50. The hardwood group is headed by the oak as typical of its class, nearly all others being compared with it in regard to hardness, durability, and strength.

51. White oak is the hardest of the several American species of the oak tree, and it grows in abundance throughout the eastern half of the United States. It furnishes a wood which is heavy, hard, cross-grained, strong, and of a light yellowish-brown color. It is used where great strength and durability are required, as in framed structures, ship building, cooperage, and carriage making.

Red oak is similar in nearly every respect to white oak, except in its grain and color, the grain being finer and closer and the color darker and redder. It is also about 12 per cent. softer.

English oak is similar to the American oaks in color, texture, and appearance, but is superior to them for such structural purposes as ship building and house framing.

The structure of the fiber, and the large, thick, and numerous medullary rays, make oak especially prized as a material for cabinet work and furniture, when the log is quarter-sawed. The silver grain and the high and durable polish which the wood is capable of receiving, make it one of the most beautiful used in joinery and cabinetwork.

52. Ash, the wood of a large tree growing in the colder portions of the United States, is heavy, hard, and very elastic. Its grain is coarse, and its color is very similar to that of red oak, which it also resembles in strength and hardness.

Ash is used sometimes for furniture and cabinetwork, where it is often supposed to be an imitation of oak, but it is never so strongly marked in the silver grain as oak, and its tendency, after a few years, to become decayed and brittle renders it unfit for structural work.

53. Hickory is the heaviest, hardest, toughest, and strongest of all the American woods. The medullary rays are very numerous and distinct, and produce a fine effect in the quarter-sawed plank. The flexibility of the wood, together with its toughness and strength, render it valuable in the manufacture of carriages, sleighs, and implements requiring bent-wood details.

As a building material, it is unfit for use: first, on account of its extreme hardness and difficulty of working; and second, on account of its liability to the attacks of boring insects even after the fibers have been filled and varnished.

54. Locust is one of the largest forest trees in the United States, and furnishes a wood that is as hard as white oak. It is composed of very wide annual layers, in which the vessels are few but very large, and are arranged in rows, giving the wood a peculiar striped grain.

Its principal use is in exposed places where great durability is required, while for posts for buildings and fences in damp locations it has no superior.

Its hardness increases with age, and on this account it is used for turned ornaments and occasionally in cabinetwork.

55. Black walnut is one of the finest and largest timber trees peculiar to the United States. Its wood is heavy, hard, and porous, and its dark, purplish color is marked by a beautiful wavy grain. Strong, durable, and not subject to the attacks of insects, it, at one time, furnished the most popular wood for interior decoration and fancy cabinetwork, but its present use is confined generally to small cabinetwork and gun stocks, which latter are made almost exclusively of this material.

The irregular and knotted roots of the tree produce, in the wood cut from them, an appearance called burl.