300 CHEMICAL DISCOVERY AND INVENTION 



ovens generally take the form of some modification of the 

 Coppee oven, in which the principle is quite different. Instead 

 of generating the requisite heat by the combustion of a portion 

 of the coal the charge in these ovens is never brought into con- 

 tact with air, but is submitted to a process of distillation by 

 heating in closed chambers. The heat required is obtained by 



Cos 



FIG. 100. COPPEE OVEN. 



combustion of the gas given off by the coal within, and further 

 economy is secured by making use of the regenerative principle, 

 that is to say the gas before being burnt and the air required to 

 burn it are both heated by passage through ducts arranged 

 between the retorts or ovens. The principle of the construction 

 of such ovens will be understood by referring to the adjoining 

 diagram. Here is seen a section across two of the ovens which 

 are chambers some 25 feet long, having a door at each end by 

 which the finished coke can be withdrawn. The coal is charged 



