AND THE PROCESS OF CHARRING. 249 



is reduced so small as to be unfit for use. It has been proved 

 that four tons of wood when charred on a correct principle will 

 yield one ton of good charcoal. This system, however, requires 

 six tons to produce the same quantity, so that the waste occasioned 

 by it is a very serious item ; and, as I have hinted before, there is 

 a constant risk of the fire breaking out beyond control, and doing 

 irreparable damage. We have therefore abandoned the open air 

 system, and adopted that of charring the wood in two large cylinders 

 or retorts, similar in every respect to those used at powder works. 

 These retorts are 7 feet long by 3 feet 6 inches in diameter. For 

 filling them the wood is cut in two lengths, averaging from 2 to 

 6 inches in thickness, the smaller size being laid in the bottom, 

 and the heavier at the top, where the fire first strikes the retort. 

 As in the old method, it is necessary to pack close, with this 

 difference, that all the wood put in here is certain to come out, 

 and well charred. Tbe retort is closed by two doors or lids, 

 raised and lowered by block and tackle, the inner one rests loosely 

 on a flange about 9 inches from the mouth ; the outer one covers 

 the entire front of the retort, and is held firmly in position by six 

 iron keys. It is also necessary, the more effectually to exclude 

 air, to fill up with clay any inequalities between the two surfaces. 

 This being done the furnace underneath is set agoing, the coal 

 used for this purpose costing 5s. a ton. On an average the process 

 of charring takes sixteen hours • it is completed when, after draw- 

 ing out a wooden stopper in the lid, and holding a lighted taper to 

 the gas, it is ignited ; the fire underneath is then drawn out, and 

 the retorts allowed to cool for five or six hours. The two lids 

 are then removed, and the charcoal is drawn smartly out into 

 large iron pans \ as each pan is filled it is shut with a close-fitting 

 cover, which quickly extinguishes the fire. At some places the 

 vapour expelled from the wood is condensed and forms the basis 

 of useful products ; but with us the gases are brought by a return 

 pipe into the back of the furnace and consumed in the fire. It is 

 not necessary to point out the obvious advantages of this system. 

 The labour involved is not heavier than any forester's daily work, 

 and it can be done at any season of the year ; indeed, in the event 

 of a snowstorm preventing other employment, this work can be 

 carried on as briskly as in midsummer. I regret that I cannot 

 yet state the exact cost of production, as compared with the old 

 system, but it will certainly be considerably less. 



