ROCKY MOUNTAIN MINE TIMBERS. 11 
dead material tested was cut from an area supposedly burned over 
in 1880. In general, the surface was covered with a network of 
shallow worm marks (made when the bark was on and probably of 
no influence on the soundness). The beams, even the larger ones, 
were very rough and knotty, and were of poorer grade in respect to 
condition of knots than those cut green. The cross sections in gen- 
eral were sound, though here and there along the length were places 
beginning to form punky pockets at the surface. The fact that this 
material under test gave values up to the elastic limit nearly equal 
to those of the air-dried beams is of considerable interest, as it indi- 
cates that it is in excellent condition for the uses to which round 
material is ordinarily put. 
CONCLUSIONS. 
The tests indicate that: 
1. An air-dried mine prop is superior to a green one as follows: 
Strength at elastic limit 2.3 times as great. 
Strength at maximum load 2.3 times as great. 
Stiffness 1.9 times as great. 
An air-dried mine cap is superior to a green one as follows: 
Strength at elastic limit 2.2 times as great. 
Strength at maximum load 1.6 times as great. 
Stiffness 1.4 times as great. 
2. With the exception of Douglas fir, there seems to be as much variation in the 
strength of one species procured in different places as among the different 
species themselves. This is probably the result of defects such as checks, 
knots, and bends, which, in this size of material (5 to 6 inch diameter round 
caps and props), apparently overbalance the differences in the actual strength 
of the clear wood. 
3. The unit strength and stiffness of 16-foot round beams decrease with an increase 
in size. The smaller beams tested, however, represented a slower growth 
material and were probably suppressed trees. 
4. Beams cut from timber standing dead for about 30 years showed a strength in- 
termediate between green and air-dried material cut from live timber. The 
tests tend to corroborate the opinion that timber cut from dead trees can be 
graded on the same basis as other material; that is, the quality of the wood has 
not changed, from the fact that it has seasoned on the stump, and deterioration, 
if present, will be indicated by signs of decay. Checking in material to be 
used in the round form can hardly be considered as a defect, as it occurs in all 
air-dried round material. 
CONSUMPTION AND DURABILITY. 
CONSUMPTION OF MINE TIMBERS IN COLORADO. 
The statistics here presented were collected to show the consump- 
tion of timber by the mining industry of Colorado * in 1911. They 
were obtained by sending a card to the mine operators of the State, 
requesting them to furnish the amounts, costs, and species of tim- 
i Colorado was chosen partly because of its importance as a mining State; partly because for the year 
1911 an estimate of the entire production of wood products, including lumber, poles, crossties, round mine 
timbers, and fuel was also available for direct comparison, and partly because the State is near the center 
of distribution of the species of mine timbers tested. 
