14 UTILIZATION OF CALIFORNIA EUCALYPTS. 
In shipment 84, taken from a tree cut near Elwood Station, Cal., 
the average strength values for green material are greater than in 
the other shipments in bending (except modulus of elasticity in 
shipment 17), in both kinds of compression,® and inshear. In ship- 
ment 66, however, which was cut from the same locality as shipment 
84, the strength values are lower than in the Berkeley. material 
(shipment 17). The trees showing the lowest strength values were 
those cut near Santa Monica, Cal. (shipment 10). This, of course, 
must not be taken to mean that all blue gum grown near Santa Monica 
is comparatively weak. The material from Colegrove (shipment 18) 
is slightly higher in strength values than that cut near Santa Monica. 
A combination of the results of the tests on green blue gum gives, in 
the bending tests, an average fiber stress at the elastic limit of 6,907 
pounds per square inch; an average modulus of rupture of 11,800 
pounds per square inch; an average modulus of elasticity of 1,788,000 
pounds per square inch; and an average elastic resilience (shock- 
resisting ability) of 1.58 inch-pounds per cubic inch. The average 
crushing strength parallel to grain is 4,919 pounds per square inch; 
the average strength perpendicular to the grain at the elastic limit 
is 1,329 pounds per square inch; and the average shearing strength, 
1,625 pounds per square inch. 
In the air-dry material the strength is increased except in com- 
pression perpendicular to the grain. Several air-dry strength values 
for blue gum and similar values for white oak are given in Table 2 for 
purposes of comparison. The average moisture of the blue gum (21.6 
per cent) is considerably higher than the average of the oak (12 per 
cent). To make the comparison perfectly fair, both woods should be at 
the same moisture content or both in a green condition. Such results 
for oak are not available. In considering Table 2, therefore, it should 
be kept in mind that the results from blue gum would be higher had 
the moisture been further reduced. 
TABLE 2.—Strength of air-dry blue gum and white oak. 
Blue gum | White oak}d 
(21.6 per cent | (12 per cent 
moisture). moisture). 
Pounds per Pounds per 
square inch. square inch. 
iBending—modulus olnipturess ee ek eee eee eee rece a= ce eeee ese eee 14, 183 13, 100 
Compression with grain—crushing strength................-..-.-...-..----- 7,218 8, 500 
Shearing with grains)+. 20 32.22 eee Soc cee eee -Beienisee ns Secs seeeeere 1, 782 1,000 
a The strength values for compression perpendicular to grain are the same in shipments 84 and 17. 
b Taken from Forest Service Circular 15, ‘‘Summary of Mechanical Tests on Thirty-two Species of 
American W oods.”’ 
[Cir. 179] 
