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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 199

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[page]199[/page] which is to be left in place. After this is done the process is merely one of widening the entry (a) by means of mining the outer wall. In this method of mining, as the work proceeds the roof sinks or falls leaving enough room along the face of the coal for work. If, however, the roof tends to fall near the face of the coal it may be propped as in room work. The roof is kept up over the entries by timbering and by piling refuse along beside the entries. In the English modification of this method, entries are driven to the farthest limits of the field to be worked, then the entries are driven around the field and the long wall work proceeds toward instead of from the shaft. In the semi-long wall method
 
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