Our National Forests Part 8

_The Science of Growing Timber._ In order to better understand the many diversified problems which are being studied at the Forest Experiment Stations, it is necessary to give the reader a few ideas concerning the science of forest ecology. This science is the basis of all problems dealing with the growing of timber and is therefore a study of the utmost importance to forestry. Forest ecology is the study of the relations of trees and forests to their surroundings. By surroundings (or environment) we mean all the factors which influence their growth and reproduction, such as soil temperature, soil moisture, soil texture, rainfall, light, wind, air temperature, relative humidity, alt.i.tude, slope, exposure, and surface. Forests, we must remember, are not warehouses of standing logs; they are not merely aggregations of individual trees; but they are complex communities of living organisms, which are affected in many ways by climate and soil and which, in turn, affect in no small degree the climatic and soil conditions in their immediate vicinity. The forester cannot treat the forest as an aggregation of individuals, for forests have laws which govern their behavior which are entirely different from those that govern the individual tree. Some foresters and botanists prefer to call this science by the name of "tree sociology," and they compare it with human sociology. Individuals, as we well know, are governed by different natural laws than communities. Just so with trees and forests. In order, therefore, to grow a never-failing supply of timber intelligently and economically we must understand these complex organisms and communities, we must study their behavior under different soil and climatic conditions and ascertain the conditions under which they grow best. Only by doing this can the forester achieve all the objects of forestry, namely, to help Nature to produce more and better timber, in a shorter length of time and at the smallest possible cost.

The experimental work of the Forest Experiment Stations is grouped under such categories as these: dendrological studies, forestation studies, studies in forest influences, studies relating to forest management, studies in forest protection, commercial tree studies, and grazing studies.

_Dendrological Studies._ Dendrological studies include studies in tree distribution and wood identification. For each tree species growing in the United States (and there are about 500 of them) it is desirable to know its geographical distribution, its commercial distribution, and its local distribution. The first of these deals with the entire range of the tree by geographical divisions; the second of these with the distribution of those bodies of timber that are of commercial quant.i.ty or size; and the last deals with the distribution of the tree by local divisions, such as lowlands, slopes, ridges, valleys, plateaus, etc. This information is usually placed on maps for permanent record.

Observations by Forest officers on the many National Forests are recorded by them and at the first opportunity sent to Was.h.i.+ngton. Very often it happens that the range of a species of tree is considerably extended and that a tree is found growing in a locality where it was never reported from before. The identification of woods is done at the Forest Products Laboratory. The distinguis.h.i.+ng characteristics of the woods of many American tree species have been determined. The wood of different trees is studied under the microscope to discover in what way it differs from other woods closely related. Many such results are published for the benefit of both the lumber dealer and the general public in the form of bulletins. Both the subject of dyewoods and that of the many woods now sold as mahogany have been investigated in this way. The resulting data have been used by many companies and have helped to protect the public from frauds.

_Seed Studies._ Experiments in reforestation are grouped under seed studies, nursery studies, and sowing and planting. Considerable work has been done in developing the best methods of seed-extraction. Much valuable information has been gathered on the largest amount of seed that may be extracted from pine cones of different species per unit of time at different degrees of temperature; the maximum temperature which may be applied to seeds of different species without impairing their vitality; the germinating power of seed extracted at different temperatures; the comparative length of time required for the germination of seed extracted with or without artificial heat; and the most economical type of seed-extracting plant. Studies have been made upon the comparative germination of tree seeds in the field and the greenhouse. The ultimate success of the plantations being established on the National Forests in a large degree depends upon the character of the seed used. Hence studies are being conducted of the effect of alt.i.tude, soil, age of the tree, density of stand, insect damage and disease infection, and other factors that affect the mother tree, upon the character of the seed collected from those trees, and the growth and form of the resulting seedling. Also tests to show the effect of the source of seed on the form and growth of young seedlings have indicated very clearly that with all species the seed grown in the locality where the trees are to be planted give as a rule better results than seed imported from another region.

