Why do boards warp?
Because they dry unevenly. If you place a damp board with one side toward the stove, the water will leave it, and the board will contract on that side and will pull the other side along; but the damp side cannot contract, because it is full of water, and so the whole board will be bent.
To keep the floors from warping, the dry boards are cut into small pieces, and these pieces are boiled in water. When all the water is boiled out of them, they are glued together, and then they never warp (parquetry).
THE DIFFERENT CONNECTION OF PARTICLES
Why are cart bolsters cut and wheel naves turned not from oak, but from birch? Bolsters and naves have to be strong, and oak is not more expensive than birch.
Because oak splits lengthwise, and birch does not split, but ravels out.
Because, though oak is more firmly connected than birch, it is connected in such a way that it splits lengthwise, while birch does not.
Why are wheels and runners bent from oak and elm, and not from birch and linden?