THE TECHNOLOGIST. 



NOTES ON THE PKOPERTIES OF WOOD. 



BY JOSEPH JUSTEN. 



Trees cut in summer give lighter wood than when felled during win- 

 ter time. The cause for this may probably be ascribed to the fact that 

 in winter a large amount of nourishment is stored in the trunk, which 

 during the spring and summer is spent for the formation of bloom and 

 leaves. 



We call hardness in wood the resistance which it opposes when 

 another body enters it. If wood were an equal body like minerals, we 

 should be able to determine its resisting power or hardness ; but it being 

 differently built, and, whilst trying its hardness, other properties inter- 

 fering, we cannot arrive at a decisive result. 



Sometimes a wood has very hard fibres but very little body ; that is, 

 it is lighter built than another wood with soft fibres and a full body ; it 

 is therefore unadvisable to judge the hardness of a wood according to 

 its fibres. Experiments to ascertain its hardness should be made across 

 the stem and not upon a longitudinal section ; and although there is no 

 instrument which leads us at once to a definite result, we can generally 

 arrive with a saw at a fair conclusion. Many persons constantly em- 

 ployed on wood are of the opinion that it becomes harder if it is worked 

 or barked whilst green. 



Wood, as a porous body, contains in its natural state — whether dead 



or alive — a certain amount of moisture ; by the loss of that moisture or 



increase of the same, the bulk of the wood either contracts or expands. 



If we have a piece of wood where this action takes place only upon 



one side, it is obvious that the piece will alter its form or shape. 



The consequence of the loss of moisture is also the warping and 

 splitting of the wood. The inner structure of a stem is irregular ; for 

 instance, we find the inner moisture of a yearly ring to be more than on its 



VOL. IV. B 



