54 BULLETIN 343, U. S. DEPARTMENT OF AGRICULTURE. 
It is very difficult to obtain reliable data on the relative strength 
of pulps from different woods, owing to the fact that it is almost 
impossible to produce them under identical conditions of grinding, — 
especially as regards power consumption per ton, a factor which 
largely influences their strength. The result of strength tests made 
at the laboratory on the experimental pulps seems to indicate, how- 
ever, that but one of them surpasses white spruce pulp. This refers, 
Fic. 42.—Aspen (Populus tremuloides). 
of course, to the uncooked pulps. Tests made on the steamed pulps 
indicate that those from the hardwoods produced with a smaller 
consumption of power surpass white spruce in bursting strength. If 
the results of tests on the breaking length in meters per horsepower 
per ton and those of the horsepower per ton per point per pound are. 
averaged for power consumptions of from 80 to 100 horsepower, 
the experimental woods can be arranged in the following order as 
regards their strength, the strongest coming first: 
ve 