_Nursery Studies._ Nursery studies endeavor to show the most efficient methods for growing young trees for field planting for each species of trees. It is of great importance to know how much seed to sow per foot in the nursery beds; what is the best time (spring or fall) for sowing; to what depth the seed should be covered in order to give the highest germination; whether better results are obtained by drill sowing or by broadcast sowing; the best methods of shading, fertilizing, watering, and cultivating the seed beds; the methods of securing the best root development of the young seedlings; the best time and method of transplanting from the nursery beds to the transplant beds; the best methods for r.e.t.a.r.ding spring growth in seedlings to be used at high alt.i.tudes; and other problems of similar nature.

_Forestation Experiments._ Experiments in forestation have, year after year, proven that planting is much safer than direct seeding and ultimately less expensive. For this reason a greater emphasis has been placed upon planting studies. These studies have attempted to show the best season for planting each species; the best methods of planting; the most advantageous cla.s.ses of stock to use; and what the most suitable sites are for each species of tree.

_Studies of Forest Influences._ Studies on the influence of forests upon stream flow and erosion are attempting to furnish important data for American conditions upon this subject. At the Wagon Wheel Gap Forest Experiment Station in Colorado such a study is being carried on. The purpose of the study for the first two or three years has been to determine the character of the two streams which are to be measured. The forest cover on the two watersheds is practically identical. The results so far obtained indicate that the influence upon the stream flow must be about the same in both cases, and, consequently, a comparison of these streams after the denudation of one watershed will be a very fair test of the influence of the forest cover upon the relative height of the flood stage and low-water stage, the amount of erosion, and the rate of melting of the snow.

[Ill.u.s.tration: Figure 29. At the Fort Valley Forest Experiment Station, Coconino National Forest, Arizona. A typical meteorological station Forest officer measuring precipitation. Note the shelter which contains thermometers and also the electrically equipped instruments to record the direction and velocity of the wind.]

[Ill.u.s.tration: Figure 30. Forest officer ascertaining the amount of evaporation from a free water surface. Fort Valley Forest Experiment Station, Flagstaff, Arizona.]

Experimental observations which have been conducted since 1908 at the various Forest Experiment Stations have shown that the forest exercises a decided moderating influence upon temperature extremes, wind motion, and evaporation. Likewise, the presence of a forest cover r.e.t.a.r.ds the melting of snow in the spring, and in this way huge s...o...b..nks in the forests feed the nearby streams until late in the summer. Forests therefore have been shown to conserve the water supply and also causing this water to run off slowly rather than in sudden floods. Studies have also been conducted on determining the effect of cutting timber upon the climate within the forest.

_Meteorological Observations._ The climatic requirements of forest types have been studied at the Fremont Experiment Station since January 1, 1910, through experimental observations, and other stations have taken up the same problem since that date. The first step in this work at the Fremont has been to obtain a complete meteorological record as a basis for determining what climatic conditions are most important in limiting the natural range of such important species as Yellow pine, Douglas fir, and Engelmann spruce. The data collected so far have shown that soil moisture and soil temperature are the controlling factors in determining the existence of the three forest types. It has also been shown what climatic conditions each of the three types of forest must have in order to succeed. This work has since been extended to include other types of forest and a meteorological station has been established at timber line on Pikes Peak. This station, which is at approximately 11,500 feet, is equipped with self-recording instruments to measure the climatic factors which obtain at that elevation and which mark the uppermost alt.i.tudinal limit of tree growth in that locality.

Such studies as these, based upon systematic meteorological observations, have an important bearing on all other forest problems.

The data secured in this way especially a.s.sist the technical foresters in solving the various problems in forest management, reforestation, fire protection, and land cla.s.sification, besides giving positive knowledge of the environment in which our trees live and of the factors affecting their growth and reproduction. These systematic observations are of prime importance if we ever hope to have a science of American Forestry.

