Tensile Strength of Colonial Timbers. 7 



roughest description, but it answered its purpose. The 

 specimens were held at each end by wrought-iron clips, as 

 shown in figure 4, and then hung and pulled by means of a 

 lever, as shown in figure 5. Using known weights and slid- 

 ing them along the lever, which was graduated, I readily 

 obtained the breaking weight of the specimen. The weights 

 were always applied in such a way as to cause a gradually 

 increasing stress upon the specimen, perhaps fifteen to 

 twenty minutes being taken to work up to the breaking- 

 weight. 



The wood was well seasoned,, and probably better on the 

 whole than the average used for engineering and building 

 purposes. 



With the exception of the blackwood and deal, all the 

 specimens of the same kind of wood were taken from one 

 piece. 



With these facts, and the numerical result of each experi- 

 ment, the true value may be placed by anyone upon what 

 has been done. 



Of course, the numerical value of the tensile strength of 

 any timber is a quantity which varies greatly, being affected 

 by age, seasoning, defects, part of tree from which the 

 specimen is cut, &c, and the limits within which it varies 

 can only be fixed after numerous experiments made under 

 different circumstances. 



Now, the experiments noted hereafter give the values of 

 tensile strength under certain stated conditions, and will, 

 therefore, I hope, though in themselves not of great 

 importance, assist in determining at some future time the 

 average value for good qualities of some of our colonial 

 timbers. 



They do also, I think, throw some light which may be 

 interesting, upon the ratio which exists between the strengths 

 of the different kinds — the value, for instance, for white 

 and blue gum being three and a half times that for 

 messmate. An examination of the fractured specimens 

 shows the character of the fibre, and indicates clearly that 

 the tensile strength is highest where the fibre is straightest. 



