ROCKY MOUNTAIN MINE TIMBERS. 
15 
Table 9. — Reported life of untreated round mine timbers in coal mines {mostly 5 to 7 
inches diameter). 
Conditions in mine. 
Average 
Poor ventilation. 
Good ventilation . 
Exceptional 
Doug- 
las fir. 
Years. 
5 
2 
10 
25 
Pine.i 
Years. 
4 
1 
Engel- 
mann 
spruce. 
Years. 
4 
1 
Alpine 
fir. 
Years. 
3 
Pinon. 
Years. 
i Includes lodgepole pine and western yellow pine. 
Table 10. — Reported life of untreated round mine timbers. in metal mines (mostly 8 to 10 
inches diameter). 
Conditions in mine. 
Douglas 
fir. 
Western 
yellow pine 
Lodgepole 
pine. 
Engelmann 
spruce. 
Average 
Very poor ventilation . 
Constantly wet 
Years. 
2 to 5 
20 to 40 
Years. 
lto 3 
15 to 25 
Years. 
7 
lto 2 
Years. 
lto 2 
15 to 20 
The conditions under which the estimates were made vary so much 
that the relative life of the different species is probably not reliable. 
For example, several operators reported that under the same condi- 
tions Douglas fir outlasts lodgepole pine or spruce two to three times; 
yet the average values show comparatively little variation among the 
species. 
The factors that cause variation in the life of the timbers are prin- 
cipally ventilation, moisture, acid mine water, and the condition 
of the timbers when placed. The influence of fresh and compara- 
tively dry air was clearly indicated in several mines which reported 
a life fully four times as long for the timbers in the intake shaft as 
for those in the return shaft (8 and 2 years, respectively). Several 
operators reported that they had increased the life of their timbers 
from two to three times by peeling and seasoning them before place- 
ment. Certain mines reported that their timbers were sound after 
standing from 25 to 35 years under conditions where they were nearly 
always wet, and in one or two cases the water was stated to contain 
" sulphuric acid" or " copper and arsenic," which probably acted as 
an antiseptic. Both constantly wet and constantly dry conditions 
appear, from the replies, to be favorable to a long life, while damp- 
ness, due to stagnant air, or alternating dryness and wetness, appears 
to furnish the best conditions for the growth of wood-destroying fungi. 
PRESERVATIVE TREATMENT. 
Preservative treatment to prevent decay was not regularly prac- 
ticed at any of the mines reporting. Sixteen operators referred to 
some use of preservatives, though none had had a long enough expe- 
rience to furnish data on the increased life from such treatment. The 
methods spoken of were dipping in creosote or crude oil, and brush 
