K3e TIMBER PHYSICS.

RESUME OF INVESTIGATIONS CARRIED ON IN THE U. 8S. DIVISION OF FORESTRY,

1889 ro 1898.

By FILTBERT ROTH,

ASSISTANT PROFESSOR, NEW YORK STATE COLLEGE OF FORES?RY, CORNELL UNIVERSITY.

Reprinted from H. Doc. No. 181, 55th Cong., 3d Sess,

WASHINGTON: GOVERNMENT PRINTING OFFICE. 1899.

eho An

"Si i f:

TIMBER PHYSICS.

RESUME OF INVESTIGATIONS CARRIED ON IN THE ies: DIVISION OF FORESTRY,

1889 ro 1898.

By FILIBERT ROTH,

ASSISTANT PRKOFESSOR, NEW YORK STATE COLLEGE OF FORESTRY, CORNELL UNIVERSITY.

Reprinted from H. Doe. No. 181, 55th Cong., 3d Sess.

WASHINGTON: GOVERNMENT PRINTING OFFICE. 1899.

|. THE WORK IN TIMBER PHYSICS IN THE DIVISION OF FORESOR

By Finiperr Rorn,

Late Assistant in the Division of Forestry.

HISTORICAL,

As in the case of other materials, exact investigation of the properties of wood did not begin until the latter part of the eighteenth and the beginning of the nineteenth century, when Girard Buffon and Duhamel du Monceau in France, and Peter Barlow, the nestor of engineering in England, laid the foundation for this inquiry by devising suitable methods and working out correct formule for the computation of the results. As might be expected, the results of this pioneer work, particularly that of the French investigators, were often contradictory, and have to-day little more than historical value.

Subsequently our knowledge of wood in general, and that of European species in particular, was increased by a number of experimenters. Among these, Chevandier and Wertheim in France, and Noérdlinger in Germany, stand out conspicuous. Unfortunately, their apparatus was crude and, in the case of the French workers, the series was too small to satisfy so complicated a problem, while Nordlinger was obliged to content himself with small and few specimens, owing to a want of proper equipment.

In England cousiderable money was expended from time to time both by Government and private enterprise, but the eagerness of making the matter as practicable as possible led, unfortu- nately, to much testing of large sizes and to the employment of insufficient (because unsystematic) methods, so that such extreme experiments as those of Fowke and others have really neither furthered science nor helped the practice. In this country the engineering world for a long time relied largely on the results of European testing, and the wood consumers in general depended on a meager accumulation of experience and crude observation concerning most of the fine array of valuable and abundant kinds of timber offered in our markets.

Ignorance and prejudice had their way. Chestnut oak was pronounced unfit for railway ties, and thus millions of logs were left rotting in the woods, though this prejudice had not a single fair trial to support it. ‘‘ Bled” longleaf, or Georgia pine, was considered weaker and less durable, millers and dealers were obliged to misrepresent their goods, causing unnecessary loss and litiga- tion, and yet there existed not a single record of a properly conducted experiment to substantiate these views. Gum was of no value, Southern oak was publicly proclaimed as unfit for carriage builders, and the views as to the usefulness of different timbers were almost as numerous as the men expounding them, ‘

The engineering world was the first to realize this deficiency, and men like Hatfield, Lanza, Thurston, and others attempted to replace the few antiquated and unreliable tables of older text- books by the results performed on American woods and with modern appliances.

In addition to these efforts of engineers, Sharples, under Sargent’s direction, in his great work for the Tenth Census of 1580, subjected samples of all our timber trees to mechanical tests, but, since in these tests only a few select pieces represented each species, the engineering world never ventured to use the results. As regards the rest of the wood testing in our country, it may be said that it generally possessed two serious defects: (1) the wood was not properly chosen, and (2) the methods of testing were defective, especially with respect to the various states of seasoning, wood being tested in almost every state from green to dry, without distinction. This is the more

330

wAY 17 1906

TIMBER PHYSICS. 33l remarkable since the important influence of moisture was recognized and emphasized by both French and German experimenters more than forty years ago.!

These facts were fully appreciated by the engineers of our country, as is well shown by. the numerous, often emphatic, approvals and recommendations of the timber-physics work undertaken by the Division of Forestry, and by the eagerness with which wood consumers generally seized on all information of this kind as fast as the Division of Forestry could supply the same.

SourHERN AND NORTHERN OAK.

Though fully planned before, the work in timber physics was really begun in order to decide an important controversy as to the relative value of Southern and Northern grown oak.

A representative committee of the Carriage Builders’ Association had publicly declared that this important industry could not depend upon the supplies of Southern timber, as the oak grown in the South lacked the necessary qualities demanded in carriage construction. Without experiment this statement could be little better than a guess,’ and was doubly unwarranted, since it condemned an enormous amount of material, and one produced under a great variety of conditions and by at least a dozen different species of trees, involving, therefore, a complexity of problems difficult enough for the careful investigator, and entirely beyond the few unsystematic observations of the members of a committee on a flying trip through one of the greatest timber regions of the world.

A number of samples were at once collected (part of them supplied by the carriage builders’ committee) and the fallacy of the broad statement mentioned was fully demonstrated by a short series of tests and a more extensive study into structure and weight of these materials. From these tests it appears that pieces of white oak from Arkansas excelled well-selected pieces from Connecticut both in stiffness and end wise compression (the two most important forms of resistance).

Results of tests on Northern and Southern white oak made in Washington University Laboratory, | J. B. Johnson, 1889.

St. Louis, Mo., by Prof.

|

Bending and cross DAS Pay ga of test piece 1§ by | Compression. | Shearing. eons | Test piece. ee ; l ; se ; =| == -- Stiffness. | ene | ee “a Endwise. | Transverse. Longitudinal. = 2 we a ee =e ee ES 8Modulus | . odulus: | | Modulus | | | of elas- 3. W. L.| | Modulus | pounds | Modulus | Modulus Evers eet LAN, Seiya | ee Woe deters inch- Fan a per sane, | POUNdS | pange| Pounds Where procured. | No. | eal pounds Hanes pounds ee pounds Bane square | Rang: ere, | | ee: per NO: per : per NO- | per cubic 2 eras ge square | * | square square square inch. | \Size 1§ by inch | inch. | | inch inch. 5 inches. | | | a | alee _———|— ——- 2 A. a. I 1 9.) 990, 000 | 3 13, 760 | 4 59 | 6 6, 160 | 1 3, 400 3 1, 375 2 | 5 | 1,280, 000 | 1 | 18, 500 | 1 92) | 7 | 5, 480 . 3, 100 1 | 1, 560 | | | Average ..----|------ 3 | 1,135, 000 | 1] 16,130 | 1 76 | 3 5, 820 1 3, 250 | 1 | 1, 468 A.D II 3 6} 1,120,000 8| 12,300 | 6 47 i 4, 740 7 eros 500))) Gy ESeeakaree 4 | 10 920, 000 5 12, 700 | 5 55 +) 4, 980 | 4 | 2, 800 | 7 1, 22 Average .-----|------ | 4 | 1, 020, 000 | 3 12, 500 3 51 | 5 4, 860 | 2 2, 650 3 | 1, 225 5 ||) aa 850, 000 | 9| 11,400 | 2 83 | 8 5, 230 5 2,700 a 1, 375 | 6 7 \ 1,140, 000 H 7 12, 300 | 7 | 45 | 10 4,820 8 | 2,500 | 2 | 1,540 Average ...---|------ 5 995, 000 5 | 11,850 | 2 64 | 4 5,025 3| 2,600 2 1, 458 | | | | | = : —— = = 1) po osos acces esas Size: 1§ by 1g by 18 inches. Size: 1g cube. | isc nel are Ree | 7 3 | 1,570,000 6; 12,380 9) 27 4) 6, 800 11 2, 000 10 860 | 8 8 1, 100, 000 2 | 14, 690 3 82 1 7, 800 2 3, 200 5 1, 260 9 4 1, 385, 000 | 11 | 11, 240 il 19 | 5 | 6, 800 9 2, 300 i 825 Average ...---|------ 2) 1,351, 667 | 2 | 12, 770 4 43 2 | 7,133 4 2, 500 5 | 982 10 1) 1,653, 000 4 13, 030 8 30 3 | 6, 900 6 2, G00 8 | 1, 050 11 2) 1,581, 000 10 | 11, 590 10 | 22 | 2 | 7, 700 10 2, 100 9 | 940 ee | | a oe amt Average ..-.--|.----- 1 1,617,000 | 4| 12,310 5 | 26 1) 7,300 5 2, 350 | 4 995

1 Fora more complete history see Bulletin 6 of Division of Forestry. 2 See Report of the Division of Forestry, 1890, page 209.

W. — total load at center in pounds W.L2 where | L- =length in inches. Young's modulus of elasticity : E=7>p,p.he Re = SO in ane Si ee ». = breadth in inches.

h, = height in inches,

A Ya FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

Description of test material and results of physical ecamination,

Notation as to station, site, and tree............-......---. A. a. I. Connecti- A. b. II. Connec-| B. Arkansas. cut upland. ticut lowland, Number of test piece 1. 3. | Exposure in tree.....-.--------.------ --- North. Southwest. | Height in tree ..-. .--| ** Butt cut.” * Butt cut.” | Position in tree (with reference to periphery)..........--. Not known. Not known. Size of test material ; | Length.... 4 { Bread pit ces cs see eee eee tee eae nte oe ee eee eae | 1§ inch. 1§ inch. Depth (measured across ring’s)...-.---.--..----------- 13 inch. 1§ inch. ~ Res Number OLMIN PS. scseccaccwes ole nvccsccesercrlunace=as=ns s Not specified. ji Waidthiofiaimpai(ayorape) sos seeescst cones seecasceeceonne 2.7 millimeters. 1.5 millimeters. SUMMEDSVOOW AS & WHOLGs cease sew uicies cme acca se sel senses 80 per cent. o4 per cent. Ric pash issues « cascee ach eeuemcclecemise cies ca= nies) 60 per cent. 37.5 per cent. Space lost by large vessels ............-.----------2ecnenes 14.7 per cent. | 24.9 per cent. Moisture conditions when tested........-....----..------- Nearly seasoned. | Half seasoned. DGNSIGY/- oo fee eae de cone steccsinesen.cccunwesianiccss=lenselnes 84 77

These particular tests can hardly settle definitely any question. Samples 1 and 2 being selected stock, second growth, can not be used for comparison with samples of Bb, except to show that for stiffness the unselected Southern stock is superior to the best Northern growth, as also in resistance to endwise compression, The samples 3, 4,5, and 6 are probably more nearly compara- ble to samples of B, and here we find the Southern oak very much superior, not only in stiffness and columnar strength, but also in ultimate cross-breaking strength, while for resistance to shock, at least one sample of Southern oak is superior to three samples of forest-grown Northern, and even to one of the best Northern second growth. This piece (No. 8) exhibits, altogether, qualities which render the verdict tenable that Southern oak is not necessarily inferior to Northern oak in any of its qualities.

Beyond this it would not be safe to use these figures for generalizations.

In 1888 the really first beginning in timber physics was made in the form of a preliminary physical and structural examination of a set of trees representing the more important lumber pines of the South and of the lake region, as well as of bald cypress. A comprehensive plan was fully worked out and the mistakes of former methods were carefully avoided. In 1891 a more extensive study of the four great Southern timber pines, the longleaf, Cuban, loblolly, and shortleaf, was begun, and the material was at the same time collected in such a manner as to enable a detailed inquiry into the relative merits of timber bled or tapped for turpentine as compared with unbled timber.

The trees were collected by Dr. Charles Mohr, of Mobile, Ala., an acknowledged authority on the botany of the region, and thus a correct identification was assured, Of each tree entire cross sections as well as the intervening logs were utilized, the former being subjected to examinations into their specific weight (the acknowledged indicator of many valnable technical properties), into the amount of moisture contained, into the shrinkage consequent on drying, and into the struc- tural peculiarities, particularly those structural features which are readily visible and may be utilized in practice for purposes of timber inspection.

The logs were sawed and tested according to definite plans in the well-equipped test laboratory of the Washington University, St. Louis, Mo., under the direction of Prof. J. B. Johnson, a recog- nized authority in engineering. The first series of test results are embodied in Bulletin No. 8 of the division, where the strength values for the longleaf pine are fully tabulated and discussed. So eagerly was this bulletin sought by wood consumers, that an edition of 5,000 copies was exhausted in a Short time.

BLED AND UNBLED PINE.

In addition, this series of tests together with an extensive chemical analysis and physical and structural examination of material from unbled and bled trees, as well as from trees bled and abandoned for five years, re-enforced by an extended study of bled and unbled timber at various points of manufacture, proved conclusively that the discrimination against bled timber was unwarranted, since the bled timber was neither distinct in appearance, behavior, nor strength.

To avoid error in so important a matter, and also for a comparison of the three most important turpentine trees—the Cuban and longleaf with the loblolly pine—the extensive chemica! analyses of Dr. M. Gomberg, of the Michigan University, were repeated and extended by Mr. O. Carr, of the Chemical Division of the Department of Agriculture, This series of additional chemical

RESINOUS CONTENTS OF PINE. 333

analyses fully substantiated Dr. Gomberg’s work, so that it was safe to announce that: (1) Bled timber is as strong as unbled timber; and (2) that it contains the resinous substances in the same amounts and similarly distributed as the wood of unbled timber, so that it seemed to follow as a simple corollary that bled timber is also as durable as unbled, and hence equal to the latter in every respect.

The importance of this fact was quite fully realized. Trautwine, in his standard work, the Engineers’ Pocketbook, at once placed the fact on eminent record, and the lumbermen of the South, as well as all trades journals, spread the welcome news in every paper and at every opportunity.

The work of Mr. Gomberg in determining the distribution of the resin through the different parts of the tree is unique in method and classical in its clear scientific procedure and statement. Since the publication in which it first appeared was at once exhausted, it appears proper to repro- duce it in full, leaving out only a few tables, as a part of the most valuable work in timber physics performed under direction of the Division of Forestry: ,

A OHEMICGAL SruUDY OF THE RESINOUS CONTENTS AND THEIR DISTRIBUTION IN TREES OF THE LONGLEAF PINE BEFORE AND AFTER TAPPING FOR TURPENTINE.

By M. GoMBERG. | " i]

Botanists tell us that resins are produced by the disorganization of cell walls and by the breaking down of starch granules of cells. Chemists believe that resins are oxidation products of volatile oils, the change being expressed by formula as follows: 2C\H +30 C2)H30.+ HO.

Whatever view be correct,' one thing is certain, and that is that the formation of either resins or essential oils requires the presence in the tree of those peculiar conditions which we call vital. The tree must live, must be active, must assimilate carbon dioxide and imbibe moisture, in order that oil of turpentine and rosin be formed.

The heart of the tree is the dead part of it. It does not manufacture any turpentine. <A part of the oleoresin in it had been formed when the heartwood was yet sapwood, and remained there after the change from sap to heart had taken place. It is also probable that the heart of the tree acts as a storehouse in which there is deposited a portion of the oleoresin formed in the leaves and sap. :

When a tree is tapped for turpentine there are two possible changes that might be supposed to take place: (1) The tree may be considered as placed in a pathological condition, when it will strive to produce a larger amount of oleoresin in order to supply the amount removed. In a few years the energy of the tree will be exhausted and the amount freshly supplied will fall far below the amount of oleoresin drawn off by the tapping. The tapping will then have to be discontinued. The oleoresin in the heartwood will in this case remain untouched. (2) The oleoresin previously stored away in the heart might, by some unknown means and ways, also be directed toward the wound.

If the first change takes place then, the tapping will have little effect upon the chemical composition of the heartwood. If, however, the second condition prevails during tapping, then of course the heartwood will be seriously affected for some time after tapping, and will contain a much smaller amount of oleoresin than it contained before tapping. Moreover, the tapping may affect not only the amount of oleoresin, but also the quality of the new product and the relative distribution of volatile products.

For this reason the chemical side of the problem has been approached by parallel analyses of tapped or untapped trees for their relative amounts of turpentine.’ It was hoped that by a large series of analyses an average might be obtained showing whether tapped and untapped trees ditter from each other in that respect.

CHEMICAL COMPOSITION OF TURPENTINE.

Under the name of turpentine is known an oleoresinous juice produced by all the coniferous trees in greater or less amount. It is found in the wood, bark, leaves, and other parts of the trees. It flows freely as a thick juice from the incisions in the bark. It consists of resin or resins

1The one view does not exclude the other.

334 FORESTRY INVESTIGATIONS U.. 8. DEPARTMENT OF AGRICULTURE.

dissolved in an essential oil; the latter is separated from the former usually by distillation with steam.

There are many varieties of turpentine, corresponding to the different varieties of conifer, but only three are commercially important, as they are the source of the three principal oils of turpentine.

(1) The turpentine of Pinus pinaster (syn. P. maritima), collected in the southern departments of France around Bordeaux. From it is obtained the French turpentine, which yields 25 per cent of volatile oil.

(2) The turpentine from Pinus palustris, P. taeda, P. heterophylia, collected in the southern sea-bordering States from North Carolina to Texas. Irom them, principally from the first source, is obtained the English or American oil of turpentine, which yields 17 per cent of volatile oil. Formerly the P. rigida was also worked for turpentine in the North Atlantic States, but it is now exhausted.

(5) The turpentine from Pints laricio var. austriaca, collected mainly in Austria and Galicia. From it is obtained the German turpentine oil, which yields 32 per cent of volatile oil.

The Russian oil of turpentine is obtained from Pinus silvestris and Pinus ledebourii, by the direct distillation of the resinous wood, without previously collecting the turpentine. It is said to be identical with the German oil of turpentine, but more variable, as it contains products of destructive distillation, both of wood and rosin.

The turpentines from the different sources differ from each other—(1) in their action upon polarized light, (2) in the relative amounts of volatile oil they yield on distillation with steam, and (3) in the nature of the volatile oils they contain.

Colophony.—The rosin in the different varieties of turpentine is practically the same. It is known as common rosin or colophony.' It consists chemically of a mixture of several resin acids and their corresponding anhydrides. The chief constituent is abietic anhydride, C,,H,.O,, abietic acid being ©,,H,,O;. The erystals that are noticed in crude turpentine are the free abietic acid; on melting the thick turpentine, or on distilling the volatile oil, the acid is changed to the anhy- dride. Colophony is nonvolatile, tasteless, brittle, has a smooth shining fracture, sp. gr. about 1.08. It softens at 50° C., and in boiling water melts completely at 135° C,

The volatile oil.—Vhe second principal constituent of turpentines are the volatile oils. The chief ingredient of the three turpentine oils is a hydrocarbon of the same composition, C\)Hy,; nevertheless the three oils have distinct hydrocarbons differing from each other in physical if not in chemical properties. The empirical formula of the hydrocarbon is ©;)H,,, and according to the latest researches of Wallach? it has the following structural formula:

CH(CH3)? i CH HC CH2 AC’ CIF CCHs

thus being a dihydro-para-cymene, paracymene being C,)Hy4,

CH(CH3)? 1 G HC CH HC CH CCH3

' Colophon, a city of Ieonia, whence rosin was obtained by the Greeks. Ann. Chem, (Liebig), 239, 49; Ber. d. Chem, Ges., 24, 1545.

RESINOUS CONTENTS OF PINE. 335

The position of this particular terpene, pinene, will be best seen from the general classifica- tion of terpenes taken from Wallach. !

I. Hemiterpenes or pentenes of the formula C;Hs.

II. Terpenes or dipentenes of the formula Ci oH),.

(1) Pinene, obtained from many varieties of turpentine.

(2) Camphene, obtained artificially from camphor.

(38) Fenchene, obtained artificially from fenchone, a constituent of many fennel oils.

(4) Lemonene occurs in orange-peel oil, in oils of lemon, bergamot, cuminin, ete.

(5) Dipentene, obtained artificially from pinene. Occurs in Russian and Swedish turpentine. (6) Sylvestrene occurs in Russian and Swedish turpentine.

(7) Phelandrene occurs in the oils of bitter fennel and water fennel, elemi, eucalyptus.

(8) Terpinene oceurs in oil of cardamom.

(9) Terpinolene, only slightly known.

Ill.—Polyterpenes, of the formula (C;Hs),, as eedrenes C,;H2, caoutchoue (C;Hs),,, ete.

The hydrocarbon of the American and French oils of turpentine is pinene. It is dextro- rotatory when obtained from the American turpentine oil, and is known as austro-terebinthene or australene; levo-rotatory when obtained from the French turpentine oil, and is known as terebinthene. Otherwise the two hydrocarbons agree entirely in specilic gravity, boiling point, and behavior toward chemical reagents.

The hydrocarbon of the Russian oil of turpentine is sylvestrene. It is dextro-rotatory, and has a higher boiling point than pinene. The latter boils at 155° to 156° C., the former at 175° to 178° C.

But even the turpentine oils of high grade as found on the market do not consist of pure pinene; especially is this true of ordinary oil of turpentine, which is obtained from the eruder turpentine by a single distillation with steam. Different samples vary from one another considerably in their specific rotatory power as well as their boiling point.

American oil of turpentine has a density of 0.864° to 0.870°. According to Allen? it begins to boil at a temperature between 156° and 160° C., and fully passes over below 170° ©. “A good sample of rectified American oil will give 90 to 95 per cent of distillate below 165°, the greater part of which will pass over between 158° and 160°”,* while in the experience of J. H. Long,! “In the examination of a large number of pure commercial samples of turpentine oil it was observed that the boiling point was uniformly at 155° to 156°, and that 85 per cent of the samples distilled between 155° and 163°. The distillation is practically complete below 185° C.”

Then, again, as found by Long, the vapor densities of many samples of oil are too high to allow the formula C,,H,, for the entire oil. Fractions of different boiling points show different degrees of specific rotation. All this would indicate that ordinary turpentine oil contains hydrocarbons heavier than pure pinene, O,,H,,. They are probably either isomeric with pinene, but of a higher boiling point, or may belong to the polyterpenes.

Still less do we know of the source of these hydrocarbons. Whether they are produced by the tree simultaneously with pinene, and are therefore to be found in the oleoresin or whether they are all or in part produced by external agencies after the turpentine has been dipped can not be answered. Probably the formation of these other hydrocarbons takes place in both ways spontaneously in the tree and by some influences outside the tree.

Indeed, all terpenes have this property in common that they easily undergo change, from optically active to inactive, from hemiterpenes to terpenes and polyterpenes. The change can be brought about either by heat alone, or by heating the terpenes with salts or acids. So, when a sample of American turpentine oil of +18.6° was heated to 200° C. for two hours it showed an opposite rotation of —9.9°.° Pinene heated to 250° to 300° C. is converted into dipentene CH, boiling at 175°, and a hydrocarbon CH, boiling at 260° C.

These illustrations will suffice to show that the transformation of pinene into isomeric and heavier hydrocarbons may occur, at least partially, after the turpentine has been removed from the tree.

‘Ann. Chem. (Liebig), 227, 300; Ber. d. Chem. Ges., 24, 1527. 5 Allen, Com. Org. Anal., 2, 441. 2 Allen, Com. Org. Anal., 2, 487. 4 Jour. Anal. and Appl. Chem., 6, 5.

°Muspratt’s Chemie, 4th ed., 1, 153.

336 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE.

The crude turpentine from Pinus palustris, or long-leaf pine, is thus made up of— (1) Rosin, 75 to 90 per cent; mostly abietic anhydride, (2) Australene, 25 to 10 per cent; boils at 155° to 156° C. (3) Some other terpenes of C,,H,,; small portions; kind not known. (4) Some polyterpenes of (C;H,),,; small portions; kind not known. (5) Cymene (?) CjoH,,; small portions, ifany; boils at 175° to 176° C. . (6) Traces of formic and acetie acids; produced probably by atmospheric oxidation during collection of turpentine, ANALYTICAL WORK.

As both the rosin and the volatile oil are easily soluble in chloroform, ether, carbon disulphide, ete., their separation from wood by any of the above solvents would appear to be an easy matter. But an exact quantitative determination of the volatile oil presents considerable difficulties, and for these reasons: (1) Wood can not be dried free from moisture without driving off some of the volatile hydrocarbons; (2) the ether extract can not be freed entirely from either without some loss of the volatile oil.

Ifa weighed quantity of wood shavings is exhausted with either, the residue dried at 100° C. and weighed, the total loss thus found will represent:

The moisture = H. The rosin= R. The volatile hydrocarbons = T.

It is sufficient to determine two of these factors; the third could then be determined by difference. But as has been mentioned before, the ether extract can not be obtained in any degree

‘1G. 85.—Method of chemical analysis of turpentine.

of purity without loss of turpentine. The evaporation of ether in a stream of dry air, as proposed by Dragendorf, for the estimation of essential oils in general, does not give satisfactory results with turpentine oil, as Dragendorf himself observed.

A weighed quantity of a mixture of rosin and oil, made up in about the same proportions as they exist in crude turpentine, was dissolved in a suitable amount of ether. The latter was then evaporated in a current of dry air till the odor of ether was hardly noticeable. The mixture was found to have gained considerably in weight by retaining ether in the thick sirupy oleorosin. It was only by heating at 100° C. for some time that all of the solvent could be driveu off, and then the mixture was found to have lost in weight. Repeated trials proved that this method could not be used safely.

An attempt was then made to determine the quantities H and R, and thus find 7 by difference A weighed quantity of wood shavings was placed in a small flask a. The latter was connected on one side with a tray of drying bottles, on the other two CaCl, tubes ) and ¢, similar in size and form, ‘The flask is immersed in boiling water and a current of dry air is passed through the whole apparatus for one and one-half hours. The flask is then cooled and air is passed for one and one-half hours longer.

