THE CONQUEST OF NATURE 



by means of numerous open lights kept constantly 

 burning. This method is effective, but since the numer- 

 ous lights consume the precious oxygen of the air as 

 well as the damp, the method has never become pop- 

 ular. Obviously, then, the question of mine ventilation 

 is closely associated with that of lighting. 



Probably the simplest method of properly venti- 

 lating a mine is that of having two openings at the 

 surface, one on a much higher level than the other 

 if the mine is on a hillside, the lower one corresponding 

 to the lowest portion of the mine where possible. By 

 such an arrangement natural currents will be estab- 

 lished, and may be controlled and distributed through 

 the mine by doors or permanent partitions, or aided 

 by fans. But of course only a comparatively small 

 number of mines are so situated that this system can 

 be used. 



It is possible, of course, to ventilate a mine from a 

 single shaft or opening by use of double sets of pipes, 

 one for admitting air and the other for expelling it; 

 but this system is obviously not an ideal one, and is 

 prohibited by law in most mining districts. Such 

 laws usually stipulate that there must be at least two 

 openings situated at some distance from each other. 



The older method of creating air currents was by 

 means of furnaces, but this method, while very effective, 

 is expensive and dangerous. In using this system a 

 furnace is built near the outlet of the air shaft, the com- 

 bustion of the fuel creating the necessary draught. 

 But in the nature of things this furnace is a constant 

 menace to the mine, besides being an extremely waste- 



