July 6, 191 1] 



NATURE 



29 



the steaming plant at two or three centres, from which 

 power is distributed to the mines by electric transmission 

 or in the form of compressed air. This has largely been 

 the work of the Victoria Falls and Transvaal Power Com- 

 pany. Electrically transmitted power is rapidly supplant- 

 ing independent steam power for mills, winders, sinking 

 engines, underground hoists, pumps, &c, owing to the 

 favourable rate at which it can be purchased from the 

 power company. The price has been fixed by agreement 

 at 0-561 pence per unit until October, 1912, and there- 

 after at 0525 pence. Transmission is effected both by 

 overhead lines (at 40,000 volts along the Rand, and at 

 80,000 volts from Vereeniging, a distance of 30 miles) and 

 by underground cables (at 20,000 volts). The length of 

 the overhead lines is 150 miles, that of the underground 

 cables 35 miles. A portion of the power supplied by the 

 company is in the form of compressed air for rock-drills. 



A considerable economy will be effected by this 

 centralisation of power generation, and the consequent re- 

 duction in the number of independent steaming plants. 

 From the price per unit at which the Victoria Falls and 

 Transvaal Company are supplying power, the cost of a 

 horse-power per annum, utilised continuously day and 

 night, can be calculated : it works out at 14/. It is not 

 so easy to arrive at the average cost of a horse-power Year 

 on the mines prior to electrification, but it is stated to 

 have been 28?. In any case, the saving due to the sub- 

 stitution of electric motive-power for steam-power is un- 

 doubted, and there is, moreover, the indirect advantage of 

 greater flexibility and more perfect control. 



The present position of the industry and the progress to 

 be expected in the future may be illustrated by a few 

 statistics. 



Since the discovery of the Field in 1S.S6 to the end of 

 1910 the Rand has milled 155 million tons of ore, and 

 produced gold to the value of 276,000,000!., this being an 

 average of 356s., or 84 dwt. of fine gold to the ton milled. 

 During the same period dividends amounting to 

 72,416,1:50/. have been distributed, equivalent to 9.35. per 

 ton milled. 



During 1910 gold to the value of close on 31,000,000!. 

 w.i^ produced by crushing 21.500,000 tons of ore; this is 

 equivalent to an average vield of 285. 6<f., or 6-7 dwt. of 

 fine gold per ton milled. The working costs averaged (from 

 the returns of fifty-six companies) was 17s. yd. per ton, 

 giving an average profit of 105. qd. per ton milled. 



Seven of the largest companies, crushing close on a 

 quarter of the whole tonnage, are working at an average 

 cost of 13-85. This very remarkable result has been 

 brought about by increasing, to their economic limit, the 

 size of the units used in the various ooerations, such as 

 trucks, stamps, tube-mills, vats, pumps, &-c. ; bv the simpli- 

 fication of the methods of handling ore; and bv replace- 

 ment, so far as it is economy to do so, of hand-labour bv 

 mechanical appliances. Larger units of development and 

 the centralisation of power plant have also contributed to 

 this result ; while the amalgamation of the properties into 

 larger units has helped to lower working costs, bv per- 

 mitting a reorganisation of the transnort and hoisting 

 arrangements, and by reducing the standing charges. 



Future of the Goldfield. — Working at a cost of 13-85. per 

 ton means that the cost of development, extraction, and 

 reduction, including administration, is covered by a 

 recovery of 31 dwt. of fine grold per ton. On 5 dwt. ore, 

 therefore, this would allow of a profit of nearly 7s. 6d. per 

 ton ; and over a considerable area of the Rand the average 

 grade of the ore-bodies is not much above 5 dwt. The 

 inclusion of large tonnatres of relatively poor reef, which 

 formerly were considered outside the range of practical 

 mining, has been made possible by lower operating costs. 

 The grade of the ore crushed has fallen in consequence. 

 This does not necessarily imply that the increased depth of 

 the mines has (per se) caused a falling-off in the actual 

 value of the ore-deposit considered as a whole. 



The effect of this increased tonnage and diminished grade 

 on the life of the Rand crnlrlfir-ld as a whole is an interest- 

 ing subject for speculation. From the data available the 

 production of gfold to be r-xpneted from the Main Reef 

 series, if worked down to a vertical depth of 6000 feet, 

 may be estimated. 



