CHAPTER XXXIII 

 DEFECTS OF WOODS 



475. Chief Defects Knots. The principal defects which 

 are liable to appear in commercial lumber are: (1) knots, 

 (2) checks, (3) warping, and (4) rottenness. Knots, such 

 as we find in boards (Fig. 193) are the marks left in the tree 



B or No. 2 A or No. 1 C or No. 3 No. 1 Common 



FIG. 193. Four Grades of Yellow Pine Timber. A, or 

 No. 1, is the best; B, or No. 2, is the next; C, or No. 3, 

 is the next; and No. 1 Common is the poorest grade. 

 Notice that the poorer grades have more knots and 

 defects in them. 



trunk by branches which have disappeared. When the 

 lower branch of a tree dies for want of light, as it frequently 

 does, the annual layer of new wood is no longer deposited 

 upon it. The dead branch, at the place where it joins the 

 tree, makes a little hole in the first coat of living tissue 

 formed over the trunk after the branch's death. The edges 



412 



