SECTIONAL TRANSACTIONS.— I, J. 377 



to recent advances in knowledge as to physiological acclimatisation and voluntary 

 adaptation to heat, and to the indirect effects of excessive loss of salt in sweating, 

 and then pass to the main subject of this paper, of which the follo-ning is an outline. 

 The great trouble met with from heat in deep Rand mines, in spite of acclimati- 

 sation and good ventilation, raises a question which can only be discussed partially 

 in to-day's meeting. In order to avoid dust inhalation in the Rand mines the air 

 is at present kept everywhere practically saturated. The precautions taken against 

 dry dust have been extraordinarily successful in reducing the risk of silicosis ; but if 

 we could avoid the saturated air without increasing the risk of silicosis we could 

 greatly dimjnish the temperature troubles, and thus make still deeper mining of low- 

 grade ore a practicable proposition. 



AVe could, I believe, avoid the silicosis risk with drier air if we could add to the 

 quartzite dust another kind of dust with the property of rendering the silica harmless. 

 In metalliferous mines elsewhere than on the Rand the effects of the quartz dust 

 seem to be, in many cases, neutralised by natural means in this way ; and in British 

 coal mines the stone dust, which is either present naturally or added in order to 

 prevent coal-dust explosions, does not produce miners' phthisis though it contains 

 about 35 per cent, of quartz and nearly 60 per cent, of total silica. 



Whether it is possible to avoid silicosis by dry methods will be discussed at 

 another meeting, but meanwhile we may consider the advantages wliich could be 

 gained by dry methods as regards the effects of heat on men. What might be 

 pictured is that the air in the shafts, inclines, and splits should, by avoidance of most 

 of the evaporation, be kept at a mean temperature not below the natural rock- 

 temperature, but about equal to it or even above it. This would naturally result 

 from adiabatic compression, since the rate of rise of temperature by adiabatic com- 

 pression with depth is very distinctly greater than the rate of rise of rock-temperature 

 on the Rand. Thus the air would reach the working places -n-jth its cooling power 

 through evaporation of sweat almost unimpaired ; and if stopes could also be left 

 dry it would pass upward to higher workings with cooling power still great and would 

 cool by adiabatic expansion as it rose, instead of being to a large extent prevented 

 from doing so by condensation. The available air could therefore be concentrated 

 on the deeper workings, where it would be needed most. 



With the rock-temperature and air-temperature at 90° to 100° in the deeper 

 workings we might have a wet-bulb temperature of at least 20° lower, permitting 

 much more work than at present. The cost of dusting with the neutralising dust 

 would probably be small in relation to diminished costs in other directions ; but in 

 any case I think we ought to consider the great possible advantages. We are being 

 beaten just now by the rock-temperature. If, as seems possible, we could make the 

 rock cool the air rather than warm it, we should not, up to much greater depth, be 

 greatly troubled by the heating from adiabatic compression. Possibly, also, rock- 

 bursts might be dimim'shed. 



The advantages from dry air in British coal mines are very great, now that the 

 dangers from coal-dust explosions have been to such a large extent overcome by 

 stone dusting. One of these advantagesisthe abolition of riskfrom ankylostomiasis ; 

 and possibly the very low death rate from tuberculosis among coal miners is coimected 

 with the dry conditions. 



Where, as in some Rand mines, the heavily timbered shafts and inclines must be 

 kept wet, the air, if concentrated in the airways, would reach the bottom quite cool at 

 depths at present reached, and its wet-bulb temperature would only rise to a quite 

 moderate extent in the stopes, if they were kept dry. 



SECTION J.— PSYCHOLOGY. 



(For reference to the publication elsewhere of communications entered in the 

 following list of transactions, see p. 429.) 



CAPE TOWN. 



Tuesday, July 23. 



Prof. R. W. WiLCOCKS. — On the Correlation between the Intelligence of 

 Siblings. 



