WOOD CHARCOAL— ITS MANUFACTURE AND USE. I 5 



well made, quite inodorous. It is perhaps needless to say that, 

 in burning, it gives off carbonic acid gas like most other 

 combustibles. 



We now come to a class of wood charcoal, namely, flake 

 charcoal, differing in the shape of the raw material used, and 

 the totally different plant necessitated by its form, which plant 

 in its turn materially affects the conditions under which it is 

 produced. As a matter of fact, the weight of acid from any 

 wood, whether in the log or in shavings (the raw material for 

 flake charcoal), is the same for equal moisture, but shavings 

 produced in the manufacture of spools for thread are made 

 from very dry wood, distil quickly, and allow of very high 

 temperatures being used in order to get a large daily output 

 per unit plant. This high temperature, however, has an effect 

 on the charcoal, which is much lighter than that produced from 

 logs, but the yield in charcoal is much less, being about 33 per 

 cent, of the weight of the logs (after deducting moisture) and 

 under 20 per cent, of the weight of the shavings. The charcoal 

 produced from the shavings is thus more difficult to ignite than 

 that made from the logs, and is also much lighter per cubic foot. 

 It is this latter quality which makes it so valuable (along with 

 its shape) for insulation. 



A word or two now about the manufacture of charcoal. 

 Originally, and following the experience of charcoal made as 

 the result of a fire of wood, wood was piled in a heap in the 

 open. It was then set on fire and covered up with earth, mud 

 or clay, which cracked in all directions, under the influence of 

 heat and the pressure of the gases. The gases oozed out through 

 the cracks thus formed in great quantities up to a certain point, 

 and then gradually fell off, till when the wood was completely 

 carbonised they stopped almost completely. The cracks were 

 then carefully plastered over and the heap left to cool. A 

 variation on this process was subsequently made by digging a 

 trench in which the wood was placed, thus diminishing the 

 surface which had to be plastered. Both these methods are 

 still in use all over the world in spite of their great antiquity. 

 I was lately in the English lake district, and was taken high up 

 into the hills, where I saw men at work making the heaps, 

 firing some and smothering others. As the entrance of air 

 during the cooling process would mean a loss of charcoal 

 through burning, and as the charcoal burners are only paid 



