248 Report S.A.A. Advancement of Science. 



partial weathering of the pyrites, the difficulty of dissolving the gold 

 owing to the lower oxygen-absorbing compounds of iron present, the 

 extra cyanide these compounds consume, and the trouble, owing to 

 the excess of lime salts in solution, of maintaining an efficient pre- 

 cipitation of the gold when it has been dissolved all combine to 

 render the treatment of this class of material unprofitable up to the 

 present. 



The disposal of cyanide residues will as time goes on become 

 an increasingly important problem. Improved methods are under 

 ■discussion of transfer from collecting to leaching vats and of final 

 discharge to the dumps, in which conveyor belts and mechanical vat 

 discharging appliances play an important part and permit of relative- 

 ly cheap forms of plant construction. Since labour has never been 

 too abundant on the Witwatersrand, and its lack at the present time 

 is more seriously felt than ever, it is probable that in the future the 

 use of labour saving appliances such as the above will be greatly 

 stimulated. In view of the very small percentage of the total ore 

 available on these fields which has been crushed to date, it is doubt- 

 ful whether available sites on producing properties will serve for 

 more than a portion of future sand and slime residues, and the 

 question of cheap removal to a distance will in time become imper- 

 ative. The matter of covering the surface of the dumps with soil 

 and cultivating suitable grasses and plants thereon — as is done to 

 prevent the shifting of sand dunes on the French coast — has been 

 discussed, and it would certainly be desirable to minimize the nui- 

 sance at present caused by the wind-blown sands from these deposits. 



Among the desiderata of the present time is that of an improved 

 elevator for battery pulp ; tailings wheels while simple and cheap to 

 run are costly to erect and not capable of increase when a few feet 

 more fall is wanted ; on the other hand, ordinary plunger pumps suffer 

 terribly from wear and involve heavy maintenance charges. 



There is an element of progress whose lack has often been felt 

 by workers on these fields, and this is a metallurgical testing plant, 

 consisting of say a 20-stamp mill and cyanide plant, with assay offices 

 and technical laboratory attached, and with a competent staff. To 

 make any radical change in the methods employed in a 200-stamp 

 mill or plant is a very serious and expensive matter, and the progress 

 of experimental work is hampered by its subordination to the carr}- 

 ing out of routine work, for the very natural reason that shareholders 

 do not wish valuable and instructive information but regular monthly 

 profits. With such an institution, supported by the Chamber of 

 Mines and with an advisory technical board of management, experi- 

 ments of great value to the mining industry could be continually 

 carried out. New machinery and methods of handling material, and 

 promising new processes and devices could be tested, and at the 

 same time such an institution might serve as a reference assay office 

 and laboratory for all Rand mining companies. Here trial crush' .igs 

 could be made, the value of ore samples or bullion could be determin- 

 ed and analyses of minerals, boiler water, coal, oil, steel, cyanide, 



