530 AUXILIARY FOREST INDUSTRIES. 



generally the wood is split and used in small pieces, large 

 pieces of wood being used in the latter. 



The length of the billets may be either that usual for fire- 

 wood, or a special length may be given to charcoal-billets (rarely 

 exceeding 6 feet). The shorter the pieces the easier it is to give 

 the kiln its requisite shape, and the less the cost of its con- 

 struction. Excepting small round billets under 2f inches (7 cm.) 

 thick, the wood should all be split; stump-wood also should, as 

 far as possible, be split into small pieces. This is especially 

 necessary for broadleaved woods, which burn slowly. In order 

 that the wood may be packed closely, all snags and uneven- 

 nesses should be trimmed off, and fairly smooth, straight pieces 

 set aside on the felling-area for charcoal-making. Crooked 

 and bent branchwood is used only in short pieces. In piling 

 the kiln, besides the round and split billets, short little pieces 

 of wood are used to fill interstices between the billets. 



ii. Shape and Size of Kilns. 

 The usual shape of a kiln is that of a paraboloid, the volume 



72 7 



of which is c X L where d is the diameter and k the 

 height of the kiln ; or, as it is easier to measure the girth than 

 the diameter of completed kilns, 2* X - X - = <^- 



As, however, the shape of a kiln is usually not quite a para- 

 boloid, but somewhat steeper and more pointed, 4 to 6 per cent, 

 may be deducted. Some useful tables* have been prepared 

 for the cubic contents of kilns. It is easy to calculate the 

 volume of a kiln whenever wood already stacked is used. 



Kilns vary greatly in size in different districts ; sometimes, 

 as in the Spessart, Thuringia, etc., they contain only 400 to 700 

 stacked cubic feet (12 to 20 st. cub. meters), whilst in the 

 Harz they may be five times as large, and ten times as 

 large in the Alps. In the common method a kiln of 1,000 

 to 1,400 st. cub. feet gives the best outturn and is easiest to 

 manage. 



* Bohmerle, "Tjii'cln /.ur Herechnung dcr Kuhicinlialtc stclicndcr Kohlcn- 

 meiler." I'.crlin, l';iul hmsy, 1*77. 



