The Encyclopedia Americana, Volume 7Grolier, 1988 - Encyclopedias and dictionaries |
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Page 137
... Mines . Mines may be classified by the method of entry into the coal seams . Where coal lies close enough to the surface and the costs of removing the overlying material are sufficiently low to permit a profit to be made , the coal is ...
... Mines . Mines may be classified by the method of entry into the coal seams . Where coal lies close enough to the surface and the costs of removing the overlying material are sufficiently low to permit a profit to be made , the coal is ...
Page 139
... mines decreased from the previous year by 14 % . There were 216 fatalities , of which 187 oc- curred underground , 13 on the surface , 15 at strip mines , and 1 at an auger mine . Three gen- eral types of accidents caused 89 % of the ...
... mines decreased from the previous year by 14 % . There were 216 fatalities , of which 187 oc- curred underground , 13 on the surface , 15 at strip mines , and 1 at an auger mine . Three gen- eral types of accidents caused 89 % of the ...
Page 141
... mines for use of parent companies . Steel companies account for most of the captive production , but some electric utili- ties and a few chemical plants operate mines . Captive production in steel companies represents about 60 % of that ...
... mines for use of parent companies . Steel companies account for most of the captive production , but some electric utili- ties and a few chemical plants operate mines . Captive production in steel companies represents about 60 % of that ...
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