THE WITWATERSRAND GOLD REGION 744 
mills located at or near the mines (Fig. 6), and it is a striking sight 
to look out from some elevated place and see the long row of immense 
milling plants following an east and west line as far as the eye can 
reach along the strike of the ore formation. The ore is partly free 
milling. About 55 to 65 per cent. of the gold is saved on amalgamat- 
ing plates, and a large part of the rest is obtained by cyaniding the 
tailings. Sometimes additional processes to make a more complete 
extraction are practiced. A well-equipped and well-managed mill, 
with the present methods, should make a total extraction of probably 
from 88 to over go per cent. of the gold in the ore. 
The Witwatersrand district is essentially a region of large quantities 
of low-grade, yet workable, ore, and there are but few places in the 
world where gold mining can be carried on so cheaply as there. The 
ore bodies extend over long distances, and their contents of gold is 
much less erratic than in most gold mines elsewhere; coal, which is 
the only available fuel, is found in large quantities in close proximity 
to the mines, in geological formations overlying the gold-bearing rocks; 
Kaffir and Chinese labor is cheap, though at present somewhat scarce; 
the climate is healthy; the mines as a rule are not troubled with any 
excessive amount of water; the temperature does not increase at a 
very rapid rate with depth; and the rock is of such a kind that the 
expense for timber to hold up the underground workings is not great 
(Fig. 5). Under all these favorable conditions mining can be carried 
on to very considerable depths so long.as the ore holds out, and it 
is probable that active mining operations will be continued in this 
region for many years. 
The production of the Rand mines from 1884 to June 30, 1906, was 
Over 134,000,000 pounds sterling, or somewhere about $650,000,000, 
which means practically almost the total production of the Witwaters- 
rand district from the start, as not much gold was obtained there 
before 1884. The production for 1906, according to the estimates of 
the Transvaal Chamber of Mines, was 24,579,987 pounds sterling. 
It is not intended in the present article to discuss the origin of the 
Witwatersrand gold ores in detail, but perhaps a few words about 
the generally accepted ideas on this subject may be well. 
« These figure8 for 1906 were kindly furnished to the writer by Mr. W. R. Ingalls, 
editor of the Engineering and Mining Journal, of New York. 
