60 ELEMENTARY WOODWORKING 
Looking at the length of the log we see that the 
lines in a board, which we call the grain, are really 
the edges of the annual rings. 
It often happens in the forest 
that the wind sways the trees 
to such an extent that the an- 
nual rings separate and slide one 
within the other; this produces 
a defect in the wood called a 
shake (see s, Fig. 74). 
There are other characteris- 
Fic. 74. Showing Weather tics of wood known as warping 
Checks and ‘‘Shake”’ and shrinkage. 
After a tree has been cut down the cut end ait first 
looks like Fig. 72. If it is allowed to lie for some 
time exposed to the weather, its 
appearance changes to Fig. 74. 
This is due to the evaporation 
of the sap, and as there is more 
sap toward the outside, the shrink- 
age is greatest there and becomes 
less toward the center where the 
heartwood is comparatively dry. 
This is an important fact to 
know, because if we had cut the log, while it was 
still green, into planks, as shown in Fig. 75, the 
Fig. 75 
