. Elementary woodworking. Woodwork; Trees. Fig. 74. Showing Weather Checks and " Shake " 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 slialie (see s, Fig. 74). There are other characteris- tics of wood known as tvarping and shrvikage. After a tree has been cut down the cut end at first looks like Fig. 72. If it
. Elementary woodworking. Woodwork; Trees. Fig. 74. Showing Weather Checks and " Shake " 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 slialie (see s, Fig. 74). There are other characteris- tics of wood known as tvarping and shrvikage. After a tree has been cut down the cut end at 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. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Foster, Edwin W. Boston, New York [etc. ] Ginn & company
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttrees, bookyear1903
