1865.] 



Smith on the Health of Metal Miners. 



223 



and, as far as figures show, it may also be seen in the report alluded 

 to, and in part in the above table. 



Summary of the Analyses of Air in Mines. — Oxygen. 



20-26 



Lowest .... 



18-27 



Average in large spaces . 



Currents .... 



20-77 

 20-65 



Just under shafts 



20-424 



In ends .... 



20-18 



In sumps .... 

 In all other places . 



20-14 

 20-32 



Air with 20*9 of oxygen was assumed as normal, or nearly so, 

 although the figure is too low. Air with less than 20-6 was assumed 

 as exceedingly bad, because it is not equalled in our most suffocating 

 assemblies. 



Let us compare the mine-air with the atmosphere of various places 

 in relation to carbonic acid. 



Analyses of atmospheres varying in carbonic acid. 



Manchester streets — usual . 

 During fogs .... 

 About middens . 

 Average .... 



Fogs excepted . 



Fogs and middens excepted 

 Where the fields begin 

 In close buildings 

 Minimum of suburbs . 

 Over North Scotland (towns exc 

 Candle goes out . 

 Lowest found in mines 

 Lowest entered for experiment 

 Average of the mines . 



epted) 



Average Carbonic Acid 

 per cent. 



. 0-0403 

 . 0-0679 

 . 0-0774 

 . 0-0442 

 . 0-0424 

 . 0-0403 

 . 0-0369 

 . 0-1604 

 . 0-0291 

 . 0-0336 

 1-8 to2-50C0 



2-5000 



4-0000 



0-7850 



These figures may be read as whole numbers ; for example, 

 average of the mines, 7,850 in a million. 



And why should we be afraid of a little carbonic acid ? Because 

 carbonic acid deranges the circulation, causing at first sometimes a 

 rapid beating of the heart, but ultimately a very low and weak pulse, 

 and a quickened respiration, although at times a somewhat slower 

 respiration. It is never indifferent, and the effect may be traced 

 when even so little carbonic acid exists as one-tenth per cent. This 

 is a sufficient reason for ventilating and for seeking pure air. 



Chemists have often asserted that foul and pure air have the same 

 composition ; this need no more be repeated. 



Calculated Composition of the Air of Mines in some Places. — If we 

 put together all the substances thrown into the air when two miners 

 are working in a space equal to 1,200 cubic feet, we have as air and 

 impurities together — 



