327 



The weights of specimens of those woods that had been 

 stored in the laboratory for over twelve months, and con- 

 tained about 12 per cent, of moisture, averaged as follow: — 



Timber. 



Weight in Pounds per cubic foot. 



The amount of moisture contained in timber has a great 

 influence upon the strength. The more moisture the timber 

 contains the weaker it is, as has been clearly shown by the 

 experiments conducted by the United States Forestry Depart- 

 ment, and this is equally true, whether the moisture is the 

 natural sap or is wat^r absorbed. The experiments carried 

 out. by Mr. Julius on behalf of the Western Australian Gov- 

 ernment have shown that the same is true for our Australian 

 timbers. It thus becomes important in chronicling the re- 

 sults of tests upon timber that the percentage of moisture 

 should be determined for each specimen, in order that com- 

 parisons may be of value. Accordingly, such determinations 

 were made for most of the pieces tested. A thin section was 

 cut out across the test piece, near the place where fracture 

 occurred, within twenty-four hours of the experiment. This 

 section was weighed and then placed in a drying-oven, where 

 it was kept at a temperature of 115 deg. Cent, for four 

 hours, when it was again weighed. Experiments showed that 

 it was unnecessary to keep it in the oven more than four 

 hours to get a determination sufficiently close for the pur- 

 pose, as a longer period of drying made a difference of only 

 1 per cent. 



The experiments were made with a Riehle screw-testing 

 machine, capable of exerting and measuring forces up to 

 100,000 ft)., and each timber was subjected to five different 

 classes of tests — I., Transverse strain to determine its 

 strength as a beam: II., direct tension: III., shearing along 



