18 



the gradual heating of the front of the retort from top to bottom. 

 When the entire front of the retort has reached a fairly uniform tem- 



FlG. 9. Charcoal cooler used with oven retort. 



perature the fires are allowed to die down, and, when the retorts or 

 ovens are sufficiently cool, the charcoal is removed. 



FIG. 10. Plan of a modern American destructive distillation plant: A., car; B, retort; C, first 

 'cooler; D, second cooler; E, acetate drying floor; a, condensers; b, liquor trough; c, gas main to 

 boilers; i, fuel conveyor; m, fire place; n, ash pit; o, hinged spout delivering fuel from i to TO. 



If retorts are used the charcoal is placed in covered cans, but with 

 ovens, coolers (fig. 9), similar in shape, are used in which the coal 



[Cir. 36] 