_Forest Management Studies._ Experiments in forest management are carried on to determine the best methods of cutting National Forest timber to secure natural reproduction and at the same time to improve the quality and productivity of the remaining stand. These studies are carried on by means of permanent sample plots, on which all the trees are carefully measured and recorded. First the timber is cut on the plots under different systems of management, or thinnings or improvement cuttings are made. An exact record is kept of the amount of timber removed and of the size and distribution of the remaining trees. Measurements taken at regular intervals show the precise effect of the method used on each plot. Close observations of the reproduction which takes place, brush and other forms of cover which may establish themselves, and changes in soil conditions are recorded. On similar sample plots methods of brush disposal, methods of marking timber for cutting, and thinning methods are studied. After logging there are several ways in which the resulting slash may be disposed, depending upon surrounding conditions. In some localities the brush must be burned immediately on account of the fire danger which its presence involves; in other places it must be removed because it interferes with reproduction; in still other places the brush may be scattered over the area because there is little fire danger and, in fact, the brush has been found to a.s.sist and protect reproduction. All these possibilities must be determined by experiments. Likewise in marking timber for cutting and in thinning practice various methods are possible, depending upon circ.u.mstances, the most important of which are the requirements of the species and the density of the forest.

Other management studies deal with the determination by actual measurement of the volumes of trees and stands, and the growth of trees and the yields of whole forests. Reliable growth and yield data for the different species and types are necessary to properly handle timber sales as well as for forest management. They are also essential for determining damages caused by fires and trespa.s.s.

_Forest Protection Studies._ Studies in forest protection endeavor to find the best methods of protecting the National Forests from fire, grazing, disease, insects, wind, snow, hail, and animals. The most efficient protection of the National Forests from fire calls for an accurate, scientific knowledge of all the factors that enter into the problem. Comprehensive studies are undertaken to secure the basis for a more scientific method of distributing National Forest fire-protecting funds. The aim has been to find the degree of intensiveness in fire protection warranted by timber, forage, and watershed values, as modified by their susceptibility to damage by fire. Under the ideal system of allotting fire-protecting funds, the most valuable resources, which at the same time are most in danger of destruction by fire, should receive the largest amount of funds and therefore the greatest amount of protection. Less valuable resources, less susceptible to fire danger, should receive protection in proportion. Other cla.s.ses of fire protection studies have to do with the various phases of fire prevention, fire detection, and fire control. Studies have also been carried on to determine the rapidity with which fire spreads in different forest types, and under a given set of climatic conditions.

_Protection from Grazing Damage._ Studies of the effects of grazing upon the natural reproduction of forests are conducted with a view to devising a system of range control which would minimize such injury without requiring the total exclusion of the stock from the range.

Studies have shown that serious damage occurs to seedlings under four feet in height during the dry season, on areas containing poor forage, or which have been overgrazed, or where there was little or no underbrush. It was found that sheep do twice as much damage as cattle.

Some of the measures that have been adopted to lessen the injury to reproduction by sheep and cattle are: the revegetation of overgrazed areas, reductions in the amount of stock, provisions for the better distribution of stock by the regulation of watering places, and the exclusion of sheep from cut-over areas on which reproduction is deficient until the seedlings reach a sufficient height to be out of the reach of the animals.

_Protection from Insects and Diseases._ In cooperation with the Bureau of Entomology and the Bureau of Plant Industry the Forest Service is conducting a large number of studies and investigations dealing with the insects and diseases that do destructive damage to forests. The direct result of these studies will be the gradual eradication of predaceous insects and dangerous tree diseases from the valuable timber forests of the Government. Control measures already taken have shown the value of exact scientific information. On the Klamath National Forest some years ago about 900 acres were treated for insect infestation. The cost was about $3,000 and the amount of timber saved by the eradication of the insects was worth over $600,000. Other studies are carried on to identify and describe certain cla.s.ses of insects, such, for instance, as those that destroy the seeds of trees in the cones. The various families, genera, and species of forest insects are studied and described, and the results are published in the form of monographs.

