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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 195

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[page]195[/page] the working face of the coal. Therefore as soon as a new "breakthrough" is opened the old one is closed. For it can easily be seen that if more than one were open the air would take the shortest passage and would not be brought up to the working face of the coal. From the side entries the rooms are turned. Turning rooms is the name given to cutting doorways in the sides of the entries for the purpose of digging out the coal. The rooms are turned from one side only of [strikethrough]the[/strikethrough] an entry. The width of the doorways is retained for from three to five yards depending upon the character of the coal and of the roof; then the room is gradually widened to twenty feet. In figure a room is shown in shape and dimensions at A B. The
 
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