Gl IvKPOKT 8. A. A. Ai)Van("i:mk\t of Scikxck. 



therefuie, comes ffoni the piesence <»f liuninu l>eings aiul tlie use of 

 explosives. HuinHU beings contaminate the air hy exhaling carl,)onic 

 acid, by producing the same gas through the combustion of candles, 

 and in other ways readily imagined. This contamination can, liow- 

 e\er, be estimated with a fair degree of accuracy, and this indeed 

 has been done very thoroughly by I)r. Mciir and others. It is very 

 (juestionable, however, whetlier tlie presence of comparatively large 

 (juantities of carbonic acid in the mine atmosphere does very much 

 harm pf'r sp to human beings, and I for one incline to this view. Pro- 

 vided, therefore, that there are reasonable meclianical arrangements 

 for sending supplies of pure air to the workings, the contamination 

 from tlie sources indicated neefl not l)e greatly feared ; in otlier words, 

 there is practically no toxic effect. 



When we come to the inHuence of explosives the case is vastl}' 

 different. The annual consumption of explosives on the Witwaters- 

 rand is about 1 "2,000 tons, and if I resolved this into the gases pro- 

 duced on explosion the figures would convey nothing to you, as they 

 are so stupendous. Practically all this e.vplosive has nitro-glycerine 

 as its base, and about 90 per cent, of tlie total is of the so-called 

 gelatinous type, i.f. a mixture of collodion cotton and nitro-glycerine 

 — both themselves explosives — but sometimes admixed with nitrate 

 and other material. Blasting gelatine, the explosive most employed 

 — indeed it forms about 70 per cent, of the total — is a gelatinous 

 body which contains about 92 per cent, nitro-glycerine and 8 per cent, 

 collodion cotton. When exploded in a steel bomb it only produces 

 carbonic acid, vapour of water and nitrogen — all harmless gases. This 

 has been verified bv so many experimenteis that it niciy be now taken 

 for granted. When exploded in practice, however, ver}' different 

 results are obtained. The usual way is to charge the drilled hole, 

 or series of holes, with the cartridges, pressing them gently, but 

 firmlv, against one another with a wooden rod. Into the last cai'tridge 

 a detonator is inserted, and it in turn is affixed to a long piece of time 

 fuse, i.i'. slow-burning fuse. When all this has been done the top 

 poi-tion of the hole is plugged up by earth or clay, the fuse is ignited, 

 and in due course the explosion takes place. To give you an idea 

 of the amounts used at a time, 1 may say that in blasting the face 

 of a so-called dri\e almost oO ll)s. of explosives are used, and in shaft 

 sinking the (piantity used at one time may be, and generally is. very 

 much larger. 



Now the fuse in burning produces carbonic acid, carbon moiioxide 

 and quantities of other gases which I shall class as (defines, produced 

 from the combustion of the tarry material of the fuse. They make the 

 atmosphere very unpleasant to breathe, but beyoiul that and slightly 

 increasing the percentage of carbon moiuixide they have no other par- 

 ticular effect. I am free to confess that before T personally investi- 

 gated these gases I was very sceptical indeed about the large (|uantitie.s 

 of noxious gases which were said to be produced, but now I know that 

 the removal of these gases from the workings is tlie most pressing 

 problem of the moment in connection with mining. It may be askcfl 



