PETER SPENCE 269 



Spence tried his hand at it. He ground the 

 ore into a fine powder, and treated it with 

 hydrochloric acid, so dissolving out the 

 sulphide of lead, the sulphide of zinc 

 remaining unacted on ; the undissolved blend 

 he calcined, and extracted the zinc by 

 volatilising it in the usual way, and the 

 residue containing the copper and silver he 

 melted, and separated the metals by one of 

 the well-known processes. He succeeded no 

 better than others who have undertaken the 

 same task. His treatment of copper ores was, 

 by two or three methods, to bring the copper 

 into solution, and out of the solution to 

 precipitate the copper as sulphide with 

 sulphuretted hydrogen obtained from chemical 

 waste. 



In his smelting processes, his patents refer 

 to the construction of calciners. His object 

 was to utilise, as much as possible, waste heat, 

 and to bring the calcined ore, while hot, direct 

 from the calciners into the melters. Some of 

 his furnaces were built directly over the 

 smelting furnaces, and others had a series of 

 floors and the ore was drawn from one to the 

 other ; then, again, he invented a mechanic al 

 rabble which worked backwards and forwards 

 at intervals, and he designed a method for 



