Coal mining in Illinois . District Average by districtsIIilll\ V \ Ivn VIII All minesexamined O w o o 66 67 68 69 70 71 72 73 74 75 76 // VII 78 79 80 81 82 7 .lx 83 84 85 86 87 88 89 90 91 92 VII] 93 94 95 97 Including cross props except at clay 140 COAL MINING INVESTIGATIONS
Coal mining in Illinois . District Average by districtsIIilll\ V \ Ivn VIII All minesexamined O w o o 66 67 68 69 70 71 72 73 74 75 76 // VII 78 79 80 81 82 7 .lx 83 84 85 86 87 88 89 90 91 92 VII] 93 94 95 97 Including cross props except at clay 140 COAL MINING INVESTIGATIONS nigger he ads or sulphur-balls which protrude from theroof have little cohesion to the roof shale. The cost of props per ton of coal and the total timberingcost per ton of coal are difficult to ascertain on account of the. ^Concrete Fig. 44. Timbering in caved area in District VII different segregations of cost items at mines in the State. Thenumber of props purchased per ton of coal varies from 2to 12 depending upon roof conditions. The figures as sup-plied by operators for cost of props vary from %-cent to 2 TIMBERING 141 cents per ton and the total timbering cost from to Depth of cover and system of mining in mines otherthan longwall seem to have no effect in the amount of tim-bering necessary. The character of the immediate roof isthe chief factor in determining whether little or much tim-bering shall be done. ACCIDENTS In the year ended June 30, 1912, only 7 accidents at coalmines in Illinois occurred on the surface. Dangerous roofinsufficiently supported, the presence of explosive gas, non-enforcement of the State Mining Law, insufficient oversightof working places, and failure to clean the roadways are allreflected for each district in the number of accidents per1,000 employees (Tah
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectcoalmin, bookyear1915
