262 THE STRENGTH AND ELASTICITY OF IRONBARK TIMBER 
and perm ect 
resistances of the materials to direct tensile and compressive — 
the grain will be developed as well as the resistances above 
referred to. J 
The data obtained by the various experimenters on transverse r 
strength and stiffness will be first considered. ES 
5 
vanish at this layer which is therefore called the neutral layer. © 
And the intensity of stress on any layer above or below this _ 
the layer in question to the stress developed along it, and the sum 
of all such products is the moment of resistance of the whole 
ection 
Let J = moment of inertia of the section with reference to an 
axis passing through its centre of gravity. 
Let y = distance from the neutral layer to the extreme fibre. 
modulus of rupture, then moment of resistance 
(Mt. R) = fo. For rectangular sections, such as those experi- | 
mented upon J = +1, 6 d*. Where 6 = breadth of the beam, and 
ad = depth. 
it: as b a 
a pete rend Dek a 
Now since in the record of the experiments made at the Sydney 
Mint a co-etticient denoted by $ is used, which is calculated from 
_ the formula § — ar and since in Molesworth’s Pocket-book 
this co-efficient is also used for calculating the strength of timber 
