Fic. 85. Cutting away rock with a compressed-air drill in a Michigan copper mine. 
Note how beams are used to support the roof and sides of galleries in mines. 
CHAPTER NINE 
THE MINING INDUSTRY 
Minine differs from other means of primary production in three ways: 
(1) There is no way of increasing the original supply of the 
product. 
(2) Production is restricted to a few localities. 
(8) Until the rocks are actually examined in detail it is almost 
impossible to tell where it will be profitable to carry on 
operations. 
Why mining is the robber industry. The mining industry takes 
from the rocks vast stores of wealth which nature has deposited, 
and which nature herself cannot renew for millions of years. For 
this reason mining is sometimes called the ¢ robber industry.” When 
man harvests a crop on a farm, the fertile soil still remains, and other 
crops can be raised; if a forest is cut down, another may grow 
in time; although many cattle are killed, the herd will increase in 
number; fish also multiply freely, even though great quantities are 
110