Many of these insects are difficult to identify and concerning others very little is known. Investigations on tree diseases have not made such good progress, because tree diseases are much more difficult to control. Tree diseases, like human diseases, must be prevented instead of controlled. A general survey of the tree diseases prevalent in the National Forests has been made, especially in California. Further studies have brought to light little known or even unknown diseases. In California, studies have shown that a certain relation exists between old age and disease. Incense cedar, for example, seems to become infested after it reaches maturity at an age of about 150 years.

_Tree Studies._ Commercial tree studies are made of important tree species. The results are published in the form of monographs dealing with the range, silvicultural characteristics, growth, yield and management of each tree. These studies bring together all the important facts known about the tree described, such as: the industrial uses of the wood, the conditions under which the tree succeeds, the rate of growth in different situations, and the most suitable methods of management to secure the highest returns. Tables are included to show the volume of the trees at different ages and sizes, in cubic feet, in cords, in board feet, etc. Studies are also made of the life history and requirements of important forest trees, often in connection with commercial studies. Such studies cover: local, geographical, and commercial occurrence of the species, the species which are a.s.sociated with it, the habit of the tree, its soil and climatic requirements for germination and growth, and the various matters connected with its reproduction. Such publications as these give the Forest officers much valuable information about the trees with which they are dealing, and also furnish the only sources of information to students in forest schools on the characteristics and requirements of the trees important in forestry in this country.

_Grazing Investigations._ Grazing investigations, being intimately connected with a great national industry, have received a considerable amount of attention. These studies are confined at present to grazing reconnoissance, the reseeding of depleted mountain grazing lands, studies in the best methods of handling sheep on the range, studies of the effect of grazing on the forest, identification of range plants, and the systematic elimination of poisonous range plants and predatory animals.

Grazing reconnoissance is a stock taking of the forage possibilities of a certain piece of range land. This work is usually done by organized parties, but a small amount is done also by Forest officers in spare time. This study aims to collect all the important grazing information, such as: the area of grazing lands, the kind of forage, the species of forage plants, the location of streams, springs, and other watering places for stock, the location of stock driveways, drift fences, and cabins, the location of timber lands that do and those that do not contain forage, and many other matters pertaining to the grazing of stock. The maps and field data secured furnish the basis for range improvement and more intensive range management. Up to date, over 12,288,885 acres of range lands have been covered in this way.

All intensive forage and range experiments are conducted at the Great Basin Experiment Station on the Manti National Forest. Here intensive problems are carried on under controlled conditions and under constant and careful observation and the necessary care and thoroughness is given to them which could only be given them at a fully equipped experiment station. All grazing investigations on the National Forests are carried on under the direct supervision of this station.

The seeding of depleted grazing lands is accomplished either by direct artificial seeding or through rotation grazing. Under the former method the seed of native or foreign gra.s.ses and other range plants are sown on the range, in the attempt to increase the forage crop. By rotation grazing, that is, permitting the stock to feed first on one area and then on another, the gra.s.ses and forage plants are allowed to recuperate from the effect of grazing and allowed to reproduce. The stock is excluded from one area while the seed is maturing, and after the seed has matured and become scattered on the area the stock is allowed to graze on it. As the stock feeds on the plants it tramples the seed into the ground and thereby furnishes favorable conditions for the germination of the seed. There are few parts of the National Forests that cannot be completely regenerated by the adoption of either one or the other of these two methods.

To reduce interference with the natural processes of reforestation, damage to tree growth and watersheds, depletion of grazing lands, and the waste of valuable forest resources, it is important to develop improved methods of managing different kinds of live stock on different types of land. These new methods of handling stock have been applied only to sheep. The lambing of sheep in small inclosures on the open range has resulted in the saving of a large percentage of the lambs. The new method of bedding sheep where they happen to be at nightfall has been found to have many advantages over the old system of returning them to an established bedding ground a number of nights in succession. The results have been better sheep, less damage to range, and more feed.

