TREATMENT OF ORES. 125 



where fuel or water is absent from the immediate neighbour- 

 hood of a mine, or when the locality is at a distance from 

 civilisation, there are many points of importance which arise 

 when the adoption of any particular plant or process has to 

 be decided upon. A very great deal of thought has for 

 many years, and is now, being bestowed in finding out more 

 effectual and cheaper ways of dealing with silver and gold- 

 bearing ores. Many a mine has to be closed on account of 

 bad management, of its too great working expenses, or due 

 to inability of a process to secure all the valuable metal in 

 the ore. Certain it is that in different parts of the world, 

 such as Western America, South Africa, &c., there is an 

 immense quantity of what to-day is called low-grade ore, 

 which, under favourable circumstances, at a future date, 

 may be turned to profitable account ; and which now might 

 be worked if only the cost of treatment per ton of ore 

 could be reduced by a few shillings, and which, so far as 

 quantity and average quality are concerned, might be more 

 lasting than many of the high-grade ore-bearing mines, 

 which not unf requently are " patchy." It is not the place 

 here to lengthily describe the different processes by which 

 the various metals are extracted from their ores; for in- 

 stance, that of obtaining iron from its oxides by means of 

 carbon, carbon monoxide, hydrogen, &c. ; or how the car- 

 bonates have sometimes, in the first instance, to be calcined 

 to reduce them to the state of oxides ; or of obtaining zinc 

 from the sulphide by roasting, heating with carbonaceous 

 matter, and by distillation ; or of mercury (from cinnabar) 

 by heating in air, or with lime, or iron oxide, and distilla- 

 tien ; or of obtaining antimony from its sulphide by means 

 of scrap iron, &c. 



At the same time the prospector may derive some 

 interest, if not benefit, by knowing a few of the principles 

 which, practically applied, are dealt with in metallurgy. 



The various methods undergo much alteration and modifi- 

 cation in not a very long space of time. As an example of 

 this may be cited that of aluminium. The sodium process 

 of not long ago has been quite replaced by electrical methods, 

 which have very greatly reduced the price of the metal. 



So it is impossible, just as it is unwise to state which is 



