266 THE STRENGTH AND ELASTICITY OF IRONBARK TIMBER 
Where S = the tensile resistance, and JW, J, b, d, have the values 
given in the formuia for transverse stress already referred to. 
It has been shown that 
6W1 
ae 4bé 
aoe gees pea 
CUiago: SS ee 
Now / in the author’s experiments = 15,000 
“. S = 865°8 lb., but the experimental result was 
S = 20,000 ib. per square inch. 
In the experiments made by Mr. Laslett 
18,994°5 
1°7325— 
f= 18,995 “= = 10,963 
It appears therefore that if the specimens which gave this high 
value for the modulus of rupture had been prepared by turning in 
a lathe, and if they had been tested in such a manner that onl 
tensile resistances could be developed the result would have 
exceeded 20,000 Ibs. per square inch. Hence it appears that Mr. 
Laslett’s results for tensile strength are unreliable, and moreover 
the formula cannot be applied to timber since the tensile 
resistance is greater not less than the modulus of rupture. 
the joint, rather than in the body of the timber. The resistance 
developed in the joint, due to tensile stress, will be the shearing 
resistance along grain, and the resistance to pressure on the 
bearing area of the bolts. 
Tensile Elasticity—May be found by measuring the strain 
produced by a given stress, thus if #H = modulus of tensile 
elasticity. = intensity stress per square inch ; = length 
along which the elongations are measured; and 7 the elongation 
produced by an intensity of stress ? then 
Pct a) See seam aa A fi Re 
The author has found from specimens shown in figs. 1 and 2 
that the modulus varies with the load. In the round specimen 
shown in fig. 2, the elongation produce with 13,333 Ib. per square 
inch was ‘04 on a length of 10 inches, so that 
E = 13883 x 10 _ 3.333 900m. 
TOO 
The elongations and loads producing them are shown for 
Specimen prepared, asin fig. 1. See fig. 4, 
De 