It was not so many years ago that practically nothing was known about the various plants which make up the forage crop on the National Forests. Forest officers could not identify the plants or say whether they were of value for forage or not. This made it difficult to secure the use of each range by the cla.s.s of stock to which it was best adapted, to apply deferred and rotation grazing and to eliminate losses from poisonous plants. This obstacle to efficient range management was overcome when a system of plant collection and identification was started by the Forest Service. Some 23,000 specimens of about 3,000 different species have been collected on the National Forests, identified by specialists and the collector informed as to the value of each species. The identification of range plants is the first step toward securing an intimate knowledge of the life history of the plant. Such information as the soil and moisture requirements, date of flowering and seeding, requirements for reproduction, and its relation to other range plants is of the utmost importance if the maximum forage crop is to be produced on the range each year. This const.i.tutes the latest stage in the development of grazing studies.

[Ill.u.s.tration: Figure 31. Forest Ranger with his pack horses travelling over his district. Meadow Creek, foot of Mt. Wilson, Montezuma National Forest, Colorado]

_Investigations Dealing with Poisonous Plants and Predatory Animals._ In cooperation with the Bureau of Plant Industry the study of poisonous plants and the means for reducing the losses from them has been undertaken. The death camas, the lupines, the larkspurs, some of the wild cherries, locoweed, and practically all species of zygadenus are plants that have been found to cause death among stock. While the handling of stock to avoid the poison areas can eliminate the losses to a small extent, it has been found that the most expeditious remedy is in digging out and destroying the poisonous plants. On the Stanislaus National Forest in California, a cattle range of about 14,000 acres, containing about 67 acres of larkspur, was cleared of this weed at a cost of about $695. The average loss of cattle in previous years had been about 34 head. Following the eradication of the larkspur the loss was 4 head. The net saving was valued at $1,800. Similar operations are conducted on other Forests.

The work of the destruction of predatory animals has been transferred to the hands of the Bureau of Biological Survey. Formerly special Forest Service hunters were detailed to hunt the animals, and these men used to kill about 4,000 a year. The Biological Survey, however, still furnishes traps, ammunition and poison for the destruction of predatory animals to Forest officers, who do this work in connection with their regular duties. Bears, coyotes, mountain lions, lynxes, wildcats, and wolves are the animals that do the most of the damage. What makes the problem a difficult one is that the wolf and the coyote, the two species which do the greatest damage to game and domestic stock, are transient visitors on the Forests which frequent the Forests only when game and stock is most abundant. They are bred, born, and spend the greater portion of their lives in the foothills outside of the National Forests. Under these conditions the animals killed on the Forests are quickly replaced by others from outside. For this reason the matter was handed over to the Biological Survey, which will destroy these animals throughout the public domain and the results will be much more permanent and effective.

Besides the investigations carried on by the Forest Experiment Stations many studies are carried on dealing with forest products. The purpose of the Branch of Forest Research of the Forest Service is to promote the most profitable and economical utilization of forest products by means of experiments and investigations. The work of the Branch falls into three divisions: National Forest utilization, the work of the Forest Products Laboratory, and industrial investigations.

_National Forest Utilization Experiments._ The work of the proper utilization of the products of the National Forests is under the supervision of the District Forester and the a.s.sistant District Forester in charge of Forest Products in the districts. Only three out of the seven districts have such an organization. These men have charge of all problems connected with the use and marketing of National Forest timber, the construction of improvements on the Forests, and related administrative questions. The following problems are included: studies of existing industries, covering methods and costs of manufacture, grades, and other specifications of manufactured products and the prices obtained for such products; the collection of market prices, mill scale studies to determine grades and overrun, and investigations in kiln drying; waste in existing industries and closer utilization possible through improved methods; new uses for National Forest species through wood preservation; introduction of industries which will result in closer or more profitable utilization, as the manufacture of pulp and paper, wood distillation, turpentining, and the manufacture of secondary wood products; overcoming prejudices against particular species or cla.s.ses of material; general questions of timber supply and demand, markets and freight rates; advice and a.s.sistance in the construction of National Forest improvements, particularly in the use of wood preservatives; advice and a.s.sistance to persons on any matter connected with the utilization of National Forest timber; the preparation of publications upon subjects covered by investigations which have practical or scientific value; and demonstrations of methods or processes developed by the Forest Service for the benefit of local communities.

