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and their much smaller need of water are other features that commend them for this sort of service. These matters have already been treated in this article, Examples of Stand-By Applications
The accompanying photos illustrate some of the uses of Diesels for stand-by and auxiliary power. Figure 5 shows a 2500-kilowatt unit which is one of three recently supplied to the Panama Canal to furnish stand-by service to the Gatun hydroelectric station, which normally furnishes power for the canal’s operation. These engines operate on the lowgrade fuel ordinarily carried in supply a t the canal, which is known as “Bunker C.” I n the factory tests one of these engines was started and the full load of 2500 kilowatts applied in 32 seconds. Such an accomplishment is, of course, far beyond the possibility of any steam plant.
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Figure 6 shows a plant with a capacity of 2000 kilowatts in four units installed by the Chicago Sanitary District to serve as emergency reserve and auxiliary to the district’s hydroelectric plant. Shortly after it was placed in operation, in 1922, the coal shortage caused it to be operated at full capacity, and its economical record has resulted in its continued operation to relieve a less efficient auxiliary steam plant. The average fuel consumption at full load is better than 460 kilowatt-hours per barrel of oil. A telephone exchange without electric power is helpless. Figure 7 shows a 135-kilowatt Diesal installed a t the Bell Telephone Central Exchange in Harrisburg, Pa., to operate the switchboard and lighting system in case of failure of the purchased current supply. It is said that it has often been used. Many chemical industries would benefit by similar applications of Diesel engines.
Experiments in Wood Preservationl’P I-Production
of Acid by Wood-Rotting Fungi By Leo Patrick Curtin
ENGINEERING LABORATORIES, WESTERNUNIONTELEGRAPH Co., SEW YORK,X. Y.
BOUT 93 per cent of It is shown that certain representative wood-rotting Lvississippi treating plant, the poles installed by fungi produce acidic substances in artificial nutrient cost $2.10. The same pole, the Western Union are media and also in wood. The production of acid imfull-length creosotedl f. 0. b. creosoted. For several years mediately accompanies the growth of the fungus. treating plant, was worth this company has operated In all cases the hydrogen-ion concentration was found $5.50, One dollar and twenthree plants for treating its to be of approximately PH 5. The acidic reactions were ty-five cents of the increase poles. Chestnuts and cedars demonstrated with indicators of proper pH, notably represented labor and other are butt-treated’ while yellow sodium alizarin sulfonate and litmus. Methyl red, plant expenses, and $2.15 t h e pine is given a full-length propyl red, and neutral red were quickly destroyed by cost of the creosote absorbed Fomes annosus. The production of acid was also shown by the pole, It is seen that creosoting under pressure. These woods are the three by the solvent action of the fungus on precipitates of the creosote in the pole costs principal Sources of pole timcalcium carbonate and strontium carbonate. This slightly more than the pole ber in the United States. The phenomenon makes possible the use of a new class of itself. Such a pole will abcedars are not members of materials as wood preservatives. sorb approximately 15gallons the genus Cedrus, but are a of creosote, worth 14 cents group of conifers which are very much alike in their charac- per gallon. A chestnut pole of the same size requires but 35 teristics, the more prominent being Chamoecyparis thyoides, cents worth (2.5 gallons) of creosote. This is because t h e Thuja occidentdis, and Thuja plicata. chestnut is butt-treated only and also because its thin layer I n 1925, according to U. S. Department of Agriculture of sapwood absorbs a relatively small amount of creosote. statistics, 2,397,978 poles were treated with preservatives The cedars are intermediate in their treating costs. They in the United States, 1,325,260 of these being cedars, 780,248 are similar to pines in having a fairly thick layer of sapsouthern pine, and 276,030 chestnuts. Of these chestnuts, wood and resemble the chestnuts in that the treatment is 150,000 were installed in Western Union lines. confined to the butt. A generation ago the chestnut was one of the principal UP to the present time coal-tar creosote has been t h e sources of pole timber. With its gradual destruction by the leading preservative because it combines toxicity and a. chestnut blight it has become a less important factor. The fair degree of permanence with desirable mechanical p r o p decrease in the supply of chestnuts has been accompanied erties, such as waterproofing, fiber-binding. and lubrication. by a rapid increase in the use of yellow pine for poles of all Its most serious disadvantages are its high cost and t h e kinds, and this wood is expected to be the principal source difficulty of obtaining it in sufficiently great quantity to of pole timber in the not distant future. Yellow pine must meet all demands. Coal-tar creosote is a by-product of he full-length treated to prevent its rapid decay both above the coke industry and constitutes but 3 per cent of the prodand below ground. When properly treated, however, it is a ucts of coal distillation. I n spite of this and other drawvery durable pole with excellent mechanical properties. backs, no cheap organic preservative has been found to The cost of full-treating such poles is rather high, as the compete with it successfully. fOllOWing typical instance Will sho\\r: I n 1925 a 20-fOOt The inexpensive preservatives are, in general, wateryellow-pine pole, 11 cubic feet in volume, delivered at a soluble inorganic salts such as zinc chloride, sodium fluoride, 1 Received March 12, 1927. and copper sulfate. Such preservatives, in wood exposed * In October, 1924, the Western Union Telegraph Company requested t o weather, are subject to loss by leaching and for this reason the writer to consider its wood-preserving problems and, if prospects a€>are expected to last are not used where timber peared favorable, to conduct a research in that field. This paper is the first more than ten or twelve pears. On certain of the larger of a series describing this research.
