While the tree is growing, the heartwood is the strongest; but after the growth has stopped, the heart is the first part to decay. It is important, therefore, that the tree should be felled at the right age. This varies with different trees, and even in the same tree under different circumstances. The induration of the sapwood should have reached its extreme limits before the tree is felled, but the period required for this depends on the soil and climate. Trees cut too soon are full of sapwood, and the heart-wood is not fully hardened. The ages at which the undermentioned trees should bo felled are as follows : - Oak, 60-200 years, 100 years the best; Ash, Larch, Elm, 50-100 years; Spruce, Scotch Fir, 70-100 years. Oak bark is sometimes stripped in the spring, when loosened by the rising sap. The tree is felled in winter, at which time the sapwood is hardened like the heart. This practice improves the timber. A healthy tree for felling is one with an abundance of young shoots, and whose topmost branches look strong, pointed, and vigorous.

The best season for felling is midsummer or midwinter in temperate, or the dry season in tropical climates, when the sap is at rest.

Squaring

Directly the tree is felled it should bo squared, or cut into scantling, in order that air may have free access to the interior.