It figures out at 1.046,000.000! , which, on the basis of 

 NO. 2175, VOL. 87] 



an average output of 30,000,000!. per annum, is equivalent 

 to a life of thirty-five years, i.e. down to a vertical depth 

 of 6,000 feet. But, if at still greater depths the banket 

 should contain sufficient gold to yield a profit, after deduct- 

 ing the cost of working, we may rest assured that it will 

 be worked. What, then, are the limiting factors? They 

 are generally considered to be (1) the mechanical difficulty 

 of raising the ore to the surface from such great depths, 

 and (2) the effect of the temperature gradient. With regard 

 to the mechanical question, the electrical transmission of 

 power applied to stage-winding has so modified the mining 

 engineer's conception of the depth from which deep hoisting 

 is practicable, that it is now generally assumed that there 

 are no mechanical difficulties that cannot be overcome if it 

 pays to do so. As to the temperature question, figures 

 based on Mr. Marriott's careful experiments, which showed 

 that the rise is only i° F. for every 208 feet of depth, 

 indicate that the rock-temperature at 7000 feet would 

 not exceed 97-5° F., and with efficient ventilation the air 

 temperature would of course be considerably lower. It 

 follows, therefore, that for all practical purposes the whole 

 question turns solely on the gold content, and what that 

 may be at a vertical depth of 7000 or 8000 feet, no one can 

 tell. This much, however, may be said : the geological 

 structure of the country clearly points to the continuance 

 of the conglomerate or banket beds to still greater depths 

 than even 7000 or Sooo feet, before the bottom of the great 

 synclinal basin of the Witwatersrand is reached ; and, 

 beyond that point, the beds must still continue until they 

 rise to form the southern lip of the basin known to exist 

 bevond the Vaal River. 



THE FUNDAMENTAL PROPERTIES OF THE 



ELEMENTS. 1 

 THE mystery that enshrouds the ultimate nature of the 

 physical universe has always stimulated the curiosity 

 of thinking man. Of old, philosophers sought to solve the 

 cosmic problem by abstract reasoning, but to-day we agree 

 that the only hope of penetrating into the closely guarded 

 secret lies in the precise estimation of that which is 

 tangible and visible. Knowledge of the actual behaviour 

 of material and of energy provides the only safe basis for 

 logical inference as to the real essence of things. Fara- 

 day was deeply imbued with this conviction ; and it is 

 widely recognised as the basis of all modern experimental 

 science. The subject of my lecture to-night concerns the 

 methods and general results of several extended series of 

 investigations, planned with the hope of adding a little to 

 the foundations of human knowledge by means of careful 

 experiment. 



At the outset let me remind you of an old saying of 

 Plato's, for it sounds the keynote of the lecture : — " If 

 arithmetic, mensuration, and weighing be taken away from 

 any art, that which remains will not be much." 2 In 

 other words, the soundness of all important conclusions 

 of mankind depends on the definiteness of the data on 

 which they are based. 



Lord Kelvin said : — " Accurate and minute measurement 

 seems to the non-scientific imagination a less lofty and 

 dignified work than looking for something new. But 

 nearly all the grandest discoveries of science have been the 

 rewards of accurate measurement and patient, long-con- 

 tinued labour in the minute sifting of numerical results." 3 

 The more subtle and complicated the conclusions to be 

 drawn, the more exactly quantitative must be the know- 

 ledge of the facts. 



Measurement is a means, not an end. Through 

 measurement we obtain data full of precise significance, 

 about which to reason ; but indiscriminate measurement 

 will lead nowhere. We must choose wisely the quantities 

 to be measured, or else our time may be wasted. 



Among all quantities worthy of exact measurement, the 

 properties of the chemical elements are surely some of the 

 most fundamental, because the elements are the vehicles of 



1 Abridced from the Faradiy lecture delivered before the Chemical 

 Society by Prof. T. W. Richard-; on June t 4 . 



- Plaio, "Philebus" (nans. Jon-ell), .875, vol. iv., p. ioj. 



S >ir w. Thomson (Lord Kelvin), address 10 British Association, August, 

 1S71, ■' Life," ii., 600. 



