150 



Preparation of Charcoal. 



part. AJong the sides are air-holes (a, h, c,) that may be closed at 

 will. 



Fig.l. 



SIDE ELEVATION 



END ELEVATION 



79. CAarcoaiiTiins.— Side elevation, with air-holes, a, 6, c. End elevation, with 

 air-holes, a, b, r., an iron door, rf, for filling with Avood and withdrawiiis coal, 

 and .'^mall door, e. for completing the filling. Cross-section, with air-holes, 

 doors, etc., as in end elevation. The figures on dotted lines are feet and 

 inches. 



601. Other kilns are cylindrical, with a low arch for a cover, but 

 the principle of their operation does not essentially differ from that 

 above represented. They all have openings for admitting air around 

 the base, and for the escape of gases from above, all of which may 

 be closed at will. 



602. In another method, the kilns are of brick or stone made 

 round and somewhat conical like a hay-stack, with openings on the 

 side for filling and emptying, and air-holes for regulating the burning. 

 They are of various capacities, but generally hold from 40 to 60 

 cords of wood. They are best built upon sloping ground, with doors 

 on the upper side for filling, and at the bottom for removing the 

 coal, and in both rectangular and conical kilns there is a further ad- 



