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 spottiness of various kinds, and is sometimes twisted. At the roots it is very often affected with burrs. It contains gallic acid, and so corrodes iron nails, clamps, etc.

(13) Uses.—Owing to its high price and great specific weight, oak has suffered in competition with spruce, larch, and pine so far as building is concerned; but its uses are very various and widespread nevertheless, and it is invaluable to the engineer and builder wherever strength and durability are aimed at.

As already said, its great value depends on its marvelous combinations of several average properties; and considerable variations in the density, durability, ease of working, and beauty when worked, and so forth, are met with according to the situation and climate in which the oak grows. Generally speaking, it is found that when the oak grows isolated in plains, in rich soil and a mild climate (habitat of Q. pedunculata), it grows rapidly, and produces a wood of very tough and horny consistency, which is regarded as the best for naval and hydraulic work, cartwrights, etc., and wherever strength, tenacity, and solidity are required in high degree (Fig. 39, top). The best should have broad and equal rings, but not broader than 7 to 8 mm., with narrow vascular zone and the smallest possible vessels, and with a pale, rather than dark, and even color on the fresh section. It should also have long fibers and a strong, fresh smell.

In close, high forest, on poor soil, and in a rougher climate, it may take 300 years to reach 0·6 metre diameter, and the wood is then softer and more porous,