USES OF WOOD. 189 



acacia}. At one time it was very highly esteemed, 

 but of late years it has somewhat fallen into 

 disrepute. It is very probable that the brittleness 

 frequently noticeable in the wood of this tree is 

 due to imperfect conditions of growth ; and when 

 grown under natural circumstances in soil not 

 rich, it progresses more slowly, and does produce 

 valuable timber. Its general colour is a greenish- 

 yellow, but it has brown veins. Its qualities are 

 hardness (which makes it susceptible of a high 

 polish) and durability ; but it is, as we have said, 

 brittle, owing to a lack of elasticity. Its hardness 

 and durability, however, make it suitable for orna- 

 ments and wooden pins, for which it is largely 

 used, for fastening planks to beams or to the ribs 

 of vessels. The name tree- nail (corrupted into 

 trenail, and pronounced trunnel) is a descriptive 

 designation of these wood-pins. For other pur- 

 poses, when its particular qualities are desirable 

 such as for fences, posts, and axle-trees it is 

 much used. 



Its waterside habitats usefully fit the Alder 

 (Alnus glutinosa) for purposes for which resistance 

 to dampness and the effects of wet is essential. 



