Many other forms of construction which we have seen daily as long as we can remember have equally sound reasons for their form. No piece of woodwork should be designed without considering how it will be affected by shrinkage and warping.
In selecting lumber always look out for "shakes." This is a defect caused by the separation of the annual rings. A tree may be considered as a series of irregular cylinders of diminishing diameters. The forest-grown tree is much more spindling, tall, and straight than the low-crowned, heavy-branched specimen grown in the open, where there is no crowding.
The swaying of the forest tree in the wind, especially when its neighbours have been cut down, is sometimes sufficient to make the rings separate and slide one within the other. This is more noticeable in some species than others and it gives the wood a serious fault. ([Fig. 239]).
"Winding" is the result when the ends and sides are no longer parallel. Like all peculiar characteristics of wood, this varies greatly in lumber of various kinds, and may be largely avoided by exposing both sides to the same conditions, or keeping equally distributed weight on it until used. When winding becomes excessive, the board is useless for any kind of work.
[LV]
LUMBER: NO. 4
The woods of the United States are classified roughly as hard and soft; and trees as broad-leaved or deciduous, and evergreen or coniferous.
In a general way, the trees which drop their leaves in the fall—the broad-leaved—produce hard woods and the evergreens soft woods. There are so many exceptions, however, that the rule is a very rough guide.
Several of the coniferous trees drop their leaves or needles in the fall, like the larch or tamarack, and some woods from evergreens are harder than some woods from broad-leaved trees. Yellow pine is harder than basswood, which, according to the rule, should be a hard wood. As a matter of fact, it is softer than the majority of woods cut from evergreens. The only way to gain a comprehensive knowledge of this interesting subject is by experience and study. Making a collection of woods, leaves, and seeds is one of the most fascinating studies a boy can take up. He will soon discover that not only is every wood different from every other wood in grain, colour, odour, and hardness, but some woods are strong and elastic, others strong and brittle, weak, etc., and that every tree has a different leaf, bark, flower, and seed from its neighbour. He will find groups or families, such as the oaks, the maples, the pines, spruces, cedars, etc., with several members of each group, all different, yet having family characteristics. He will be surprised at the endless extent of the subject; the willow for instance has a hundred and fifty known varieties. He will find himself, like our boys, dipping into botany and geology to discover perhaps, as Harry did, that the oak was once an evergreen, and that it still holds a good proportion of its leaves all winter.