It was thought that while ) would retain all the moisture and a portion of the volatile com- pounds, ¢ would retain about the same amount of the volatile products only. Gain in weight of

INVESTIGATIONS INTO RESINS. 337

e subtracted from that of ) would then give the moisture H. The sample of wood shavings is

then exhausted with ether, the latter evaporated, and the residue heated at about 140° to 150° to

constant weight; this gives the rosin k. If L be the total loss by extraction with ether, we have L—H+R=T.

But it was soon found by experiments upon pure turpentine oil that the two CaCl, tubes did not retain an equal amount of volatile oil. The quantity retained depended upon many circum- stances, the chief one being the amount of moisture already present in the CaCl, tubes.

Even had the tubes retained quantities of turpentine oil, this method would still have the objection that one of the constituents was to be determined by difference—an objection especially serious when the ingredient to be so determined is small in comparison with the materials to be weighed.

The writer has therefore attempted to make use of a somewhat different principle. A few trials were sufficient to show that the method promised to give satisfactory results. The basis of the method is the same which seryed for the production of Russian turpentine oil on a large scale, namely, the distillation of the volatile products from the wood itself, without previously obtaining the turpentine. But instead of condensing the volatile products, their vapors are passed over heated copper oxide, whereby they are burned to water and carbon dioxide. Many trials were made with this method upon pure materials and on samples of resinous wood. As the results were found to be entirely concordant and satisfactory, the method was adopted, and by it were obtained the results presented in this report.

DESCRIPTION OF THE METHOD EMPLOYED.

A weighed amount of wood shavings is placed in a straight CaCl, tube a. The tube is con- nected on one side by means of a capillary tube with a drier A, which serves for freeing the air from moisture and CO,. The other end of the tube is connected with an ordinary combustion

7/4

7 ul ali Gy tit > Sig) WOR is=2

— i

Fic. 86.—Methoi of distillation of turpentine.

tube b containing granulated CuO. The tube is drawn out at one end as is shown in the figure, and the narrow portion is loosely filled with asbestus wool. The connection is made glass to glass, so that the vapors of distillation do not come in contact with any rubber tubing. The forward end of the combustion tube is connected with a CaCl, tube c, one-half of which is filled with granulated CaCl, and the second half with P.O;. Then follows a potash bulb d provided with two straight tubes, the first one filled with solid KOH, the second with P,O;. The last tube is connected with an aspirator.

All the connections having been made air-tight, the connection between the tube a and the drier A is shut off by means of a clamp and the aspirator turned on. When the combustion tube has been heated to dull redness the burner under the air-bath BD is lit and the temperature raised to 110°-120° C. The moisture contained in the tube escapes quite rapidly, carrying with it some turpentine oil. The capillary tube at the other end of A practically checks backward diffusion

H. Doe. 181 22

338 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE,

or any accumulation of condensed vapors. In about fifteen minutes all the moisture appears.at the forward end of the combustion tube. The clamp is now opened and a stream of air at the rate of somewhat over one liter an hour is passed through the whole apparatus, while the tem- perature of the air bath is raised to 155° to 160° C., and kept at that point for about forty-five minutes. Toward the end of the operation the temperature is raised to 165° to 170° C. for ten minutes. Then the light under the air bath is turned off and air aspirated for twenty to twenty- five minutes longer. As the air bath is in close contact with the combustion furnace, the whole length of the tube is kept at a temperature above the boiling point of turpentine oil. In this way a complete distillation is insured.

All the moisture is retained by ec, while the CO, is absorbed in the potash bulb d. The gain of weight in c¢ represents the moisture originally present in the sample of wood plus the water produced in the combustion of the hydrocarbons. The gain in weight of d represents the amount of CO,, derived from the combustion of the volatile products.

The tube a is now transferred to an ordinary Soxhlet’s extraction apparatus and exhausted with ether. The latter is distilled off, the residue dried for about two hours at 100° C., and weighed. This represents the amount of rosin in the sample of wood taken.

As has been previously mentioned, the volatile oil of the oleoresin is not pure australene, C,, Hy; =(CsH,)... It probably contains some other hydrocarbons, either of the same formula or belonging to the class of polyterpenes (C;H,),. It is clear that whichever they be their percentage composition is alike in all; they all have C=88.23 per cent, H=11.77 per cent. Therefore, so far as the combustion of the volatile terpenes is concerned, they can all be represented by the equation:

CiH5 + 140 =10 CO,,=8 H,O

136 ey

In other words, 440 parts of CO, are derived from 156 parts of volatile terpenes. 440 :136=1:X; X=0.3091, i.e., 1 part of CO, obtained in the combustion represents 0.309 parts of the volatile hydrocarbons.

For every 440 parts of CO, produced there are 144 parts of H,O formed.

440:144 =1:X; X =0.3272, i.e., simultaneously with 1 part of CO, there is produced 0.527 parts of HO. Let the weight of the sample taken = W, Let the weight of CO, obtained = W’, Let the weight of H,O obtained = W”, Then—W’ x 0.509=T, the amount of volatile hydrocarbons. W! x 0.827 =H’, the amount of H,O corresponding to the volatile hydrocarbons. W” x —H’,=H1 the amount of moisture in the wood. - = per cent of 1; ae per cent of moisture.

Thus the moisture, the volatile hydrocarbons, and rosin are obtained directly from the same sample. Where many estimations are to be made, it is of course unnecessary to cool down the combustion tube between successive combustions.

The temperature of distillation —Some experiments were made to determine at what tempera- ture it is safe to conduct the distillation. Although pure turpentine boils at 156-160° C., yet in open air it can be volatilized at a much lower temperature, even on the water bath, without any difficulty. Especially is this the case when the vapors are removed as soon as formed by a stream of air, but it must be remembered that the volatilization of the essential oil directly from the wood might be considerably hindered by the large amount of rosin.

A sample of wood distilled by the method outlined above gave the following results at different temperatures:

120° | 140 | 150 1600 | 1700

|

Per cent.| Per cent.| Per cent.) Per eent. | Per pe || i} — 1.09 1.30 | 1. 26 1. 32 0 | 11.17 :

oan

INVESTIGATIONS INTO RESINS. 339

Another sample gave:

| Per cent. Per cent. | 4.00 3. 98

The results would indicate that the distillation is practically complete at 160°, and that ihe wood itself does not contribute any CO, by partial decomposion at that high temperature; for, should the latter be the case, higher results might be expected at 180° than at 160°, and then the sapwood would give much higher numbers for turpentine oil than those actually obtained.

Even if this method does not give the absolute amounts of volatile hydrocarbons, yet it certainly gives results very near the truth, and, what is more important, under the same conditions it gives constant results. Therefore, by employing strictly parallel conditions in the analysis of the different samples, results are obtained which can be safely used as indices of comparison of the relative amounts of volatile hydrocarbons in the samples under analysis.

MATERIAL FOR ANALYSIS AND METHOD OF DESIGNATION,

Materials.—Trees No. 52 and 53, abandoned five years. Trees No. 60 and 61, abandoned one year. Trees No. 1 and 2, not tapped. Trees 54-57, abandoned five years. Trees 58-59, abandoned five years. Trees 63-65, abandoned one year. Trees 66-69, abandoned one year. Trees 17-19, not tapped. Generally Disk II is 23 feet from ground. Disk III is 33 feet from ground. Disk IV is 43 feet from ground.

Method of designation.—It was thought best to make a somewhat detailed analysis of a few bled and unbled trees in order to gain an insight into the quantitative distribution of turpentine in the trees. Each disk was divided into pieces of about thirty rings each, the heart and sapwood being kept separate. The number of the disk is designated by a roman figure, the kind of wood by either s for sapwood or h for heartwood. ‘The arabic figure which precedes the h or s designates the number of the piece, counting for the sapwood from the bark; for the heartwood, from the line of division between sap and heart.

Preparation of material.—The first six tables give the results of what might be called “detail” analysis, where each piece of about thirty rings has been analyzed separately. The material for analy- sis was prepared in the following way: A radial section of the disk, about 1 to 2 inches thick, is he et ee eae nae a aCe sea (DEEN

: B : ‘ x 52 IL means tree No. 52, disk III, the second piece of the selected. A piece of 1 inch is cut off transversely, heart.) and the strip is then divided into pieces of about thirty rings each. From the freshly cut transverse surface about 15 grams of thin shavings are planed off and placed in a stoppered bottle. The exact amount used for analysis, usually from 3 to 5 grams, is found by weighing the bottle before and after taking out the portion for analysis.

The second set of tables, VII to XII, inclusive, give the results of “average” analysis. The material for these analyses was obtained by mixing equal quantities of shavings from the corre- sponding portions of several trees and taking for analysis an average sample of the mixture. The sapwood furnish one analysis and the heart wood was either analyzed as a whole or divided into portions, 1h and 2h, if of considerable thickness.

PITH

Notes ON TaBLeEs I ro XII.

Each table contains a column ‘calculated for wood free from moisture,” giving the per cent of volatile hydro- carbons and rosin obtained by calculation from results actually found. Objections might be raised to this mode @f interpreting the results. It might be said that the moisture in the wood can not be disregarded, because it is as much an essential proximate constituent of wood as the turpentine itself is. But since the analyses were not made soon after the trees had been felled, the moisture found in the samples does not represent the original moisture, nor

340 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

does it represent equal portions of it in all samples. The numbers given in the column ‘‘water” are of course suggestive as to the comparative degree of retention of moisture by the different samples, since the latter were all exposed to about the same influences. But it seemed best to compare the amounts of volatile hydrocarbons and rosin on wood free from that variable constituent; the more so as some time elapsed between the analysis of the first and last samples. ;

The last column in each table contains the ratio between the volatile hydrocarbons and rosin. This ratio ig multiplied by 100, and means that for every 100 parts of rosin as many parts of the volatile hydrocarbons are found as is indicated in the column. This ratio (1) is of little value in cases when the amount of turpentine is small,

‘

because a very small increase of the first constituent—an increase within experimental error—will change the quotient considerably. An increase of 0.07 per cent of volatile hydrocarbons in 60, IV, 1s will bring up

T from 7.2 to 10. A decrease of 0.07 per cent in 52, IV, 28 will change 2 from 25.20 to about 19. These numbers v v

are therefore of very little significance when applied to the sapwood of all samples, to entire tree 52, and to some parts of trees 60 and 1, all of which show only small portions of turpentine.

DISCUSSION OF RESULTS OBTAINED,

Relation of rosin and volatile hydrocarbon to moisture.—The amount of moisture retained by different samples does not seem to have any direct relation to the amount of oleoresin in these samples. Yetin the same tree, or rather in the different parts of the same disk, there seems to exist

something likearelationofthetwo. This is especially notice- (FS able in tree No. 53. The moisture retained seems to vary in- versely with the amount of oleoresin in the sample. Compare, for example, in 53 II, 1h, 2h, 3h; in 53 TT, 1h, 2h, Sh, 4h; in “—~ S53 1V,2h,3h,4h. The piece richest in oleoresin is generally Ih | 2h sh 4h the poorest in moisture. But this is by no means a universal rule. Some trees show about the same per cent of moisture Fic. 88.—Relationship of different parts of same 12 parts widely differing from each other in the amounts of disk. turpentine, and in many instances a smaller amount of tur-

pentine is associated with a smaller per cent of moisture.

Saupiwood and heartwood.—All the analyses, detail and average, show conclusively that the sapwood is comparatively very poor in turpentine; if is immaterial whether it comes from a rich tree or a poor one, from a tapped tree or an untapped one. The turpentine in sapwood reaches 3 to 4 per cent in very rich trees, as in Nos. 53, 61, and 2; in the remaining trees it is 2 to 3 per cent. Consequently the results obtained for sapwood are not taken into account in the following paragraphs. When differences between trees are spoken of, it applies entirely to heartwood.

The different parts of the same disk show a constant relation in nearly all instances. In most cases 1h is the richest, and the heartwood grows poorer as we approach the pith of the tree. In a few cases, as in 1 IIT and in 1 TV, 1h and 2h are practically identical, while in some instances, in 2 111, 61 II, 61 IL, and 53 II, 1h is poorer than 2h. In nearly all cases the decline is marked in 3h, and 4h is usually found to be the poorest part of the disk. This relationship can be represented in a general way by the following curve:

Relation of volatile hydrocarbons to rosin.—As the turpentine in the tree is a solution of rosin in an essen- tial oil, it will follow that the richer a tree is in tur- pentine the richer it will be in the constituents that go to make up this mixture. One would also expect that the ratio between the volatile hydrocarbons and rosin | would be tolerably constant in the different parts of the same tree, but the results of analysis do not indi- 7! ® Yield of ae sciise.: ore aE ‘ate it. They show that this ratio increases with the amount of rosin. A part of heartwood having twice as much rosin as another part will contain more than twice as much volatile products as the second part. This is true in a general sense of parts of the same disk, of parts of different disks in the same tree, and parts from different trees. There is no distinction in that respect between bled and unbled trees. This relationship san be formulated in the following way: The crude turpentine from heartwood rich in oleoresin will yield a comparatively larger amount of turpentine oil than the turpentine from heartwood poor in oleoresin.

INVESTIGATIONS INTO RESINS. “341

It has been shown that the heartwood grows poorer from 1h toward the pith of the tree. It

will therefore follow from what has been said in the preceding paragraph that p will also grow

smaller from 1h to the pith. The yield of volatile oil from a constant quantity of turpentine can be expressed in a general way by a graphic illustration similar to that which expresses the yield of total oleoresin from different parts of the disk.

It is difficult to explain satisfactorily this decrease of Rr: The two parts of the radial sec- tions that have been the longest exposed to air are 1s and the last h. The question naturally

; fh : ; arises, May not the decrease of R be due to a greater evaporation of volatile hydrocarbons from : t

these two ends? But this can hardly be so. No. 53, II, 4h was analyzed at intervals of two months and furnished the following data:

| I, Sept.28. | IT, Nov.27.| |

| |

H,O=11. 23 (or. | aU = SRN 1. 34 8.12

| Te = 7H fl

|

Calculated for wood free from moisture:

ie, ==1530 | 1.30 | R=8. 96 8 |

Sufficient experimental data are lacking to prove conclusively that the volatile hydrocarbons do not evaporate to any extent from the heartwood except from freshly cut surfaces of it.

Relation between different disks of the same tree.—There is no constant relation between the different disks of the same tree so far as the amount of oleoresin is concerned. Although the disks do vary from each other, the variation can not be connected with gravitation, by virtue of which the lower disks would contain a larger amount of turpentine than the upper ones; for dif- ferent trees vary from each other considerably in this respect, the variation being apparent in both bled and unbled trees. If a, >, ¢ stand for the amounts of oleoresin in disks denoted by Roman numerals, the relative magnitudes being represented by the letters in the alphabetic order, then the results of analysis can be condensed in the following table for the trees denoted in Arabic numbers:

| 53. | 60. | GL. | Tee | fie ie OE “ [ete y

| Yeas | a (deme a ci

|| aL ieeas) b c a c b

| JOU BS sce j/aae 7 b b a | | a |

Tt is evident that no constant relation as to amounts of oleoresin exists between the disks of the same tree.

Comparison of tree 52 with 53.—These two trees were both supposed to have been sound, healthy trees at the time of felling, and yet they differ from each other as much as two trees could differ. The heartwood of one is very rich in turpentine; that of the other contains comparatively very small quantities—only a trace. How to explain the difference? Previous to felling they had both been tapped for four consecutive years; consequently both must have contained considerable amounts of turpentine. Since the last tapping they stood for five years side by side, both exposed to the same influences. This great difference can not be traced directly to tapping, for the latter, itmay be assumed, would have affected both treesequally. Thecauseof the difference between 53 and 52 ought to be looked for, rather, in the condition of the two trees before tapping. In connection with this it would be interesting to know how much turpentine each tree had yielded when tapped.

Comparison of trees GO and 61.—There is a decided difference between the two trees. The high- est numbers in 60 are 0.84 per cent for volatile hydrocarbons and 5.35 for rosin, while in 61 0.75

342 FORESTRY INVESTIGATIONS U. $8. DEPARTMENT OF AGRICULTURE.

and 5.67 are the lowest numbers for the corresponding constituents, the highest being 3.49 and 16.29, respectively. Here again we have two trees of about the same age, under apparently the same conditions of growth, tapped at the same time and abandoned for the same length of time before felling, and yet differing very widely from each other. It is difficult to conceive why tap- ping should have affected the heartwood of these two trees in such a strikingly different manner. If the assumption is made that the tapping had drained both trees equally, what explanation can be given for the fact that within one year of abandonment one tree is very rich in turpentine while the other has less than one-fourth as much?

Comparison of trees 52 and 53 with GO and 61.—Compare 53 and 61. Here we have two trees both very rich in turpentine, but while 53 had five years of rest after tapping, 61 had only one year. Had the tapping forced the trees to pour out their oleoresin previously stored up in the heart, we should expect to find in the time of rest the prime factor for the tree in resuming its natural condition; but, on the contrary, results of analysis show that time of abandonment before felling is of little importance. While we can have a tree very rich in turpentine within five years aiter tapping, we can also have trees rich and poor even within one year, and trees almost totally deprived of turpentine in the heartwood within five years after tapping.

Comparison of 1 with 2,—These two trees had never been tapped, and yet neither is rich in turpentine. No. 2 contains about twice as much turpentine as No. 1, the difference becoming smaller as we go up the tree. The highest numbers for 2 are 1.93 and 14.19 for T and R, respee- tively, the lowest 0.86 and 5.89, with an average of about 1 and 7. We can say that there is as much difference between untapped trees as there is between trees that have been tapped.

Average analyses.—The average analyses cover 16 trees. Thirteen trees furnish four sets of analyses of tapped trees and 3 trees furnish one set of untapped. The results obtained are summarized in the following table:

< Per cent.| Per cent. | | Per cent.| Per cent.

54-57 0.93 | 5. 88 | 15.58 | 0.58 | 3.98 14.04 | Abandoned 5 years.

57-59 | . 80 4.06 | 19. 63 2 4.29 19. 10 Do.

91 | 5.32 | Vis Abandoned 1 year. 66-69 89 | 4.95 | | Do. } | Not tapped.

17-19 . G4 2. 98 |

These results show a pretty constant average number for turpentine in tapped trees. The heartwood of untapped trees is poorer in both volatile oil and rosin than that of tapped trees. And here again it is worthy of notice that time of abandonment is of little importance to tapped trees. The trees that had been abandoned for one year are fully as rich as those that had five years to recover from tapping.

Comparison of tapped with untapped trees.—If now the heartwood of tapped trees be compared with that of untapped, one is at a loss as to what conclusions should be drawn from so few analytical data. It is remarkable that the two richest trees and the poorest tree are among those that had been tapped. Of the remaining 19 trees, there is no difference between the 14 tapped and 5 untapped. Whatever differences are found among bled trees.are equally found among those that have not been tapped.

Indeed, from the study of the results of analyses the writer is of the opinion that the difference in untapped trees is due to the same cause as the difference in trees that have been tapped. As stated above, the cause of the difference among tapped trees can not be traced directly to tapping; it ought to be looked for, rather, in the condition of the trees previous to tapping.

The difference between trees 52 and 53 can be explained on the following hypothesis: 53 had been a rich tree from early growth and had a large amount of turpentine stored up in the heart- wood; 52 for some reason or other had very little stored away. When the two trees were sub- jected to tapping they gave up whatever turpentine they had in the sapwood and whatever they could produce from season to season, till at the end of four years the production became too smalj in amount and too poor in quality. The trees were then abandoned. But tree No. 53 had its oleoresin in the heartwood untouched, while No. 52 had hardly any before tapping, and for the same unknown cause did not store away any in the heartwood after the tree had been abandoned.

RESIN IN BLED AND UNBLED TREES. 343

The explanation offered in the preceding paragraph gains still more probability when trees 60 and 61 are compared with each other and also with 52 and 53. The difference between 1 and 2, the results of average analyses—all these are very suggestive of the theory that the sap, and not the heart of the tree, supplies the turpentine when the tree is tapped. The fact that the heartwood of trees felled one year after tapping is fully as rich or as poor as that of trees felled five years after tapping, seems to the writer of especial significance, for it shows that the richness of the heart- wood in a tapped tree is independent of time of rest before felling.

It is a well-known fact that when a pine tree is cut transversely, liquid turpentine immedi- ately appears on the fresh surface of the sapwood, while the heartwood remains perfectly clear. It would seem as if the turpentine in the sap is far less viscid than that in the heart of a tree. It is probable that the turpentine in the sap is richer in volatile hydrocarbons than that in the heart. (A difference of cell structure and manner of existence of oleoresins may also account for this difference in part.—B. E. F.)

It is generally stated that crude turpentine as obtained on a large scale yields from 10 to 25

per cent of volatile oil. This gives Rd to 30, with an average of over 20. This average yy"

is somewhat higher than that for the Ros found for the turpentine from heartwood of the 21

trees analyzed. Although experimental data are wanting to show conclusively that the difference in the consistency of the oleoresin from sapwood and heartwood is due to a difference in the relative amount of volatile oil, yet it is quite probable that this should be the cause. The oleoresin in the heartwood of trees has been produced for the most part when the ‘heartwood was yet sapwood. Therefore that part of turpentine which is found in the heartwood is the oldest in age and consequently has been exposed the longest to oxidizing influences of air, which gradually replace the water when the sapwood changes to heartwood. It is the same kind of oxidation and of thickening which takes place when crude turpentine is exposed to the air and sun, or when a

gal

fresh cut is made in the bark of a tree. It is probably for the same reason that R becomes smaller

as we approach the pith of the tree, because the parts nearest the pith are the oldest.

It is difficult to conceive how the thick oleoresin of the heartwood could be made to flow toward the incision when a tree is tapped. It is also difficult to explain by what means the tree could change this thick turpentine into a less viscid solution in order that it may flow toward the wound.

One would judge, a priori, from the great difference in the consistency of the turpentine in the heart and sap that only the liquid turpentine will flow when a tree is tapped. Tapping will then have little effect, if any, upon the oleoresin stored up in the heartwood of the tree. A tree whose heartwood is rich in turpentine will remain so after tapping.

The writer is not willing to generalize too hastily from so few results and consider them as a solution of the problem. <A large number of analyses, devoid of the possibility of chance selection of samples, is necessary before a positive or a negative answer can be given to the question, does the tapping of trees for turpentine affect the subsequent chemical composition of the heartwood?

But, however few in number the results are, they admit of the following conclusions:

(1) Trees that have been tapped can still contain very much turpentine in the heartwood.

(2) Trees that have been abandoned for only one year before felling can contain fully as much turpentine in the heartwood as trees that have been abandoned for five years.

(3) Trees that have not been tapped at all do not necessarily contain more turpentine in the heartwood than trees that have been tapped.

The following diagram serves to show what proportion of each disk was involved in each of the detail analyses, and the results in each case. The right-hand vertical line represents the pith of the tree, the horizontal lines represent the radical extension of each disk, as numbered by roman number, the position of the disk in the tree being maintained as in nature, IV being the top, II the lower, and III the intervening disk. The subdivisions of radii represent the actual divisions of the disk to scale of one-half natural size, the portions to the left of the heavy subdivision line representing sapwood s 1 and s 2; the portions to the right heartwood h, h, divided according to the method as indicated above. The four columns of figures over each disk piece represent results pertaining to that piece; they stand in order from the top for (1) number of rings, (2) volatile

344 FORESTRY INVESTIGATIONS

U. S. DEPARTMENT OF AGRICULTURE.

hydrocarbons, (3) rosin, (4) ratio — (2) and (3) as caleulated on wood free from moisture. For

instance, for tree No. 53, disk IV, s2, we find—

40 — Number of rings. 0.40— Per cent of volatile hydrocarbons. 3.81— Per cent of rosin.

fh 1033 —— R 40. 30. 34. 33. 81. 35. _— 0.40 0.46 4.56 4.49 3. 86 2. 66 3.81 3.96 24, 01 22,23 17.74 15.19 Tree | 10.37 | 11.60, 119.02 | _ 20.12 | 2.97 | _17.53 TV. No. 53 40. 37 35. 38. 30. 18. 0.39 0.42 3.87 3.81 2.10 1.25 2. 96 3.02 21.77 20. 09 11.97 9.71 SEO sR EPS ST aia | 18.94 | 17.53 | 13.10 TIT. 37. 40. 33. 32 32. 28, 0.18 0.19 2.56 4.39 2, 22 1.46 0.97 0.96 12. 02 24.70 12.30 8.96 |___ 18.39 | 19.77 feats | 22.43 | 18.29 | 16. 33 II. 40. 35. BP 34 30. 30. 0.26 0.34 0.15 0.22 0.23 0.26 1.40 1.34 1.65 1.97 1.72 1.92 Tree Wo. 52 18. 78 [eee 25820) tet 33 eee | meet | 13.38 | 13.64 Iv. 30. 40. 30. 20. 32. 27. 11. 0.25 0.25 0.15 0.20 0.14 + 0.18 0.18 1.99 1.87 1.77 1.87 1.86 1.60 1.53 | 12.71 |_ 13.67 1 8.64 | 10.51 7.65 | 9.65 | 9.26 TIT. 40. 40. 36. 32. 35. 24. 0.30 0.31 0.30 0. 26 0.17 0.17 2.19 2.01 2.17 1888 1.98 1.51 13.64 i | 14.14 | 14.38 | 3. 83 | 11.60 TI. 30. 36. 40. 33, 35. 30. pao. 0.22 0.28 3.07 3.49 3.14 1.08 3.01 2.75 13.55 16.29 14.18 8. 04 Tree 7.35 | 10.20 12265 | 42 ere | 13.39 II. No. 61 35. 35. 36. 33. 30. 35. 0.20 0.26 1.57 2.69 2.92 0.75 3.01 3.11 7.88 13.57 11.34 5. 67 | 6.50 | 8.36 1 19.85 19.86 |__-25.81 | __ 13.28 II. ; 30. 27. 36. 40. 0.16 0.24 0.41 2.32 2. 66 3.13 AC 8s | |___12,.85 | Ivy. 30. 34. 30. 36. 36. 20. 0. 28 0.35 0.58 0.40 0.42 0.50 . Pree No. 60. 2.65 2. 88 3. 60 2.99 2.42 3.39 |__ 10.33 (e256 [ton | 18h93 |___ 17.04 14. 70 IIt. 30. 35. 37. 33. 35. 97. 0.29 0.33 0.71 0.51 0.73 0.47 2.26 2. 63 5.08 2.71 5.19 3. 62 |__ 12.74 | 12.56 He et4k0T aii 18562)0 ie dasog | 13.00 II. 30. 28. 32. 19. 0. 22 0.25 1.07 1.06 1.43 1.57 7.61 6.62 ee af at) | 16.04 Iv. 30. 33. 30. 25. 13. 0.32 0. 34 0.94 0.73 0.40 2.25 2.25 4.90 5.12 3.57 TresNoule |__14.49 | 13.90 19 1 oT | 11.20 IIT. 30. 35 35. 34. 15. 0.20 0.17 0.18 0. 66 0.37 1.06 1.32 6.57 3.92 2.23 J) 18355) eet sh72 nie 74078 elles lea67! | 16.50 106 3.55 x 7. 6. ‘ 30. 36. 30. 30. 0.31 0.34 1.13 0.87 2.52 2.71 8. 10 6.41 [12:12 1236 18.98, _ 13.53 Iv. 30. 36. 23 28. 17. 0.18 0. 24 1.37 0.92 0. 86 1.95 2.24 9.14 5.89 7.40 Tree No.2. | 8.94 | 10.06 § 1477 | 15.61 | 11.64 III. 30. 26. 34. 30. 30. il. 0.20 0.31 1.55 1.93 1.39 1.16 4.29 3.05 10.10 14.19 8.78 8.94 | 4.56 | 10.00 | 15.35 [aaa | 15.75 | 12.99 II.

