TOUGHNESS OF WOOD.

Toughness may be defined as the ability to resist sudden shocks and blows. This requires a combination of various qualities, strength, hardness, elasticity and pliability. The tough woods, par excellence, are hickory, rock elm and ash. They can be pounded, pulled, compressed and sheared. It is because of this quality that hickory is used for wheel spokes and for handles, elm for hubs, etc.

In the selection of wood for particular purposes, it is sometimes one, sometimes another, and more often still, a combination of qualities that makes it fit for use.[¹⁰]

It will be remembered that it was knowledge of the special values of different woods that made "the one horse shay," "The Deacon's Masterpiece."

"So the Deacon inquired of the village folk

Where he could find the strongest oak,

That couldn't be split nor bent nor broke,—

That was for spokes and floor and sills;

He sent for lancewood to make the thills;

The cross bars were ash, from the straightest trees,

The panels of whitewood, that cuts like cheese,

But lasts like iron for things like these.

The hubs of logs from the "Settler's Ellum,"—

Last of its timber,—they couldn't sell 'em.

Never an ax had seen their chips,

And the wedges flew from between their lips,

Their blunt ends frizzled like celery tips;

Step and prop-iron, bolt and screw,

Spring, tire, axle and linch pin too,

Steel of the finest, bright and blue;

Thorough brace, bison skin, thick and wide;

Boot, top dasher from tough old hide,

Found in the pit when the tanner died.

That was the way to "put her through."

'There!' said the Deacon, 'naow she'll dew!'"

[Footnote 1:] Hygroscopicity, "the property possessed by vegetable tissues of absorbing or discharging moisture and expanding or shrinking accordingly."—Century Dictionary.

[Footnote 2:] This is shown by the following table, from Forestry Bulletin No. 10, p. 31, Timber, by Filibert Roth:

POUNDS OF WATER LOST IN DRYING 100 POUNDS OF GREEN WOOD IN THE KILN.

	Sap-wood or outer part.	Heart-wood or interior.
1. Pines, cedars, spruces, and firs	45-65	16-25
2. Cypress, extremely variable	50-65	18-60
3. Poplar, cottonwood, basswood	60-65	40-60
4. Oak, beech, ash, elm, maple, birch, hickory, chestnut, walnut, and sycamore	40-50	30-40

[Footnote 3:] The following table from Roth, p. 37, gives the approximate shrinkage of a board, or set of boards, 100 inches wide, drying in the open air:

	Shrinkage Inches.
1. All light conifers (soft pine, spruce, cedar, cypress)	3
2. Heavy conifers (hard pine, tamarack, yew, honey locust, box elder, wood of old oaks)	4
3. Ash, elm, walnut, poplar, maple, beech, sycamore, cherry, black locust	5
4. Basswood, birch, chestnut, horse chestnut, blue beech, young locust	6
5. Hickory, young oak, especially red oak	Up to 10

The figures are the average of radial and tangential shrinkages.

[Footnote 4:] How much different woods vary may be seen by the following table, taken from Filibert Roth, Timber, Forest Service Bulletin No. 10, p. 28:

WEIGHT OF KILN-DRIED WOOD OF DIFFERENT SPECIES.

	Approximate.
	Specific weight.	Weight of
	Specific weight.	1 cubic foot.	1,000 feet of lumber.
		Pounds	Pounds
(a) Very heavy woods: Hickory, oak, persimmon, osage, orange, black locust, hackberry, blue beech, best of elm, and ash	0.70-0.80	42-48	3,700
(b) Heavy woods: Ash, elm, cherry, birch, maple, beech, walnut, sour gum, coffee tree, honey locust, best of southern pine, and tamarack	.60-.70	36-42	3,200
(c) Woods of medium weight: Southern pine, pitch pine, tamarack, Douglas spruce, western hemlock, sweet gum, soft maple, sycamore, light sassafras, mulberry, grades of birch and cherry	.50-.60	30-36	2,700
(d) Light woods: Norway and bull pine, red cedar, cypress, hemlock, the heavier spruce and fir, redwood, basswood, chestnut, butternut, tulip, catalpa, buckeye, heavier grades of poplar	.40-.50	24-30	2,200
(e) Very light woods: White pine, spruce, fir, white cedar, poplar	.30-.40	18-24	1,800

[Footnote 5:] For table of weights of different woods see Sargent, Jesup Collection, pp. 153-157.

[Footnote 6:] See Forestry Bulletin No. 70, pp. 11, 12, and Forestry Circular No. 108.

[Footnote 7:] For table of strengths of different woods, see Sargent, Jesup Collection, pp. 166 ff.

[Footnote 8:] For table of elasticity of different woods, see Sargent, Jesup Collection, pp. 163 ff.

[Footnote 9:] For table of hardnesses of different woods, see Sargent, Jesup Collection, pp. 173 ff.

[Footnote 10:] For detailed characteristics of different woods see Chapter III.

THE PROPERTIES OF WOOD.

References*
- Moisture and Shrinkage.
  - Roth, For. Bull., No. 10, pp. 25-37.
  - Busbridge, Sci. Am. Sup. No. 1500. Oct. 1, '04.
- Weight, Strength, Cleavability, Elasticity and Toughness.
  - Roth, For. Bull., 10, p. 37-50.
  - Boulger, pp. 89-108, 129-140.
  - Roth, First Book, pp. 229-233.
  - Sargent, Jesup Collection, pp. 153-176.
- Forest Circulars Nos. 108 and 139.

* For general bibliography, see [p. 4.]