nds squared smoothly and evenly. They
are carefully weighed, measured, rate of growth and proportion
of late wood determined, as in bending tests. After the test a
moisture section is cut and weighed. Ordinarily these specimens
should be free from defects.

_Sketching_: Sketches are made of each end of the specimens to
show the character of the growth. After testing, the manner of
failure is shown for all four sides, and the various parts of
the failure are numbered in the order of their occurrence.

_Adjusting specimen in machine_: The compressometer collars are
adjusted, the distance between them being 20 inches for the
posts and 6 inches for the blocks. If the two ends of the blocks
are not exactly parallel a ball-and-socket block can be placed
between the upper end of the specimen and the movable head of
the machine to overcome the irregularity. If the blocks are true
they can simply be stood on end upon the platform and the
movable head allowed to press directly upon the upper end.

_Measuring the deformation_: The deformation is measured by a
compressometer. (See Fig. 33.) The latter registers to 0.001
inch. In the case of posts the compression between the collars
is communicated to the four points on the arms by means of brass
rods; with short blocks, as in Fig. 33, the points of the arms
are in direct contact with the collars. The operator lowers the
fulcrum of the apparatus by moving the micrometer screws at such
a rate that the set-screw in the rear end of the upper lever is
kept barely touching the fixed arm below it, being guided by a
bell operated by electric contact.

_Log of the test_: The load is applied continuously at a uniform
rate of speed. (See SPEED OF TESTING MACHINE, above.) Readings
are taken from the scale of the compressometer at regular
increments of either load or compression. The stress-strain
diagram is continued to at least one deformation point beyond
the maximum load, and in event of sudden failure, the direction
of the curve beyond the maximum point is indicated. A brief
description of the failure is entered on the log sheet. (See
Fig. 34.)

[Illustration: FIG. 34.--Sample log sheet of an endwise
compression test on a short pine column.]

In short specimens the failure usually occurs in one or several
planes diagonal to the axis of the specimen. If the ends are
more moist than the middle a crushing may occur on the extreme
ends in a horizontal plane. Such a test is not valid