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Electric blasting switches, underground mines, Lake Superior district
Support of ground, iron-ore mines, Lake Superior district
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Published Year
1940-1949 (2)
Subject
Ground control (Mining)--Lake States (2) *
Iron mines and mining--Lake States (1)
Iron mines and mining--Lake States--Safety measures (1)
Mine safety--Lake States (1)
Author
Cash, Frank E. (2)
Petersen, Max S. (2) *
