Preparation of Charcoal. 



151 



vantage from having several near together, that they may be watched 

 and attended at less expense. 



603. In kilns of every form it will be found that the acid vapors 

 of the smoke tend to act upon the lime in the mortar, and to corrode 

 the iron-work exposed to its action, requiring attention, .in order to 

 prevent failure or accident from this cause. It is this action of 

 smoke upon the mortar in chimneys that sometimes renders them 

 unsafe when they become old. 



604. Charcoal made at low temperatures contains relatively more 

 carbon and other gaseous elements than at a high degree of heat. 

 The quantity also depends on the temperature, and the duration of 

 the process. The weight and excellence is generally in proportion 

 to the dry weight of the wood from which it is made, and it is 

 more easily kindled, if made at a low heat. 



605. The average yield in weight and volume varies, as will be 

 seen by the following table : 



Percentage of Charcoal made in Standing Metiers, as shmvn by European 



Experiments. 1 



606. In laying-raeilers, the average per cent of the coniferous 

 woods is about 23 by weight, and 60 by volume and for beech woods 

 22 per cent of weight, and 50 by volume. 



1 From Fromme's Austrian Forest Calendar, 1882, p. 255, upon various 

 authorities there cited. 



