407 



and across the grain. The tests were made in the same manner 

 as those described in the author's paper on "The Strength of 

 South Australian Timbers," in Trans. Roy. Soe. S. Austr., 

 vol. xxxii. On the whole over 350 tests were made on the 

 three species, so that fair average determinations could be 

 made. In addition a number of tests were made upon samples 

 of oregon purchased at local timber mills. As this is an 

 imported timber largely used for construction it was thought 

 that the comparison would be useful. 



With every test a determination was made of the moisture 

 contents of the wood as soon as possible after the test was 

 completed. In the case of beams this was done by boring two 

 large auger holes into the beam near the break. The shavings 

 from these holes were then put into weighing bottles, to 

 protect them from the drying effects of the air, and weighed. 

 The bottles were then put in a drying oven, the tops being 

 removed, and they were kept there at a temperature of about 

 104° C. for 5 hours. The tops of the bottles were then replaced 

 and, after being allowed to cool the bottles were again weighed. 

 The moisture determination is very essential, because the 

 strength of many species of wood diminishes very greatly as 

 the moisture contents increase, and a test of its strength is 

 practically valueless unless it is accompanied by a measurement 

 of the moisture contained in it. It makes no difference whether 

 this moisture be in the form of the original sap or whether it 

 be due to water that has soaked into the wood after seasoning. 

 In either case the strength of the wood with a given percentage 

 of moisture will be the same. 



In order to examine the question of the variation of 

 strength with moisture contents more thoroughly than could 

 be done by making tests on the timber as it was seasoning, 

 48 blocks, each 2 in. x 4 in. and 5 in. long, were cut out of a 

 seasoned beam of Pinus insignis. The determinations showed 

 that this beam contained 11 percent, of moisture, as calculated 

 on the dry wood, and as it had been stored in the Laboratory 

 for two years in a dry place, the moisture contents were fairly 

 uniformly distributed. The blocks were each separately 

 marked and weighed, and three of them were tested in com- 

 pression along the grain, the average strength being 4,462 lbs. 

 per sq. inch. The remainder were then kept immersed in 

 water for four days. They were then removed and allowed to 

 gradually dry out to their original condition. At first they 

 dried rapidly, and two or three blocks were weighed each day, 

 to determine their moisture contents, and then tested. The 

 first block tested had 50 per cent, moisture, and its strength 

 had fallen to 1,710 lbs. per sq. inch. Afterwards the process 

 of drying was slower and the interval of time between the tests 



