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Coal Measures and Coal Mining in Iowa, including paleontology and a discussion on the coal formation; also the methods of mining by Russell T. Hartman, 1898

Coal Measures and Coal Mining in Iowa by Russell T. Hartman, 1898, Page 198

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[page]198[/page] the amount of timber required and in the larger amount of excavation. The main entries are usually timbered in this manner. The method of mining in which there is such a system of entries, rooms, and pillars is called the room and pillar method. Other methods are the long wall and the semi-long wall methods. [image: sketch of mine with 2 entries (A and B), central shaft, two coal pillars, and perimeter opening (a)] In the long wall method there is a large block or pillar of coal left around the bottom of the shaft. Two entries A and B are driven in opposite directions from the foot of the shaft; from these an entry (a), is driven around the pillar of coal
 
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