CHARCOAL-MAKING. 199 



liumeroias and important. In the first place, the heating power of 

 charcoal is very nearly twice that of the same weight of wood, being 

 just a little inferior to that of English coal and superior to that, 

 of Indian coal. In the second place, charcoal is easier to light 

 and maintain burning than wood, and gives out a very much more 

 steady heat. In the third place, charcoal makes a clear, smokeless 

 fire, and on this account is preferable, for metallurgical purposes, to 

 coal in the production of the finer varieties of iron and steel. In 

 the fourth place, it is always ready for immediate use, whereas wood 

 has to be cut or split up to convenient sizes. In the fifth and last 

 place, in addition to being so very much more effective and conve- 

 nient a fuel, it is less than a quarter of the weight of the original 

 wood and less than half the bulk, so that it can stand very much 

 longer carriage (at least three times as long) than wood, and thus 

 enables us to utilise the small produce of distant forests that would 

 otherwise be quite unsaleable and have to be left behind in the 

 forest to feed forest fires, favour the unchecked multiplication of 

 destructive insects and fungi, and impose a forced limit on the 

 improvement of the stock. 



There are numerous methods of making charcoal, but they may 

 all be reduced to three main systems, according to the care taken 

 to exclude air. These three systems are (1) carbonisation in re- 

 torts and close ovens, (2) carbonisation in ordinary kilns, and (3) 

 carbonisation in open pits. 



Whichever method is adopted, it is necessary that all the wood in 

 process of carbonisation should be converted into charcoal as nearly 

 as possible simultaneously; otherwise those pieces which were car- 

 bonised first would become partially or wholly consumed, or would 

 at any rate deteriorate under continued exposure to the intense 

 heat, while the carbonisation of the remaining wood was being 

 completed. Hence, woods of very different densities, as well as 

 pieces of very different thicknesses, should never be mixed toge- 

 ther. There is also another objection to carbonising woods of dif- 

 ferent densities together. The quality and, consequently, also the 

 use to which the charcoal is put, depends to a great extent on the 

 density of the wood ; so that the different qualities of charcoal 

 should be kept apart from the beginning, as it would be impossible 

 to separate them afterwards. Very thick pieces must, in any case, be 

 split up in order to hasten the carbonisation, and the thicker billets 

 may also be split up so that they may be carbonised with thin- 

 ner ones. The pieces to be carbonised should be dressed straight, 

 in order that they may pack close together. Unsound wood should 

 never be used, as it will yield no charcoal. Lastly, if the wood is 



