COPPER 



929 



transference, and that the heat communicated may be greater towards the termination 

 of the operation than at the commencement thereof. 



528 



Gcrstenhofer's Furnace for calcining Copper Ores. 



This invention -will be fully understood by the accompanying drawings of apparatus. 



Fig. 529 is a side view of the furnace, a,udjig. 530 a longitudinal section, in both 



of which the two ends only are shown, the whole being of considerable length. One 



529 



] 



Spence's Furnace for calcining Copper Ores. 



now in operation is fifty feet long, with twelve doors for the transference of the ores ; 

 but these dimensions may be varied, and aro only mentioned for the purpose of 

 Vol.. I. 30 