A
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INDUSTRIAL, AND ENGILVEERI-L7G CHE.VISTR Y
railroads a tie is dest’royed by mechanical shock in six to twelve years, and in such cases zinc chloride has met with some success, pstrticularly in the more arid regions. I n 1925,3 167,642,790 gallons of creosote were used for wood preservation in the United States, 53.3 per cent of which was imported. This compares with a consumption of 13!048,539 gallons of petroleum’ and 26,378,658 pounds of zinc chloride in the same period. Other preservatives were consumed in relatively insignificant quantities. The present cost of creosoting poles is a serious problem, which with the disappearance of t’he chestnut is certain to become more acute. A somewhat similar difficulty confronts the railroads and other users of creosoted wood. To meet this situation t,he Western Union Company decided to attempt the development of wood preservatives d i i c h would be (1) available in large quantity, (2) of high toxicity t’o low forms of regetable and animal life, (3) a t least as permanent as creosote, and (4) of low cost. The present is the first of a series of papers which will tell of the progress toward this goal. Discussion
Leaving mechanical injuries out of consideration, the principal agents in the destruction of wood are rot,ting. due to consumption of parts of the wood by fungous; organisms, and attack by insects. It appeared probable that low-cost preservatives could be found only among inorganic substances. Petroleum, the most abundant and least expensive organic liquid, is strictly non-toxic, as will be shown in a later paper. It also seemed certain that the toxic agent must be in solution to kill fungi, sirice regetable organisms cannot ingest solid particles. I n the wood-preserving industry it is axiomatic that a substance must be soluble in order to be toxic. This idea is well expressed by Rateman and Henningsen, of the United States Forest Products Laboratory Research on the mechanism of the protection of wood by preservatives began with two working hypotheses; first, t h a t any wood preservatix-e must be capable of exerting a poisonous or toxic action on timber-destroying organisms, and second, that for the poisons t o be effective they must be sufficiently soluble to exert a poisonous effect in the body fluids of the organism which they are intended to inhibit. In the case of timber-destroying fungi, at least, this means t h a t the preservative must be soluble in water to the extent t h a t the organism may be given a lethal dose.
It would therefore seem that high toxicity and permanence in an inorganic preservative are mutually exclusive properties; if the salt is highly toxic it must be fairly soluble, and if it is soluble it will be lacking in permanence when exposed to rains. If, hoxTever, it could be shown that a secretion of the fungus or some decomposition product of the material upon which it lives has capacity for dissolving certain salts of low solubility, the problem of obtaining a n inorganic preservative which is both toxic and permanent would be greatly simplified. For several years the writer has been of the opinion that the production of acidic substances is fairly common and perhaps general in all plants which do not contain chlorophyl. It has long been known that many bacteria, such as B. lactis m i d i and B. acetis acidi, produce acids, and also that acidic products attend the growth of certain molds. Woodrotting fungi are saprophytes, living on dead regetable matter. Since they lack chlorophyl, they are unable t o synthesize carbohydrate from atmospheric carbon dioxide. They are able, however, to hydrolyze, make soluble, and 3 Helphenstine, “Quantity of Wood Treated a n d Preservatives Used i n t h e United States,” U. S. Dept. Agr., Forest Service, 1925. Paper delivered a t 21st Annual Meeting of -4merican M‘ood Preservers Assocn., Chicago, Ill., February, 1926.
