66 Men, Mines, and Animals in South Africa. 



The ore, which near the surface of the ground is 

 a friable conglomerate, free from pyrites, becomes 

 at the deeper levels hard conglomerate rock, 

 almost impervious to the ordinary drill and 

 hammer worked liy manual labour, and highly 

 pyritic. These two qualities have necessitated the 

 installation of American air-drilling machinery of 

 such power as to be capable of drilling a hole four 

 feet deep into the rock in fifteen minutes, which a 

 native would be luiable to complete working an 



General view of the Robinson Gold Mines at Johannesburg:. 



entire day. The abundant presence of pyrites 

 compels the chemical treatment of the concen- 

 trates and tailings, the stamps alone being unable 

 to extract more than fifty per cent, of the gold. 

 The Mc Arthur-Forrest process, or, in other words, 

 the treatment of the ore by cyanide of potassium, 

 is being tried upon the tailings, and a chlorination 

 plant is being installed for the treatment of the 

 concentrates. It is too soon to pronounce upon 

 the respective merits of these processes, and it is 

 possible that the ex^^ense per ton may be greater 



