a 
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3. Mine ties. These are of two kinds—room ties and motor ties. 
The former are of smaller size and are used by the miners in mining the 
coal out of a “room”; while motor ties must be larger, since over them 
the heavy motors run which convey coal to the hoisting shaft. Room ties 
are about 5 feet in length, of any kind of hardwood, hewed on two sides, 
and with a 4-inch by 6-inch face. Motor ties are usually 5% feet long, 
hewed on two sides, with a face 5 by 7 inches. Sometimes the smaller 
ties are sawed out by a portable mill. So far as we have seen, creosoted 
mine-props are not being used, since it is not intended that they shall give 
a service of over three or four years. For more permanent construction 
near shafts and in fluor-spar mines, cement or steel may be used. 
4. Mine caps. “Cap pieces.” These are pieces of boards of mixed 
oak, 1 inch by 6 inches by 16 inches in length, which are placed on top of 
mine props to tighten them up. Some of the sawmills use defective lumber 
for this purpose. 
5. Wooden tracking. ‘This is used in pieces usually 8 feet long and 
3 by 4 inches in diameter, to take the place temporarily of rough or poor 
grade lumber which may be used to keep coal from falling down. It may 
be sawed at portable mills, and is worth about $20 per thousand board feet. 
6. Riprap lumber. This term is used to designate a kind of rough 
or cheap grade of lumber which may be used to keep coal from falling 
down in mines or is used in cars and may be sawed at portable mills. It 
is worth about $20 per thousand board feet. 
7. Lagging. Small round poles or poor-grades of slabs from port- 
able mills used to keep coal from falling through. 
8. Sprags. Pieces of hardwood, preferably hickory, 2 inches in 
diameter and 18 inches long, used by miners to thrust between the spokes 
of coal cars to stop them. 
Besides the kinds enumerated, large amounts of yellow pine and 
other kinds of lumber not considered here are used for tipples, sheds, 
buildings, and offices. 
Amount of timber required to mine a ton of coal_—This is a very hard 
point to determine. One operator states that ten times as much timber is 
required in the Danville district to mine a ton of coal as in the Taylor- 
ville district, due largely to a difference in roof conditions. 
Figuring it, however, by four different methods from data given us 
by some of the largest coal companies on timber used and coal mined for 
a single period, we find by averaging the figures from five different 
sources, that it takes not far from .25 cubic foot of timber to mine one ton 
of coal, or 20,000,000 cubic feet for the whole state, not including lumber 
used for buildings and other construction purposes. Hall and Ingall’s 
(711) estimate that it takes one-fifth of a cubic foot of wood to mine one 
