LASLETT'S TABLES 



In order that the careful and painstaking experiments made bj' 

 Thomas Laslett {Timber and Timber Trees) on a great variety of 

 woods, a work which was carried out in a conscientious manner over 

 a prolonged period, should not be lost sight of, his tables of tests are here 

 reprinted complete. Much of machinery used by Laslett in determining 

 these results is no longer available, and the circumstances which brought 

 about the necessity of the tests in his time are not likely to re-occur. In 

 the same way, many of the tests made during the European War on timbers 

 used in aircraft construction will possibly not be required again for a 

 number of years. While these tables are not exhaustive, yet their 

 value is great and they form an important addition to our knowledge of 

 the subject, and more frequent reference should be made to them. 



Especial care was taken to carry out the experiments upon wood 

 brought to a well-seasoned condition and fit for appropriation to works of 

 construction ; and in many instances he tried not only a series of pieces 

 taken from different trees, but a series of jjieces from the same tree, with 

 a view to find, if possible, in what part the maximum strength lay. 



The tests for the transverse strength were conducted in every case 

 with pieces 2" x e" x 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 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. 



In Laslett's time apparatus for determining the moisture contents of 



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