is commonly known as wild black cherry. It grows from Maine to eastern North Dakota and southward to central Florida and central Texas. Its scattered distribution over a large area insures a steady supply. Approximately 42 million feet of cherry lumber are produced annually. Cherry wood is strong and moderately hard. It has good shock-resisting ability, a moderate degree of stiffness, and a

Figure 27.-All items of furniture in this picture are of fabricated hardwood lumberbookcases, radio, desk and chair, parquet flooring, letter file, venetian blinds, end table, painted interior trim, and even the turned lamp base.

very moderate shrinkage. The heartwood varies in color from light to dark reddish brown and has a beautiful and distinctive luster. The wood has a fairly uniform texture, containing numerous small scattered pores. It is exceptionally well suited for engravers' blocks and patterns. Other important uses are for paneling, furniture, woodenware, toys, and novelties.

Dogwood is usually referred to as "flowering dogwood" because of the large white blossoms which appear early in the spring before the foliage. It is sometimes used as an ornamental tree. The tree has a broad range, extending from New England to Florida and westward to Minnesota and Texas. It is usually found scattered in small openings in hardwood forests. The wood is brown in color, heavy, strong, tough, hard, and takes a high polish. These properties have given the wood a high reputation for bobbins and shuttles, machinery bearings, engraving, and specialty turned products.

Hackberry lumber is produced from two trees known as sugarberry and hackberry, although the latter is more common and accounts for most of the lumber cut. Hackberry is found scattered in our hardwood forests from New England to Virginia and westward to North Dakota and Kansas. Sugarberry grows from Virginia to Florida and westward to Texas and Kansas. Hackberry trees are usually found in commercial sizes in river bottoms of the Middle West. The cut of hackberry lumber is not large; in fact, it is often sold with the lower grades and for the less exacting uses of ash and sometimes with elm. The lumber is yellowish in color, heavy but limber, good in shock resistance, and moderately hard. It is utilized for boxes and crates, furniture, sporting and athletic goods, motor vehicles, and other sundry purposes.

Holly is a tree closely associated with Christmas, since its lustrous, persistent green foliage and the red berries of the female trees are very decorative. Holly is one of few hardwoods that has distinct male and female trees. The wood of holly is cream-white, closegrained, tough, moderately hard and heavy, and easily worked. The white color makes an excellent inlay wood for cabinet work. Other products from the comparatively small annual cut are engravings, small handles, miscellaneous turned products, and novelties.

Ironwood is a name often used locally to refer to two species commonly known as blue beech and hop hornbeam. It is the latter tree which produces the ironwood of commerce in the United States. It is found scattered east of the Great Plains region. The wood is close-grained, very strong, hard, heavy, tough, and durable. Its uses are primarily of a special nature such as furniture parts, wedges, levers, and handles.

Locust wood is usually produced from black locust trees which are quite common in the Appalachian Mountains from Pennsylvania to northern Georgia, extending also into Illinois, Indiana, Arkansas, Oklahoma, and Tennessee. The wood of black locust is one of the heaviest and hardest of our native hardwoods. It has only a moderately small shrinkage and the heartwood is very durable. Among its specialty uses are insulator pins and wagon hubs, although it is also utilized for boxes and crates, woodenware, and novelties.

Persimmon wood is usually closely associated with dogwood in commercial uses. The tree has about the same range and the wood about the same properties. The better grades are used principally for bobbins and shuttles, sporting and athletic goods, and handles, while the lower grades are used for boxes and crates.

Osage orange is likewise known in many localities as "bois d'are," since the early Indians made bows and arrows of it. Large quantities are still used for this purpose, to supply archery equipment for our

modern sport. The tree is native to our Gulf and neighboring States, but has been cultivated as windbreaks in States farther north. The wood is usually hard and strong, close-grained, heavy, very flexible, and takes a fine polish. It is used for nonmotor vehicles, machinery parts, and numerous outdoor uses such as paving blocks, posts, etc.

Willow trees are invariably associated with low, wet locations such as streams and rivers. There are numerous species of willow in the United States, one of which, often referred to as osier or basket willow, is cultivated, the saplings being used for weaving baskets and furniture. The willow lumber of commerce is produced from several of the species, generally grouped as black willow. The wood is soft, light, and weak but works very easily. It is used for numerous purposes such as artificial limbs, furniture, and boxes.

