CHARCOAL-MAKING. 547 



(a) Kind of wood. All wood being converted into charcoal 

 naturally shrinks. Dry wood shrinks less than green wood, 

 and consequently gives a larger return. Large pieces of wood 

 also yield in volume more charcoal than small pieces, as more 

 of the former can be piled in a kiln. 



(b) Situation of kiln. The nature of the site of a kiln has 

 an important effect on the yield of charcoal, a new site yielding 

 less than one repeatedly used. 



(c) State of the weather. The weather has important 

 effects on the yield of a kiln. Uniformly still weather, which 

 occurs frequently in late summer and autumn, is best ; change- 

 able weather, accompanied by storms, is most unfavourable. 



(d) Process of burning. Slow, careful progress, especially 

 during the earlier part of the burning, not only yields heavier 

 charcoal, but also a larger volume of it. 



(e) Duration of the burning. The length of time during 

 which a kiln should burn is very variable and depends on its 

 size, on the dimensions and degree of dry ness of the billets, the 

 quicker or slower action of the fire (according to the site, 

 arrangement of the wood, weather, etc.) and many other 

 circumstances. Small kilns of sprucewood containing 700 to 

 1,000 stacked cubic feet are carbonised in 6 to 8 days, beech- 

 wood in somewhat less time. Large kilns containing 3,500 to 

 7,000 cubic feet, in favourable weather, require about 4 weeks 

 to burn, and in unfavourable weather, 5 to 6 weeks. 



(f) Methods of carbonisation. It is difficult in practice to 

 decide which method gives the best outturn, as there are so 

 many intervening facts. It appears, however, that the common 

 method, with kindling from below, gives the best results. The 

 comparative outturn of charcoal in quantity and quality 

 depends greatly 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 latter being more frequent and large baskets or 

 rectangular measures being used for the purpose. 



Coniferous wood yields more charcoal than broadleaved 

 species ; soft, broadleaved woods less than coniferous wood, 



N N 2 



