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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 184

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[page]183.[/page] a true sample of the encountered formations. The samples obtained from the work of the churn drill are fragments which are brought to the surface by means of a current of water caused to flow down the center of the hollow drill shaft. The data sought in prospecting are: 1st the depths and kinds of the strata overlying the coal; 2nd the probable amount of water which will be encountered in sinking the shaft; 3rd the thickness and quality of the coal and the character of the roof of the coal; 4th the shape and profile of the coal seam. The third and fourth items are perhaps the most important. It readily can be seen why the third item is important, that is, it determines whether or not the coal can be economically worked. Upon the
 
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