SELECTION OF HARDWOODS FOR SPECIFIC PURPOSES 1a

Intelligent selection of wood for a given purpose necessitates an analysis of the requirements of that use. Good engineering judgment and careful observation are essential to determine which properties are required for satisfactory service and which properties are the most important. The selection of the proper wood is primarily the responsibility of the engineer or the architect, because the requirements of use vary with conditions, the quality desired, and the conditions to which the products will be subjected in service.

For example, in considering the use of wood paneling for a home or building, the question of beauty or character of grain, the color, freedom from warping and splitting, and suitable finishing properties would be very important. In addition, there would be the question of whether the cost must be kept down to a moderate figure.

After the requirements of use are determined, the next step is the selection of a wood with suitable properties. Again, good engineering judgment is needed, since it is only in exceptional uses that one wood will excel all others in the properties desired. Again referring to wood for paneling: there are several American hardwoods which would fulfill the requirements satisfactorily, although certain specific properties would probably have a higher rating in one wood than in another. One wood may have exactly the desired color and character of grain but would be more costly. The question then is just how much this feature is worth for the particular job. To evaluate the difference in properties, especially when they improve but do not increase the service life, calls for good judgment.

Investigations of the Forest Products Laboratory have resulted in the publication of much information on the properties of wood. This information furnishes a basis for the selection of the wood best adapted to a given use. A larger number of the Laboratory's publications contain detailed data on such properties as strength. weight, decay, and painting characteristics. Recently there was published the Wood Handbook 13 which gives under one cover the accumulated information previously scattered through a number of

12 Based upon Selection of Wood for Industrial Uses, by R. P. A. Johnson, Forest Products Laboratory, April 1937.

13 Wood Handbook, by Forest Products Laboratory, U. S. Department of Agriculture, September 1935. For sale by the Superintendent of Documents, Government Printing Office, Washington, D. C., 25 cents.

bulletins. It contains information on strength, shrinkage, specific gravity, thermal conductivity, electrical resistance, and other properties in units and terms with which the engineer or architect is familiar and which he knows how to use.

Properties which are not so readily expressed in engineering terms often determine the selection of wood for industrial use. The absence of extensive engineering data on such properties has resulted in wide differences of opinion as to the extent to which individual species possess or do not possess merit for some particular use. Prej

Figure 28.-Lobbies in ships, hotels, theaters, auditoriums, and office buildings are made "home-like" by the use of hardwood panels, trim, furniture, and floors.

udice and misconceptions regarding such properties have been the cause of considerable loss and poor practice in the use of wood. Recently the Forest Products Laboratory has begun to attack the problem of measuring and recording these properties. The work is still in progress, and new methods of measuring, as well as units for recording, have been and must continue to be developed. As a result of the work thus far there are now available data which make possible a comparison of a number of hardwood species important in industrial use.14

SOME IMPORTANT PROPERTIES OF HARDWOODS 15

HARDNESS

Resistance of a wood to wear, as in flooring, is dependent upon its hardness and toughness, and upon the size and arrangement of its wood fibers. The latter is most important from the standpoint of evenness of wear. Also, the harder a wood the less it crushes or smashes under load, as in flooring, and the less it will scar or mar, as in trim, paneling, etc.

On the other hand, the harder a wood, the more difficult it may be to work with hand tools, the harder it is to nail, and usually the more often it splits in nailing. However, a smaller nail may be used with harder woods to give the same strength.

Figure 29.-The comparative hardness of hardwoods.

A high degree of hardness is desired in flooring; a reasonable degree of hardness is desired in trim, veneers, paneling, built-in equipment, and other woodwork.

Figure 29 shows the comparative hardness of hardwoods. The values in this chart are comparative; that is, by a combination of the several individual mechanical properties of wood affecting hardness, an index value representing the relative hardness of each wood is derived. Thus these values do not represent pounds per square inch of resistance to indentation of the surface of the wood. But, being

15 Taken from Lumber Grade Use Guide, Pamphlet XV, Hardwood Lumber and Timber, issued by the National Lumber Manufacturers Association.