Art. XVIII. — The Want of a Uniform System in Experi- 

 menting upon Timber. 



By Frederick A. Campbell, C.E. 



[Read 9th December, 1886.] 



As the streiigth of timber varies not only according to the 

 tree from which it is taken, but also in accordance with a 

 number of minor conditions which affect it often in a very 

 marked degree, it is evident that unless such conditions be 

 fully and carefully recognised and recorded in connection 

 with any series of experiments upon timber, comparison 

 with other experiments will be impossible, and what other- 

 wise might be valuable work will be rendered almost useless. 



The great importance of this subject was impressed upon 

 me very forcibly when collecting information some time ago 

 as to the strength of colonial timbers, and as this interesting 

 field of investigation has as yet been barely entered upon in 

 these colonies, and as much of the work hitherto done 

 suffers from the omission of the details referred to, the 

 present has appeared to me a seasonable opportunity of 

 bringing the matter before this Society, and endeavouring 

 to secure the co-operation of the members in an attempt to 

 introduce some system as a guide for future workers in this 

 direction. 



The most important of the minor conditions referred to 

 as affecting the strength of timber are as follow : — (1) Age 

 of tree; (2) nature of locality where grown; (3) part of tree 

 from which timber is taken; (4) length of time seasoned; 



(5) deflection as affecting the bending moment of a beam; 



(6) size of piece tested. To each of these conditions I will 

 allude in the order given. 



1. Age of tree. — In relation to this point, it is only of 

 consequence to know that the piece for experiment has been 

 taken from a tree neither in its earlier nor later stages of 

 existence, for in the former the wood is imperfectly formed^ 

 soft, and weak, while in the latter it has entered upon a 

 process of decay ; it is in the intermediate or mature stage 

 that the wood is fitted for use practically, and should supply 

 specimens for the purpose of experiment. 



2. Locality where grown. — The geological nature of the 

 place where the tree grows has a very great influence upon 

 the character of the timber formed. Trees growing in a 