DISTRIBUTION OF RESINOUS CONTENTS.

TABLE I.—TREE No. 53.

o

Caleulated on wood free Volatil from moisture. “ = olatile Pee ee a a No. of disk. Part of |Numberof) ywiath. | Water. | hydro- | Rosin. | yolatite Reine 100 ee? a carbon. nvadeo Rosi ere ydro osin. carbon. Om. Per cent. Per cent. Per cent. Per cent. Per cent. 1s 37 3.3 10. 51 0.16 0. 87 0.18 0. 97 18. 39 28 40 4.0 10. 05 0.17 0. 86 0.19 0.96 19.77 1h 33 3.0 +e i) 2.32 10. 98 2.56 12, 02 21.23 TT, name oe n=-cmnrensennes 2h 32 2.9 8.79 4.00 17.83 4.39 24.70 22.43 3h 32 5.0 8.47 2. 08 11. 26 2.22 12. 30 18. 29 4h 28 10.0 *11, 23 1.30 7.96 1.46 8.96 16. 33 1s 40 Pave 9. 08 0.35 2. 69 0.39 2.96 13. 01 2s 37 2.6 8.90 0.38 2.75 0. 42 3. 02 13. 82 lh 35 3.5 7.89 3.57 20. 05 3. 87 21.77 17. 85 TIT ...------------------ 2h 38 4.1 8. 04 3.50 18.48 3.81 20. 09 18. 94 3h 30 6.5 8.55 1.92 10, 95 2.10 11.97 17. 53 4h 18 7.0 8.79 1.14 8. 86 1,25 971 13.10 1s 40 4.0 8.96 0. 36 3.47 0,40 3.81 10. 37 28 30 3.0 8. 67 0,42 3. 62 0.46 3.96 11. 60 Iv 1h 34 3.9 8. 04 4.20 22. 08 4.56 24. 01 19. 02 ae ae eget ocean rin “tga 2h 33 3.0 7.93 4.13 20, 56 4.49 22. 33 20.12 | 3h 31 5.8 8. 65 3.58 16. 21 3. 86 17. 74 21.77 4h 15 5.3 9.55 2.41 13.74 2. 66 15.19 17.53 “53, II, 4h has been analyzed some three weeks earlier than the remaining parts of this tree, hence a large per cent of moisture. TABLE II.—TREE No. 52. 1s 40 3.1 9.72 0.27 1.98 0.30 2.19 13. 64 2s 40 3.9 Oey ie 0. 28 1.81 0.31 2. 01 15.47 Ir lh 36 4.6 8. 67 0. 28 1.98 0. 30 2.17 14.14 ee ge a wari a RY tr 2h 2 3.0 8, 44 0. 24 1. 68 0.26 1.83 14. 38 3h 35 6.8 8. 80 0.16 1.81 0.17 1.98 8.83 4h 24 7.4 8.55 0.16 1.38 0.17 1551 11. 60 1s 30 3.0 9.12 0.23 1.81 0.25 1.99 12.71 2s 40 3.5 9. 00 0. 23 1. 68 0.25 1.87 13. 67 lh 30 3.4 8.44 0.14 1. 62 0.15 1.77 8. 64 IDO Ee seca soecnosocns 2h 30 3.0 8.51 0.18 1.71 0. 20 1.89 10.51 3h 32 4.8 8.37 0.13 1.70 0.14 1.86 7.65 4h 27 6.9 9.35 0. 14 1.45 0.15 1. 60 9.65 5h 11 5.0 9.21 0.13 1.39 0.14 1.53 9, 26 1s 40 3.5 8. 88 0.24 1.28 0. 26 1.40 18.78 2s 35 3.3 8.49 0,31 1, 23 0. 34 1.34 25. 20 IV lh 32 3.0 9. 08 0.14 1.50 0.15 1.65 9.33 pen cy fe meagan Gen eg ge 2h 34 2.8 8. 86 0. 20 1,80 0.22 1.97 11.11 3h 30 3.6 8.48 0.21 1.57 0. 23 1.72 13, 38 4h 30 6.8 8.10 0, 24 1.76 0. 26 1.92 13. 64 Taste III.—TREE No, 61. 1s 35 3.0 7.9L 0.18 2.77 0. 20 3.01 6.50 23 35 3.0 7.90 0, 24 2.87 0. 26 3.11 8.36 Ir dh 36 2.8 7.35 1.45 7,30 1.57 7.88 19. 85 I aaa a 2h 33 3.2 7.58 2.49 12. 54 2. 69 138. 57 19. 86 3h 30 4.5 7. 64 2.70 10. 46 2.92 11. 34 25.81 4h 35 955 7.10 0.70 5. 27 0.75 5, 67 13. 28 1s 30 3.0 7.65 0, 20 2.78 0. 22 3.01 7.35 28 36 2.7 7.43 0, 26 2.55 0, 28 2.75 10. 20 Tr 1h 40 3.1 7.14 2.85 12.58 3. 07 13.55 22. 65 Rae Me cae hee 2h 33 3.2 7.46 3. 23 15. 08 3.49 16. 29 21.42 3h 35 6.0 7.41 2. 91 13.59 3.14 14.18 21.42 4h 30 8.0 7.09 1.00 7.47 1.08 8. 04 13.39 TABLE IV.—TREE No. 60. 1s 30 2.7 9. 91 0. 26 2. 04 0, 29 2.26 12. 74 2s 35 258) 9.34 0. 30 2.39 0, 33 2.63 12.56 I th 37 3.5 8.72 0, 65 4.62 0.7L 5. 03 14. 07 cee eee cee n ee cee eee eee oh 33 4.5 9.15 0, 46 2.47 0.51 2.71 18. 62 3h 35 4.6 8.01 0.67 4.71 0.73 5.19 14, 02 4h 27 6.5 8.45 0.43 3.31 0.47 3. 62 13. 00 ls 30 3.1 8.74 0. 25 2.42 0. 28 2.65 10, 33 28 34 2.8 8. 60 . 0.32 2. 63 0. 35 2. 88 12.16 TI lh 30 3. 2 8. 68 0.53 3.47 0.58 3. 80 15. 27 rereceeeeeseneeeee ae 2h 36 4.4 9.02 0.36 2.72 0. 40 2.99 13. 23 3h 36 4.5 7.73 0. 38 2.23 0.42 2.42 17. 04 4h 20 6.0 7.73 0. 46 3.13 0, 50 3.39 14.70 1s 30 2.6 7.51 0.15 2.15 0.16 2.32 7.02 28 27 2.6 7. 84 0. 22 2.45 0, 24 2. 66 9.09 TOE ssracssascososccoared lh 28 3.7 7.77 0,77 4.94 0, 84 5, 35 15, 59 2h 36 5.0 8.12 0.37 2. 88 0.41 3.13 12. 85 oh 40 8.0 7.92 0. 26 2.81 0. 28 3.05 9.18

346 FORESTRY INVESTIGATIONS U. S8. DEPARTMENT OF AGRICULTURE.

TABLE V.—TREE No. 1.

| | | Calculated on woed free | Volatil from moisture. G $a Part of | Number ef = re Ven eee Vol. hydroc, _ No. of disk. dink: rings. Width. Water. hyde: Rosin. Volatile TRENT <100 oe 7 hydro- Rosin. | | | | carbon. — — — _ — | —- 1 | —— — | cm, Per cent. | Percent. | Per cent. Per cent. | Per cent. } ls 380 2.0 8, 67 0.18 0.97 1.06 | 28 35 3.0 0.16 1, 21 1. 1 0 (OEE aR RRR e Ree aan ac 1h 35 3.6 | 1.08 | 6.01 6. | 2h 3d 6.5 0. 60 3. 60 3. | Sh 14 3.0 0. 34 2. 06 2. | ls 30 | 2.8 2.07 2. 28 83 3.0 2. 23 2. 1D a eeacee cee coscee lh 30 3.8 4,50 4. 2h 25 | 4.2 4.72 5. 3h 13 3.5 3.30 3.6 | Is 30 | 2.2 1.31 | 1. 7 28 28 | 2.8 1.44 1.5 LV wnnto sone ernne nnn = th 32 5.0 | 7.01 | 7. | 2h 19 5.2 6.11 | 6.6 | | u bs TABLE VI.—TREE No. 2 ls 30 3.0 7. 65 | 3.95 | 0. 20 4.29 | 4.56 | 28 26 2.7 8.19 2.80 | 0.31 | 3.05 10. 00 Th 34 3.5 7.31 9.25 | 1. 55, 10.10 15. 35 IL ....------2------2-+-+ 2h 30 5.0) 811 13.05 1.93 | 14.19 14.41 3h 30 6.0 8.16 | 8.06 1.39 | 8.78 15.7 4h il 4.2 7. 88 | 8.24 1.16 | 8.94 12.99 ls 30 Peri 8.00 1.79 | 0.18 | 1.95 | 8.94 2s 36 3.0 | 8.01 | 2.06 | 0.24 | 2.24 | 10.06 JD ferences SESS SOCIO 1h 33 3.2 | 7.44 | 8.46 | 1.37 | 9.14 | 14.77 2h 28 5.5 7.78 5. 44 0. 92 5. 89 15. 61 | i 7 3h 17 | 13)| 7.12 | 6.87 | 0.86 | 7.40 11. 64 1 30 2.7 8. 20 2.31 | 0.31 2502 12.12 IV | 38 36 3. 0 | 8.08 | 2.49 | 0.3: | 271 12. a a ak pe a lh 30 | 3.6 8.10 | 7.44 | 1.13 | 8.10 | 13.98 | 2h 30 | 7.6 | 7.81 | 5.91 0. 87 6.41 13.53 | | | = all “ = ——e iia 9 as = a = TABLE VII—SvumMARY OF RESULTS OF TREES Nos. 54 TO 69 AND Nos. 17 T0 19. Disk II. Disk III. Serial ber of trees. IDM || |= sie MM isp) Tnil==ewesael 1 \keGicas erial number of trees | art of disk Volatile hy- Rania Vol. hydr. ea Volatile hy- ae Vol. hydr. Se O0 drocarbons. eee Rosin. drocarbons. | canine Rosin. “~ oe || — i ar, =e. eae s 2 ae | Per cent. Per cent. Per cent. Per cent. } 8 | 0.18 1.48 | 3.14 0, 26 1.93 | 13.33 by WET GURY ( Soe ose Ac bonSacbcror cosas | 1hy f) 1.16), 9< f| 6. 78\- 9. f\ 1714 a eee f 4. 3. ; any Al opzosP 28 iva. a7se: 25 ni ag: 01/788) 0) 2 9 f 8 | 0. 28 1.76 15. 76 1. 3% REG) cecscboaorsanodsmocctoceacicastt \ h | 0.80 4.06 19. 633 | 4.5 8 0,18 1.74 70. 00 GS 5U) SCG resaanonm cos cuesestasoaccqos lh f, 0.81) fj 4.35). « {|| 18. 55\a, 70 ait & {i roof-92 {| @:aas>32 {| a5: a0s27- 18 . f 8 0.14 | 1.78 8. 00 66, 67. 68, 69 ...-....-...------------- \ h 0.89 4.95 18,00 | i s 0.14 1.49 ‘ WY Ap po Eee ea aR OS=S5 an BoDAS lh | 0.78 6 3, 48). os Nant om {lg Beloves {| 3 aRlace a7 | | | 4 | |

TIMBER PrHysics WoRK.

The timber physies work was continued actively and the investigation extended to other kinds of timber, both conifers and hard woods. In 1896 the Division was in position to announce its findings with regard to the mechanical, physical, and structural study of the four principal Southern pines (Cireular 12), Based, as these results are, on over 20,000 mechanical tests and over 50,000 weighings and measurements, they may fairly be regarded as final, and thus avoid future discus- sion and much fruitless and expensive private testing. According to this exhaustive study, the Cuban and long-leaf pine rank foremost among our timber pines, and are fully 20 to 25 per cent stronger than had previously been assumed. It also appeared that the wood of these species varies in strength directly as the weight (little discrepancies being well accounted for by varia- tions in resin contents, which add only to weight and not to strength); that in the same tree the wood varies according to certain definite laws, being heaviest at butt, lightest in top, heavier in the interior, and lighter and weaker in the outer parts of saw-size timber; that thus the age when formed, as well as the position in the tree, exercises a definite influence which is generally far greater than the much-quoted influences of soil, locality, ete. In this latter respect it was clear

TIMBER PHYSICS—SOUTHERN PINE. : 347

from the results that the oft-claimed superiority of the timber of certain localities is not substantiated by experiment, but that there is heavy and strong as well as lighter and weaker timber in every locality throughout the range of these species. The all-important effect of moisture was carefully considered throughout the work, and it was established that in general an increase in strength of at least 50 to 75 per cent takes place during ordinary seasoning, so that for all designing of covered work, as in ordinary architecture, this improvement may be depended upon and considered in the proportioning of the timbers.

The manner in which the valuable information was secured and communicated will appear from the following reprint of Circulars 12 and 15, issued in 1896 and 1897:

SouTHERN PINE—MECHANICAL AND PITYSICAL PROPERTIES. THE MATERIAL UNDER CONSIDERATION.

The importance of reliable information regarding the pines of the South is evident from the fact that they furnish the bulk of the hard-pine material used for constructive purposes with an annual cut hardly short of 7,000,000,000 feet B. M., which, with the decline of the soft-pine supplies in the North, is bound to increase rapidly.

Although covering the largest area of coniferous growth in the country (about 230,000 square miles), proper economies in their use are nevertheless most needful, since much of this area is already severely culled and the cut per acre has never been very large. Hence the demonstration (a result of the investigations in this Division) that bled pine is as strong and useful as unbled, and the assurance that long-leaf pine is in the average 25 per cent stronger than it is often supposed to be, and therefore can be used in smaller sizes than customary at present, must be welcome as permitting a saving in forest resources which may readily be estimated at from eight to ten million dollars annually, due to this information.

The pines under consideration, often but imperfectly distinguished by consumers in name of substance, are:

(1) The long-leaf pine (Pinus palustris), also known as Georgia or yellow pine, and in England as ‘‘pitch pine,” and by a number of other names, is to be found in a belt of 100 to 150 miles in width along the Atlantic and Gulf coasts from North Carolina to Texas, furnishing over 50 per cent of the pine timber cut in the South—the timber par excellence for heavy construction, but also useful for flooring and in other directions where strength and wearing qualities are required.

(2) The Cuban pine (Pinus heterophylla), found especially in the southern portions of the long-leaf pine belt, known to woodsmen commonly as ‘‘slash pine,” bat not distinguished in the lumber market. It is usually mixed in with long leaf, which it closely resembles, although it is wider ringed (coarse grained), and to which it is equal if not superior in weight and strength.

(3) The short-leaf pine (Pinus echinata), also known, besides many other names, as yellow pine and as North Carolina pine, but growing through all the Southern States generally north of the long leaf pine region; much softer and with much more sapwood than the former two, useful mainly for small dimensions and as finishing wood, being about 20 per cent weaker than the long-leaf pine.

(4) The loblolly or old-field pine ( Pinus taeda), of similar although more Southern range than the short leaf, also known as Virginia pine, much used locally and in Washington and Baltimore, destined to find more extensive application. At present largely cut together with short leaf and sold with it as ‘yellow pine,” or North Carolina pine, without distinction, although sometimes far superior, approaching long-leaf pine in strength and general qualities.

The names in the market are often used interchangeably and the materials in the yard mixed. AI] four species grow into tall but slender trunks, as a rule not exceeding 30 inches in diameter and 100 feet in height; the bulk of the logs cut at present fall below 20 inches. The sapwood forms in old trees of long leaf (with 2 to 4 inches) about 40 per cent of the total log volume; in Cuban, short leaf, and loblolly 60 per cent and over.

A reliable microscopic distinction of the wood of the four species has not yet been found. As a rule long leaf contains much less sapwood than the other three. The narrow-ringed wood of long leaf (averaging 20 to 25 rings to the inch) usually separates it also from the other three, while the especially broad-ringed Cuban excels usually also by broader summer-wood bands. In the log short leaf and loblolly may usually be recognized as distinguished from the former by the greater proportion of sapwood and lighter color due to smaller proportion of summer wood. The general appearance of the wood of all four species is, however, quite similar, The annual rings (grain) are sharply defined; the light yellowish spring wood and the dark orange-brown summer wood of each ring being strongly contrasted produce a pronounced pattern, which, although pleasing, especially in the curly forms (which occur occasionally), may become obtrusive when massed.

348 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

The following diagnosis may prove helpful in the distinction of the wood:

Diagnostic features of the wood.

Long-leaf pine (Pinus | Cuban pine (Pinus | Short-leaf pine (Pinus oul pine (Pinus a

Name of species. palustris Miller). | heterophylla (Ell) Sud). echinata Miller). teda Linn.). ee a Ls = = a, | | = Specifie gravity of kiln-fPossible range --.--- - 50 to .90 - 50 to .90 - 40 to . 80 -40 to . 80 dried wood. \Most frequent range - -55 to .65 -55 to .70 -45 to .55 -45 to .55 Weight, pounds per eubic foot, kiln-dried | WOO0d.) ((CAWOlrag6) -- secnsecemececeesenance= 36 37 30 31

Character of grain seen in cross section Fineandeven; annual! Variable and coarse, | Very variable; me- | Variable, mostly very

rings quite uni-! rings mostly wide; dium, coarse; rings coarse; 3 to 12 rings formly narrow; on averaging on large wide near heart, fol- to the inch, gener- large logs averag- logs 10 to 20 rings to lowed by zone of ally wider than in ing generally 20 to the inch. narrow rings; not the short leaf.

25 rings to the inch. less than 4 (mostly

about 10 to 15) rings to the inch, but often very fine

grained.

Color, general appearance. --.-.-..-----.----- Eyen dark reddish | Darkstraweolorwith | Whitish to reddish or | Yellowish to orange yellow to reddish tinge of flesh color. yellowish brown. brown. brown. | |

Sapwood, proportion .-......-...-.<......... Little; rarelyover2to | Broad; 3 to6inches..) Commonly over 4 | Very variable, 3 to 6 3 inches of radins. inches of radius. inches of the radius.

ROSIN oatene wasn cin wien oom awe n enna em saeienarns Veryabundant; parts | Abundant, sometimes | Moderatelyabundant, Abundant; more than often turning into yielding more pitch least pitchy; only short leaf, less than “light wood;’’ than long leaf; near stumps, knots, long Jeaf and Cuban, pitchy throughout. “bleeds” freely, and limbs. but does not‘ bleed"’

yielding little if tapped.

scrape.

The sapling timber of all four species is coarse grained, that of loblolly exceeding the rest in this respect. The grain varies most in the butt, least in the top, is very fine in the outer portions of all old trees. Loblolly in the center of the log frequently shows rings over one-half inch wide, and timber averaging eight rings to the inch is not rare, while short leaf will average 10 to 15 rings to the inch. The greater or less proportion of the sharply defined dark-colored bands of summer wood of the ring furnish the most reliable and ready means of determining quality.

At present distinction is but rarely made in the species and in their use. All four species are used much alike, although differentiation is very desirable on account of the difference in quality. Formerly these pines, except for local use, were mostly cut or hewn into timbers, but especially since the use of dry kilns has become general and the simple oil finish has displaced the unsightly painting and ‘“‘graining” of wood Southern pine is cut into every form and grade of lumber. Nevertheless, a large proportion of the total cut is still being sawed to order in sizes above 6 by 6 inches, and lengths above 20 feet for timbers, for which the long leaf and Cuban furnish ideal material. The resinous condition of these two pines make them also desirable for railway ties of lasting quality.

MECHANICAL PROPERTIES.

In general the wood of all these pines is heavy for pine (31 to 40 pounds per cubic foot, when dry); soft to moderately hard (hard for pine), requiring about 1,000 pounds per square inch to indent one-tweutieth inch; stiff, the modulus of elasticity being from 1,500,000 upward; strong, requiring from 7,000 pounds per square inch and upward to break in bending, and over 5,000 pounds in compression when yard-dry.

The values given in this circular are averages based ona large number of tests, from which only defective pieces are excluded.

In all cases where the contrary is not stated the weight of the wood refers to kiln-dried material and the strength of wood containing 15 per cent moisture, which may be conceived as just on the border of air-dried condition. The first table gives fairly well the range of strength of commercial timber.

Average strength of Southern pine.

Air-dry material (about 15 per cent moisture).

Compression strength. Bending strength. At BEDCuiey | t With grain. modulus 3WL pacer 753 = —{ = FA(CTOSS | eee ——————|At elastic, Elasticity -_.{ Tensile | Shearin Name. Average. ||;2-werage grain. versace Average limit | (stiffness) Relate streneth. Seong of all ea for the weakest. 3 per cent) of all valid for the weakest modulus modulus masts ms tests one-tenth indenta- Leute | one-tenth | 3 Wil 3 Wis One a of all the testa.| tion. yas jof all the tests., “9/2 4A Dh 3 Rela-| [Rela-| |Rela-| _ |Rela-| te: level cee ve: Abeolnteitive. Absolute. ive | | 1 Lbs, per Lbs. per | Lbs. per | Lbs. per Lbs. per | Lbs. per | Lbe.per | In.-lbs. | Lbs. per | Lbs. per | sq. inch. | sq. inch. | sq. inch. | 89. inch. sq. inch, | | 8q- inch. | sq.inch. |per cu.in.| sq.inch. | sq. inch. Cuban pine ..-- 7,850 | 100 6,500 100 1, 050 11,950 | 100 | 8,750 | 100 | 9,450 | 2,305, 000 245) 14, 300 680 Longleaf pine... 6,85C | 387 5, 650 | 87) 1,060 | 10,900 | 91 8,800 | 101) 8,500 | 1,890, 000 2. 15, 200 706 Loblolly pine -.| 6, 500 83 | 5, 350 82 | 990 | 10, 100 84 8.100 | 92) 8,150 | 1, 950, 000 2.20 14, 400 690, Shortleaf pine.) 5,900 | 75 4, 800 | 74 940 9,230 | 77 7, 000 | 80} 7,200 | 1,600, 000 2.05 13, 400 688 | |

TIMBER PHYSICS—SOUTHERN PINE. 349

RELATION OF STRENGTH TO WEIGHT.

The intimate relation of strength and specific weight has been well established by the experiments. The aver- age results obtained in connection with the tests themselves were as follows:

Since in the determination of the specific gravity above given, wood of the same per cent of moisture (as is the case of the values of strength) was not always involved, and also since the test pieces, owing to size and shape, can not perfectly represent the wood of the entire stem, the following results of a special inquiry into the weight of the wood represents probably more accurately the weight and with it the strength-relations of the four species.

WEIGHT RELATIONS.

[These data refer to the average specific weight for all the wood of each tree, only trees of approximately the same age being involved. ]

|

a The values of strength refer to all tests and therefore involve trees of wide range of age and consequently of quality, especially those of longleaf, involve much wood of old trees, hence the relation of weight and strength appears less distinct.

From these results, although slightly at variance, we are justified in concluding that Cuban and longleaf pine are nearly alike in strength and weight and excel loblolly and shortleaf by about 20 per cent. Of these latter, contrary to common belief, the loblolly is the heavier and stronger.

The weakest material would differ from the average material in transverse strength by about 20 per cent and in compression strength by about 30 to 35 per cent, except Cuban pine, for which the difference appears greater in transverse and smaller in compression strength. It must, of course, not be overlooked that these figures are obtained from full-grown trees of the virgin forest, that strength varies with physical conditions of the material and that, therefore, an intelligent inspection of the stick is always necessary before applying the values in practice. They can only represent the average conditions for a large amount of material.

