with straw, fern, &c. kept on by earth or 

 sand to keep in the fire, giving it air by vent-holes as may 

 be found necessary. This mode of charring is uncertain in 

 its operation, and defective in every respect for the purpose 

 of making good charcoal ; and therefore no dependance cotdd 

 ever be placed on the charcoal so made. 



The method now adopted for making charcoal for gun- 

 powder, consists in distilling N(if I may so call it) in iron cy- 

 linders and collecting the pyro-ligneous acid, the carbon re- 

 maining in the cylinder or retort. The wood to be charred 

 is first cut into lengths of about nine inches, and then put 

 into the iron cylinder, which is placed horizontally. The 

 front opening of the cylinder is then closely stopped : at the 

 further end are pipes leading into casks. The fire being made 

 under the cylinder, the pyro-ligneous acid, attended with a 

 large portion of carbonated hydrogen gas, comes over. The 

 gas escapes, and the acid liquor is collected in the casks. The 

 fire is kept up till no more gas or liquor comes over, and the 

 carbon remains in the cylinder. 



This, it is evident, is a more eligible method than the 

 former ; and, indeed, the only proper one. The difference 

 in the vStren^th of the powder made from the two sorts of 

 charcoal will be more particularly mentioned hereafter. I 

 shall here only remark, that the proportion of powder used 

 for the several pieces of ordnance by the navy, &c. has been 

 reduced one-third in consequence of the increased strength of 

 he composition into which this cylinder charcoal enters. 



The wood, before charring, has the bark taken off; for 

 which purpose it is felled in the summer season, when the sap 

 is up, and it will flow clean. One reason for taking off the 

 bark is, that it would render the powder therefrom full of 

 sparks ; which would be of course injurious, and dangerous 

 in the use*. 



The wood made use of is either alder, willow, or (black) 

 dog-wood ; but the distillation in the cylinders making the 



* This is clearly seen by the combustion of charcoal, with the bark on, 

 in oxygen gas. 



charcoal 



