246 Report S.A.A. Advancement of Science. 



supply and demand and whose sale may be hampered by compe- 

 tition. The result is that a free exchange of ideas and information, 

 much fostered by the local technical Societies and the close proximi- 

 ty of any mining companies to each other, exists among workers, and 

 details of practice in any plant are open to inspection without difficul- 

 ty. The workers in the metallurgy of gold being drawn from all 

 parts of the world, conservative prejudices disappear by mental at- 

 trition amid the new surroundings and continual advances in practice, 

 whilst advancements in knowledge elsewhere are contributed to the 

 general stock and rapidly adopted when applicable. It is observable 

 nowadays that many of the younger men engaging in gold extraction 

 work are possessed of considerably more technical training than was 

 common in the past. This tendency promises to increase and is of 

 good augury for future progress and effective specialization. Cheap 

 fuel and labour have been important factors of progress, and also 

 the liberal supplies of money which investors, actuated by enlightened 

 self-interest and with a confidence strengthened by past experience 

 of the capacity of their technical advisers, have provided for the 

 development and exploitation on an enormous scale of the mining 

 properties. The actual scale of these operations is also much in- 

 creased by the recognition of the fact that if a mine will supply ore 

 for a hundred stamps for say forty years or more, it is profitable 

 practice to put up at least double that number of stamps so as to 

 exhaust the ore in half that time ; on the ground that the ultimate 

 profit is realized more cheaply and quickly and that the equipment of 

 the mine will in any case be obsolete in twenty years. 



In one respect these fields differ from most goldfields in other 

 countries, which lies in the absence of customs mills or smelters. 

 On the Rand all metallurgical as well as mining operations are car- 

 ried out by each individual company, except as regards the minor 

 matter of by-products. The absence of small private enterprises, 

 the comparatively simple and uniform nature of the recovery work, 

 and the adequate working capital possessed by the mining companies 

 no doubt account for each mine having its own complete equipment. 



In reference to the future it hardly seems likely that any radical 

 changes in methods will take place. Good modern practice of wet 

 crushing, amalgamation and subsequent cyaniding the whole of the 

 crushed ore yields 90 % recovery on half-ounce ore at a low cost. 

 The bulk of the gold in this remaining pennyweight is encased in 

 the matrix and hence inaccessible to any solvent without further 

 crushing. Whilst if reduction be carried to a sufficient degree of 

 fineness almost 100 % recovery can be secured, the economic limit, 

 when more gold is won than money expended in obtaining it, is at 

 present considerably below, and likely always to be below the extrac- 

 tions obtainable in trials where no account is taken of cost. The 

 scope for higher economic recovery is consequently limited to a 

 fraction of a pennyweight per ton, and probably reduction in working 

 costs to an equivalent value. It hardly seems probable that recovery 

 working costs will decrease materially, any saving over present fig- 

 ures beirig ofif-set by an increased expenditure necessitated in obtain- 