The presence on a Forest of large quant.i.ties of unmarketable timber, or dead timber, or of material not used in current sales would mean an investigation of methods for its utilization. Local problems affecting wood-using industries in manufacturing or marketing timber, such as sap stain in lumber, difficulties in seasoning lumber, and the effect of different silvicultural methods upon the average grades of lumber manufactured, are also taken up with the Products experts at the District Office. Also in the construction of National Forest improvements the Forest Supervisor may need a.s.sistance in applying wood preservatives to telephone poles, fence posts, and other material.

Sometimes timber treating plants are erected, if necessary, to treat not only material used on the National Forests, but also material used by local residents near a Forest.

One of the important problems which confronts the Office of Products in the various National Forest districts is the utilization of the so-called low grade or inferior tree species. The terms "high grade"

and "low grade" or "inferior," as used at present, merely indicate the lumberman's valuation of the timber from his point of view and according to his standards of value. If a certain species will not produce clear lumber, which is straight-grained, easily worked, and not subject to splitting or warping, it is at once cla.s.sed as inferior. But the Forest Products specialists each year are making progress in demonstrating that wood, in order to be of marketable value, does not necessarily need to be cut in the form of lumber. It is also being shown that proper methods of drying lumber make possible the use of inferior woods for lumber and manufacturing purposes.

The Office of Forest Products in California has made considerable progress in overcoming the lumberman's prejudices against the inferior species in the California National Forests and the species are beginning to find wider use and to command better prices. The discovery that Incense cedar was valuable for making lead pencils caused the price of this so-called "inferior" species to jump from an average of $10 per thousand feet in logs f. o. b. cars to as high as $16. White fir, a species religiously avoided by lumbermen in the woods, was found to have special properties which make it very valuable as a pulpwood. One mill in California now uses annually upwards of 30,000 cords of it for making paper. Lodgepole pine has been shown to have a great value for telephone and telegraph poles when treated with preservatives. It was found to be 12 per cent. stronger than Western Red cedar, the standard pole timber, has a more desirable taper and can be s.h.i.+pped for less money. Many other cases could be cited from this and other National Forest Districts.

_Forest Products Laboratory Experiments._ The work of the Forest Products Laboratory includes investigations on the mechanical properties of wood; the physical and chemical characteristics and properties of wood; air seasoning and artificial drying of wood; agencies destructive to wood; wood preservation; wood distillation; production of naval stores; and the production of pulp and paper and other chemical products of wood. This work is carried on at the Laboratory and sometimes in cooperation with the National Forests and district experts.

At the Laboratory there is a director and a large staff of technical and scientific men, such as chemists, physicists, and engineers, each of whom is an expert in his particular line of work.

A good deal of attention is given to testing the strength of woods grown in the United States, as a means of a.s.sisting users to select the species best adapted to a given purpose, or to find subst.i.tutes for species which are becoming difficult to obtain. The strength of a good many species used for structural timbers has been tested. The species most used for this cla.s.s of timber are the Southern pines, Douglas fir, Norway pine, Tamarack, and Red spruce. An important discovery was made several years ago that Western hemlock, generally considered an inferior timber, showed an average strength 88 per cent. as great as that of Douglas fir, one of the best construction timbers in the United States.

Strength tests have also been made on fire-killed timber and these have shown that timber killed by fire is almost as strong as green timber.

Other tests have been made to determine the effect of preservative treatment upon the strength of timber. As a result of the large number and variety of strength tests carried on by this Laboratory the United States Government now has a more thorough and comprehensive collection of data on the mechanical properties of wood than any other nation.

Many studies are also conducted to determine the physical properties and the structure of the different kinds of wood grown in this country.

