CHARCOAL-BURNING. 



325 



The usual Continental method is very similar (Fig. 92) ; but the kiln 

 is built up with billets about 3 ft. long, and those over 6 in. diameter 

 are split ; and in building up the kiln the largest pieces are put halfway 

 between the centre and the circumference, where the heat is strongest, 

 while the lighting usually takes place from below by withdrawing a pole 

 originally laid on the ground when the kiln is being built up. The lowest 

 layer of billets rests directly upon the ground, and not on a staging, and 

 split billets are set face inward. The kiln is first covered with turf, moss, 

 bracken, conifer sprays, &c., and then top-covered with earth and charcoal 



Fig. 92. 



Dome-shaped (Parabaloid) Charcoal- Kiln. 



a. Central section ; showing arrangement of wood in kiln (with largest billets about 



half-way between centre and circumference). 

 6. Outer view ; showing smoke- vents, and lower and upper supports. 



dross, this surface-coating varying from about 3 in. to 10 in. in thickness, 

 according to circumstances, and being supported by wooden rests. The 

 kilns are large, up to 2000-3000 cubic ft. on permanent hearths, but about 

 1000 cubic ft. on temporary hearths ; and the hearth is made to slope 

 slightly from centre to circumference, sheltered places being of course 

 chosen, and, if necessary, protecting screens erected against winds. Old 

 hearths are best, and the kilns are built up, so far as possible, of only 

 one kind of wood, to equalise the rate of carbonisation. For the first 

 hour or two the kiln "sweats ".and gives out pungent, acrid smoke, and 

 there is always a chance of an explosion through rapid conversion of the 

 moisture into steam. Carbonisation begins about an hour or two after 



