Page:Timber and Timber Trees, Native and Foreign.djvu/62

42 unnecessarily weakening those which remain. There are, undoubtedly, many examples to be found where larger scantlings have been experimented upon, and the results of these are, of course, more reliable and trustworthy.

The tests for the transverse strength in my experiments were conducted, in every case, with pieces 2″ × 2″ × 84″ =336 cubic inches. Each piece was placed upon supports exactly 6 feet apart, and then water was poured gently and gradually into a scale suspended from the middle until the piece broke, note being taken of the deflection with 390 lbs. weight, and also at the crisis of breaking.

After this a piece 2 feet 6 inches in length was taken, wherever it was found practicable, from one of the two pieces broken by the transverse strain, and tested for the tensile strain by means of a powerful hydraulic machine, the direct cohesion of the fibres being thus obtained with great exactness. Further, for the purpose of determining the proportions of size to length best adapted for supporting heavy weights, a great many cube blocks were prepared, of various sizes, as also a number of other pieces of different form and dimensions, which were then, by the aid of the same machine, subjected to gradually increasing vertical pressure in the direction of their fibres, until a force sufficient to crush them was obtained.