DISTRIBUTION OF WEIGHT AND STRENGTH THROUGHOUT THE TREE,

In any one tree the wood is lighter and weaker as we pass from the base to the top. This is true of every tree and of all four species. The decrease in weight and strength is most pronounced in the first 20 feet from the stump and grows smaller upward. (See fig. 91.)

This great difference in weight and strength between butt and top finds explanation in the relative width of the summerwood. Since the specific weight of the dark summerwood band in each ring is in thrifty growth from -90 to 1.00, while that of the springwood is only about .40, the relative amount of summerwood furnishes altogether the most delicate and accurate measure of these differences of weight as well as strength, and hence is the surest criterion for ocular inspection of quality, especially since this relation is free from the disturbing influence of both resin and moisture contents of the wood, so conspicuous in weight determinations.

The following figures show the distribution of the summerwood in a single tree of longleaf pine, as an example of this relation: :

Tn the 10 In the 10 A 7 Average Peery * rings, Nos. | ¢ S Specific rings next) 100 to 110 | TC entire | weight.

|tothe bark.) ¢rom bark.

| Percent. | Per cent. Per cent. At the stump.--.....-- Pees cite te nae See eee ees cee ee ey 52 50 0.73 32 feet from stump 25 38 33 | 59

87 feet from stump 15 37 26 55

350 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

Weight and strength of wood at different heights in the tree.

Specific Weight.

40

Feet from Stump.

Fic. 91.—Variation of weight with height of tree.

Pounds per Cubtc Foot.

TIMBER PHYSICS—-SOUTHERN PINE. 351

Logs from the top can usually be recognized by the larger percentage of sapwood and the smaller proportion and more regular outlines of the bands of summer wood, which are more or less wavy in the butt logs. The variation of weight is well illustrated in the foregoing table, in which the relative values are indicated in

italics. For comparison the figures for strength of long-leaf pine are added.

Both weight and strength vary in the different parts of the same cross section from center to periphery, and though the variations appear frequently irregular in single individuals, a definite law of relation is nevertheless discernible in large averages, and once determined is readily observable in every tree.

A separate inquiry, avoiding the many variables which enter in the mechanical tests, permits the following deduc- tions for the wood of these pines, and especially for long leaf, the data referring to weight, but by inference also to strength:

1. The variation is greatest in the butt log (the heaviest part) and least in the top logs.

2. The variation in weight, hence also in strength, from center to periphery depends on the rate of growth, the heavier, stronger wood being formed during the period of most rapid growth, lighter and weaker wood in old age.

3. Aberrations from the normal growth, due to unusual seasons and other disturbing causes, cloud the uniformity of the law of variation, thus occasionally leading to the formation of heavier, broad-ringed wood in old, and lighter, narrow-ringed wood in young trees.

4, Slow-growing trees (with narrow rings) do not make less heavy, nor heavier, wood than thriftily grown trees (with wide rings) of the same age. (See fig. 92.)

EFFECT OF AGE,

The interior of the butt log, representing the young sap- ling of less than 15 or 20 years of age, and the central portion of all logs containing the pith and 2 to 5 rings adjoining is always light and weak.

The heaviest wood in long-leaf and Cuban pine is formed between the ages of 15 and 120 years, with a specific weight of over 0.60 and a maximum of 0.66 to 0.68 between the ages of 40 and 60 years. The wood formed at the age of about 100 years will have a specific weight of 0.62 to 0.63, which is also the average weight for the entire wood of old trees. The wood formed after this age is lighter, but does not fall below 0.50 up to the two hundredth year; the strength varies in the same ratio.

In the shorter-lived loblolly and short leaf the period for the formation of the heaviest wood is between the ages of 15 and 80, the average weight being then over 0,50, with a maximum of 0.57 at the age of 30 to 40. The average weight for old trees (0.51 to 0.52) lies about the seventy-fifth year, the weight then falling off to about 0.45 at the age of 140, and continuing to decrease to below 0.38 as the trees grow older.

That these statements refer only to the clear portions of each log, and are variably affected at each whorl of knots (every 10 to 30 inches) according to their size, and also by the variable amounts of resin (up to 20 per cent of the dry weight), must be self-evident.

Sapwood is not necessarily weaker than heartwood, only usually the sapwood of the large-sized trees we are now using is represented by the narrow-ringed outer part, which was formed during the old-age period of growth, when naturally

Q SPECIFIC. WEIGHT,

SCALE VERTICAL 19 IN.=1FT. » HORIZONTAL 181 <1IN.

Fia. 92.—Schematic section through stem of long-leaf pine, showing variation of specific weight, with height, diame- ter, and age, at 20 (aba), 60 (ded), 120 (cece), 200 (S/ff) years.

lighter and weaker wood is made; but the wood formed during the more thrifty diameter growth of the first eighty or one hundred years—sapwood at the time, changed into heartwood later—was, even as sapwood, the

heaviest and strongest.

352 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE.

RANGE OF VALUES FOR WEIGHT AND STRENGTH,

Although the range of values for the individual tree of any given species varies from butt to top and from center to periphery by 15 to 25 per cent and occasionally more, the deviation from average values from one individual to another is not usually as great as has been believed; thus of 56 trees of long-leaf pine, 42 trees varied in their average strength by less than 10 per cent from the average of all 56.

The following table of weight (which is a direct and fair indication of strength), representing all the wood of the stem and excluding knots and other defects, gives a more perfect idea of the range of these values:

Range of specific weight with age (kiln-dried wood).

[To avoid fractions the values are multiplied by 100.]

1 Cuban. Tongleat. Loblolly. Short, |

| Number of trees involved -. = 24 96

| Trees over 200 years old ..-. 61 57 Trees 150-200 years old ... 63 59 |

| Trees 100-150 years old .........-------------02 2 eee ener eee eee lene eee eee 60.5

| ‘Trees 50-100 years old .. 61 62 | ‘Trees 25-50 years old -.--- = 55 61

| Trees under 25 years Old.....-.------------ +2 eee ee eee eee eens 51 55 |

Though occasionally some very exceptional trees occur, especially in loblolly and short leaf, the range on the whole is generally within remarkably narrow limits, as appears from the following table:

Range of specific weight in trees of the same age approximately; averages for whole trees.

(Specific gravity multiplied by 100 to avoid fractions. |

| No. of a ,

| Name. oe (enn). | Single trees. ae Senne 4 150-200 ee eee. 62.5 Cuban. ------------- 5 502100). ||) 160) (58 (G0) 50" Cyn mae eee gee Gc Suet 60.9 | Long-leaf pine- 13 100-150 | 59 66 57 62 66 58 59 57 57 66 59 62 57 60.5 Loblolly pine - - 10 125-150 SU 51 453/15 bo ocn Wauseon bom e) coon ee 52.8 12 100-150 | 45 47 53 47 50 51 55 55 53 51 50 53 .. 50.8

|

1 Short-leaf pine

From this table it would appear that single individuals of one species would approximate single individuals of another species so closely that the weight distinction seems to fail, but in large numbers—for instance, carloads of material—the averages above given will prevail.

INFLUENCE OF LOCALITY.

In both the Cuban and long-leaf pine the locality where grown appears to have but little influence on weight or strength, and there is no reason to believe that the long-leaf pine from one State is better than that from any other, since such variations as are claimed can be found on any 40-acre lot of timberinany State. But with loblolly, and still more with short leaf, this seems not to be the case. Being widely distributed over many localities different in soil and climate, the growth of the short-leaf pine seems materially influenced by location. The wood from the Southern coast and Gulf region, and even Arkansas, is generally heavier than the wood from localities farther north. Very light and fine-grained wood is seldom met near the southern limit of the range, while it is almost the rule in Missouri, where forms resembling the Norway pine are by no means rare. The loblolly, occupying both wet and dry soils, varies accordingly.

INFLUENCE OF MOISTURE.

This influence is among the most important; hence all tests have been made with due regard to moisture contents. Seasoned wood is stronger than green and moist wood. The difference between green and seasoned wood may amount; to 50 and even 100 per cent. ‘The influence of seasoning consists in (1) bringing by means of shrinkage about 10 per cent more fibers into the same square inch of cross section than are contained in the wet wood; (2) shrinking the cell wall itself by about 50 per cent of its cross section, and thus hardening it, just as the cow skin becomes thinner and harder by drying.

In the following tables and diagram this is fully illustrated. The values presented in these tables and diagrams are based on large numbers of tests and are fairly safe for ordinary use. They still require further revision, since the relations to density, etc., have had to be neglected in this study.

TIMBER PHYSICS—SOUTHERN PINE. 353

Influence of moisture on strength.

Average of all v and tests. | Relative values. | Per ce nt | (ore Long- Tobe | Short- Bence Cu- | Long: | Lob- | Short-| Aver- | ‘mois | ban. | leat. lolly. leaf. z ae ban. | leaf. | lolly. | leaf. | age. a = — asses ~ — ~ = —— J 33 | 8,450 7, 370 6, 900 | 33 100 100 100 100 Ne ‘ 30)\| 1105050) 1) 82900)|) (S650 Si 70i ll) ees ee 20 118 116 117 118 | it 3ending strength --- | 15 | 11,950 | 10,900 | 10,100 | 9, 230 | Bending strength--.---.--- ) 15 142 142| 138 134 139 || 10 | 15,300 | 14,000 | 12,400 | 11, 000 | 10 181 182 j 168 160 173 \ 33 | 5,000] 4/450] 4,170] 4,160 | 38 100 100 | 100 100 300 . . . | 20 6, B00 5, 450 5, 350 5, 100 tn . . | 20 32 122 | 128 122 26 Crushing end wise - --. 15 | 7 850 | 6,850 | 6 500 | 5,900 || Crushing end wise .--.---- ) 15 157 154 | 156 142 | 152 | 10 | 9,200 | 9,200) 8,650 | 7, 000 || | 10] 184) 206) 206) 168 191 | | 33 | | | | Mean of both bending and { 33 ron a | 1M oe ie | crushing strength --.-.. 15| 149] 148| 147] 138 146 | 10 182 194 187 164 182 | | | | | | |

@33 per cent green, 20 per cent half dry, 15 per cent yard en 10 per cent room dry.

Fi Ge ae aX SSa00 pa eee

BOT WG STE De JE es PER eu

Fic. 93.—Variation of compression strength with moisture.

It will be observed that the strength inereases by about 50 per cent in ordinary good yard seasoning, and that it can be increased by about 30 per cent more by complete seasoning in kiln or house.

Large timbers require several years before even the yard-season condition is attained, but 2-inch and lighter material is generally not used with more than 15 per cent moisture.

WEIGHT AND MOISTURE,

So far the weight of only the kiln-dry wood has been considered. In fresh as well as all yard and air-dried material there is contained a variable amount of water. The amount of water contained in fresh wood of these pines forms more than half the weight of the fresh sapwood, and about one-fifth to one-fourth of the heartwood; in yard-dry wood it falls to about 12 to 18 per cent, while in wood kept in well-ventilated and especially in heated rooms it is about 5 to 10 per cent, varying with size of piece, part of tree, species, temperature, and humidity of air. Heated to 150° F. (65° C.) the wood loses all but about 14 to 2 per cent of its moisture, and if the temperature is raised to 175° F. there remains less than 1 per cent, the wood dried at 212° F. being assumed to be (though it is not really) perfectly dry. Of course large pieces are in practice never left long enough exposed to become truly kiln-dry, though in factories this state is often approached.

As long as the water in the wood amounts to about 30 per cent or more of the dry weight of the wood there is no shrinkage! (the water coming from the cell lumen) and the density or specific gravity changes simply in direct

'In ordinary inne and all large size pintenal the ee parts commonly dry so much sooner than the ane of the stick that checking often occurs, though the moisture per cent of the whole stick is still far above 30.

H. Doe. 181 23

354 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE.

proportion to the loss of water. When the moisture per cent falls below about 30 the water comes from the cell wail, and the loss of water and weight is accompanied by a loss of volume, so that both factors of the fraction

. Ss z weigh Specific gravity — gut volume

are affected and the change in the specific gravity no longer is simply proportional to the loss of water or weight. The loss of weight and volume, however, being unequal and disproportionate, a marked reduction of the specitic eravity takes place, amounting in these pines to about 8 to 10 per cent of the specific weight of the dry wood,

SHRINKAGE,

The behavior of the wood of the southern pines in shrinkage does not differ materially. Generally the heavier wood shrinks the most, and sapwood shrinks about one-fourth more than heartwood of the same specilic weight. Very resinous picces (‘light wood”) shrink much less than other wood. In keeping with these general facts, the shrinkage of the wood of the upper logs is usually 15 to 20 per cent less than that of the butt pieces, and the shrinkage of the heavy heartwood of old trees is greater than that of the lighter peripheral parts of the same, while the shrinkage of the heavy wood of saplings is greatest of all. On the whole, the wood of these pines shrinks about 10 per cent in its volume, 3 to 4 per cent along the radius, and 6 to 7 per cent along the tangent or along the yearly rings.

After leaving the kiln the wood at once begins to absorb moisture and to swell. In an experiment with short pieces of loblolly and shortleaf, representing ordinary flooring or siding sizes, these regained more than half the water and underwent more than half the total swelling during the first 10 days after leaving the kiln (see fig. 94). Even in this less than air-dry wood the changes in weight far excel the changes in volume (sum of radial and tangential swelling), and therefore the specific gravity, even at this low per cent of moisture, was decreased by drying and increased by subsequent absorption of moisture. Immersion and, still more readily, boiling, cause the wood to return to its original size, but temperatures even above the boiling point do not prevent the wood from

“working,” or shrinking, and swelling.

PERCENT OF MOISTURE AWNO FER MILLE OF SHRINKAGE AND SWELLING

AIR ORY KN ORY 0 20 aw Fic. 94.—Loss of water in kiln drying and reabsorption in air, shrinking, and swelling.

In fig. 94 are represented the results of experiments on the rate of loss of water in the dry kiln and the reab- sorption of water in the air. The wood used was of loblolly and shortleaf pine kept on a shelf in an ordinary room before and after kiln-drying. The measurements were made with caliper.

EFFECT OF KILN-DRYING.

Although kiln-drying has become quite universal, opinions are still divided as to its effects upon the strength of the material and other qualities. Many objections and claims as to physical and chemical changes produced by the treatment remain unsubstantiated. The method most widely used and most severely criticised is that of the “plower” kiln, where hot air (180° F.) is forced into the drying room by means of powerful fans. Besides the

TIMBER PHYSICS—SOUTHERN PINE. 355

many, in part, unreasonable and contradictory claims about closing or opening of pores, chemical or physical influence on the sap and its contents, albumen, gum, resin, sugar, etc., substances whose very existence in many cases is problematical or doubtful, the general claims of increased checking and warping, ‘casehardening,” “honeycombing,” etc., as well as reduction of strength, are still prevalent even among the very manufacturers themselves. The manner and progress of the kiln-drying may render this otherwise useful method of seasoning injurious. Rapid drying of the heavier hardwoods of complicated structure, especially in large sizes and from the green state, is apt to produce inordinate checking and thus weakening of the material. For Southern pine, however, it is entirely practicable to carry on the process without any injury, as is evidenced by the following experiment, in which wood of Cuban pine in small dimensions (4 by 4) was seasoned in warm air (about 100° F.) and parts of the same scantling were dried at temperatures varying from 150° at the entrance end to 190° F. at the exit>

Bending strength. | [ peas aes __| Compression

Absolute. |Atelasticlimit.| St™ensth.

Mean of material not kiln-dried (reduced to 15 per | Lbs. per aq. in. | Lbs. per sq.in. | Lbs. per sq.in. Cent/ob moisture): =~. oc = ss ancseeaeeeoe eee tee 12, 200 9,070 7, 630 Average of kiln-dry material . = 11, 500 9, 180 8, 550 |

Well-constructed “blower kilns,” where the hot air is blown in at one end and escapes at the other (this latter always the entrance end for the material), are giving satisfaction. The best kiln, however, seems to be one in which ample piping in the kiln itself insures sufficiently high (up to 180° F.), uniform temperature in all parts of the kiln, and where the circulation, promoted by a suction fan, is moderate and under perfect control. In such kilns even timbers of large size can be dried satisfactorily with a temperature not over 150° F.

EFFECT OF HIGH-TEMPERATURE AND HIGH-PRESSURE PROCESSES.

Forsome time a process employing high temperature under high pressure (temperature over 300° F., pressure 150 pounds) has been discussed and applied, claiming as a result of the treatment (1) increase in strength; (2) increase in durability; (3) absence of shrinkage.

The result of a series of experiments in which a number of scantlings of longleaf pine, one-half treated, the other untreated, is as follows:

Bending | Cammmerstn | strength. | strength.

Lbs. per sq.in.| Lbs. per sq. in. Treated seccosee sere camer ss cate nb se ae eee ones eee cea tneeeeeee 7,770 5, 600

hie Wiley et) com ond Gonna coo Deep BOS OHDOcSSeR SEs SSC asecaoooeersesesc 12, 340 7, 400

The same difference in favor of the untreated material obtained in every single case. The chemical analyses performed on wood lying side by side along the same radius, being of the same annual rings and same position in tree, gave the following:

Per cent of rosin and phenols calculated to dry weight of wood.

Tree No. 476. Average of both.

‘Tree No. 475. ‘|

Treated. | Untreated. Treated. | Untreated. Treated. | Untreated.

a

{c appears that the protective rosin is rather decreased by the treatment, and the antiseptic phenols not increased in an adequate amount to be of value since it requires at least 20 times as much heavy oil in wood impregnation to be effective. It is, however, possible that the change of color due to the process may be accom-

- plished and be produced by the formation of empyreumatic bodies (allied to the humus substances) which may act as preservative against the attacks of fungi.

The claim that the shrinkage of the wood is favorably influenced by the process was not sustained by a series of experiments with oak and pine, which showed that the treated wood absorbs water from air or in the tub, swells and shrinks in the same manner and to about the same extent as the untreated wood.

EFFECT OF IMMERSION ON THE STRENGTH OF WOOD.

The notion frequently expressed is that “soaking wood by floating, rafting, ete., reduces its tendency to decay and shrinkage, but injures its strength.” The same was claimed for boiling or steaming preparatory to bending. The last position was disproved by Peter Barlow in the first quarter of this century. The following figures (results of an experiment involving several hundred separate tests) disprove the former assertion.

356 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

The soaked wood was kept immersed six months, each piece having its check pieces from the same scantling, which were not subject to the same process, but were tested—one green and one dry. All soaked pieces were seasoned in dry kiln before testing. All values were reduced to 15 per cent moisture.

Compression strength.

| Bending strength.

Lobolly pine.

| Lbs. per sq. in. | Lbs. per sq. in. Soaked 6 months, and then dried ......--........-...20.---seesee--- | 10, 820 | Not soaked (mean of green and dry tests) -....---.-.-----+-+------- | 10, 570 | 7, 060

EEFECT OF ‘‘ BOXING” OR ‘‘ BLEEDING.”

“Bleeding” pine trees for their resin—to which only the longleaf and Cuban pine are subjected—has generally been regarded as injurious to the timber. Both durability and strength, it was claimed, were impaired by this process, and in the specifications of many architects and large consumers, such as railway companies, ‘‘bled” timber was excluded. Since the utilization of resin is one of the leading industries of the South, and since the process affects several millions of dollars’ worth of timber every year, a special investigation involving mechanical tests, physical and chemical analyses of the wood of bled and unbled trees from the same locality were carried out by this division. The results prove concusively (1) that bled timber is as strong as unbled if of the same weight; (2) that the weight and shrinkage of the wood is not affected by bleeding; (3) that bled trees contain practically neither more nor less resin than unbled trees, the loss of resin referring only to the sapwood, and, therefore, the durability is not affected by the bleeding process.

The following table shows the remarkable numerical similarity between the average results for three groups of trees, the higher values of the unbled material being readily explained by the difference in weight:

— a = = ——— =

|

| test pieces. | aie Ss

|

| Lbs. per sq. in. | Lbs. per sq. in. |

The amount of resin in the wood varies greatly, and trees growing side by side differ within very wide limits. Sapwood contains but little resin (1 to 4 per cent), even in those trees in which the heartwood contains abundance. In the heartwood the resin forms from 5 to 24 per cent of the dry weight (of which about one-sixth is turpentine and can not be removed by bleeding), so that its quantity remains unaffected by the process. Bled timber, then, is as useful for all purposes as unbled.

To give an idea how necessary it is that a large series of material be tested before making statements of the strength of wood of any species, we reproduce one of the many tables contained in Bulletin 8, which at the same time exhibits the variation of strength throughout the tree and from tree to tree.

357

SOUTHERN PINE,

TIMBER PHYSICS

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NIq AVATONOT 10 SaaUT, INANAAAI 10 HLONAYLS AALLVUVIN

U. S. DEPARTMENT OF AGRICULTURE.

INVESTIGATIONS

FORESTRY

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TIMBER PHYSICS—BEAMS AND COLUMNS. 309

SIZE OF TEST MATERIAL,

The long-standing idea of engineers and other consumers to have wood tested more nearly in the sizes used in ordinary practice led to the adoption of test sizes, generally varying from 3 by 3 inches to 4 by 4inches. Besides this, special inquiries with different kinds of timber into the relation of large and small tests were instituted to ascertain the correctness of the general dogma which claimed that tests on small pieces could not be utilized, since such pieces for their very size gave higher values of strength. This investigation involved full-size columns as well as beams, and was continued throughout the entire period of the timber-physics work. It led to a number of the most interesting and highly valuable results, as will appear from the following statements:

Selected tests of columns and compression pieces from the same trees compared.

In these columns (nearly one-tenth of all longleaf pine columns tested) the strength was so nearly the same as that of the short pieces that it appears as if flexure had but little to do with the failure, the small differences being amply accounted for by a larger number of defects in the columns. Should this prove true in general for wooden columns as ordinarily designed, the problem would become simply a study of the influence of defects and of proper inspection.

The nature of the failures would also point in this direction:

Of 86 columns 32 failed normally, i. e., in simple compression; 22 were crushed near the end; 14 failed at knots, and 19 by shearing, the rupture usually beginning at or near the ends; a small knot proved sufficient to cause a large column, 20 times as long as its diameter, to fail at 14 inches from the end.

The deflection in the average for all columns (12 to 20 feet long) was only about 1 inch for the maximum load, when, to be sure, destruction had progressed for some time; at the elastic limit the deflection was only about one-half as much. These results would seem to warrant the statement that for pine columns at least, in which the ratio of height to least diameter does not exceed 1 in 20, none of the accepted column formule are applicable, the nature of the failure being mostly in simple compression, and depending more on specific defects than on the design of the column.

STRENGTH OF LARGE BEAMS AND COLUMNS.

Owing to the fact that much wood testing has been done on small, select, and perfectly seasoned pieces, usually from butt logs, the values thus obtained seemed to differ very markedly from the results on large timbers usually very imperfectly seasoned, and it was claimed that tests on small sizes always furnished too high values, just as if the differences were due to sizes alone.

While, to be sure, a small piece may be so selected that defects are excluded, the grain straight and in the most favorable position with regard to the load, the assumption of the difference in strength of small pieces from that of large-sized sticks has never been made good experimentally.

Since if appears desirable to compare the results from large beams and columns not only with the average data obtained from the general test scries on small 4 by 4 material, but also with the average strength of small pieces cut from the same beams and columns, a special inquiry into the legitimacy of such a comparison was made. This study involved over 100 separate tests, and proved the very important fact that uninjured parts of broken beams and columns do not suffer in the test. The large-sized beams varied from 4 by 4 to 8 by 16 inches.

Tests of large and small beams—Bending strength.

Large beams.

“ ; z

Seal vei: Seams from | Steal! beams gener: ate i

test series. Total. which large beams.

small beams | were cut.

Ton pleai-e---sece<2 so s= se cms 11, 300 11, 500 9, 800 10, 100

To blollveeseeen eee z 10, 000 10, 800 10, 300 10, 000

Shortleaf 9, 300 9, 200 8, 700 8, 700

From the preceding table it would appear that large timbers, when symmetrically cut (i. e., with the center of the log as center of the beam), develop as beams practically the same strength as the average of the small pieces that may be cut from them, and sometimes even higher values; the explanation being that cut in this manner the extreme fibers which are tested in a beam come to lie in that part of the tree which, as a rule, contains the strongest timber.

360 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

Results discordant from these may be explained by differences in the degree of seasoning of the outer layers and also by the fact that especially in the northern pineries timbers are often cut from the top logs, which are weaker and more defective.

Test of large and small columns—Compression strength.

Regular series | Columns (sim- | Small pieces

fromsametrees| ple compres- cut from as the columns. sion). columns. Number of tests involved ............-..---------- 949 95 97 —_ —)- ———-= —— — | Lbs. per sq. in.| Lbs. per sq. in. | Lbs. per aq. in. | Ton Pleaivccs ese esacasieeeeaweeeneete ne -cecten inne ete 6, 600 5, 300 7,100 Loblolly . 6, 800 4,700 | 6, 300 Shortleaf 5, 900 4,100 6, 200 Gubanteceos ston nceeaeneee cccaneccenecceeeectcces 7,400 5, 000 8, 700

The square columns were mostly & by 8 inches, some 10 by 10 inches, a few of larger and also some of smaller dimen- sions. Theratioof length to width varied from 12 to 27, about one-half being under and the other halfover 18 tol. The compression pieces of the regular series, and those cut from the broken columns, were in general about 4 by 4 by 6 inches.

