RESPIRATION 319 



Whichever form of apparatus is used it is very necessary that 

 it should be extremely reliable in its action, and that the users 

 should be thoroughly instructed and trained in its proper use and 

 upkeep. A number of lives have been lost or endangered through 

 defective supervision and mode of use, or defective design, of 

 apparatus; and as a consequence of these defects men wearing 

 the apparatus in quite breathable air have often had to be rescued 

 by men without apparatus. With proper and scientific supervision 

 these accidents do not occur, as has been shown again and again 

 during extensive operations in irrespirable air. 



By white damp miners understand a poisonous form of gas 

 coming off from coal which has spontaneously heated. The term 

 seems to have arisen from the fact that steam commonly comes 

 off from the warm coal with this poisonous gas and causes a white 

 mist. By experiments on animals and analyses I have frequently 

 found that the poisonous constituent of the gas was CO. 



Freshly broken coal is, as already mentioned, liable to a slow 

 oxidation process. This of course produces heat, and if sufficient 

 coal is present, so that the heat is not lost as quickly as it is pro- 

 duced, the coal will heat, and the heated coal will oxidize faster 

 and faster until at last it is red hot or bursts into flame if sufficient 

 oxygen is present. It is for this reason that coal may be a danger- 

 ous cargo on long voyages, and that coal cannot be stacked safely 

 in very high heaps. In many seams there is great trouble and no 

 little danger from spontaneous heating of broken coal under- 

 ground ; and the residual gas coming off from heated coal is often 

 called white damp. The higher the temperature of coal which is 

 slowly oxidizing, the greater the proportion of CO in the residual 

 gas. The effects of white damp are thus much the same as those 

 of afterdamp ; and the same precautions are required. 



Smoke in mines may come either from fires or from blasting. 

 The smoke from a fire is usually, of course, visible and irritates 

 the air passages and eyes owing to the irritant properties of the 

 suspended particles. If, however, smoke has slowly traveled some 

 distance in a mine, the particles have subsided and the smoke has 

 become a more or less odorless and transparent gas. Many very 

 serious accidents, involving sometimes the loss of 100 lives, have 

 occurred through the poisonous action of smoke from fires in 

 mines. In these cases the deaths have always, so far as hitherto 

 ascertained, been due to CO poisoning. A large amount of un- 

 burnt CO is given off from smoky or smoldering fires, so that the 

 gases from a fire are almost as dangerous as the afterdamp of an 



