Figure 17. — Mining requires large quantities of wood. 



mine boards are used to form large boxes to catch 

 the coal from steeply pitched veins. Boards are used 

 to construct brattices that aid in directing the flow of 

 air as it is drawn through the various passages to 

 provide ventilation. Flumes are built of wood to 

 conduct water above and below ground. Boards are 

 needed also for shoring. 



The lumber used in the mines does not need to be 

 of high quality. Good oak planks, however, are 

 needed to construct and repair mine cars. High- 

 grade hickory is required for the springboards used 

 to suspend screens in grading coal. Good -quality 

 lumber is used in offices, breakers, and other mine 

 buildings. 



The mines also use large quantities of cross ties, 

 mostly 5 inches square by 6 feet long. Sprags, 

 double-pointed pieces of wood 22 inches long and 

 about 3 inches in diameter, are used to brake the 

 wheels of mine cars. 



Since mine timbers need high compression strength 



and should be of a material that will give way grad- 

 ually with a cracking sound to warn miners when 

 there is danger of a break-down, some woods are 

 favored over others. Mixed oaks, sugar maple, red 

 maple, and hemlock are most frequently used. Miners 

 say that beech does not give sufficient warning of an 

 impending break, and even with mine timbers diffi- 

 cult to obtain, only a limited proportion of beech 

 will be accepted. A few other species — aspen, pin 

 cherry, basswood, and white pine — are also unsuited 

 for the mines. 



The diversion of transportation facilities to the 

 war effort compelled the mines to depend to a large 

 extent on the region's own timber resources. The 

 inaccessibility of many stands and the rise in labor 

 costs forced the prices for timbers delivered at the 

 mines upward from about $5 per ton in 1940 to 

 $6.50-$7.50 per ton in 1945. Prices 'for mine boards 

 similarly rose. These relatively high prices led local 

 operators to cut into stands hitherto considered un- 



18 



Miscellaneous Publication 648, U. S. Department of Agriculture 