It wili appear from this statement of average results that columns develop only from 62 per cent (in Cuban) to 78 per cent (longleaf) of the compression strength of ordinary short pieces. ‘The explanation may be due to several reasons, natural and mechanical. In a column, unlike a beam, all the fibers are under great strain; hence all the defects, which are by necessity found in every column, influence the results; the flexure of a column under strain is an element of weakness, to which the short compression piece is not subject. In addition the difficulty of determin- ing the average moisture condition of the large timber throughout the cross section and that of the small pieces cut from them afterwards would render this method for columns less satisfactory; a larger number of tests will still be required to establish comparable average conditions in the two kinds of tests. It would, therefore, be unsafe to generalize too hastily from these average figures, at least as to the numerical difference, for there are remarkable individual exceptions. Not only do individual columns show differences in strength 50 per cent and more lower than the compression pieces from the same log, but sometimes they show practically the same or even a higher value of strength, as will appear from the following selected cases, in which the data for the columns are placed in com- parison with those obtained on compression pieces from the same tree.

ADDITIONAL SERIES ON BEAMS AND COLUMNS,

Aseries more extended as regards beams, involving 68 large and 777 small beams, besides over 1,000 compression tests on the same material on which the beam tests were made, and tests on 6 large columns, has fully confirmed the indications of the previous experiments.

TESTS ON COLUMNS.

The colunms were 12 by 12 inches and 8 by 12 inches in cross section, with a length of 152 to 168 inches. From these were cut, as near as possible from the place of failure, two blocks 24 inches long, and these blocks were tested on the same large testing machine (described in Bulletin 6), so that inaceuracies of machinery do not enter into consideration. The results, tabulated as follows, prove conelusively the statement made upon the former more extensive series (see Circular 12), that wooden columns in which the diameter and length are to each other as 1 to 18 or less behave like short blocks and fail in simple compression. The four columns of long-leaf pine exhibit practically the same strength as the short blocks—i. e., within 10 per cent—which, as has been shown above, is within the limits of maximum uniformity.

Strength of large columns and short (24-inch) blocks cut from these columns.

Compression . _| strength in pounds rT : Dimensions | Moisture | Modulus of ar equare dele Kind of wood. of columns of wood elasticity i (inches). (per cent). (pounds). | Short Columns. | Blocks! Shortleaf pine. - i44 | 12 | 12 14.2 2, 274, 000 4, 840 | 6, 090 132 | 12 | 12 12.9 | 1, 740, 000 4,840 | 5, 660 168/12] 8| 30.9] 1,628,000] 2,940 | 2,950 | 168 | 12 8 32.3 1, 570, 000 3,170 38, 530 156 | 12 8 40.8 | 1, 764, 000 3, 030 3, 310 156 | 12 8 29.7 1, 776, 000 | 3, 710 3, 780

BEAM TESTS.

The experiments, of which the following tables contain the principal results, were performed on beams generally 8 by 12 by 192 inches. After breaking the large beam 12 small beams were cut from the uninjured portion of the large beam! in such a way that the entire cross section of the large piece was represented by two sets of 6 small beams each. Besides these tests on small beams, the compression strength of part of the material was tested on small blocks, part of which was sawed and part split from portions of the large beam. (See diagram at head of

'The legitimacy of using such material for such purpose has been fully established by a long series of experi- ments. (See Circular 12, Division of Forestry, p. 11.)

TIMBER PHYSICS—SIZE OF TEST MATERIAL. 361

table.) To avoid any complications due to differences or changes in moisture, the fests on large and small beams were performed the same day.

Strength of large beams and of small beams, and of compression pieces cut from them.

(Usually 12 small beams cut from the uninjured part of each large beam.]

SAWED. SPLIT Ae] eel ado opol leva 7 oo A Compression, | | Strength Average | Moisture. | endwise strength. Ki his Number strength | Kind of wood. enritl| of large ofamall : © *| beams. Keane Large Small Sawed Split eams. | peams. | beams. | pieces. pieces. Lbs. per | Lbs. per | Lbs. per | Lbs. per 8q- in. sq. in. | Per cent.| Per cent.| sq.in. sq. tn. ODKy ieee ee emei eee | L 7,400 8, 560 69.5 68.5 3, 960 4,120 2 5, 880 8, 660 70.3 69. 0 4, 340 4,700 3 6,570 6, 220 75.3 75.2 3, 080 3, 190 4 8, 640 8, 800 66.6 67.6 4, 0S0 4, 460 5 8, 150 7,710 64.8 65.8 3, 680 3, 750 6 7,450 6, 910 63.0 66.6 3, 330 3, 330 | 8 6, 870 6,890 | 67.4 70.5 3,470 3, 190 Shortleaf pine......-...-- 9 8, 300 7, 950 48.1 57.7 4, 030 4, 160 10 7,440 7, 250 42.1 56.3 3, 840 3, 850 | 11 5,110 6, 760 38.9 33.3 3, 870 3, 630 | 12 7,360 6, 930 35. 2 33.5 3, 890 3, 850 13 7, 320 7, 300 37.4 40.6 4, 090 3, 800 White pine.............-. | 14 3,110 3, 560 84.9 83.6 2, 440 2,500 | 15 | 4, 280 4, 340 43.8 41.2 2,710 2,840 | 16 | 3,770 4,590 50.7 50.5 2, 660 2,760 | | 17 | 3, 460 3,590 60.0 48.6 2,410 2,570 | 18 3, 990 3, 640 42.8 43.0 2, 800 2, 620 19 4, 040 4,400 62.4 60.4 2,760 2,780 20 4,410 4, 180 53. 6 51.8 2, 680 2, 700 21 } 4,900 4, 320 50.1 51.0 3, 010 2, 900 22 | 3, 860 4, 320 50, 2 60.8 2,500 2,430 22 4, 660 4, 890 | 52.0 58.2 2, 850 2,880 | 24 3, 960 4, 440 76.3 71.5 2,520 2,710 25 3, 920 4,410 53.6 60.5 2, 84C 2, 730 Shortleaf pine...--.--.--. | 26 4, 560 6, 290 31:2 30.5 3, 660 3, 850 | 27 4, 390 5, 610 33. 9 36,0 2, 830 3,110 28 6, 670 6, 830 28.6 28.9 3, 540 3, 590 29 7,410 7, 630 28.6 29.0 4, 450 4, 250 30 6, 600 7, 160 28.3 28.9 4, 200 4,190 3L 5, 750 6, 000 34.3 35.5 3, 630 3, 530 32 6, 210 7,500 26.4 27.2 3, 940 4,050 | 33 7, 450 8, 390 29.5 30.1 4, 350 4,220 | 34 7, 000 7, 800 28.4 29.5 4,070 4,120 35 6, 030 6,740. 28.8 29.4 3, 810 3, 640 36 6, 520 6, 890 31.6 31.6 4,320 4, 370 37 7, 030 7, 890 29. 2 29.9 4,380 4,920 38 7,710 8, 510 26.2 25.4 4, 500 4,610 39 8,090 | 8, 210 32.5 31.9 4,550 4, 670 40 7, 680 7,980 31.1 32.3 4, 290 | 4, 380 41 7, 330 8, 230 31.7 31.5 4, 680 | 4, 820 Longleaf pine.-..-.-.-.---- 42 7,290 8, 740 30.9 31.2 4,950 5,120 43 8, 850 9,720 28.1 | 28.9 5, 300 5, 440 44 8, 040 8, 870 26.3 | 26.9 4,730 5, 070 45 8, 090 8, 850 25.8 | 25.4 5, 000 5, 050 46 | 7, 620 7, 670 32.6 33.9 4,730 | 4, 830 | 47 | 6,710 7,610 33.0 | 33, 4 4,200 | 4, 520 48 8, 480 8, 300 29.3 29.3 4, 870 | 4, 890 ; 2 49 5, 630 6, 250 34.5 33.7 3, 600 3, 630 iWiahite;pine== =. -eees— see 50 4, 900 5, 020 87.2 | 75.7 2,970 | 3,200 | 51 5, 300 5, 210 71.4 | 69.6 | 3, 330 3,240 52 4, 810 4, 470 77.2 64.7 2, 940 | 3,100 | 53 3, 610 3, 610 54.5 58. 2 2,400 2,550 | " 54 4,440 4,720 97.6 94.9 2,710 2, 900 Shortleaf pine.--........-- | 55 6, 400 7,610 27.0 27.2 4, 340 4,500 | 56 6, 690 6, 880 28. 4 | 26.6 4, 050 4,210 | 7 6, 670 6, 990 27.0 | 26.4 4,100 4,340 ae ~ 58 7, 310 7,490 28.5 | 26.8 4, 100 4, 030 WLS OT ercoocnecesacs 101 5, 070 7, 200 15.4 16, 2 5, 410 5, 720 102 6, 340 6, 890 11.0 ib Ae 4,920 5, 520 103 7, 070 8, 750 12. 2 10.5 5, 140 5, 760 104 4, 900 6, 680 12.1 8.2 4, 360 4, 700 105 6, 640 6, 890 10. 6 11.2 5, 450 5,310 106 6, 180 7, 650 11.6 11.3 5, 190 5, 420 107 6, 080 6, 090 11.5 11.5| 4,810 5,170 108 5,510 | 5, 810 11.1 10.7 5, 100 4,710 109 6, 930 7, 300 11.4 10.5 5, 330 5, 080 110 5, 930 6, 010 12,1 | 11.6 4, 600 4, 670 | 111 4,010 5, 040 13.0 13.0 4, 270 4,390

362 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

OBSERVATIONS AND DEDUCTIONS.

(a) The difference between the values for the large beam and the average for the small beams is not at all constant, either in character or quantity; the large beam may be stronger (20 per cent of the cases) or practically as strong—i. e., within 10 per cent (57 per cent of the cases)—or it may be weaker, and vary often considerably from the average (23 per cent of the cases).

Of 696 tests on small beams 235 furnished results smaller than that of the large beam. Again, out of 396 small beams fully 40 per cent were weaker that the large beam, while of another series of 300 only 24 per cent gave lower values.

(b) There are in every case some small beams which far excel in strength the large beam; even in such cases, where the average strength of the small beams is practically the same as that of the large beam, some small beams show values 25 to 30 per. cent greater than the large beam.

(ce) In only 6 per cent of the eases each of the small pieces gave a higher result tham was obtained from the large beam, but in these cases the latter was evidently defective.

(d) In all beams the differences observed between the several small beams themselves are far greater than that between the average value of the small beams and the value of the large beam from which they are cut.

From these observations, which are fully in accord with the observations on the numerous tests of the large general series, it would appear that—

(1) Size alone can not account for the differences observed; and, therefore, also that a small beam is not propor- tionately stronger because it is smaller, for it may be either stronger or weaker; but that if it is stronger, the cause of this lies in the fact that the larger beam contains weak as well as strong wood, besides other defects, which may or may uot appear in the small stick.

(2) Generally, but not always, a large timber gives values nearer the average, since it contains, naturally, a larger quantity as well as a greater variety of the wood of the tree; and, therefore, also—

(3) Small beams, for the very reason of their smallness, containing, as they do, both a smaller quantity and variety of the material, give results which vary more from the average than results from large beams, and, there- fore, can be utilized only if a sufficient number be tested; but it also appears that—

(4) To obtain an average value, even a very moderate number of smaller pieces, if they fairly represent the wood of the entire stem, give fully as reliable data as values derived from a large beam.

(5) Average values derived from a large series of tests on small but representative material may be used in practice with perfect safety, and these averages are not likely to be modified by tests on large material.

It might be added that both the practicability and need of establishing a coefficient or ratio between results from tests on large and small beams or columns falls away. ‘To deserve any confidence at all, only a large series of tests on either large or small beams would satisfy the requirement of estabiishing standard values, while a series of small pieces has the preference, not only on account of greater cheapness and convenience in establishing the values, but still more for the reason that only by the use of small, properly chosen material is it possible to obtain a sufficiently complete representation of the entire log.

Before these results, part of which were published by installments, had all been computed and arranged, the results of the work made it possible to publish, for the first time in the English language, a brief exposition of the technical properties of wood in general, which appeared as Bulletin 10 of the Division. This little booklet was copied verbatim several times by different tech- nical journals of this country, was embodied in toto in one of the best works on the materials of engineering, and was even translated into French by one of the foremost publishers of France, besides being used itself as a text-book by several of our largest colleges. In addition to the discussions of the several technical properties of wood, this booklet contains the first attempt in the English language at a key by which our common woods may be safely recognized from their structure alone. The key and some of the tables in this bulletin have been reproduced in an earlier part of this report. By this time, when the work was interrupted by superior orders, there were brought together the strength values for the wood of 52 species, of which 26 were represented by more than 200 tests each (the longleaf pine by over 6,000), 17 of them by over 400 tests per species, and seven by over 1,000 tests. These results were published in fall in Cireular No, 15 of the Division, from which the following extract is here repeated:

SuMMARY OF MECHANICAL TESTS ON THIRTY-TWO SPECIES OF AMERICAN Woops, GENERAL REMARKS.

The chief points of superiority of the data obtained in these investigations lie in, (1) Correct identification of the material, it being collected by a competent botanist in the woods; (2) selection of representative trees with record of age, development, place and soil where grown, etc.; (3) determination of moisture conditions and specific gravity and record of position in the tree of the test pieces; (4) large number of trees and of test pieces from each tree; (5) employment of large and small-sized test material from the same trees; (6) uniformity of method for an unusally large number of tests.

The entire work of the mechanical test series, carried on through nearly six years intermittently as funds

TIMBER PHYSICS—STRENGTH OF SPECIES.

363

were available, comprises so far 32 species with 308 test trees, furnishing over 6,000 test pieces, supplying material for 45,336 tests in all, of which 16,767 were moisture and specific gravity determinations on the test material.

In addition to the material for mechanical tests, about 20,000 pieces have been collected from 780 trees (including the 308 trees used in mechanical tests) for physical examination to determine structure, character of growth, specific gravity of green and dry wood, shrinkage, moisture conditions, and other properties and behavior.

In addition to the regular series of tests, the results of which are recorded in the subjoined tables, special series, to determine certain questions were planned and carried out in part or to finish, adding 4,325 tests to the above number.

Account of test material.

Name of species.

Num- ber of

trees. |

10

cocoa Na TF BO NY

Longleaf pine (Pinus palustris.)

Cuban pine... (Pinus heterophylla.) Shortleaf pine... - (Pinus echinata. Loblolly pine (Pinus tzeda.) White pin wanes ee oe eee (Pinus strobus.) Red pine (Pinus resinosa.) Spruce pine (Pinus glabra.) IBAIUICYDrenS an --— cence ee (Taxodium distichum.) White cedar... - (Chamecy paris t Douglas spruce.------.------- (Pseudotsuga taxifolia.) White oak (Quereus alba.) Overcup oak (Quereus lyrata.) | Post oak (Quercus minor.) Cow oak (Quercus michany Red oak (Quercus rubra.) Mexanionlkeaseeeasenaasemecies (Quercus texana.) Wellow Oake- ce eee none (Quercus velutina.) Water oak (Quercus nigra.) Willow oak .... (Quercus phello: Spanish oak (Quercus digitata.) Shagbark hickory (Hicoria ovata.) Mockernut hickory (Hicoria alba.) Water hickory...-.-..--..-.. (Hicoria aquatica.) Bitternut hickory. --.-------- (Hicoria minima.) Nutmeg hickory (Hicoria myristiceformis.) Pecan hickory (Hicoria pecan.) Eieruk hickory ---......... se (Hicoria glabra.) White elm (Ulmus americana.) Cedar elm (Ulmus crassifolia.) White ash (Fraxinus americana. Greeniasheenee eee eee (Fraxinus lanceolata.) Sweet gum (Liquidambar styraciflua.)

ro

w 68

Number |

of me- chanical tests.

6,478

2,113 1, 831 3, 335

540

Average specific gravity Localities and number of trees from each. of dry wood, 0.61 | Alabama, coast plain (22) a; uplands (6); hill district (6); Georgia, undulat- ing uplands (6); South Carolina, coast plain (7); Mississippi, low coast plain (2); Louisiana, low coast plain, gravelly soil (7); sandy loam (6); ‘Texas, low coast plain (6). .63 | Alabama, coast plain (6); Georgia, uplands (1); South Carolina, coast (5). 51 | Alabama, uplands (4); Missouri, low hilly uplands (6); Arkansas, low hilly uplands (6); ‘Texas, uplands (6). -53 | Alabama, mountainous plateau (8); low coast plain (6); Arkansas, level flood plain (5); Georgia, level coast plain (6); South Carolina, low coast plain (7). -38 | Wisconsin, clay uplands (5); sandy soils (4); sandy loam (5); Michigan, level drift lands (3). -50 | Wisconsin, drift (5); Michigan (3). -44 | Alabama, low coast plain. -46 | South Carolina, pine barren (6); river bottom (4); Louisiana, coast plain, border of lake (4); Mississippi, Yazoo bottom (3); upland (3). .37 | Mississippi, low plain. -51 | (From lumber yard.) -80 | Alabama, ridges of Tennessee Valley (5); Mississippi, low plain (7). .74 | Mississippi, low plain (7); Arkansas, Mississippi bottoms (3). .80 | Alabama, Tennessee Valley (5); Arkansas, Mississippi bottom (3). -74 | Alabama, Tennessee Valley (4); Arkansas, Mississippi bottoms (3); Missis- sippi, low plain (4). ; 73 | Alabama, Tennessee Valley (5); Arkansas, Mississippi bottom (2).b / .73 | Arkansas, Mississippi bottom. 72 | Alabama, Tennessee Valley (5). -73 | Mississippi, low plain (4). 72 | Alabama, Tennessee Valley (5); Arkansas, Mississippi bottom (3); Missis- sippi, low plain (4). .73 | Alabama, Tennessee Valley (5); Arkansas, Mississippi bottom (3); Missis- sippi, low plain (3). -81 | Mississippi, alluvial plain (3); limestone (3). -85 | Mississippi, low plain. 73 | Do. 77 | Do. 78| Do. -78 Do. -89 | Do. -54 | Mississippi, bottom. 74 Arkansas, bottom. 62 | Mississippi, bottom. . 62 Do. 59 Arkansas, bottom (3); Mississippi, low plain (4).

a Sixteen of these were bled trees to study the effects of boxing.

b These two should probably be classed as Southern red oak. ‘They were collected before the distinction was finally decided upon.

Norre.—The values for specific gravity here moisture below 15 per cent; the moisture effect

iven refer to ‘dry’ wood of test material—i. e., wood containing variable amounts of as therefore not been taken into account, but more careful experiments indicate that its

nfluence on specific gravity at such low per cent is so small that it may be neglected for practical purposes.

on these (which have been published more in detail in Circular No. 12) may be taken as authoritative.

As will be observed, some species, notably the Southern pines, have been more fully investigated, and the results

With those

species of which only a small number of trees have been tested this can be claimed only within limits and in proportion to the number of tests.

364 FORESTRY INVESTIGATIONS U. 8S. DEPARTMENT OF AGRICULTURE. The great variation in strength which is noticeable in timber of the same species makes it necessary to accept with caution the result of a limited number of tests as representing the average for the species, for it may have happened that only all superior or all inferior material has been used in the tests. Hence we would not be entitled to conclude, for instance, that pignut hickory is 14 per cent stronger than shagbark, as it would appear in the table, for the 30 test pieces of the former may easily have been superior material. Only a detailed examination of the test pieces or a fuller series of tests would enlighten us as to the comparative value of the results.

The following data, therefore, are not fo be considered as in any sense final values for the species, except where the number of trees and tests is very large:

Results of tests in compression endwise.

{Pounds per square inch. ]

| anes E f | Proportion Proportion Average Average 4 4 No Snecies Number} Highest Lowest | highest 10 lowestno Average | Cee Oe oboe Sr St of tests. | single test. single test.| per cent percent | of alltests.| W??0™ ab UD eS. | Of. tests: oritoatee per cent of percent of | average. average. Reduced to 15 per cent moisture | | | | Per cent. | Per cent. Pal Lone leafipine!.~.c.- st... aneis<= 1, 230 11, 900 3, 400 8, 600 5, 700 6, 900 53 90 2 | Cuban pine --- 410 | 10, 600 | 2, 800 9,500 6,500 7, 900 61 93 3. Shortleaf pine 330 8,500 | 4,500 7, 600 4,800 5, 900 47 | 90 4 | Loblolly pine...........-.-.------+----- | 660 11, 200 3, 900 8, 700 5, 400 | 6, 500 49 84 | | | | Reduced to 12 per cent moisture. | | | Bi EWIDACG DIN Glstc seo nie on eo ate ste =raicte m= == 130 | 8,500 3, 200 6, 800 4, 000 5, 400 49 93 6 | Red pine....-... Bee aCBaSAnE DS 100 8, 200 4, 300 8, 100 4, 900 6, 700 54 96 7 | Spruce pine. 170 10, 000 4, 400 8, 800 5, 600 7, 300 66 95 8 | Bald cypress 655 | 9, 900 | 2, 900 8, 500 4, 200 6, 000 31 res 9 | White cedar. .--..-. 87 | 3, 200 6, 000 4, 400 5, 200 79 99 10 | Douglas spruce a 41 4,100 8, 100 4, 200 5, 700 28 5 11 | White oak .-... 218 5, 100 11, 300 6, 300 &, 500 40 81 12) Overcup oak 216 | 3, 700 8, 600 6, 000 7,300 70 95 13 | Post oak .. 49 | 5, 900 8, 100 6, 000 7, 100 58 100 14. Cow oak 256 | 4, 600 9, 800 5, 600 | 7, 400 51 89 15 Red oak 57 9, 700 5, 400 9, 200 5,500 | 7, 200 36 o4 16))|Vexan’ Oakiss en secce ne sees e encom 17 11, 300 | 5, B00 9, 800 6, 900 8, 100 62 | 98 17 | Yellow oak.. 40 8, 600 5, 500 | 8, 300 5, 800 7, 300 58 | 100 18 Water oak... 31 | 9, 200 6, 200 | 9, 000 6, 300 7, 800 75 | 100 19 Willow oak - 153 11, 000 4, 200 8, 700 5, 500 7, 200 51 | 88 20 | Spanish oak 251 | 10, 600 3, 700 ~ 9,500 5, 100 7, 700 61 | 94 21 | Shagbark hickory....--.--- 137 | 13, 700 5, 800 10, 900 | 7, 500 | 9,500 79 | 97 22) Mockernut hickor 75 12, 200 6,200 | 11, 600 | 8, 000 10, 100 65 | 99 23 Water hickory-.- 14 | 10, 000 6,700 9, 600 7, 000 8, 400 71 | 100 24 -Bitternut hickory 25 11, 500 7,300 11, 200 | 7, 800 9, 600 60 | 100 25 | Nutmeg hickory. 72 12, 300 6, 400 | 11, 000 | 7,100 | 8, 800 79 | 97 26 Peean hickory 37 10, 500 5, 800 10,400 | 7, 300 | 9, 100 51 95 27 -Pignut hicko: 30 13, 000 8, 700 | 12,700 | 8, 900 10, 900 72 | 100 28 White elm. 18 8, 800 4, 900 8, 800 | 5, 000 | 6, 500 28 | 88 29 Cedar elm. 44 10, 600 6, 200 10, 100 6,500 8, 000 66 95 30 White ash. 87 9, 600 5, 000 8, 700 5,700 | 7, 200 48 96 31 Green ash. 10 9, 800 6, 600 9, 800 6, 600 8, 000 29 | 100 32) | SWeet) SUM: seseeeeces cen eee = a= 118 8, 900 4, 600 8,500 | 5, 600 | 7,100 60 | 97 | |

parts of the same tree, and values differing 100 to 200 per cent within the same species.

a Actual tests on ‘‘dry’’ material not reduced for moisture.

The variation in strength in wood of the virgin forest, as will be seen from the tables, is in some species so great that by proper inspection and selection values differing by 25 to 50 per cent may be obtained from different

their definite recognizable causes, to find and formulate which is the final aim of these investigations. The tests are intentionally not made on selected material (except to discard absolutely defective pieces), but on

These differences have all

material as it comes from the trees, so as to arrive at an average statement for the species, when a sufficient number of trees has been tested. How urgent is the need for data of inspection as above indicated will appear from the wide range of results recorded.

To enable any engineer to use the data here given with due caution and judgment, not only the ranges of valnes and the average of all values obtained, but also the proportion of tests which came near the average values, have been stated, as well as the average results of the highest and lowest values of 10 per cent of the tests. With this information and a statement of the actual number of tests involved, the comparative merit of the stated values can be judged. With a large number of tests, to be sure, it is more likely that an average value of the species has been found. The actual test results have been rounded off to even hundreds in the tables.

FACTORS OF SAFETY.

With such lowest standard values, also lowest factors of safety could be employed. As to factors of safety, it may be proper to state that the final aims of the present investigations may be summed up in one proposition, namely, to establish rational factors of safety. It will be admitted by all engineers that the factors of safety as used at present can hardly be claimed to be more than guesswork. ‘There is not an engineer who could give account as to the basis upon which numerically the factors of safety for wood have been established as ‘‘8 for steady stress; 10 for varying stress; 15 for shocks” (see Merriman’s Testhbook on the Mechanics of Materials); or as 4 to 5 for “dead” load and 5 to 10 for “live” load (see Rankine’s Handbook of Civil Engineering).

TIMBER PHYSICS—FACTOR OF SAFETY. 365

The directions for using these indeterminate factors of safety given in the text-books would imply that the student or engineer is, after all, to rely on his judgment as to the modification of the factor, i. e., he is to add to this general guess his own particular guess. The factor of safety is in the main an expression of ignorance or lack of confidence in the reliability of values of strength, upon which the designing proceeds, together with an absence of data upon which to inspect the material. With a larger number of well-conducted tests, coupled with a knowledge of the quantitative as well as qualitative influences of various factors upon strength, and with definite data of inspection which allow ready sorting of material, the factor of safety, as far as it denotes the residuum of ignorance which may be assumed to remain, as to the character and behavior of the material, may be reduced to a minimum, restricting itself mainly to the consideration of the indeterminable variation in the actual and legitimate application of load.

