THE PRINCIPAL SPECIES OF WOOD. 



lines or glistening plates according to the way in which the 

 wood is cut. Woods differ in the size and number of these rays, 

 which are by no means always visible to the eye (see plate 3). 

 Woods are easy or difficult to work in proportion as their 

 fibres are arranged in a simple or a complicated manner. This 

 is shown in the figures on plate 4. A knife pressed upon 

 the oak must crush or cut into the fibres themselves, whereas 

 with the pine it finds some natural passage between the cells. 

 Wood may bs cut so as to develop cross-sections (C, Fig. 3), 

 radial sections (R), or tangential sections (T). The respect- 

 C 



FIG. 3. 



ive markings are in a general way indicated on the boards in 



the figure. 



Logs are sometimes sawn into quarters and then into pieces 



crossing and exposing the yearly rings. (See Fig. 4.) These 



"quarter-sawn" surfaces are structurally stronger and better, 

 but are, by reason of waste or small pieces, more 

 costly than others. The pith-rays of some woods, 

 such as oaks, are very prominent when split as they 

 are in "quarter-sawing," and the appearance of 

 such woods is consequently improved.* "Vertical 

 grained," ''straight grained," "edge grained," "rift 



grained" and " quartered woods " are names that mean the 



FIG. 4. 



* Some woods, as birdseye maple, are well developed by the rotary cut. 

 A revolving log is advanced against a tool which pares a broad thin ribbon suit- 

 able for veneered work. 



