MECHANICAL PROPERTIES OF WOODS GROWN IN UNITED STATES. 45 
Table 3. — -Approximate figures for change of properties with change of moisture con- 
tent; variation of properties with specific gravity; reliability of averages, and probable 
deviations from averages of individual trees and specimens. For use with Tables 1 
and 2. 
Property. 
Average 
increase 
(or de- 
crease) in 
value ef- 
fected by 
raising (or 
lowering) 
the mois- 
ture con- 
tent 1 per 
cent when 
at about 
12 per cent. 
(Seep. 18.) 
Approxi- 
mate 
power of 
specific 
gravity 
according 
to which 
property 
varies. 
(Seep. 18.) 
Probable 
variation 
of present 
average 
(when 
from 5 
trees) 
from true 
species 
average. 
(Seep. 19.) 
Probable 
variation 
of random 
tree from 
average 
for species. 
(Seep. 19.) 
Specific gravity based on volume when green 
Weight per cubic foot l 
Shrinkage 2 .' 
Static bending: 
Fiber stress at elastic limit . . ; 
Modulus of rupture 
Modulus of elasticity. 
Work to elastic limit , 
Work to maximum load 
Impact bending: 
Fiber stress at elastic limit 
•Work to elastic limit : 
Height of drop , 
Compression parallel to grain: 
Fiber stress at elastic limit 
Crushing strength 
Compression perpendicular to grain— fiber stress at 
elastic limit 
Hardness, end 
Hardness, side 
Shearing strength parallel to grain , 
Tension perpendicular to grain 
Per cent. 
Per cent. 
1.7 
Per cent. 
3. 
1 See explanation, p. 11, 
2 See explanation, p. 12. 
The minus sign indicates decrease. 