Results of tests in compression endwise on green wood (above 40 per cent moisture, not reduced).

[Pounds per square inch.]

While the values given in these tables may claim to contain more elements of reliability than most of those published hitherto, much more work will have to be done before the above-stated aim will be satisfied.

In explanation of the table recording tests in bending at relative elastic limits it should be stated that since an elastic limit in the sense in which the term is used for metals, namely, as a point at which distortion becomes disproportionate to load and a permanent injury and set results, can not be readily determined for wood, Prof. J. B. Johnson has proposed to utilize a point where the rate of distortion becomes 50 per cent greater for the amount of load than it was for the initial load, which point can be tolerably accurately determined (see Bull. 8, p. 9). This point he has called the ‘relative elastic limit.” The assumption is that such a point would be near the limit to which the material can be strained without permanent injury, and the strength values obtained at that point would serve for indications of safe loads.

The practical utility of determining this point and the strength values relating to it remains, however, still open for discussion. A comparison of the values obtained for the strength at rupture and at relative elastic limit shows a parallelism which would make it questionable whether much is gained by the use of that point, which in reality lies beyond the limit where practical injury has begun, as indicated by the increased distortion.

We would be inclined to consider that point more serviceable where the curve begins to deviate from the straight line, at which point we may assume no permanent injury has as yet been experienced. This point we may call provisionally the ‘“‘safe limit.”

Objection has been made to utilizing this point because if can not be located with as much nicety and mathe- matical precision as the point of ‘relative elastic limit.” But even this point is only approximately definable; and since no strength values can claim to be more than approximately correct, it would suffice to determine the safe- limit point and the correspondent strength values also only approximately. This point has the advantage that it lies on the safe side.

Special series of tests fo investigate the legitimacy of the use of any of these limits for practical purposes were designed, but have as yet not been taken up, and hence the values in the table on p. 367 are given only as suggestions for what they are worth. :

366 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE.

Results of tests in bending, at rupture.

{Pounds per square inch.]

Average | Average Proportion | Proportion

average. | average. Reduced to 15 per cent moisture.

Reduced to 12 per cent moisture. | | | |

5) | “Wihiteminossecces-ecose- es cs ace nt 120 11, 100 4, 600 10, 100 5, 000 | 7, 900 43 81 6 | Red pine ---- : 95 | 12, 900 3, 100 12, 300 4, 900 9, 100 28 60 7 | Spruce pine - = 170 16, 800 3, 100 13, 600 5, 800 10, 000 43 81 8 | Bald cypress : 655 14, 800 2, 300 | 11, 700 5, 000 | 7,900 25 69 9 | White cedar. -- . 87 9, 100 3, 500 | 8, 400 4, 000 | 6, 300 32 78 10 | Douglas spruce a -| 41 | 13, 000 3, 800 12, 000 4,100 7,900 22 58 11 | White oak.---- 5 218 | 20, 300 5, 700 18, 500 7, 600 | 13, 100 39 5 12) Overcup oak 216 19, 600 4, 900 14, 900 | 6, 300 11, 300 47 81 13 | Post oak -- 49 16, 400 5, 100 15, 300 | 7,400 | 12, 300 47 92 M4 | Cow oak 256 23, 000 3, 300 12, 500 6, 500 11, 500 32 68 15 | Red oak - | 57 16, 500 5, 700 | 15, 400 9,100 11, 400 46 84 16 | Texan oak. -| 117 j 19, 500 | 8, 200 16, 900 10, 000 13, 100 64 86 17 | Yellow oak. - -| 40 15, 000 5, 100 14, 600 5, 700 10, 800 28 65 18 | Water oak... | 31 16, 000 | 5, 800 15, 700 7,200 12, 400 40 76 19 | Willow oak - 153 16, 000 3, 200 13, 800 5, 400 10, 400 33 70 20 | Spanish oak. 257 17, 300 | 5, 000 15, 600 6, 900 12, 000 40 72 21 | Shagbark hickory 187 | 23, 300 | 5, 700 20, 300 9, 400 16, 000 46 84 22 | Mockernut hickory SSE Hcee odor 75 | 20, 700 | 5, 300 | 19, 700 7,900 15, 200 45 78 23 | Water hickory --- 14 | 18, 000 | 5, 300 | 17, 800 5, 400 12, 500 21 64 24 | Bitternut hickory 25 19, 500 7, 000 | 19, 300 8, 700 15, 000 28 60 25 | Nutmeg hickor, 72 16, 600 6, 700 15, 600 8, 100 12, 500 40 88 26 | Pecan hickory. - 37 18, 300 5, 600 18, 100 10, 300 15, 300 38 95 27 | Pignut hickory. 30 | 25, 000 11, 100 24, 300 11, 500 18, 700 43 77 28 | White elm-.--- 18 14, 000 7, 300 13, 600 7, 300 10, 300 44 72 29 | Cedar elm . 44 19, 200 6, 600 17, 300 8, 500 13, 500 50 86

30 | White ash. 87 15, 000 5, 000 14, 200 6, 300 10, 800 37 7 31 | Green ash . 50 10 16, 000 5, 109 16, 000 5, 100 11, 600 20 60 32 | Sweet gum .....--.---.---------------+ | 118 14, 400 5, 100 12, 700 6, 000 9,500 | 39 19

|

a Actual tests on ‘dry’ material not reduced tor moisture.

RELATIONS OF WEIGHT AND STRENGTH,

That within the same species the strength of wood varied with the dry weight (specitic gravity), i. e., that the heavier stick is the stronger, has been known for some time, That this law of variation held good not only for a given species, but irrespective of species for the four principal pines of our Southern States was indicated in Cireular 12 of this Division. This fact becomes the more important in practical application, as the wood of these species of pines so far can not be distinguished at all by its anatomical structure and only with difficulty and uncertainty by other appearances, while in the lumber market substitution is not infrequent. It will therefore be best with these pines, where strength alone is desired, to inspect the material by weight (specific), other things being equal, disregarding species determination.

While this result of the exhaustive series of tests reasonably well demonstrated for these pines may be considered of great practical value, we can now extend the application of the law of relation between weight and strength a step farther, and state as an indication of our tests that probably in woods of uniform structure strength increases with specific weight, independently of species and genus distinction, i. e., other things being equal, the heavier wood is the stronger. We are at present inclined to state this important result with caution, only as a probability or indication, until either the test material and tests can be more closely scanned, or more carefully planned and minutely executed series of detail tests can be carried on to confirm the truth of what the wholesale tests seem to have developed.

In the following two diagrams the average strength of the different species in compression endwise and bending, as found in the preceding tables, has been plotted with reference to the dry weight as given in preceding table.

Considering that these tests and weight determinations (especially the latter) were not carried on with that finesse which would be required for a scientific demonstration of a natural law, that other influences, as crossgrain, unknown defects, and moisture conditions may cloud the results, and that in the averaging of results undue consid- eration may have been given to weaker or stronger, heavier or lighter, material, the relaxation is exhibited even by this wholesale method with a remarkable degree of uniformity borderirg on demonstration.

An exception is apparent in the oaks in that they do not exhibit this relation of weight and strength with reference to other species, and also with less definiteness among the various species of oak in themselves. The structure of oak wood being exceedingly complicated and essentially different from that of the wood of all other species under consideration, it may reasonably be expected that it will not range itself with these.

TIMBER PHYSICS—-STRENGTH AND WEIGHT.

Results of tests in bending, at relative elastic limit.

[Pounds per square inch. |

367

Average | A

verage Proportion ; Proportion 5 Namber Highest | Lowest | of high- | of lowest| Average} of tests of tests eda aE of No Species. of cORES single single |est10 per) 10 per of all within 10 | within 25 (avi aan y f ee test. test. cent of | cent of tests. | per cent of per cent of all t ae Y tests. tests. average. | average. altDESis)- Teduced to 15 per cent moisture. erica | Rericents tpl Hons leaimine--c. assem sees eee 1, 160 13, 500 2, 400 11,100 5, 400 8,500 43 | 81 1, 890, 000 2 | Cuban pine --- = 390 12, 900 2, 200 11, 500 5, 600 9, 500 42 83 2, 300, 000 3 | Shortleaf pine 330 11, 900 2, 900 9, 700 4, 800 7, 200 48 81 1, 600, 000 4s Gio blollyspine 2-222 sees neee eee ee 650 | 12,700 3,100 | 10,800 5, 400 8, 200 46) 85 | 1, 950, 000 Reduced to 12 per cent moisture. Lt} WAL ey ON ame econ coacorenesaee 130 10, 000 4,100 , 200 4, 500 6, 400 58 85 1, 390, 000 6 | Red pine---- 95 11, 300 3,100 10, 300 4, 500 7, 700 38 73 1, 620, 000 7 | Spruce pine- 170 13, 700 3, 000 11, 200 5, 000 8, 400 51 82 1, 640, 000 8 | Bald cypress 655 12, 000 2, 200 9, 900 4, 200 6, 600 25 66 1, 290, 000 9 | White cedar 87 8, 200 3,400 7, 390 4, 000 5, 800 44 86 910, 000 10 | Douglas sprucea -.-.-.-.---- 41 13, 700 2, 800 9, 600 3,400 6, 400 32 56 1, 680, 000 11 | White oak-..---..- c 218 15, 700 4,400 14, 100 6, 100 9, 600 37 73 2, 090, 000 12 | Overeup oak = 216 11, 600 4,000 9, 500 5, 400 7,500 47 91 1, 620, 000 13 | Postoak.... = 49 10, 600 5, 100 9, 600 6, 000 8, 400 34 76 2, 030, 000 14 | Cow oak 256 14, 200 3,400 11, 600 5, 000 7, 600 50 95 1, 610, 000 15 | Red oak -. 57 14, 500 5, 100 13, 600 5, 600 9, 200 15 49 1, 970, 000 16 | ‘Texan oak : 117 12, 000 5, 900 11, 400 7, 800 9, 400 62 94 1, 860, 000 17 | Yellow oak. : 40 11, 800 4,900 11,100 5,100 8, 100 35 75 1, 740, 000 18 | Water vak c) 31 11, 800 4, 500 11, 400 5, 500 8, 800 40 84 2, 000, 000 19 | Willow oak. z 153 13, 100 2, 700 10, 000 4,300 7,400 42 81 1, 750, 000 20 | Spanish oak 257 13, 500 5, 100 11, 600° 6, 600 8, 600 41 80) 1,930, 000 21 | Shagbark hickory - 187 16, 100 5,400 14, 200 7, 700 1], 200 50 89 2, 390, 000 22 | Mockernut hickory 75 15, 400 4,300 14, 600 7, 800 11, 700 39 83 2, 320, 000 23 | Water hickory -- 14 11, 900 4,100 11, 800 4, 800 9, 800 21 86 2, 080, 000 24 | Bitternut hickory - 25 14, 300 7,500 14, 000 | 7, 600 11, 100 44 84 2, 280, 000 25 | Nutmeg hickory .--- 72 12, 200 4, 200 11, 200 6, 400 9, 300 46 93 1, 940, 000 26 | Pecan hickory 37 15, 000 5, 800 14, 400 7, 900 11, 500 65 89 2, 536, 900 27 | Pignut hickory 30 17, 500 7, 400 16 400 8, 300 12, 600 40 83 2, 730, 000 28 | White elm -. 18 9, 700 5, 300 9, 600 | 5, 400 7, 300 33 71 1, 540, 000 29 | Cedar elm .- 44 10, 700 4,700 10, 100 5, 800 8, 000 57 91 1, 700, 000 30 | White ash .- 87 14, 500 3, 600 10, 400 5, 200 7,900 43 83 1, 640, v00 31 | Green ash -- 10 18, 200 3, 200 13, 200 38, 200 8, 900 40 70 2, 050, 000 32 | Sweet gum 118 11, 000 | 3,500 10,100 | 5,100 | 7, 800 46 82 1, 700, 000 aw Actual tests on ‘‘ dry” material not reduced for moisture. 13000 4000 1G000

9000

8000

7000

Compression endwise; pounds per square inch.

6000

5000

20

dO

40

Weight per cubic foot in pounds.

Fic. 95.—Relation of strength in compression endwise to weight of material. The figure at each point indicates the species thereby represented.

BS

45

50

LS

GO

368

gth at rupture in pounds per square inch.

g stren

Bendin

FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

19000

18000

/7000

16000

15000

M4000

13000

12000

HO00 \—

7

1Q000

9000

8000

7000

6000 ZO

25 JO BS 40 FS 30 IF 60

Weight per cubic foot in pounds.

Fic. 96.—Relation of weight to bending strength at rupture. The figure at each point indicates the species thereby

represented.

TIMBER PHYSICS—UNIFORMITY OF STRENGTH. 369

In addition, the difficulty of seasoning oak without defects or even securing perfect material may have influenced the results of tests so as to cloud the relationship with the genus.

If further close study, supplemented by additional series of tests carefully devised to investigate this relation- ship, Should uphold the truth of it, this result may be set down as the most important practical one that‘could be reached by these tests, for it would at once give into the hands of the wood consumer a means of determining the relative value of his material as to strength and all allied properties by a simple process of weighing the dry material ; of course with due regard to the other disturbing factors like crossgrain, defects, coarseness of grain, etc.

Results of tests in compression across grain (a) and shearing with grain.

{Pounds per square inch. |

| Shearing | | | Shearing Num. |Compres- with ; iSre \Compres-| with ‘ r Shana . sion grain no Sete -| sion grain not No. Spe es: Bence across | reduced ||X° | Shecies: peror | across | reduced BuS- il Veraanc.) |) stor | a8 grain. for | | moisture. | moisture. | | | Reduced to 15 per cent moisture. | | | Reduced to 12 per cent moisture— | | | Continued. | 1 | Longleaf pine.......----.---------- 1,210 | 1, 000 700 2) Cuban pine --- 400 1, 000 700 | 16 | Southern red oak....---.--.-------- 117 2, 000 | 900 3 | Shortleaf pine. : 330 900 | 700 || 17 | Black oak...... 40 1, 800 | 1,100 AW oblotivapmess 2.2 2n-<s=4 === === | 690 1, 000 700 | 18 | Water oak - 30 2, 000 1, 100 | | 19 | Willow oak 153 J, 600 900 Reduced to 12 per cent moisture. | | 20 | Spanish oak-.--. 255 1, 800 | 900 | | | || 21 Shagback hickory 135 2,700 1, 100 5 | White pine..-........2-.----..----- 130 700 400 || 22 | White hickory -- 75 1, 100 6 | Red pine -- 100 1, 000 | 500 | 23 | Water hickory --- Shc 14 1, 000 7 | Spruce pine - 175 | 1, 200 | 800 | 24 | Bitternut hickory--------.-.---..-- | 25 | 1, 000 8 | Bald cypress - . 650 | 800 500 | 25 | Nutmeg hickory -| 72 1, 100 9 | White cedar... 87 700 400 | 26 | Pecan hickory. 37 1, 200 10 | Douglas spruce b-- an 41 | 800 500 | 27 | Pignut hickory 3c 30 1, 200 11 | White oak....- = 218 | 2, 200 1,000 || 28 | White elm .-.-..-------..----- Bee 18 800 12 | Overeup oak .- 216 | 1, 900 1,000 || 29 | Cedarelm.........--..------------- 44 1, 300 13 | Post oak ..-.- 49 | 3, 000 1,100 || 30 | White ash.........----+--.--------- 87 1, 100 14 Cow oak . A 256 | 1,900 900 || 31 | Green ash............-.------------ 10 1, 000 15 | Red oak... .-.---- 2 ---- 22-5 - oe netewe 57 | 2, 300 1;100 || 32 | Sweet gum....-.....--.---- Secorock 118 800 | | | | aTo an indentation of 3 per cent of the height of the specimen. b Actual tests on ‘dry ” material not reduced for moisture.

Having fully established the great influence of moisture on the strength of wood, the practi- tioner still needed information as to the rate and manner of drying and as to the way in which moisture is distributed during seasoning. Several thousand moisture determinations were made and it was established beyond doubt that moisture is generally least abundant at tle ends, is quite evenly distributed throughout the length, but is not always uniform in different parts of the same cross section, often varying in this respect within astonishing ranges, so that the use of timber in a half-seasoned condition, and where uniform seasoning can not be obtained by the material, requires that these facts be duly considered in designing.

TESTS OF MAXIMUM UNIFORMITY.

30th in this country and abroad small differences in strength values were often interpreted as deciding for or against any given material. This same problem arose also in every case where many results were to be compiled, and it seemed especially desirable once for all to find just how much uniformity could be expected of wood materials. From a large series of well-selected quarter-sawed pieces representing several kinds of pine, cypress, and hardwoods it was found that even contiguous blocks, 24 inches long, may differ by as much as 2 to 4 per cent in conifers and as much as 13 per cent in oak, and that in a scantling only 6 feet long the butt might differ from the top by 10 to 20 per cent in conifers and over 35 per cent in oak. This extremely valuable set of results throws much light upon discussions of the past, and is well suited to show that many boastful claims rested on very flimsy and entirely unreliable differences, such as might well be accounted for by a little more extended examination of materials. It will also assist in judging test results in the future and help to avoid useless controversy and prejudice. The following more fully illustrates the results of this series:

Scantlings of air-dry material, 6 to 10 feet long, of white pine, longleaf pine, tuliptree (poplar), and white oak, and of perfectly green material of loblolly pine and cypress, fresh from the saw, were cut partly into blocks 2 by 2 by 2} inches, but mostly into cubes of 2% inches. All material was quarter sawed, carefully prepared, anel in all cases treated alike, either perfectly green or dried together at the same temperature. Altogether 529 tests in endwise compression were made, namely, 100 on white pine, 72 on longleaf pine, 99 on loblolly pine, 40 on white oak, 115 on tuliptree (poplar), 103 ou eypress.

H. Doe. 181 24

370 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE.

From these tests the following table of averages is derived, together with fig. 97:

Average of tests for maximum uniformity.

It will be observed that green cypress excelled in its uniformity; that green loblolly proves not more uniform than dry white and longleaf pine; that wood of the conifers far excel even the tuliptree (poplar) with its uniform grain and texture; and that oak, as might be expected, is the least uniform. It will also be noticed that even in one and the same short scantling (6 to 10 feet) of select quarter-sawed longleaf pine differences of 10 per cent may occur, and that in all others these differences were even greater.

Incidentally in this and the following experiment a small number of the blocks were thoroughly oven-dried (to about 2 per cent moisture), and it was found that the strength of both cypress and loblolly was increased by about 150 per cent during drying, so that wood at 2 per cent is about two and one-half times as strong as perfectly green or soaked material; and also that drying from 8 to 10 per cent to the lowest attainable moisture condition (1 to 2 per cent) still adds about 25 per cent to the strength of the wood.

In the following diagram and table a part of the results are presented in detail :

HL000,

100004

9000

6000

bal gaes

a Eee ee

Z000

ame care

ene See ee

Bil

ACA

3O00

| |

2000 BLOCH NUMBER :/ 3 on 7 g // /3 1 VA 19 YS WER GS

Fia. 97.—Strength of contiguous blocks, showing maximum uniformity of select quarter-sawed material in compression endwise.

TIMBER PHYSICS—VARIATION IN STRENGTH. y(t

Strength of contiguous blocks of the same scantling, select material, in compression endwise.

[Dimensions generally, 2.76 by 2.76 by 2.76 inches. ]

+ a ee

Kind of wood.

Pounds per square inch.

4,850} 11,580 | 4,860 | 11,530 4,690 | 11,310

2,720 4,170| 5,740! 9,970 2, 700 4,190 5,700} 9,370 2.79 4,170 5,770 | 8, 260

4, 840 11, 060 5,700 | 8, 120

4, 760 8, 250 5, 430

4,720 10, 740 5, 430

4,730 11, 180 5, 420

4, 760 11, 220 5, 560

4, 750 10, 980 5, 440

4,770 11, 130 a7, 070

4,730 11,510 4, 230 5, 770

4, 760) 11, 490 2, 4,180 6, 030

4,770 11, 320 2,780 | 4,130 6,170

4, 670 11, 220 2, 800 4,160 5, 840

4, 600 11,320} «@5,840 4, 160 5, 440

4, 660 11, 340 2, 880 4,160 5, 360

4,590 11, 470 2, 870 CEl OU esas

4, 600 10, 790 2, 870 4, 090 5, 530

4, 610 10, 740 2, 860 4,070 | 5, 530

4, 850 11, 030 a6, 480 a6, 880 |..

4,920 11,110 2, 760 DO 20 wna aaa

4, 870 11, 450 2, 760 5, 930 9, 030

4,970 12, 250 2,720 5, 770 8, 660 : 4, 940 12, 760 2, 640 5, 780 8, 060 ones Roo eel 10, 740 a7, 050 6, 120 7, 740

5, 070 10, 350 2, 680 6, 480 7, 580

4,940 10, 280 2, 650 6,310

5, 020 10, 150 2, 650 6, 220

5,110 9, 860 2,780 6, 310

5, 020 10, 900 a7, 320 a7, 420 |.

4,950 10, 120 2,730 6, 340

4, 820 10, 370 2, 780

4,950 10, 320 2,720

4,900 10, 250 2, 660 4

5, 040 10, 400 a5, 360

5, 160 10, 050 2,610

5, 120 10, 050 2, 560 |.---

5, 100 10, 350 2, 580

5, 230 10, 100 2,580

5, 280 10, 030 a5, 220

5, 260 9, 970 2, 620

5, 280 9, 880 2, 600

5, 300 10, 050 2,640

5, 310 10, 220 2,610

5, 300 10, 470 a6, 440

5, 350 10, 860 2,6

5, 400 10, 590 2, 620 | 5, 360 10, 350 2, 600 5, 360 11, 150 2, 680

5,510 | 10,970} a6, 440 5,070 | 10, 890 2,710 | 5,150 | 10,790 2,750

5,020) 10,970 2,760 |- 4,770 | 11, 040 2,720

4,770 | 10,940 | @6,850 |_. 4,920 10,970 2,710 |.

4,950 | 10,840 2, 680 |. 4,840 | 10,710 2 660 |. 4,860} 10,890 2,660 |. a6,460 | 10,710) @7,030

a Dried to about 2 per cent moisture before testing.

As was indicated at the outset and is fully explained in Bulletins 6 and 8, the plan of this investigation also included among the objects to be sought the establishment of the following:

(1) The relative value of each species.

(2) The outward signs or physical and structural properties, easily used in inspection.

(3) The relation of the properties among themselves; and

(4) Their relation to the conditions under which the wood is formed, such, for instance, as the age of the tree when wood is laid on, influences of soil, climate, ete.

As has been explained, some of these relations were more or less fully determined, at least, qualitatively; nevertheless, the relation of the several forms of resistance, as well as the mutual relations of the properties in general, seemed to escape observation in the manner of inquiry generally pursued. It became clear before long that these laws must be established by special series, planned each to seek answer to some specific question. Several of these were carried out,

dz FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE.

and, thougna little more was accomplished than to find proper ways, the study of these results, amplified by the large ordinary series, led to several interesting discoveries, the most important of which is the discovery of the relation between the strength in cross bending at elastic limit and the compression endwise, this latter being equal to the fiber stress of the former. Though still requiring special experiments to become convincing, it is fair to state at this point that a great deal of useless testing will be saved in the future, since the test in compression is by all means the simplest, the selection and treatment of the material for it the easiest, and the result the most satisfactory. The importance of this discovery by Mr. 8. T. Neely is such that a reprint of Mr. Neely’s discussion here will be found justified.

RELATION OF COMPRESSION-ENDWISE STRENGTH TO BREAKING LOAD OF BEAM.

In testing timber to obtain its various coefficients of strength, the test which is at once the simplest, most expedient, satisfactory, and reliable is the ‘‘compression-endwise test,” which is made by crushing a specimen parallel to the fibers, All other tests are either mechanically less easily performed, or else, as in the case of cross- bending, the stresses are complex, and the unit coefficient can be expressed only by reliance upon a theoretical formula, the correctness of which is in doubt. It would, therefore, be of great practical value to find a relation between the cross-bending strength, the most important coefficient for the practitioner, and the compression strength, when the study of wood would not only be greatly simplified and cheapened, but the data could be applied with much greater satisfaction and safety.

The consideration of such a relation resolves itself naturally into two parts, namely, a study of the relation ot the internal stresses in a beam to the external load which produces them, and a study of the relation of the internal stresses in a beam to the compression-endwise strength of the material of which the beam is made.

The first relation has been a subject of study for more than two centuries, and from the time of Galileo down to the present day the theory of beams has been gradually evolved. Within recent years several eminent physicists and engineers have given a true analysis of both the elastic and ultimate strength of a beam, a clear exposition of which is made by Prof. J. B. Johnson in his work on Modern Framed Structures. He points out that the ‘ordinary cquation” for obtaining the extreme fiber stresses, when the external load and dimensions of the beam are given, is not applicable to a beam strained beyond its elastic limit; and he follows this statement with a discussion of the true distribution of internal stresses in a beam at time of rupture, and with a ‘‘ Rational equation for the moment of resistance at rupture,” devised by M. Saint-Venant, which really does connect the extreme fiber stress in abent beam with the compression-endwise strength and also with the tension strength. Professor Johnson’s final conclusion, however, is that for practical use the ‘‘ ordinary formula” may be applied to a beam at rupture, providing the fiber stress involved is obtained from cross-bending tests; and this is the present practice among engineers.

RELATION OF INTERNAL STRESSES.

Assume for the discussion of the relation of internal stresses to external load the simple conditions of a beam of rectangular cross section loaded at the middle.

