_Calculating the results_: The formulæ used in calculating the results of tests on large rectangular simple beams loaded at third points of the span are as follows: 0.75 P (1) J = -------- b h l (P_{1} + 0.75 W) (2) r = -------------------- b h^{2} l (P + 0.75 W) (3) R = ---------------- b h^{2} P_{1} l^{3} (4) E = --------------- 4.7 D b h^{3} 0.87 P_{1} D (5) S = -------------- 2 V b, h, l = breadth, height, and span of specimen, inches. D = total deflection at elastic limit, inches. P = maximum load, pounds. P_{1} = load at elastic limit, pounds. E = modulus of elasticity, pounds per square inch. r = fibre stress at elastic limit, pounds per sq. inch. R = modulus of rupture, pounds per square inch. S = elastic resilience or work to elastic limit, inch-pounds per cu. in. J = greatest calculated longitudinal shear, pounds per square inch. V = volume of beam, cubic inches. W = weight of the beam. In large beams the weight should be taken into account in calculating the fibre stress. In (2) and (3) three-fourths of the weight of the beam is added to the load for this reason. BENDING SMALL BEAMS _Apparatus_: An ordinary static bending machine, a steel I-beam bearing two adjustable knife-edge supports to rest on the platform, and a special deflectometer, are required. (See Fig. 31.) [Illustration: FIG. 31.--Static bending test on small beam. Note the use of the deflectometer with indicator and dial for measuring the deflection; also roller bearings between beam and supports.] _Preparing the material_: The specimens may be of any convenient size, though beams 2" X 2" X 30" tested over a 28-inch span, are considered best. The beams are surfaced on all four sides, care being taken that they are not damaged by the rollers of the surfacing machine. Material for these tests is sometimes cut from large beams after failure. The specimens are carefully weighed in grams, and all dimensions measured to the nearest 0.01 inch. If to be tested in a green or fresh condition the specimens should be kept in a damp box or covered with moist sawdust until needed. No defects should be allowed in these specimens. _Marking and sketching_: Sketches are made of each end of the specimen to show the character of the growth, and after testing, the manner of failure is shown for all four sides. In obtaining data regarding the rate of growth and the proportion of late wood the same procedure is followed as with large beams.