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ingest carbohydrat’e and other solid organic material previously organized by higher plants. The explanation of the method by which the fungus brings its food into solut’ion has been that the organism secretes an enzyme or (‘ferment” which decomposes the solid carbohydrate iiit’o soluble substances. For example, Zeller,5 in a study of the wood-rotting fungus, Lenzites sepiaria, mentions a dozen enzymes whose presence was detected in this organism-malt’ase, raffinase, emulsin, tannase, diastase, ligninase, cellulase, hemicellulase, pectase, pectinase, oxidase, and catylase. The better known enzymes, such as invertase, have been studied very carefully. I n the cases of certain ot’hers, however, the only proof of their existence is a chemical reaction, usually a hydrolysis, which might also be brought about by dilute acid. While a search of chemical and myco!ogical literature failed to disclose any direct evidence of the production of acid by wood-rotting fungi, there were a number of suggestive references, such as that by Sullivan6 mho, in a research on vanillin, recovered lignoceric acid by sublimation from rotten oak wood. Bray and Staid17 found that rotten wood contains considerable matter which is soluble in alkali. They did not show whether these acidic substances are produced by fungi, by atmospheric oxidation, or otherwise. Wehnier,* in a research which tends to show that lignin is the parent substance of coal, found liumins in newspaper pulp in which a fungus had been growing. Rose and Lime9 showed that a sound specimen of Douglas fir contained 58.96 per cent of cellulose and 10.61 per cent of matter soluble in 1 per cent sodium hydroxide solution, while a fully decayed piece of the same wood contained 8.47 per cent of cellulose and 65.31 per cent of matter soluble in 1 per cent sodium hydroxide. As t’he lignin content had varied but slightly, it was evident that’ the alkali-soluble material had increased a t the expense of the cellulose. Other investigators haire likewise found that the cellulose is principally att’acked, although one or two cases are known where the lignin mas more readily destroyed by fungi.’O Bray and Indrewsll did some careful work on wood destroyed by Fornes roseus, Lentinus lepicleus, and ot’her fungi. I n their opinion the material soluble in alkali comes from cellulose partially disintegrated by fungi. Such alkali-soluble material need not be organic acid; in fact, it may be organic compounds commonly regarded a? neutral substances. It probably consists mainly of carbohydrates of lower molecular weight than cellulose. The reactions of many carbohydrates with alkali are well known. One need only mention the insoluble calcium salt, or pseudosalt, of dextrose, the soluble compound of calcium with levulose, the various alkaline-earth compounds with the higher sugars. and the numerous compounds of glycerol and other polyhydroxy alcohols with alkali and heavy metals. Animals may be poisoned by a difficultly soluble substance, such as copper arsenite, because their acidic digestive juices bring the toxic material into solut’ion. If it’ could be shown that acids are a by-product of fungous growth, then certain difficultly soluble salts might be brought into solution by these acids. Such salts should, of course, contain a t least one ion which is toxic to fungi if they are to be of value in wood preservation. They should also be 5 “Studies in t h e Physiology of the Fungi,” Pt. 2, Missouri Botanical Garden .4na;tls, 19U6. 8 THIS JOURNAL, 8 , 1027 (1916). 7 Ibid.,14, 35 (1922). 8 ByennsLo.f-Chem., 6, 101 (1925). 0 THISJ O U R N A L , 9, 284 (1917). 10 H a w l e y a n d Wise, “The Chemistry of Wood,” p. 296,Chemical Catalog Co., 1926. 1 1 THIS J O U R N A L , 16, 137 (1924).
