What Forests Give

NAVAL STORES

From inside the living tree we get another liquid which has been important to man for thousands of years. This is oleoresin. In the United States we use it in the form of turpentine and rosin, and call them naval stores—probably, because when our young country built its ships of wood, turpentine and rosin were used to make them watertight.

This oleoresin serves a strange purpose in the conifers from which it comes. Of all these, the longleaf pine produces the most oleoresin with the slash pine a close second. The longleaf pine grows only in a warm, moist, even climate. It is a tree very fussy about climate but extremely easy about soil—sand or loam, moist or dry, even clay, are all the same to the longleaf pine. It has found a region to suit itself extending from the lower corner of Virginia, down through North Carolina, South Carolina, Georgia, and Florida, around through Alabama and Mississippi and over beyond the river into Louisiana and Texas. At the northern edge of this region the longleaf pine has 200 days without frost in which to grow, and at the southern edge about 100 more. In March the winds blow up from the Gulf of Mexico heavy with warm rain and keep on bringing moisture until September, when they swing about and blow in from the cooler Atlantic until December. Then they shift and veer undecidedly until March comes again. During the time that they blow in from the Gulf and the Atlantic, they bring from 48 to 62 inches of rain—all that a tree needs.

Chipping

It is necessary to know something about the structure of these resin-producing trees in order to understand how they can give us oleoresin, just as it is necessary to know the structure of a bird's wing in order to understand how it can fly. As in other trees, there is the column of dead heartwood at the center, and a layer of sapwood around it through which the sap travels to the leaves. Outside the sapwood is a thin layer of new living cells called the cambium. These cells have thin, soft walls, and they grow with remarkable speed—dividing and redividing—increasing on the inside to make new sapwood and on the outside to make more bark. So far such trees as the longleaf pine and slash pine are built on the same plan as all other trees. But they have, in addition, tiny pipes surrounded by living cells, and these extend up and down through the tree and back and forth horizontally within it, so that there is a sort of plumbing system, network of interconnecting pipes. The cells of which these pipes are built exude soft gum—the oleoresin. Now the use the tree makes of this gum, which is soft enough to flow through the slender pipes, is to heal its own injuries. The pipes are in a sense military roads like those the Romans built in Britain, like the top of the Great Wall of China, like the ones the Italians laid down in Ethiopia. Along them rushes the oleoresin to repel attack. Through the pipes and out to the surface of the tree it flows when a cut is made through the bark into the living wood beneath. In 5 minutes after the ends of the resin pipes have been cut, tiny drops ooze out and spread over the wound, hardening as the air strikes them and forming something which is like the new skin that grows over a cut in the hand. It is this healing cover with which the tree tries to stanch its wounds, that we take away to use, and in order to get it we wound the tree again and again—cut through the ends of the pipes higher and higher up by a process that is called "chipping."

Every week during the growing time of the tree which is the time when the warm wet winds are blowing in, gangs of men go through the forests of the pines and cut fresh wounds just above those which the trees have been so desperately trying to heal. How word of these repeated attacks is carried through the tree, we do not know. No internal telegraph system has been discovered, but the beleaguered tree puts in more and more resin pipes—military highways—leading from above down to the point of attack. Sometimes these roads extend 20 feet above the chipped face. Through them the tree sends fresh oleoresin as fast as the cells can create it, and when this pours out at the newly scarred surface, we set metal troughs to lead it into pails, gather it up, and carry it away.

But what do we do with this oleoresin? It is not the thick, sticky molasseslike stuff which the workmen haul away through the pine woods that we want, but the two chief things which it contains—turpentine and rosin.

The "Stiller"

Somewhere out in the woods is a copper still. It stands under a shed open at the sides. Into the boiler the men pour some 15 barrels of oleoresin at a time, leave it in charge of a man called the "stiller", and go back for more.

This stiller has an uncertain job, for he must regulate the whole process of distillation not by thermometers or time clocks, but as a man tunes a piano—by ear. Inside the boiler the heat is beginning to change the turpentine into a gas, and it bubbles out of the heavy rosin as steam out of boiling water; as a gas it is led away through a long spiral pipe called a "worm", down under water and gradually cooled till it becomes a liquid again. As the turpentine is led off, the stiller listens near the lower end of the worm to tell what to do next.

There is a danger point when he hears a tumultuous gurgling from his listening post and knows that his brew is likely to froth over. To stop it, the bubbles in the rosin must be broken as one breaks the bubbles in a coffeepot by quick stirring. But the stiller cannot get at the mixture to stir it, so he rushes the fire to make the rosin so thin that the bubbles will break of themselves.

After the fire is once lit under the still, it is kept up day and night. All day the heavy smoke rolls through the forest; all night the flames shoot up. When all the turpentine of one boiling has been led away through the worm, and the rosin allowed to flow out into a tank, a fresh supply of olesresin is poured into the boiler, and the men pile up the fire.

We sail the seas these days in ships of steel. What do we use these naval stores for?

The greater part of turpentine finds its way into paints and varnishes; that is, it is one of the chief things used to preserve wood from the effects of the weather, from fungi, from disease. It perlorns for other wood very much the same function that it was intended for by the tree that grew it. It is used in the printing of cloth to keep the colors from running together. From it is derived in small quantities and at a high cost a substance much like camphor. And in the making of rubber, turpentine is used as a solvent. Yes, turpentine is a good gift.

Rosin too is used in the making of quick-drying paints and enamels and the colors used in firing pottery. And it is used as size for writing and printing papers so that they will take ink. Mixed with a little turpentine, it is used to coat the insides of beer barrels as the ancient Greeks coated their wine jars with pitch. It can be divided further into gases and oils. One of the oils will burn like kerosene; others are used in printers ink; the heaviest in wagon grease.

Rosin, too, is an important gift from the forest.

We have learned how to get turpentine from trees without killing them—how to chip them for 10 or 15 years and leave them in such good condition that they can be used for lumber. We have learned also how to get more oleoresin from fewer trees for a longer time than we once did, and this is the same as saying that we get more of it from smaller forests.