Regarding the distribution of internal stresses, it must be agreed that the neutral plane lies in the center of the beam so long as the beam is loaded within the elastic limit; this follows from the fact that the modulus of elasticity is the same whetber derived from compression tests or from tension tests (i. e., E. = E;), as proved by experiments of Nirdlinger, Bauschinger, Tetmayer, and others.

Since the distortion of any given fiber in the beam is proportional to its distance from the neutral plane, the distribution of stresses in a longitudinal section of a beam loaded up to its elastic limit may be represented by the following diagram, in which the vertical scale represents increments of distortion and the horizontal scale the fiber stresses.

In this diagram the angle a = angle b, since E, = Ey; and furthermore, since these latter quantities are each equal to the modulus of elasticity obtained from cross-bending tests (according to the same authorities), this angle a (ov b) can be obtained by platting the results of the cross-bending test itself.

It is a well-established fact that the tension strength of wood is much greater than the compression strength, and also, as shown by the German experimenters quoted, that the elastic limit in either case is not reached until shortly bofore the ultimate strength. Furthermore, it seems reasonable to suppose, and is essential to the construc- tion of the above diagram, that the true elastic limit of the beam (shown on the strain diagram of a beam at the point where it ceases to be a straight line) is reached at the same instant that the elastic limit of the extreme com- pression fiber is reached; for when the loading is continued beyond this latter condition the line OC must begin to curve upward (since the proportion of load to distortion on that side begins to increase more rapidly), while the line OT continues in its original direction. Therefore, in order to maintain the equilibrium, the whole distribution of stresses will necessarily be changed, the position of the neutral axis will be lowered, and these changes will, of course, show an effect on the deflection of the beam.

Now, even at rupture the proportionality of fiber distortion to distance from neutral axis is maintained (because a plane cross section will always remain a plane), and therefore the distribution of internal stresses just at the point of rupture can be represented by a diagram similar to fig. 99, in which, as before, the vertical scale represents incre. ments of distortion and the horizontal seale fiber stresses. The fibers on either side of the neutral plane are under stresses which vary from zero at the neutral plane to the maximum stress in the extreme fiber, changing in proportion

TIMBER PHYSICS—RELATION OF CRUSHING TO BENDING. 373

as the increments of load in the test machine vary. Therefore, the distribution of stresses on the compression side of the neutral plane will be shown by an ordinary strain diagram for compression, and on the tension side by a similar tension-strain diagram. Unfortunately there are no reliable diagrams of these kinds now on record. The compression pieces tested have usually been too short to afford reliable measurements of distortion, and, owing to structural and mechanical difficulties, satisfactory tension tests seem to be impossible.

STHESSES /N 1000 LBS. STRESSES /N _1000 LBS. OHARA SEAR GIAO) GAB NE AMABIG F A a ONES

Ze Q 10 11 e. 10 we o2 we x0 SE = = 8 yy Ss Ae) ao We 84 1 ~ | @_ WEUTAAL _AX/S i Ss? 2 = SS 2 < S — : : oS S4 58 S S 47 40 Q a JE DRET OR ETL EG 8 BG EFI LG 4 IO Fic. 98.—Relation of fiber stresses and distortions. Fig. 99.—Distribution of internal stresses in a beam at rupture.

Experience in testing, however, has taught that when a piece of green wood is tested in tompression it will undergo a great distortion after the maximum load has been applied without actually breaking down—in fact, while sustaining the same load. A piece tested in tension, on the other hand, breaks suddenly as soon as the maximum load is applied. A beam in failing may, therefore, sustain an increasing load long after the extreme compression fiber has been loaded to its ultimate strength; the fibers on the compression side continue to be mashed down, while the neutral plane is lowered and the stress in the tension fiber increases until, very oftenin practice, the beam “fails in tension.” With these facts and observations before us it is possible to con- FORCES IN 1000 LBS. struct a diagram so that it will represent, Wh i ee Sur Ou aS ON /ONI Ae approximately, at least, the distribution of internal stresses in a beam at rupture. (See fig. 100.)

In this figure OA represents the position of neutral plane at time of rupture, OU the distortion in the extreme compression fiber,

S

= INCHES. CES

UC the stress on same fiber, OL the distor- \ SF tion in extreme tension fiber, and LT the RZ stress on that fiber. It can readily be seen that the manner = 2 of breaking will influence slightly the form of this diagram. If the beam fails in com- = oO pression before the tension fiber reaches its S elastic limit the line OT will be straightas K 2 shown, otherwise the line will assume some X such position as Ol,T, (diagram 99), in which R cA 1, is the elastic limit in tension. % From the approximate distribution of S o internal stresses their relation to the external = SPY BA. Sh ea, eon (ra teh WE) TO a}

load may be determined. The two funda- mental equations—(1) that the sum of inter- Fic. 100.—Position of neutral axis and internal stresses at rupture of beam. nal stresses on the tension side equals the sum

of internal stresses on the compression side, and (2) that the sum of the external moments equals the sum of the inter- nal moments—apply at the time of rupture as well as at the elastic limit. From (1) it follows that area OUCI= area OLT, and the position of the neutral plane at rupture is thereby fixed. If now the line LU be assumed to represent the depth of the beam in inches instead of indicating the distortion of the fibers, the sum of the internal moments about the point O is found by multiplying the area of either the compression or tension diagram by the sum of the distances of their respective centers of gravity from the neutral plane. By putting this sum equal to the moment of the external load about the same point O the first relation is established.

374 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE.

RELATION OF CRUSHING-ENDWISE STRENGTH,

The second relation (that of crushing-endwise strength to internal stresses) was touched upon in discussing the first, when it was stated: (1) That the true elastic limit of the beam is probably reached at the same instant that the extreme fibers on the compression side reach their elastic limit in compression. (2) That this latter limit lies close to the ultimate compression-end wise strength (so close that former experimenters have been unable satisfactorily to separate them). (3) That a piece of green wood will stand a great deal of distortion after the ultimate load is applied before actually failing. And to these statements may be added the evident fact (4) that the stress on any fiber on the compression side can not exceed the compression-endwise strength of the material. (5) Finally and most important it appears from (1) and (2), but especially from an examination of the several thousand test results on the several species of conifers made by the Division of Forestry, that the extreme fiber stress at the true elastic limit of a beam is practically identical with the compression-endwise strength of the material. (This last observa- tion, which was forced upon the writer by its continual repetition in the large series of tests under review, lies at the basis of this discussion.) The observation of this identity makes the distribution of internal stresses appear more simple than was hitherto assumed, and the desired relation between compression and cross-bending strength capable of mathematical expression.

DEVELOPMENT OF FORMULA.

From these considerations the distance UC in tig. 100, which represents the ultimate compression-end wise strength of the material, becomes practically equal to the distance el, which represents the compression strength at the true elastic limit, and hence the line IC straight and vertical; and if OT is taken as straight, the diagram will be made up of simple geometric figures, as in fig. 100.

The line LU will represent the total fiber distortion at time of rupture, and is equal to the sum of the amounts by which the extreme compression fibers shorten and the extreme tension fibers elongate.

Let a test in which the following quantities have been observed and recorded be considered :

Let P,— the external load at rupture (pounds). 4,=the corresponding deflection of the beam (inches). C = compression-endwise strength of the material (pounds). E= modulus of elasticity (pounds). d—depth of beam (inches). b=breadth of beam (inches). 1—length of beam (inches). A. = detlection at true elastic limit.

Then, based upon the above statements, by means of formulas derived from the geometric relations of the diagram and the fundamental equations of equilibrium, the following quantities can be calculated: ;

Let /). = total tiber distortion due to bending at true elastic limit (inches).

I}, = total fiber distortion due to bending at rupture — LU (inches).

d, — distortion in extreme tension fiber at rupture — LO (inches); also the proportional dis- tance of neutral plane from tension side of beam.

d,—real distance of neutral plane at rupture from tension side of beam (inches).

d, real distance of neutral plane at rupture from that fiber on compression side which has just reached the elastic limit, in inches = Oe.

T stress in extreme tension fiber (pounds).

T,—sum of forces on tension side —area OLT (pounds).

C,=sum of forces on compression side = area OUC! (pounds).

d,— distance of center of gravity of tension area from neutral plane (inches).

d. = distance of center of gravity of compression area from neutral plane (inches).

M,=sum of the internal moments about the point O (inch-pounds).

The formulas connecting these quantities are derived as follows: To find FE, let fig. 101 represent a portion of the beam one unit in length bent to its elastic limit; then,

Ee d

Via. 101.—Fiber dis- 1 7 tortion in unit : 5 EP rey length of beam, at where r is the radius of curvature, but trom,fundamental formulas true at elastic limit

elastic limit.

ay EU Bah DE _ 124d Tiwi an oS Sa

Since this involves only geometric relations, it is true also at rupture (since the beam preserves its original form). 5 124,d Q) A=

To find d, and T: Since the sum of stresses on the tension side —sum of stresses on compression side,

dy E.C d,C the area OLT = area OUCL.:. 4 T=(E;—d)) CO— —_ and T= iE.

TIMBER PHYSICS—RELATION OF CRUSHING TO BENDING. 375

from the similar triangle OLT and Oel (fig. 100), PAGES a Boe 22 C,

whence,

anes Ee

(3) dp=V ErX 1D Dy

and after d, is found, T can be obtained: EL FE. Now, when the vertical line LU is assumed to represent the real depth of the beam in inches — d, every verti-

(3)

d cal measure will be changed in the ratio E, (see fig. 102); whence, ie d (5) =~ dy L/ (& r (real distance of neutral plane from tension side). ad. (6) d.=4 E. Eo

(4 because FE, total distortion, while d, is the distance on one side of the neutral plane). The area OLT would then become:

dT : (7) Ta=~—), and the area OUCI— di, (8) Ca—=(d—d,)C SG x C)

(C, must equal T,).

The distance of centers of gravity would be:

(9) d= dr,

1 — d. if (10) d= GO +9) and tht sum of internal moments. Fig. 102.—Position of neutral plane at rupture. (11) M,—= (Cad. + Tadt)b, and since C,—=T,, hence M,;=C,(de+ dt)b. But since the sum of internal moments equals the sum of external moments: Prt “f= Mi =Ca(detae)d. And since P, is the breaking load of the beam, and C, involves only the compression endwise strength and lineal dimensions, we have a formula directly connecting the breaking load of a beam with the compression strength.! Application of these formule.—Unfortunately no tests have been made to study the application of these formule directly and in particular. The tests on beams published in this circular were made for a different purpose. For the purpose of ascertaining the correctness of the formule only the tests made on large beams have been utilized, since in these the deflections were specially accurately measured. In addition to the quantities to be calculated already given in this discussion, the fiber stress at the true elastic limit is also calculated, and called S., to be compared with C, and the load producing it, P., is also set down as an observed quantity. If the modulus of P F 52 RR le rupture, R, has already been calculated by the ‘‘ordinary formula,” 8, can be obtained from the relation =p- and x Ie (2) S=p-R. r The modulus of elasticity at true elastic limit E, is recomputed as a check, and of course is: RE & 4K Since P, is an arbitrary quantity within certain limits, and can not be determined with any degree of accuracy, S. will be found to differ more or less from C. For these reasons, however, C is a more reliable value for the true elastic limit than §, itself, and in the formule is used as such; for instance, E. is the fiber distortion produced by the same load which produces a fiber stress—C, not by the load which produces . The following table exhibits the results of applying the formule to the data from these tests:

(13) E

[' The factors d.-+d;, within such limits as the cross-bending strength is constant, are constants; they will have to be ascertained by actual experiment for each species and quality, and might then be expressed as a proportion of the depth. In the material used, pine as well as oak, it appears to be about 3/5. The material on which this rela- tionship has been mainly studied was green wood, and it may be questioned whether the factors d, and d; would remain the same in material of all moisture conditions. There is no logic which would lead us to expect a difference greater than the limits of ‘‘maximum uniformity,” i. e., 10 per cent. A few comparisons of data obtained from material of other species with varying moisture percentage indicate that a difference does not exist,—B, E, F.]_

AGRICULTURE.

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TIMBER PHYSICS—METHODS. Silee

In order to see how far the formulis may be applicable to beams of the same material the data obtained on the small beams cut from one of the large beams were subjected to scrutiny, basing the calculations on the data from the adjoining compression block. The caleulated result compared with the actual breaking load showed a most convincing similarity, as will he apparent from the table herewith presented :

Strength of small beams, calculated by Neely’s formula from compression strength, on the assumption that the relative position of the neutral plane at rupture is the same as found in large beams,

(Shortleaf pine, large beam No. 13, special series. |

Data obseryed in testing. Results calculated by Neely’s formule. } A h _ —____________||- 4 as = 272 | a | a | 4 Real dis- 8 Distance 9° iD; “A . = } denite| Us Se) tance of _ | Sums of forces | from neu- 2 pimensions or ns | 3 to | neutral a for unit width | tral plane | 3 Lorre ese | #8 = plane at r=) of beam. lof center of| & | | os | BR £ rupture. Z |. gravity. | ¥ . — —_ == = o LA nD a = = | 5 eal erie ae | Ba bs mow te 32 E | Sa ¢ | 33 e.| 2 122 || % 23 at| | as | | ao 2 bates Racer) 22 An = | | Venous: ; 5 se B | 2 |o2s8] ae mie = a | | | | AS i = iH) iS |} w |loSg| of 4 a a a 3S am | oa iS) Se = 6 |sc8! - = | os o Sry il ee Ss | heel jhe Bor asa eae ae lese| 3 ; a eyes |e 2 as 2 & || gg So) Wie eestss||) 1S 3 a fe ee || tere. |e = | ae i = 3s | 8 | a |Beal| 5 = 2 ou coe eae 2 2 | E04 | OG hans 2 WRENS it Seiaiec| uate a | ere les al veiilinse cet) 0784 ¢ a srt “4 mos D er = 2 rt a FlS| al ie A Pill Siete lip soba cat lepers g EG isles REA Ve ray 22 aJA|A | Aa] A Sy iis A | A | BO B S S ©: || FOr eco es A = ue | Hee | See See oe = Ef = : widi| @ | db R c Pe |enePs ulus Iieremn liars ae a Gaur een ieee As F — = — —— —|— al | — —— ast = — 2 Inches. Lbs. per sq. in. Lbs. ea Inches heres Lhs. Lbs. Inches. Petr Lbs. | Inch. | i ae = = = 2 7,350 4,430 | 4,300 4,708 1 3,760 | 1.46 | 1.23 | 10,517 7, 677 7,719 | 0.97 | 1.18 | 58,760 2,200 | 0.296 3 4.610 | 5,000 | 5,390 | 4.480 | 1.56 | 1.31 10,979 8, 564 8, 552 | 1.04 | 1.26 | 2,800 | 0. 391 4 4,560 4.710 | 5,057 | 3,969 | 1.48 | 1.24 10,885 | 8,055 | 8,026] 099 | 1.19 2,400 | 0.413 5 4,070 | 4.680 | 4,203 | 4,220 | 1.45 | 1. 9, 675 7, O14 7,061 | 0.97 | 1.17 2,535 | 2,400 | 0.345 6 | 4.150 | 4.690 | 4,571 | 4,296 | 1.49 | 1. 9,894 | 7,371 7,376 | 0.99 | 1.20 | 2,600 | 0.356 if 4,160 4,540 4,420 | 4,129 | 1.47 1 9, 943 7, 808 7,290 | 0.98 | 1.18 2,400 | 0.431 8 | | 3,870 | 4,470 | 4,578 | 4,178 1.48 | 1. 9,164} 7,381 | 6,840 | 0.99 | 1.20 | 2,500 | 0. 440 |aQ | 3.880 3,000 4,169 | 8,078 | 1.47 | 9, 274 6,816 | 6,751 | 0.98 | 1.18 | 1,800 | 0.328 | 10 3,680 4,280 3,854 | 3,860 | 1.47 8,796 | 6,465) 6,403 | 0.98 | 1.18 | 2,200 | 0.387 | 1] | 3,750 3,600 3,312 | 3.893 | 1.44 | 8, 926 6, 427 6,485 | 0.96 | 0.87 ' 41,400 | 2,200 | 0.372 | 12 3.540 3,760 3,697 | 3,395 | 1.45 8,415 | 6,101 | 6, 124 | 0.97 | 1.17 46,219 | 1,940 0. 300 | | i | ——————eEEE— = = — = Es a

a Failed, due to knot. Nore.—Columns of figures in same distinctive type to be compared one with the other.

On the whole, it is in no way boastful to assert that this work has already furnished prac- tical data enough to more than pay the expenses incurred ten times over; that its fruits are not half gathered, and that for more than a quarter of a century its results will serve as a basis for the user of wood and as the guide to the teacher and experimenter.

DEVELOPMENT OF THE SCIENCE OF ‘TIMBER PHYSICS AND MErrnops EMPLOYED IN THE INVESTIGATION.

Since the elaborate plan and methods of this study of our woods denotes an -entirely new departure in timber investigations, at least in our country, it is only fitting to place the credit for its conception, for the elaboration of the plan, the organization of the work, and the persistent prosecution of the same in spite of many drawbacks and lack of support. This credit belongs to Dr. B. E. Fernow, chief of the Division of Forestry. The plan was first foreshadowed in his second report (1887, p. 37) as chief of that division, and the word “timber physics” was there used for the first time, and the essentials of the future plan were there discussed. Ina small tentative manner the first steps to put it in operation were made in 1888. In the report for 1889 we read:

The inyestigations into the technology of our timbers and especially into the conditions upon which the qual- ities of our timbers depend—for which Mr. Roth of Ann Arbor has begun preliminary studies—has also made but slow progress for lack of means.

In the report for 1890 we find, besides an account of the tests on Northern and Southern oaks referred to before, the statement that ‘by the increase of appropriations the forest technological investigations referred to in former reports have become possible on a scale which was hitherto unattainable,” and a description of the plans is given. But the first fuller statement of the

318 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

development of the investigation and its methods was not published until 1892, in Bulletin 6, in which Mr. Fernow described the aims, objects, and methods at length. In the report for 1890 the following language is used:

TIMBER TESTS.

While the use of wood pulp and other substitutes may displace in many ways the use of wood in its natural state, there will always be desirable qualities inherent in the latter that make its use indispensable. Hence the desirability of knowing the qualities of our timbers and, if possible, of knowing the conditions under which the wood erop will develop the desirable qualities.

Much work and useful work is done in the world by the rule of thumb. All such work is not reliable and certainly not economical. With the need of greater economy in production, the need of more accurate measuring arises, and with that the need of more specific knowledge of the thaterials to be measured.

Wood is one of the materials which has been measured by the rule of thumb longer than others. Iron and other metals used in the arts have their properties much more accurately determined than wood material. Especially in the United States, when we speak of quality of our timbers, it can only be in general terms; we lack definite data.

One difficulty in determining reliably the qualities of our timbers lies in the fact that living things are rarely precisely alike. Every tree differs from every other tree, and the material taken from the one has a different value from that taken from the other of the same species. Yet every tree has some characteristics in common with all those grown under similar conditions. But even these common properties differ in degree in different individuals. Individual variation tends to obscure relationship.

The factors which determine the quality of timbers are found directly in the structure of the wood, and it is possible from a mere ocular examination to judge to some extent what qualities may be expected from a given piece of timber, although even in this direction our knowledge is very incomplete, and but few definite relations between structure and quality, or between physical and mechanical properties, are established. We know that the width of the annual rings, their even growth, the closeness of grain, the length, number, thickness, and distribution of the various cell elements, the weight, and many other physical appearances and properties of the wood influence its quality, yet the exact relation of these is but little studied. Conjectures more or less plausible, suppositions, and a few practical experiences preponderate over positive knowledge and results of experiments. Again we know, in a general way, that structure and composition of the wood must depend upon the conditions of soil, climate, and surroundings under which the tree is grown, but there are only few definite relations established. We are largely ignorant as to the nature of our wood crop, and still more so as to the conditions necessary to produce desirable qualities, and since forestry is not so much concerned in producing trees as in producing quality in trees, to acquire or at least enlarge this knowledge must be one of the first and most desirable undertakings in which this Division can engage.

Accordingly a comprehensive plan has been put into operation to study systematically our more important timber trees.

It will at once be understood that as Jong as the qualities are to be referred to the conditions under which the tree is grown, the collection of the study material must be made with the greatest care, and the material must be accompanied with an exhaustive description of these conditions. Since, further, so much individual variation seems to exist in trees grown under seemingly the same conditions, a large number must be studied in order to arrive at reliable average values. For the present it has been decided to study the pines, especially the white pine and the three Southern lumber pines.

In selecting localities for collecting specimens, a distinction is made between station and site.

By station is understood a section of country (or any places within that section) which is characterized in a general way by similar climatic conditions and’ geological formation. Station, then, refers mainly to the general geographical situation. Site refers to the local conditions and surroundings within the station, such as difference of elevation, of exposure, of physical properties and depth of the soil, nature of subsoil, and forest conditions, such as mixed or pure growth, open or close stand, ete.

The selection of characteristic sites in each station requires considerable judgment.

On each site five full-grown trees are to be taken, four of which are to be representative average trees; the fifth or ‘‘check” tree, however, should be the best developed tree that can be found on the site. Some additional test trees will be taken from the open and also a few younger trees. ‘The trees are cut into varying lengths, and from each log a disk of 6-inch height is secured, after having marked the north and south sides and noted the position of the log in the tree.

The disks are sent for examination of the physical and physiological features to the Michigan University, while the logs, and later on special parts of the disks are to be sent to the test laboratory of the Washington University of St. Louis. Here, for the first time, a systematic series of beam tests will be made and compared with the tests on the usual small laboratory test pieces. Such tests with full-length beams in comparison with tests on small speci- mens promise important practical results, for a few tests have lately developed that large timbers seem to have but little more than one-half the strength they were credited with by standard authorities, who relied upon the tests on small specimens.

From the ‘‘check” tree mentioned before only clear timber is to be chosen, in order to ascertain the possibilities of the species and also to establish, if possible, a relation between such clear timber and that used in general practice, where elements of weakness are introduced by knots and other blemishes,

TIMBER PHYSICS—-METHODS AND AIMS. 379

An authority on engineering matters writes regarding this work:

“Inasmuch as what passes current among engineers and architects as information on the strength of timber is really misinformation, and that no rational designing in timber can be done until something more reliable is furnished in this direction, the necessity for making a competent and trustworthy series of such tests is apparent. This is a work which the Government should undertake if it is to be impartial and general.”

A careful record of all that pertains to the history and conditions of the growth from which the test pieces come, and of their minute physical examination, will distinguish these tests from any hitherto undertaken on American timbers.

The disk pieces will be studied to ascertain the form and dimensions of the trunk, the rate and mode of its growth, the density of the wood, the amount of water in the fresh wood, the shrinkage consequent upon drying, the structure of the wood in greatest detail, the strength, resistance, and working qualities of the wood, and lastly, its chemical constituents, fuel value, and composition of the ash.

In Bulletin 6 we are introduced to the science of “timber physics” in the following language:

Whenever human knowledge in any particular direction has grown to such an extent and complexity as to make it desirable for greater convenience and better comprehension to group it, correlate its parts, and organize it into a systematic whole, we may dignify such knowledge by a collective name as a new science or branch of science. The need of such organization is especially felt when a more systematic progress in accumulating new knowledge is contemplated. In devising, therefore, the plans for a systematic and comprehensi-+e examination of our woods it has appeared desirable to establish a system under which is to be organized all the knowledge we have or may acquire of the nature and behavior of wood.

To this new branch of natural science I propose to give the name of ‘‘timber physics,” a term which I haye used first in my report for 1887, when, in devising a systematic plan of forestry science the absence of a collective name for this class of knowledge became apparent.

While forest biology contemplates the forest and its components in their living condition, we comprise in timber physies all phenomena exhibited in the dead material of forest production.

The practical application of timber or wood for human use, its technology, is based upon the knowledge of timber physics, and under this term we comprise not only the anatomy, the chemical composition, the physical and mechanical properties of wood, but also its diseases and defects, and a knowledge of the influences and conditions which determine structure, physical, chemical, mechanical, or technical properties and defects. This comprehensive science, conceived under the name here chosen, although developed more or less in some of its parts, has never yet been dignified by a special name, nor has asystematic arrangement of its parts been attempted before. It comprises various groups of knowledge derived from other sections of science, which are neither in themselves nor in their relations to each other fully developed.

While plant physiology, biology, chemistry, anatomy, and especially xylotomy, or the science of wood structure, are more or less developed and contribute toward building up this new branch of science, but little knowledge exists in regard to the interrelation between the properties of wood on one side and the modifications in its composition and strueture on the other. Even the relation of the properties of various woods, as compared with each other, and their distinet specific peculiarities are but little explored and established. Less knowledge still exists as to the relation of the conditions which surround the living tree to the properties which are exhibited in its wood as a result of its life functions. Suppositions and conjectures more or less plausible preponderate over positive knowledge derived from exact observation and from the results of experiments. Still less complete is our knowledge in regard to the relation of properties and the methods and means used for shaping or working the wood.

The close interrelation of all branches of natural science is now so well recognized that I need not remind my readers that hard and fast lines can not be drawn whereby each field of inquiry is confined and limited; there must necessarily be an overlapping from one to the other. Any system, therefore, of dividing a larger field of inquiry into parts is only a matter of convenience; its divisions and correlations must be tosome extent arbitrary and varied according to the point of view from which we proceed to divide and cerrelate.

There are two definite and separate directions in which this branch of natural science needs to be developed, and the knowledge comprised in it may be divided accordingly. On one side it draws its substance largely from the more comprehensive fields of botany, molecular physics, and chemistry, and on the other side it rests upon investi- gations of the wood material from the point of view of mechanics or dynamics. In the first direction we are led to deal with the wood material as it is, its nature or appearance and conditions; in the second direction we consider the wood material in relation to external mechanical forces, its behavior under stress.