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salts of feeble acids, since the weak organic acids evolved by the fungi would have littIe solvent effect on a difficultly soluble salt of a strong acid, such as barium sulfate. It seemed probable that the fungus acids, if they actually exist, might dissolve such substances as zinc carbonate and copper arsenite but would have no solvent effect on the sulfides of these metals. Experimental Before commencing work with wood preservatives, it was essential that the correctness of the theory that woodrotting fungi produce acids be fully demonstrated in the laboratory. There were practical difficulties. at least in the beginning, toward showing such reactions on wood. It seemed advisable, therefore, first to investigate the chemical reactions in nutrient media in which the growth is much more rapid than in wood. REACTIONS I?: KUTRIEA-T iL1~~1a--ii great many cultures were made in which various indicators were dissolved in the nutrient jelly, the idea being that any acid produced by the fungus would react with the indicator and bring about the charac:eristic change in color. These tests showed conclusively that acid was produced by every fungus under trial. I n all cases uninoculated samples of the nutrient jelly dyed with the indicator mere kept for comparison. These sterile blanks retained their original basic color, showing that the indicator changes which occurred in the inoculated specimens were due solely to acid produced by the fungi. The original cultures of the wood-rotting fungi were obtained from the U. S. Forest Products Laboratory. They included fungi which are common in rotting oak, chestnut, and other hard woods, as well as the coniferous woods. These and all other experiments with growing fungi were made under conditions of high asepsis to avoid infection of the cultures by air-borne spores of bacteria or fungi. Reactions of Fungi in Agar-Malt Sirup Culture Medium ORIGINAL FINAL INDICATOR (BASIC)COLOR (ACIDIC) COLOR
FUNGUS Wood-rotting .. . ~ - :
LPC nnlZ0sus Fori+ - . . ... . Fomes annosus Fomes annosus Fomes annosus
Methvl oranze Cons; >ed Methyl red Sodium alizarin sulfonate Propyl red Fomes annosus Fomes annosus Litmus Rosolic acid Fomas annosus Fomes annosus Neutral red Lenzites sepiaria Methyl orange Lenzites sepiaria Sodium alizarin sulfonate Lentinus lepideus Methyl orange Lentinus lepideus Sodium alizarin Methyl orange Polyphorus pilolae Polvahorus pilotae Sodium alizarin _sulfonate Polyphorus sulphureus Methyl orange Polyphorus sulphureus Sodium alizarin sulfonate . ~ Mold: Methyl orange Rhizopus nigricans Congo red Rhizopus nigricans R h i z o m s nigricans Sodium alizarin sulfonate Litmus Rhizopus nigricans Penicillium Methyl orange Penicillium Sodium alizarin sulfonate ~
~
No change
Yellow Red Yellow Red
-
Avo cknnee
1ndccaTZ:destroyed Greenish yellow
Yellow Blue Red Colorless Yellow Red
Indicator destroyed Purplish red Pale yellow Indicator destroyed N o change Greenish yellow
Yellow Red Yellow Red
hTochange
Yellow Red
KOchange
~
~
N o change Greenish yellow Greenish yellow Greenish yellow
.
~
Yellow Red Red
Red Violet Greenish yellow
Blue
Red A-o change Greenish yellow
Yellow Red
The tests shown in the accompanying table were made in a nutrient medium composed of 1.5 per cent agar and 2.5 per cent malt sirup. This gave a rigid gel containing about 3.5 per cent dry matter. The experiments proved conclusively that fungi growing in this medium liberate acid. The change in the color of the indicator preceded the visible growth of the fungus by 1 or 2 mm. in the case of the wood-rotting organisms, and by 1 to 2 cm. in the cases of Rhizopus nigricans and several other mold fungi. Looking through the bottom of a Petri dish culture dyed
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with sodium alizarin sulfonate, the jelly appeared as a brilliant red disk by strong transmitted light. A day or two after the fungus showed evidence of growth, a pale yellow spot appeared under the transplant. A few days later the culture showed a good-sized greenish yellow disk in the center surrounded by a wide red rim. I n 2 weeks, or less, the entire culture had assumed a pale greenish yellow color with no trace of the original basic red. While this greenish yellow color is characteristic of the alizarin sulfonic acid, to avoid any possibiIity of error the entire culture mas melted in hot water and sodium carbonate solution added. This immediately restored the strong red basic color of the indicator, showing that the change in color was due solely to acid produced by the fungus. All the cultures described above were repeated with an agar-starch culture medium and those listed under Fomes annosus were also repeated with a gelatin-sugar medium. Litmus, sodium alizarin Sulfonate, and methyl orange were the only indicators used in these tests. The indicator reactions exactly checked those obtained with the agarmalt sirup cultures. The only differences noted were that the starch and sugar cultures gave less vigorous growths and the gelatin cultures tended to liquefy with the growth of the fungus. Methyl orange is a very satisfactory indicator for testing many of the molds. It is too insensitive for those of the wood-rotting fungi which have been tried. Congo