third-point loading and a long platform
bearing knife-edge supports, is required. (See Fig. 29.)

[Illustration: FIG. 29.--Static bending test on large beam. Note
arrangement of wire and scale for measuring deflection; also
method of applying load at "third-points."]

_Preparing the material_: Standard sizes and grades of beams and
timbers in common use are employed. The ends are roughly squared
and the specimen weighed and measured, taking the
cross-sectional dimensions midway of the length. Weights should
be to the nearest pound, lengths to the nearest 0.1 inch, and
cross-sectional dimensions to the nearest 0.01 inch.

_Marking and sketching_: The butt end of the beam is marked _A_
and the top end _B_. While facing _A_, the top side is marked
_a_, the right hand _b_, the bottom _c_, the left hand _d_.
Sketches are made of each side and end, showing (1) size,
location, and condition of knots, checks, splits, and other
defects; (2) irregularities of grain; (3) distribution of
heartwood and sapwood; and on the ends: (4) the location of the
pith and the arrangement of the growth rings, (5) number of
rings per inch, and (6) the proportion of late wood.

The number of rings per inch and the proportion of late wood
should always be determined along a radius or a line normal to
the rings. The average number of rings per inch is the total
number of rings divided by the length of the line crossing them.
The proportion of late wood is equal to the sum of the widths of
the late wood crossed by the line, divided by the length of the
line. Rings per inch should be to the nearest 0.1; late wood to
the nearest 0.1 per cent.

Since in large beams a great variation in rate of growth and
relative amount of late wood is likely in different parts of the
section, it is advisable to consider the cross section in three
volumes, namely, the upper and lower quarters and the middle
half. The determination should be made upon each volume
separately, and the average for the entire cross section
obtained from these results.

At the conclusion of the test the failure, as it appears on each
surface, is traced on the sketches, with the failures numbered
in the order of their occurrence. If the beam is subsequently
cut up and used for other tests an additional sketch may be
desirable to show the location of each piece.

_Adjusting specimen in machine_: The beam is placed in the
machine with the side marked _a_ on top, and with the ends
pro