106 TIMI'.KK P.KAMs. 



It is not usual to measure the elastic deflections <>t 

 timber beams with instruments of precision so as to 

 ascertain the elastic modulus, but this may be don^ 

 in some cases. A beam treated in this way will I it- 

 found to possess a definite modulus, although there is con- 

 siderable variation in its value, even in specimens of what 

 is apparently the same material. 



Some care is required in carrying out timber tests. 

 Sharp knife edges should not be used, and where the 

 testing machine is provided with supports of this kind, 

 small steel plates must be inserted between the specimen 

 and the knife edges, so as to distribute the pressure and 

 prevent the edges penetrating the wood. 



