718 WOOD-CARBONISATION. 



fillinf,', while owing to the thick covering the weather has hardly 

 any influence on the process ; but in spite of these advantages 

 V. Berg has shown that the yield is less than in vertical kilns. 

 As the firing proceeds lengthwise in order that the ends of 

 the logs may burn, one end of the kiln is exposed to the fire too 

 long, and when the charcoal is removed at that end, air is 

 admitted and much charcoal burned. This method therefore 

 yields not only lighter charcoal but a smaller volume in pro- 

 portion to the amount of wood than the others. 



It therefore appears that the common method, with kindling 

 from below, gives the best results. The comparative outturn of 

 charcoal in quantity and quality, however, greatly depends on 

 the skill and foresight of the burners, which is really the most 

 important of all factors, as experience shows in the case of 

 permanent sites of kilns where the burners are frequently 

 changed. 



(g) General results. — Charcoal may be measured by weight or 

 volume, the hitter being more usual and large baskets or 

 rectangular measures being used for the purpose. 



Coniferous wood yields more charcoal than broad-leaved 

 species ; soft, broad-leaved woods less than coniferous wood 

 but more than hardwood. Branchw^ood and wood in the round 

 yield less than split wood. The yield from horizontal kilns is 

 often given as greater than that of common kilns, but these 

 results are of doubtful accuracy. 



The average yield from forest kilns may be considered good 

 for broad-leaved wood with 48 — 50% by volume, and for conifer- 

 ous wood with 55 — C0%. 



V. Berg* gives the following percentages : — 



Auleituu"' ziim Verkolileu dcs Ilolzes. 



