hi es 
THE ‘BLUE’ WOOD. 13 
Numerous white strands of fungus mycelium make their appearance 
after six months or more. As the wood of the trunk dries, the bark, 
loose at first, tightens, so that in the ‘*black-top” stage it adheres 
quite firmly to the trunk. When cut into, it peels off in large sheets 
very readily, however. 
The ** blue” wood differs very little from the sound wood in general 
appearance, except its color. It is full of moisture at first, but loses 
this rapidly, so that in two years after the beetle attacks the wood 
it may be almost perfectly seasoned, even when completely covered 
with its bark. The ‘*blue” wood is said to be very much tougher 
than the green wood, so much so that the tie makers in the Black 
Hills can be induced to cut wholly blued wood only with difficulty. 
This toughness and a possible reason therefor are discussed hereafter. 
STRENGTH OF THE **BLUE” TIMBER. 
Ever since its first appearance there has been considerable discussion 
as to the strength and durability of the **blue” timber when com- 
pared with sound timber. It was universally believed that it would 
prove very much inferior in both respects. A test was made in the 
testing laboratory of the department of civil engineering of Washing- 
ton University, St. Louis,” to determine the comparative strength of 
the **blue” and the healthy timber. Sections of tree trunks 5 feet 
long were cut from trees at points 10 to 15 feet from the ground, and 
were shipped to St. Louis, where they were sawed into blocks of sey- 
eral sizes. For the compression tests, blocks 2 by 2 by 4 inches and 
3 by 3 by 6 inches were cut and planed to the exact dimensions, or as 
nearly so as possible. 
For the cross-breaking strength, sticks 2 by 2 inches by 4 feet, and 
3 by 3 inches by 4 feet were prepared. The blocxs for these tests were 
kiln-dried at a temperature of 172° F. until an approximately constant 
weight was reached. It was found that completely dried blocks would 
not shear atall. The moisture content of the green blocks was slightly 
higher than that of the ** blue” blocks. 
Three kinds of timber were used: A—Green timber: B—** Blue” tim- 
ber taken from **sorrel-top” trees, i. e., trees dead about one year: 
C—‘‘ Blue” timber taken from ‘‘red tops” and ‘* black tops” (mostly 
the latter), i. e., trees dead about two years. 
The tests were made with the machinery described by Johnson 
in early reports’ of the Division of Forestry. Every block was 
carefully measured. The results, reduced to the average crushing 
strength and the average cross-breaking strength per square inch, are 
@4The machinery was put at the writer’s disposal through the courtesy of Prof. J. L. 
Van Ornum. 
bTimber Physics, Bulls. Nos. 6 and 8, Division of Forestry, U. S. Department of 
Agriculture. 