The minute structure of the wood of many of our native species has been studied by means of microscopic slides. A study has also been made of a large number of species to determine the specific gravity of the actual wood substance. Other tests are made to determine the specific heat of woods.

The drying or seasoning of woods, more especially of certain species which have been found difficult to season, has received a good deal of attention. A new type of kiln, invented by a Forest Service man, has been devised to season such woods as the eucalyptus, which has always been very difficult to handle in drying. Western larch has been seasoned with a loss of only 5 per cent., whereas the loss in ordinary commercial kilns usually ran between 60 and 70 per cent. As a result, many manufacturers have remodeled their old kilns to embody the new Forest Service methods. A new method has also been developed for the rapid dry-kilning of Eastern hemlock, which has great commercial possibilities.

Experiments in wood preservation have to do with the kind of preservatives it is best to use, the character of the wood to be treated, and the methods of injection. Experiments have developed the best methods for treating railroad ties, mine timbers, fence posts, wood paving blocks, telephone and telegraph poles, and wharf piling.

Untreated mine timbers have been found to last only from 1 to 2 years, while treated ones are usually entirely sound at the end of 4 years.

Untreated railroad ties last from 5 to 10 years, while treated ones will last over 15. Such experiments as these have shown the advisability of treating all kinds of timbers with creosote or zinc chloride, or some other preservative. Many new preservatives are being proposed or marketed each year by various companies or individuals. These are all tested to determine their value to prevent the growth of fungi in the wood. Their efficiency varies greatly and many of them have been shown to have very small value.

Studies in wood distillation seek to find new woods which can be used for this industry, new and more efficient methods which can be employed, and new uses for wood waste and stumps. Charcoal, wood alcohol, acetate of lime, and tar are derived from the distillation of such woods as beech, birch, and maple, to which tar oils and turpentine are added for the pines and other resinous woods. These by-products of wood distillation have many uses, as well as the many products which are, in turn, made from these by-products. Charcoal is used in the manufacture of black powder, acetic acid is used in the manufacture of explosives, and wood alcohol is converted into formaldehyde for disinfection against contagious diseases. By means of temperature control methods developed at the Laboratory in the destructive distillation of hardwoods, the net gain per annum of one company's plant was over $17,000. About one-half of the plants of the country have adopted the new method developed by the Forest Products Laboratory.

Experiments have been conducted by the Laboratory in the distillation of the needles of coniferous trees and the distillation of the crude gum of some of the important timber trees of the South and West. The oils distilled from many trees in this way have found great use for various purposes. s...o...b..acking owes its peculiar aromatic odor, faintly suggestive of the deep spruce and hemlock woods, to an oil which is distilled from these same kind of needles. Evergreen tree leaf oils are used for the perfume of soap, and in the manufacture of liniments, insecticides, and medicinal preparations.

Investigations have been carried on at the Forest Products Laboratory in making artificial silk from sawdust. The industry has already attained considerable proportions. It consists princ.i.p.ally of converting cellulose into viscose, which, in turn, is manufactured into an almost endless number and variety of silk and other goods varying from sausage casings to silk hose and tapestries. Sawdust is used also in the manufacture of inlaid linoleum and dynamite.

Experiments in naval stores are attempting to improve the old methods of harvesting turpentine, which have proven very destructive to the forests. With the approaching exhaustion of the Southern Pinery as a field for the naval stores industry, it has become more and more important to find other species for this purpose. Consequently the Laboratory has conducted experiments with the various pines on the National Forests in California, Colorado, Arizona, and New Mexico.

[Ill.u.s.tration: Figure 32. A plank of Incense cedar affected by a disease known as "pin rot." By cutting the cedar timber when it is mature this can be largely avoided. La.s.sen National Forest, California. Photo by the author.]

[Ill.u.s.tration: Figure 33. The western pine forests will some day be a great source for naval stores. By distilling the crude resin of the Jeffrey pine a light volatile oil--abietene--is secured which has great healing and curative properties. La.s.sen National Forest, California.

Photo by the author.]