746 R. A. F. PENROSE, JR. 
number ranging from 1,500 to 2,500 feet, and a few deeper. Those 
located on the outcrop of the ore are known as “outcrop”? mines; 
the adjoining ones to the south, which are not on the outcrop, but 
which require a shaft to be sunk to reach the ore on its dip, are known 
as the ‘‘first row of deeps,” those next farther south are known as 
the “‘second row of deeps,” etc. The general term “deep” is thus 
applied to any of the mines not on the outcrop, and the first, second, 
third, and even fourth rows of deeps are common terms. The word 
Fic. 6.—Photograph of surface at the Robinson and the Robinson-Deep Mines, 
Witwatersrand District, Transvaal, showing tailings, dumps, and general surface 
conditions. ‘ 
‘“‘deep” does not refer in any way to the depth of the mine, but only 
to the fact that a shaft has to be sunk to reach the ore. 
It is not within the scope of this article to discuss the metal- 
lurgical treatment of the Witwatersrand ores. It may be said, how- 
ever, that nowhere else in the world have the mining and treatment 
of gold ores been carried on with greater efficiency and skill than by 
the able engineers and metallurgists who have conducted the opera- 
tions on the Rand; and nowhere has the gold-mining industry been 
conducted on such a large scale. The ores are treated in large stamp 
