THE CONQUEST OF NATURE 



the top of the main horizontal shaft. By this arrange- 

 ment the ore, when loosened in these perpendicular 

 shafts, falls directly into the bins placed for its recep- 

 tion about the openings, or into the rows of cars in 

 waiting to receive it. In this method dynamite and 

 powder take the place of hand labor, the main mass of 

 ore being dislodged and thrown into the shaft by 

 blasting, instead of by hand labor. 



But all these methods are overshadowed in mag- 

 nitude by the great "open pit" systems, where the ore 

 is taken from the surface and handled entirely by ma- 

 chinery, the only part played by the miner 's pick being 

 that of assisting in loosing certain fragments so that 

 they may be more easily seized by the machines. 

 Indeed, this system of mining partakes of the nature 

 of quarrying rather than that of mining in the ordinary 

 sense, the ore being scooped from the surface of the 

 ground. One naturally thinks of a mine as being 

 subterranean; but in the great open- pit mines in the 

 Lake Superior region, which are the largest mines in 

 the world, all the mining is done at the surface of the 

 earth. 



It should not be understood, however, that in such 

 mines nature has left the red iron ore exposed at the 

 surface in any great quantities. On the contrary, it 

 is usually covered by a layer of earth ranging from a 

 yard to ten or more yards in depth, and this, of course, 

 must be removed before open-pit methods can be prac- 

 tised. Prospecting for such deposits is therefore just 

 as necessary as in cases where the deposit is situated 

 much deeper in the earth; and the business of pros- 



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