TIMBER AND TIMBER TREES. [CHAP. 



and when so used in decks, flooring, &c., rendering it 

 dangerous to walk upon. 



In the transverse section of a tree will be found a 

 number of lines radiating from the centre and pre- 

 senting a star-like appearance. These are the medullary 

 rays of the botanists, but are best known to carpenters 

 as the silver grain, or felt (a, Fig. 3). This peculiarity of 

 appearance is due to thin plates of compressed cellular 

 tissues, which usually run continuously from the pith to 

 the bark. Although, as a general rule, this is the case, 



yet in some 

 species a se- 

 condary series 

 is found, over- 

 lapping or 

 scarfing by, 

 -< but very sel- 

 dom touch- 

 ing, the pri- 

 mary rays (b y 



Fig. 3). If, 

 th erefo re, 

 we carefully 

 examine the 

 smooth sur- 

 face of a transverse section of the stems of most trees, 

 we can generally trace these thin plates or rays. They 

 can be seen to great advantage in the Beech, ajnd, more 

 or less, in all the varieties of Oak ; but they are far less 

 distinct in the Lime, Yew, and Chestnut, and in the 

 Firs and Pines they cannot be traced, although botanists 

 believe them to be present. 



Before converting or employing most kinds of woods, 

 particularly in dealing with unseasoned timber, it will be 



FIG. 3. 



