326 THE UTILISATION OF WOODLAND PRODUCE. 



lighting, but sweating continues for most of the first day. At about 

 12 to 16 hours shrunken hollows are opened and quickly filled with wood ; 

 and when the sweating-stage is ended smoke-holes are opened with a 

 pointed stick to regulate combustion, as shown by the colour of the smoke 

 issuing, and the success of the charcoal- burn ing depends greatly on the 

 manipulation of these smoke - holes. When carbonisation is completed 

 down to the circumference of the kiln all the vents are closed, moist earth 

 is thrown over the kiln, and it is allowed to cool down for twenty-four 

 hours before being opened. Large kilns on permanent hearths take about 

 10 or 12 days to burn, while kilns of about 1000 cubic ft. take 5 or 

 6 days. The charcoal is drawn at night while still hot, and is sprinkled 

 with water to prevent its glowing again. Then it is assorted into foundry 

 and smithy charcoal, and smaller pieces are passed through wire-screens 

 and also assorted. But everywhere on the Continent charcoal-burning is 

 now a decadent industry owing to the new wood - pulp and cellulose 

 factories. 



Good charcoal should be deep black in colour, with a steel- 

 blue metallic sheen, and lustrous across a transverse section, 

 and when two pieces are clinked together they should give a 

 metallic sound. Charcoal that is reddish-brown is incompletely 

 carbonised, while softness and dull colour indicate over-burning 

 or unsound wood. Its specific gravity averages about 0*20 ; 

 but hardwoods produce heavier and better charcoal than soft- 

 woods, well -seasoned wood more than greenwood, and large 

 billets more than small billets ; and the slower the process of 

 carbonisation, the heavier is the charcoal. Good kiln-burned 

 charcoal should give in volume from 50 to 60 per cent of the wood 

 used, and in weight about J of its original weight; and it 

 usually weighs about one stone per bushel. A ton-weight of 

 wood produces about 40 bushels of charcoal on the average, 

 but only about 36 if all hardwood, and about 43 if all soft- 

 wood though these average figures may vary greatly according 

 to circumstances. 



Charcoal-making costs about Id. per bushel, or 13s. 4d. per 

 ton, and it sells at about 60s. per ton ; and as 4 tons of cord wood 

 give about 1 ton of charcoal, this shows 46s. 8d. in all, or 11s. 8d. 



