The Encyclopedia Americana: The International Reference Work, Volume 7Americana Corporation, 1960 - Encyclopedias and dictionaries |
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Page 152
... mine . Underground Mining Systems . - Most of the world's coal is obtained from underground mines . The two principal systems employed in mining underground coal are the room - and - pillar method and the longwall method . In the first ...
... mine . Underground Mining Systems . - Most of the world's coal is obtained from underground mines . The two principal systems employed in mining underground coal are the room - and - pillar method and the longwall method . In the first ...
Page 154
... mines drilling , shearing , loading , and underground transportation , as well as the prep- aration of the run - of - the - mine coal for the market , are handled by complicated , electrically powered machinery . Mining Mechanization ...
... mines drilling , shearing , loading , and underground transportation , as well as the prep- aration of the run - of - the - mine coal for the market , are handled by complicated , electrically powered machinery . Mining Mechanization ...
Page 155
... mines . An indication of how far mechanization , and therefore increased production , has gone in saving manual labor in coal mining may be seen in a comparison of the number of miners employed in the United States and in several ...
... mines . An indication of how far mechanization , and therefore increased production , has gone in saving manual labor in coal mining may be seen in a comparison of the number of miners employed in the United States and in several ...
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