340 
again, upon the specifications under which the contractors are working, but 
varying from two to three hours. The pressure is then removed, the 
preservative is withdrawn to the storage tanks, and the material is allowed 
to drip for some time before being returned on the trams into the yards. | 
The amount of preservative is usually specified at so many pounds per 
cubic foot, a “full cell treatment” requiring 12 pounds per cubic foot of 
wood. Owing to the large amount of material kept on hand for season- 
ing and the space needed for storing, receiving, and dispatching it, these 
timber-treating plants are usually located at some distance from towns and 
adjacent to railway lines, with a large tract of land for buildings, spurs, 
and yards.” 
Some of these plants have been equipped for treating wood-block 
paving, the blocks being made at the plant from southern pines, and the 
process being similar to that for treating railway ties, except that the 
blocks are put in containers with perforated sides instead of being loaded 
upon trams. The plant at Granite City specializes on paving blocks and 
piling, and does not treat over 3,000 ties a year. It uses the Rueping 
process entirely. 
TIMBER USED IN COAL MINES 
Of the four counties coming within the scope of this report, only Jack- 
son county mines any coal. It is credited with an output of 1,204,949 
tons for the year ending July 30, 1921. The timber supply of the other 
three counties, however, is very important as furnishing a supply of mine 
timbers to adjoining counties—to Williamson, which mined 10,822,566 tons, 
and to Franklin, which produced during 1921 12,723,700 tons, exceeding 
the amount produced by any other county in the state. High freight rates, 
of course, have their effect upon the distance to which mine timbers are 
shipped, but in general we may say that the coal-mining counties have 
naturally preferred to save some of their own timber and buy from out- 
side sources. 
Kind and description of timber used in coal mines—The main kinds 
of timber used in coal mines may be listed as follows: 
1. Cross-bars or legs. These must be made of white or bur oak. 
They vary from 10 to 16 feet in length, and must be not less than seven 
inches at the top end, inside the bark. Thrifty young white oaks are often 
cut for bars when by leaving them for a few years they might grow into 
trees of tie size. 
2. Mine props. Mine props may be in the round, or split from large 
trees, and are from 5.5 to 10 feet in length and not less than four inches 
at the top end. They are classed as mixed oak, which brings the best 
prices, and miscellaneous, which includes almost any of the bottomland 
species except willow and cottonwood. 
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