Approximate time required to produce different wood crops (U. S. Forest

Service)

1 Species tolerant of shade which should show better results in second growth.

2 Species growing under favorable conditions when measured.

Yield of white pine per acre in southern New Hampshire (Margolin)

Quality I

Quality II

Quality III

Second growth

Volume in board feet is round-edged box board material. White pine thinnings

Life of Fence-Posts and Shingles

Durability of fence posts in Minnesota (Green).

Years

Red cedar.....................      30

White cedar (quartered 6 in. face).............    10-15

White oak (6 in. round)................ 8

Red and black oak.................. 4

Tamarack (red wood)................. 9

Elm.......................      6-7

Ash, beech, maple.................. 4

Black walnut....................      7-10

Prolonging the life of fence-posts (Willis).

Measures for posts named in ascending order of efficiency: —

Peeling and seasoning.

Charring.

Painting.

At best, surface brush paintings are not very durable. Some of the substances which may be applied with a brush are whitewash, petroleum-tar creosote, coal-tar creosote, and various patented products of coal tar and petroleum tar. Paint and whitewash are inferior to antiseptic preservatives; products of coal tar (creosote, etc.) are the best. These are best applied hot, in two or more coats. A barrel (50 gallons) of creosote should be sufficient to paint at least 300 posts with three coats for the butts and two for the tops.

Dipping.

One defect of brush treatment is that the preservative does not enter readily the cracks and checks. This defect may be overcome by dipping the posts in the preservative. Another advantage of dipping, as compared with painting, is a saving in labor. On the other hand, dipping requires a larger quantity of preservative, and, in addition to the amount consumed, there must be enough surplus to keep the barrel or tank filled to the proper depth. This usually forbids the use of any expensive preservative for dipping. Petroleum tar, coal tar, and the creosotes, however, may often be advantageously employed.

Posts have been treated by dipping the butt in cement. This is hardly satisfactory, owing to the ease with which the protective covering may be broken; moisture is absorbed after treatment; and causes the wood to expand and crack the cement.

Cold-bath treatment.

This differs from dipping because penetration of the wood is secured by leaving the post in the bath for ten hours or more. As a rule, only the cheaper preservatives can profitably be used in the cold-bath treatment. Coal tar is so ropy and sticky that it will scarcely penetrate even the most easily treated woods. Crude petroleum enters the wood rather readily, but lacks strong antiseptic qualities. A long bath in crude petroleum may, however, prove a feasible method of treatment where petroleum is very cheap and the woods used are readily impregnated. Creosote is usually the best preservative to employ. Coal-tar creosote requires a slight heating to liquefy it. Water in the wood cells resists the penetration of the oil. Thorough seasoning before treatment, therefore, is necessary to allow the oil to penetrate readily and to prevent checking after treatment. The cold-bath method of treatment has not yet been thoroughly investigated. It is probable, however, that it will impregnate but few woods. The woods which are likely to prove most suitable are beech, cottonwood, the gums, pin and red oaks, the pines, sycamore, and tulip tree.