Structure of Wood. 



71 



^> /: .'.vlfcX?*'. 



58. Teak Wood. 



strongest of woods, and present- 

 ing in its best conditions the 

 texture shown in the annexed 

 engraving, becomes brittle and 

 soft, w T hen rapidly grown, and 

 does not harden into heavy, 

 strong, and durable wood, until 

 it has ripened with age. 



253. Trees grown as reserves, 



in a coppice, and exposed alter- 57 - Wood of Ra P id Growth, but Spongy Text- 

 nately to the open air and to 

 the shade of other trees at dif- 

 ferent periods of their growth, 

 have a harder wood than those 

 grown in masses, but it is apt 

 to be knotty from lateral 

 branches and such trees being 

 more exposed to the winds and 

 to other accidents, do not have 

 so straight and regular a body, nor do they grow as high as when 

 many are grown together. Such wood does not readily split into 

 staves. A difference in the width of wood layers may be caused by 

 the greater or less shade in which it has grown, so that the character 

 of the seasons can never be learned definitely in the cross section of 

 a tree, unless it has grown in an isolated position. Still, from the 

 comparison of a great number of facts it might perhaps be possible 

 to determine with some certainty the general character of the cli- 

 mate by this method. 



254. The wood of conifers, as a ride, is heavier, more elastic, and 

 more durable, according as its growth has been slower, and the an- 

 nual rings are narrower. We see this shown in the timber from the 

 Baltic, and in the Siberian larch. These qualities are found greatest 

 in the timber grown in cold climates, and differences may sometimes 

 be detected in the north and south sides of the same tree. As a 

 general rule, trees growing in swampy land have a more open and 

 spongy texture than the same species grown on dryer land. 



255. Cellulose, which constitutes the principal body of wood-fiber, 

 is alike in all kinds of wood, when separated from other substances, 



