382 SCIENCE PROGRESS 



10,000 of air, or higher ; and much stress had been laid on the 

 gaseous impurities of the air as explaining the ill-health of the 

 miners. The physiological data already mentioned prove, 

 however, that although an actual rise of i or i per cent, in the 

 alveolar CO2 pressure would have most violent physiological 

 effects, no such rise actually occurs when air containing h or 

 I per cent, of CO. is breathed. The only effect is that the 

 breathing becomes very slightly deeper, the difference being 

 subjectively quite inappreciable. Less than i per cent, of CO2, 

 or 100 volumes per 10,000, is therefore of no importance in air 

 at ordinary pressure, provided no other harmful inpurity is 

 present. Except in exceptional cases — for instance, just after 

 blasting — there was no evidence of any other harmful gaseous 

 impurity in the mine air; and by far the greater part of the 

 CO2 was found to arise from the slow oxidation of mineral 

 matter such as iron pyrites (FeS.), with consequent liberation of 

 CO2 from carbonates by the sulphuric acid formed. 



What, then, was the cause of the ill-health of the Cornish 

 miners ? Further examination ^ into the facts disclosed two 

 causes. The first was that certain of the mines were badly 

 infected with ankylostomiasis, which, as has so often been the 

 case during the last hundred years, had not been recognised, and 

 which was soon brought under control by suitable measures. 

 The second, and by far the more serious, cause was the fact 

 that dust raised locally by drilling and blasting granite, quartz, 

 and other hard stone was being inhaled by the miners and 

 causing injury to their lungs w^hich produced a marked 

 predisposition to tubercular phthisis. The increased death- 

 rate among the miners was due entirely to lung disease, 

 chiefly tubercular phthisis. During middle life, for instance 

 (age thirty-five to forty-five), the death-rate from lung disease 

 was 33 per 1,000 among Cornish miners, as compared 

 with 34 per 1,000 among coal and iron miners; and from all 

 other causes 5*8 per 1,000 among Cornish miners, and &s per 

 1,000 among coal and iron miners. An investigation of the 

 working history of each man who had died in one of the mining 

 districts during a period of three years revealed the fact that the 

 extra deaths — at any rate during middle life — were confined 

 almost entirely to men who had been engaged either locally or 



^ Report on an Outbreak of Ankylostomiasis in Cornish Alines ; and Report on 

 the Health of Cornish Miners^ Parliamentary Papers, 1902 and 1904. 