red is also lacking in sensitivity and in color is inferior to methyl orange. Sodium alizarin sulfonate is an excellent indicator for the wood-rotting organisms. It is less toxic than many other indicators and does not change color with carbon dioxide which is evolved in quantity by fungi. Methyl red, propyl red, and neutral red are quickly destroyed by the fungi. The first two are yellow in the basic condition and all three are red in presence of sufficient acid. I n the cultures of the methyl and propyl reds it was noted that after the fungus started to grow the bright yellow color quickly disappeared with no production of red. After the yellow color had vanished the cultures were melted, some being tested with alkali and others with dilute sulfuric acid. Yo trace of the indicator was found by these tests. As the uninoculated blanks had retained their yellow color unimpaired, it was evident that the fungus had destroyed the indicators. Litmus is a satisfactory indicator for these reactions but not nearly so desirable as the alizarin sulfonate. Rosolic acid showed the usual acid reaction with the fungus, but was discontinued because of its tendency to fade, even in the uninoculated specimens, It is also very toxic, as might be expected from its phenolic nature, and for this reason it could only be used in very low concentrations. TESTS ON FUXGUS GROWING ox WooD-while it appeared certain, because of the chemical similarity of the nutrient substances, that the acidic reactions found to accompany fungous growth in culture media also take place in rotting wood, it seemed desirable to demonstrate the correctness of this supposition by means of a fungus actually growing on wood. After several failures, proof was obtained in the following manner: A number of sapwood sticks of short-leaf southern yellow pine and white cedar, about 15 em. in length and 1 sq. em. in cross section, were boiled for 3 hours in 0.05 per cent sodium carbonate solution to neutralize the acids occurring naturally in the wood. They were next boiled for 3 hours in water t o remove excess sodium carbonate. The sticks were then soaked in sodium alizarin sulfonate solution until they were definitely red. After sterilization with steam a t 15 pounds per square inch (1055 grams per sq. em.) pressure,
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they were placed in 8-inch (20-em.) test tubes in contact with a small block of wood on which was growing a pure culture of Forries annosus. It was not desirable to place the colored sticks in contact with a nutrient medium of the jelly type, as some of the material would penetrate the wood by capil1:arity and give reactions which might be credited to the wood itself. To avoid such a possibility, sticks of sterilized yellow pine about 15 cm. long were placed in test tubes in the bottom of which were 5 cc. of 1-ery stiff gel in which a pure culture of Fomes annosus mas growing. The tubes were kept in the vertical position and the fungous growth gradually ascended the sticks. At the end of 6 weeks a dense growth of fungus completely covered all parts of the wood. Blocks about 1 cc. in volume were cut from the tops of these sticks and served as the inoculating medium in the tests with sticks colored with indicator. A plug of cotton in the top of the test tube served to bring the colored stick in firm contact with the mat of mycelium covering the inoculating block. Growth soon commenced on the colored sticks and the acidic reaction was clearly apparent 24 hours later. The sticks were progressively decolorized, and after 3 weeks onethird to one-half of the lower ends of the sticks had 1o.t their red color, the upper ends retaining their origins1 appearance. Because of the toxicity of the indicator, the growth was frail and there was no difficulty in seeing the wood beneath it. At this time the sticks were taken out for examination. Some of them shon-ed no suggestion of redness in their lower parts, while several showed a few streaks of red because of deposits of indicator considerably below the surface. The sticks first described were held in ammonia fumes, which quickly restored the basic red color of the indicator. This step lvas necessary as the acidic greenish yellow color of alizarin sulfonic acid is scarcely detectable on yellow pine. The sticks which showed one or two streaks of red were then marked with a pencil to enclose areas having no trace of redness. Ammonia fumes restored the red color to all these sticks, including the areas so enclosed. Evidently, the production of acids by fungi takes place in wood as well as in artificial nutrient media. -kCTIOX O F FGNGUS O S C-4RBOhT.4TE PRECII'IT.4TES-The production of acid in the agar-malt sirup gels was also shown by means of certain insoluble carbonates, notably strontium and calcium carbonates. A nutrient medium was prepared containing strontium chloride in solution equivalent to 1.5 per cent strontium carbonate. To this hot solution was added exactly sufficient sodium carbonate solution to precipitate the strontium as carbonate. Such gels without the precipitate of carbonate are translucent and transmit light very well. With the finely divided strontium carbonate precipitate, the culture assumes an opaque appearance somewhat resembling ground glass.
