WBIGHT, 



As said before, the soil affects the -weight of wood by the amount 

 of moisture it contains, and by its mineral composition. Excess 

 of moisture for any species in question tends to make the wood 

 spongy. Where it prevails, added high temperature and bright 

 illumination merely increase the width of the concentric rings, 

 without at all increasing the weight of the wood. In the case of 

 conifers growing in wet places, the wood may be extremely light 

 in spite of narrow rings. The effect of the mineral composition 

 of the soil on the nourishment of woody tissue is too well known 

 to be repeated here. Even an abundance of moisture and free 

 enjoyment of light may fail to produce dense wood in a soil that 

 is poor in the mineral food of plants. 



The general conclusion to be drawn from the three immediately 

 preceding paragraphs is that the rule establishing a direct connec- 

 tion between the weight of a piece of wood and the width of the 

 concentric rings composing it, may often be misleading, if these 

 rings are unusually wide or unusually narrow, but generally holds 

 good in all other cases. 



The density of wood is influenced in a large measure also by the 

 awe of the tree. As said before, the wood substance formed by a 

 young tree is heavier than what is produced by the same tree at a 

 more advanced age, the difference sometimes exceeding 60 per 

 cent. But it is also an established fact that all trees as a rule form 

 heaviest wood in an absolute sense when young. Thus it is that 

 in young trees there is usually no appreciable difference in weight 

 between the heartwood and the adjacent sapwood ; whereas the 

 difference between the weight of this sapwood and that of heart- 

 wood formed in later years may be really appreciable. The word 

 " may " is used advisedly, because, although in most species the 

 heartwood is notably heavier than the sapwood, this assertion can- 

 not be generalised into a rule, since the mere circumstance of a 



