An Elementary Course of Instruction for Mine Foremen and Pit Bosses

accidents airway amount angle applied base becomes body called cars cause cent circle coal mines consists contained cube cubic curve danger decimal depends determined difference direction distance divided employed engineer entries equal explosive expressed face falling figures fire foot force fraction furnace gases given gives gravity Hence inches increase length less LESSON lever longwall means meant measured method miner minute moving multiplied occur operator passes person pillars plane pounds pressure prevent produce proper proportion ratio reduced relation removed represents result right angles roadways rock roof rooms rubbing safety seams shaft shots sides sometimes square feet square root station sufficient surface survey takes tens thickness timbers tion tons triangle units velocity ventilation volume walls weight