88 1
Stront'ium carbonate is of low toxicity, and a transplant, of
Fomes annosus gave a slow but dense and vigorous growth in these cultures. -4s the growth of the fungus progressed, the opaque appearance disappeared and the jelly became translucent, indicating that the strontium carbonate had been brought into solution. After several weeks the entire culture medium had become translucent, showing no evidence of the presence of st'rontium carbonate. As with the indicator reactions, the translucent disk in the opaque culture increases in radius as the growth of bhe fungus progresses. Blank, uninoculated cultures, which also contained a precipitate of strontium carbonate. retained their opacity throughout the test. This experiment was later repeated with cultures cont'aining 0.75 per cent of calcium carbonate, with identical results. Solution of such difficultly soluble carbonates by the fungus acids is quite convincing and would in itself constitut'e proof of the existence of t'hese acids, since there is no indication of solvent action by the nutrient medium itself. Value of Research
A study of the indicator react'ions shows that the acid solution produced by the wood-rotting fungi is of approximately pH 5 . While this is a feebly acidic solution, it must be remembered that its action on rotting wood may extend over a period of several gears. From this point of yiew the acid produced by the fungus may be of considerable help in making carbohydrate available for ingestion by the wood-rotting organism. Kothing has been done t o ascertain whether the acid liberated is a secretion of the fungus or a degradation product of the nutrient substance. The production of acid by fungi may be of interest to botanists by clearing up a detail in connection with the peculiar vegetable organisms called lichens. The lichen is really two plants, generally a blue-green alga and a fungus, living in a symbiotic and, apparently, mutually helpful relationship. The alga contains chlorophyl and, by photosynthesis, obtains its needed carbohydrate from the atmosphere. The fungus extracts nutrient from the alga osniotically by means of hyphae. or directly by haustoria which penetrate the algal cells. The contribution to the partnership by the fungus is of a mechanical nature. Because of its t,ough, fibrous composition, it protects the more delicate alga and, by holding moisture, retards desiccation. If it could be shown that such fungi make mineral nutrient material available by liberat'ion of acid, then the part'nership would appear much more equitable than a t present. I t would help explain how the lichen, although composed of two delicate plants, is able to thrive on the rocks of arctic regions.
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Trees Tested for Pulp Suitability The suitability of 94 species of American woods for paper pulp has been tested experimentally by the Forest Service, Department of Agriculture, in an effort to find satisfactory woods t o take the place of the decreasing supply of spruces, firs, and hemlocks. The use of the more plentiful and less commonly used species of wood may be greatly increased, and expanded in the South, according t o H. S. Betts, engineer of the Forests Products Division. At present, the spruces furnish 55 per cent of the wood consumed by the paper industry in the United States and, with the firs and hemlocks, furnish 77 per cent. The Forest Service does not attempt t o recommend definite species as substitutes for the three established woods, but only t o report the results of treatment of the woods by various processes. The experiments are intended to serve as a guide for further investigation by the industry and indicate that :
T h e sulfate process applied to the Southern pines, in combination with the gums and similar hardwoods of the South, will yield pulps which may be bleached by proper methods and used in the manufacture of book, magazine, and similar high-grade printing papers a t reasonable manufacturing cost. The value of this experimental work is emphasized by the fact t h a t the South is advantageously situated in respect t o nearness t o the publishing centers and availabi!ity of fuel, chemicals, and other raw materials. h-ot only has i t enormous quantities of suitable woods available. but owing t o climatic conditions the amount of wood which can be Rrown in the South is approximately 85 per cent of the potential productivity of the entire area of forest land in the United States. T h e growing capacity of unit areas is also very high. On the other hand, for pulps which require spruce, hemlock, and fir, woods of established value for making paper, there are stands in Oregon, Washington, and Alaska sufficient, under proper timber growing methods, to supply It has been due largely to economic approximately 5,000,000 cords a year. conditions t h a t the extensive development of these pulp resources has so long been retarded.
