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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 202

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[page]202.[/page] mine through the air shaft, allowing pure air to pass down the main shaft and through the m ine. Second, by forcing the air down the air shaft, through the mine, and out at the main shaft. The former method is seldom used, since by that means the air in the mine is rarefied and does not penetrate the rooms so well. The second method is the one in general use. By this method the air in the mine is kept somewhat above the atmospheric pressure and good circulation is kept up. The pressure is given the air by means of a large circular fan, driven by steam, and placed at the top of the shaft. Usually the fan is connected directly on the main shaft of a steam engine. Sometimes, however, the fan is driven by a cable
 
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