The first part is largely descriptive, concerned in examining gross and minute structures, physical and chemical conditions and properties, and ultimately attempting to explain these by referring to causes and conditions which produce them. This is a field for investigation and research by the plant physiologist in the laboratory in connec- tion with studies of environment in the forest. The second part, which relies for its development mainly upon experiment by the engineer, deals with the properties which are a natural consequence of the structure, physical condition, and chemical composition of the wood as exhibited under the application of external mechanical forces. It comprises, therefore, those studies which contemplate the wood substance, with special reference to the uses of man, and forms ultimately the basis for the mechanical technology of wood or the methods of its use in the arts.

The correlation of the results of these two directions of study as cause and effect is the highest aim and ultimate goal, the philosophy of the science of timber physics. Timber physics, in short, is to furnish all necessary knowledge of the rational application of wood in the arts, and at the same time, by retrospection, such knowledge will enable us to produce in our own forest growth qualities of given character. —

380 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE,

Conceived in this manner it becomes the pivotal science of the art of forestry, around which the practice both of the consumer and producer of forest growth moves.

The first part of our science would require a study into gross and minute anatomy, the structure of the wood, form, dimensions, distribution, and arrangement of its cell elements and of groups of structural parts, not only in order to distinguish the different woods, but also to furnish the basis for an explanation of their physical and mechanical properties. We next would class here all investigations into the physical nature or properties of the wood material, which necessarily also involves an investigation into the change of these properties under varying conditions and influences. A third chapter would occupy itself with the chemical composition and properties of woods and their changes in the natural process of life, which predicate the fuel value and durability as well as the use of the wood in chemical technology.

Although, philosophically speaking, it would hardly seem admissible to distinguish between physical and mechanical properties or to speak of ‘ mechanical” forces, for the sake of convenience and practical purposes it is desirable to make the distinction and to classify all phenomena and changes of nonliving bodies, or bodies without reference to life functions, into chemical, physical, and mechanical phenomena and changes. As chemical phenomena or changes, and therefore also conditions or properties, we class, then, those which have reference to atomic struc- ture; as physical phenomena, changes, and properties those which refer to and depend on molecular arrangement, and as mechanical (molar) changes and properties those which concern the masses of bodies, as exhibited under the influence of external forces, without altering their physical or chemical constitution.

There is no doubt that this division is somewhat forced, since not only most or all mechanical (as here conceived) changes are accompanied or preceded by certain alterations of the interior molecular arrangement of the mass, but also many physical phenomena or properties, like density, weight, shrinkage, having reference to the mass, might be classed as mechanical; yet if we conceive that physical phenomena are always concerned with the ‘‘ quantity of matter in molecular arrangement” and with the changes produced by interior forces, while the latter are concerned rather with the “position of matter in molecular arrangement” and with changes under application of exterior forces, the distinction assumes a practical value.

Our conception of these distinctions will be aided if we refer to the physical laboratory as furnishing the evidence of physical phenomena and to the mechanical laboratory as furnishing evidence of mechanical phenomena.

These latter, then, form the subject of our second or dynamic part of timber physics, which concerns itself to ascertain mainly by experiment, called tests, under application of the laws of elasticity, the strength of the material and other properties which are exhibited as reactions to the influence of applied stresses, and those which need consideration in the mechanical use of the material in the various arts.

Having investigated the material in its normal condition, we would necessarily come to a consideration of such physical and chemical conditions of the material as are abnormal and known as disease, decay, or defects.

Finally, having determined the properties and their changes as exhibited in material produced under changing conditions or differing in physical and structural respects, it would remain the crowning success and goal of this science to relate mechanical and physical properties with anatomical and physiological development of the wood substance.

The subject-matter comprised in this branch of applied natural science, then, may be brought into the following schematic view :

TIMBER PHYSICS, OR THE SCIENCE OF WOOD,

I.—Woopb stRUCTURE OR XYLOTOMY. (a) Exterior form.

Here would be described the form development of timber in the standing tree, ditterentiated into root

system, root collar, bole or trunk crown, branches, twigs; relative amounts of material furnished by each, (b) Interior structural appearance; differentiation and arrangement of groups of structural elements.

Here would be described the gross structural features of the wood, the distribution and size of medul- lary rays, vessels, fibro-vascular bundles, as exhibited to the naked eye or under the magnifying glass on tangential, radial, and transverse sections; the appearance of the annual rings, their size, regularity, dif- ferentiation into summer and spring wood, and all distinguishing features due to the arrangement and proportion of the tissues composing the wood.

(c) Minute anatomy or histology; differentiation and arrangement of structural elements. Here the revelations of the microscope are recorded, especially the form, dimensions, and structure of the different kinds of cells, their arrangement, proportion, and relative importance in the resulting tissues. (d) Comparative classification of woods, according to structural features. (e) Laws of wood growth with reference to structural results. Discussion of the factors that influence the formation of wood in the standing tree. (f) Abnormal formations. Burls, bird’s eye, curly, wavy, and other structural abnormities and their causes. II.—PuysICAL PROPERTIES, i. e., properties based on molecular (physical) constitution. (a) Exterior appearance.

Such properties as can be observed through the unaided senses, as color, gloss, grain, texture, smell, resonance.

(b) Material condition.

Such properties or changes as are determined by measurements, as density or weight, water contents and their distribution, volume, and its changes by shrinkage and swelling.

TIMBER PHYSICS—EARLIER WORK. 381

(ec) Classification of woods according to physico-technical properties, i. e., such physical properties as determine their application in the arts. III.— CHEMICAL PROPERTIES, i. e., properties based on atomie (chemical) constitution.

(a) General chemical analysis of wood (qualitative and quantitative).

Here would be discussed the chemical constitution of different woods and different parts of trees and their changes due to physiological processes, age, conditions of growth, etc.

(b) Carbohydrates of the wood.

Here would be more specially discussed cellulose and lignin, cork formations, organic contents and their changes, and snch properties as predicate the fuel value of woods, their manufacture into charcoal, their food value, pulping qualities, ete.

(ce) Extractive materials.

A knowledge of these underlies the application of wood in the manufacture of tan extracts, resin, and turpentine, tar, gas, alcohol, acids, vanillin, ete.

(ad) Antiseptic materials.

A knowledge of those chemical properties which predicate durability and underlie processes of increasing the same.

(e) Mineral constituents.

A knowledge of these in particular will establish the relation of wood growth to mineral constituents of the soil and also serve as basis for certain technical uses (potash).

IV.—MECHANICAL PROPERTIES, i. e., properties based on elastic conditions exhibited by the aggregate mass under influence of exterior (mechanical) forces.

(a) Form changes without destruction of cohesion, commonly called elasticity, flexibility, toughness.

(b) Form changes with destruction of cohesion, commonly called strength (tensile, compressive, torsional, shearing),

cleavability, hardness. V.—TECHNICAL PROPERTIES, i. €., properties in combination.

Here would be considered the woods with reference to their technical use, their application in the arts, which is invariably based upon a combination of several physical or mechanical properties.

VI.—DISEASES AND FAULTS.

Here would be treated the changes in structure and properties from the normal to abnormal conditions,

due to influences acting upon the tree during its life or upon the timber during its use. VII.—RELATION OF PROPERTIES TO EACH OTHER.

Here would be discussed the connection which may be established between structure, physical, chemical, and mechanical properties, and also between these and the conditions of growth under which the material was produced. The philosophy of the entire preceding knowledge would here be brought together.

To contribute toward this important branch of human knowledge and to help in the building of its foundation, the work undertaken by the Division of Forestry described in this bulletin was designed by the writer; and, in order to build with a knowledge of what has been done before on this structure, a brief review of the progress in the development of timber physics seemed advisable.

This historical review is then given. From this we deem it appropriate to quote the portion whieh refers to efforts in the United States up to the time of the writing to establish data regarding the mechanical properties of our timber:

AMERICAN WORK.

While it may be possible to work out the general laws of relation between physical and mechanical properties on material of European origin, for practical purposes we can not rely upon any other data than those ascertained from American timbers, and so var as dependence of quality on conditions of growth are concerned this truth is just as patent. Although in the United States probably more timber has been and is being used than in any other country, but little work has been done in the domain of timber physics.

Among the earliest American experiments falling in the domain of timber physics may be cited those of Marcus Bull to determine ‘‘the comparative quantities of heat evolved in the combustion of the principal varieties of wood and coal used in the United States for fuel,” made in the years 1823 to 1825 and published in 1826. Here the experiments of Lavoisier, Crawford and Dalton, and Count Rumford on similar lines are discussed and followed by an able series of experiments and discussion on American woods and coals.

The only comprehensive work in timber physics ever undertaken on American timbers is that of Mr. T. P. Sharples, in connection with the Tenth Census, and published in 1884, Vol. IX, on the Forests of North America. Comprehensiveness, however, has been sought rather in trying to bring under examination all the arborescent species than in furnishing fuller data of practical applicability on those from which the bulk of our useful material is derived. ‘The resu!ts obtained,” the author says, ‘are highly suggestive; they must not, however, be considered conclusive, but rather valuable as indicating what lines of research should be followed in a more thorough study of this subject.”

Not less than 412 species were examined in over 1,200 specimens. The results are given in five tables, besides four comparative tables of range, relative yalues, averages, etc. The specimens were taken ‘in most cases from the butt cut and free from sap and knots;” the locality and soil from which the tree came are given in most cases, and in some its diameter and layers of heart and sapwood; determinations were made of specific gravity, mineral ash per cent, and from these data fuel values were caleulated.

382 FORESTRY INVESTIGATIONS U. 8S. DEPARTMENT OF AGRICULTURE.

The specimens tested were ‘‘caretully seasoned.” For transverse strain they were made 4 centimeters (1.57 inches) square, and a few of double these dimensions, with 1 meter (3.28 feet) span. a‘

One table illustrates “the relation between the specific gravity and the transverse strength of the wood of species, upon which a suflicient number of tests has been made to render such a comparison valuable.” This table seems to show that in perfect specimens weight and strength stand in close relation. A few tanning determinations on the bark of a few species are also given.

The object of the work as stated, namely, to be suggestive of a more thorough study of the subject, has certainly been fully and creditably attained. Of compilatory works, for use in practice and for reference, the following, published in the United States, may be cited:

De Volson Wood: Resistance of Materials (1871), containing rather scanty references to the work of Chevandier and ‘Wertheim.

R. G. Hatfield: Theory of Transverse Strain (1877), which, besides other references, contains also twenty-three tables of the author’s own test on white pine, Georgia pine, hemlock, spruce, white ash, and black locust, on sticks 1 by 1 inch by 1.6 feet in length.

William H. Burr: The Elasticity and Resistance of Materials of Engineering, third edition, 1890, a compre- hensive work, in which many references are made to the work of various American experimenters.

Gaetano Lanza, in Applied Mechanics, 1885, lays especial stress on the fact that tests on small select pieces give too high values, and quotes the following experiments on long pieces. He refers to the work of Capt. T. J. Rodman, United States Army, published in Ordnance Manual, who used test pieces 27 by 5} inches and 5 feet length, without giving any reference to density or other facts concerning the wood; and to Col. Laidley’s United States Navy test (Senate x. Doe. 12, Forty-seventh Congress, first session, 1881), who conducted a series of experiments on Pacifie slope timbers, ‘‘ white and’ yellow pine,” 12 feet long and 4 to 5 by 11 to 12 inches square, giving also account of density and average width of rings.

Lastly, the author’s own experiments, made at the Watertown Arsenal for the Boston Manufacturers’ Mutual Fire Insurance Company, on the columnar strength of “ yellow pine” and white oak, 12 feet long and 6 to 10 inches thick, are brought in support of the claim that such tests show less than half the unit strength of those on small pieces. Data as to density, moisture, or life history of the specimens are everywhere lacking.

R. H. Thurston, Materials of Engineering, 1882, contains, perhaps, more than any other American work on the subject, devoting, in Chapters II and III, 117 pages to timber and its strength, and in the chapter on Fuel several pages to wood and charcoal, and the products of distillation. "It also gives a description of some twenty-five kinds of American and of a few foreign timber trees, with a description of the structure and their wood in general; directions for felling and seasoning; discusses briefly shrinkage, characteristics of good timber, the influence of soil and climate on trees and their wood, and of the various forms of decay of timber, methods of preservation and adaptation of various woods for various uses, much in the same manner as Rankine’s Manual of Civil Engineering, from which many conclusions are adopted. The author refers, besides foreign authorities, to the following American investigators :

G. H. Corliss (unpublished?) is quoted as claiming that proper seasoning of hickory wood increases its strength by 15 per cent.

R. G. Hatfield is credited with some of the best experiments on shearing strength, published in the American House Carpenter.

Prof. G. Lanza’s experiments are largely reproduced, also Trantwine’s on shearing, and some of the author’s own work on California spruce, Oregon pine, and others, especially in torsion, with a specially constructed machine, an interesting plate of strain diagrams accompanying the discussion.

In connection with the discussion by the author on the influence of prolonged stress, there is quoted as one of the older investigators, Herman Haupt, whose results on yellow pine were published in 1871 (Bridge Construction).

Experiments at the Stevens Institute of Technology are related, with the important conclusion that a load of 60 per cent of the ultimate strength will break a stick if left loaded (one small test piece having been left loaded fifteen months with this result).

In addition the following list of references to American work in timber physics is here inserted, with a regret that it has not been possible to include all the stray notes which may be in existence but were not accessible. Those able to add further notes are invited to aid in making this reference list complete:

Abbott, Arthur V. Testing machines, their history, construction, and use. With illustrations of machines, includ- ing that at Watertown Arsenal. Van Nostrand’s Magazine, 1883, vol. 30, pp. 204, 325, 382, 477.

Day, rank M., University of Pennsylvania. ‘The microscopic examination of timber with regard to its strength. Read before American Philosophical Society, 1883.

Estrada, E. D. Experiments on the strength and other properties of Cuban woods. Investigations carried on in the laboratory of the Stevens Institute. Van Nostrand’s Magazine, 1885, vol. 29, pp. 417, 441.

Flint, ——. Report of tests of Nicaraguan woods. Journal of Franklin Institute, October, 1887, pp. 289-315.

Goodale, Prof. George L., Harvard University. Physiological Botany, 1885, chapters 1, 2, 3, 5, 8, 11, and 12.

Ihlseng, Magnus C., Ph. D. On the modulus of elasticity in some American woods, determined by vibration. Van Nostrand’s Magazine, 1878, 19.

On a mode of measuring the velocity of sounds in woods. Read before the National Academy of Science, 1877; published in American Journal of Science and Arts, 1879, vol. 17.

Johnson, Thomas H. On the strength of columns. Paper read at annual convention of American Society of Civil Engineers, 1885. Transactions of the Society, vol. 15.

TIMBER PHYSICS—EARLIER WORK. 383

Kidder, F. E. Experiments at Maine State College on transverse strength of southern and white pine. Van Nostrand’s Magazine, 1879, vol. 22.

—— Experiments with yellow and white pine. Van Nostrand’s Magazine, 1880, vol. 23.

— Experiments on the strength and stiffness of small spruce beams. Van Nostrand’s Magazine, 1880, vol. 24.

Influence of time on bending strength and elasticity. Journal of Franklin Institute, 1882. Proceedings Institute of Civil Engineering, vol. 71.

Lanza, Gaetano, professor Massachusetts Institute of Technology. Address before American Society of Mechanical Engineers, describing the 50,000-pound testing machine at Watertown Arsenal and tests of strength of large spruce beams. Journal of Franklin Institute, 1883.

Report of Boston Manufacturers’ Mutual Fire Insurance Company of tests made with Watertown machine on columns of pine, whitewood, and oak of dimensions used in cotton and woolen mills. See summary and tables of same in Burr's Elasticity and Resistance of the Materials of Engineering, p. 480.

Macdonald, Charles. Necessity of government aid in making tests of materials for structural purposes. Paper read before the American Institute of Mining Engineers. Van Nostrand’s Magazine, 1882, vol. 27, p. 177.

Norton, Prof. W. A., Yale College. Results of experiments on the set of bars of wood, iron, and steel after a transverse set. Experiments discussed in two papers read before the National Academy of Science, 1874 and 1875. Published in Van Nostrand’s Magazine, 1887, vol. 17, p. 531.

Description of maching used is given in proceedings of the A.A.A.S., eighteenth meeting, 1869.

Parker, Lieut. Col. F. H., United States Ordnance Department. Report of tests of American woods by the testing machine, United States Arsenal, Watertown, under supervision of Prof.C.S.Sargent, for the Census Report, 1880. Senate Ex. Doc. No.5, Forty-eighth Congress, first session, 1882-83.

Report of experiments on the adhesion of nails, spikes, and screws in various woods, as made at Watertown

Arsenal. Senate Ex. Doc. No. 35, Forty-ninth Congress, first session, 1883-84, and in report on tests of metals

and other materials for industrial purposes at Watertown Arsenal, 1888-89.

Also in report on tests of iron, steel, and other materials for industrial purposes at Watertown Arsenal,

1886-87, pp. 188, 189.

Report on cubic compression of various woods, as shown by tests at Watertown Arsenal, 1885-86, in report on tests of metals, etc., for industrial purposes. .

Philbrick, Professor, lowa University. New practical formulas for the resistance of solid and built beams, girders, ete., with problems and designs. Van Nostrand’s Magazine, 1886, vol. 35.

Pike, Prof. W. A. Tests of white pine, made in the testing laboratory of the University of Minnesota. Van Nos- trand’s Magazine, 1885, vol. 34, p. 472.

Rothrock, Prof. J. T., University of Pennsylvania. Some microscopic distinctions between good and bad timber of the same species. Read before American Philosophie Society.

Smith, C. Shaler, C. E. Summary of results of 1,200 tests of full-size yellow-pine columns. See W. I. Burr’s Elasticity and Resistance of the Materials of Engineering, pp. 485-490.

Thurston, Prof. R. H., Cornell University. The torsional resistance of materials. Journal of #ranklin Institute, 1873, vol. 65.

Experiments on torsion. Van Nostrand’s Magazine, July, 1873.

— Experiments on the strength, elasticity, ductility, etc., of materials, as shown by a new testing machine. Van Nostrand’s Magazine, 1874, vol. 10.

The relation of ultimate resistance to tension and torsion. Proceedings of Institute of Civil Engineers,

vol. 7, 1878.

The strength of American timber. Experiments at Stevens Institute. Paper before A. A. A. S., 1879.

Journal of Franklin Institute, vol. 78, 1879.

Effect of prolonged stress upon the strength and elasticity of pine timber. Journal of Franklin Institute.

vol. 80, 1880.

Influence of time on bending strength and elasticity. Proceedings A. A. A. S., 1881. Proceedings Institute of Civil Engineers, vol. 71.

Watertown Arsenal. Summary of results of tests of timber at, in Ex. Doc. No. 1, Forty-seyenth Congress, second session. See Burr’s Elasticity and Resistance of Materials of Engineering, pp. 486 and 535.

Wellington, A. M., c. &. Experiments on impregnated timber. Railroad Gazette, 1880.

ORGANIZATION AND METHODS.

Although in the course of the investigations many minor and some more important changes in methods became necessary, the general plan was in the main adhered to. We consider it, therefore, desirable to restate from the same bulletin such portions as will explain the methods pursued. The work at the test laboratory at St. Louis, Mo., was described in full by Prof. J. B. Johnson, in charge, and the methods in the examination of the physical properties of the test material by the writer.

There are four departments necessary to carry on the work as at present organized, namely:

(1) The collecting department.

(2) The department of mechanicai tests.

354 FORESTRY INVESTIGATIONS U. 8S. DEPARTMENT OF AGRICULTURE.

(3) The department of physical and microscopic examination of the test material.

(4) The department of compilation and final discussion of results.

The region of botanical distribution of any one species that is to be investigated is divided into as many Stations as there seem to be widely different climatic or geological differences in its habitat. In each station are selected as many sites as there seem widely different soils, elevations, exposures, or other striking conditions oceupied by the species. An expert collector describes carefully the conditions of station and site, under instructions and on blanks appended to this report. From each site five mature trees of any one species are chosen, four of which are average representatives of the general growth, the fifth, or “check” tree, the best developed that can be found. The trees are felled and cut into logs of merchantable size, and from the butt end of each log a disk 6 inches in height is sawed. Logs and disks are marked with numbers to indicate number of tree and number of log or disk, and their north and south sides are marked; their height in the tree from the ground is noted in the record. The disks are also weighed immediately, then wrapped in oiled paper and packing paper, and sent by mail or express to the laboratory, to serve the purpose of physical and structural examination. Some disks of the limbwood and of younger trees are also collected for other physical and physiological investigations, and to serve with the disks of the older trees in studying the rate of growth and other problems.

The logs are shipped to the test laboratory, there sawed and prepared for testing, carefully marked, and tested for strength.

The fact that tests on large pieces give different values from those obtained from small pieces being fully established, a number of large sticks of each species and site will be tested full length in order to establish a ratio between the values obtained from the different sizes. Part of the material is tested green, another part when seasoned by various inethods. Finally, tests which are to determine other working qualities of the various timbers, such as adapt them to various uses, are contemplated

The disks cut from each log and correspondingly marked are examined at the botanical labora- tory. An endless amount of weighings, measurings, countings, computings, microscopic examina- tions, and drawings is required here, and recording of the observed facts in such a manner that they can be handled. Chemical investigations have also been begun in the Division of Chemistry of the Department of Agriculture, the tannic contents of the woods, their distribution through the tree and their relation to the conditions of growth forming the first series of these investigations.

It is evident that in these investigations, carried on by competent observers, besides the main object of the work, much new and valuable knowledge unsought for must come to light if the investigations are carried on systematically and in the comprehensive plan laid out. Since every stick and every disk is marked in such a manner that its absolute position in the tree and almost the absolute position of the tree itself or at least its general condition and surroundings are known and recorded, this collection will be one of the most valuable working collections ever made, allow- ing later investigators to verify or extend the studies.

This significant prophetic language also occurs in this connection, which has finally been realized by the discovery of the relation between compression and beam strength:

By and by it is expeeted that the number of tests necessary may be reduced considerably, when for each species the relation of the different exhibitions of strength can be sufficiently established, and perhaps a test for compres- sion alone furnish sufficient data to compute the strength in other directions.

WORK AT THE TEST LABORATORY AT ST. LOUIS, MO. SAWING, STORING, AND SEASONING.

On arrival of the logs in St. Louis they are sent to a sawmill and cut into sticks, as shown in fig. 103.

In all cases the arrangements shown in Nos, 1 and 2 are used, except when a detailed study of the timber in all parts of the cross section of the log is intended. A few of the most perfect logs of each species are cut up into small sticks, as shown in Nos. 3and 4. The logs tested for determining the effects of extracting the turpentine from the Southern pitch pines were all cut into small sticks.

In all cases a ‘‘small stick” is nominally 4 inehes square, but when dressed down for testing may be as small as 34 inches square. The “large sticks” vary from 6 by 12 to 8 by 16 inches in cross section.

All logs vary from 12 to 18 feet in length. They all have a north and south diametral line, together with the number of the tree and of the log plainly marked on their larger or lower ends. The stenciled lines for sawing are

TIMBER PHYSICS—TESTING. 385

adjusted to this north and south line, as shown in the figures. Each space is then branded by deep dies with three 95 numbers, as, for instance, thus: 2, which signifies that this stick was number 4, in log 2, of tree 25. A facsimile of 4 the stenciling is recorded in the log book, and the sticks there numbered to correspond with the numbering on the logs. After sawing, each stick can be identified and its exact origin determined. These three numbers, then, become the identification marks for all specimens cut from this stick, and they accompany the results of tests in all the records,

The methods of sawing shown in Nos. 2 and 4 are called ‘boxing the heart;” that is, all the heart portion is thrown into one small stick, which in practice may be thrown away or put into a lower grade without serious loss. In important bridge, floor, or roof timbers, the heart should always be either excluded or ‘‘boxed” in this way, since its presence leads to checking and impairs the strength of the stick.

After sawing, the timbers are stored in the laboratory until they are tested. The “green tests” are made usually within two months after sawing, while the ‘dry tests” are made at various subsequent times. One end (60 inches) of each small stick is tested green, and the other end reserved and tested after seasoning. The seasoning is hastened in some cases by means of a drying box. ‘The temperature of the inflowing air in this drying box is kept at about 100° F., with suitable precaution against checking of the wood, and the air is exhausted by means of a fan. The air is, therefore, somewhat rarefied in the box. The temperature is at all times under control. It operates when the fan is rnnning, and this is only during working hours.

The mechanical and moisture test are then made according to known methods.

. . &

No. 2. No. 3. Fig. 103.—Method of sawing test logs.

EXAMINATION INTO THE PHYSICAL PROPERTIES OF TEST MATERIAL.

The physical examination consists in ascertaining the specific weight of the dried material, and incidentally the progress and amount of shrinkage due to seasoning; the counting and measuring of the annual rings, and noting other microscopic appearances in the growth; the microscopic investigation into the relation of spring and summer wood from ring to ring; the frequency and size of medullary rays; the @umber of cells and thickness of their walls; and, in short, the consideration of any and all elements which may elucidate the structure and may have influence upon the properties of the test piece. The rate of growth and other biological facts which may lead to the finding of relation between physical appearance, conditions of growth, and mechanical properties are also studied incidentally.

SHAPING AND MARKING OF THE MATERIAL.

The object of this work being in part the discovery of the differences that exist in the wood, not only in trees of different species or of the same species from various localities, but even in the wood of the same tree and from the same cross section, a careful marking of each piece is necessary. The disks are split, first into a north and south piece, and each of these into smaller pieces of variable size. In one tree all pieces were made but 3 em. thick radially, in another 4 cm., in still others 5 em., while in some trees, especially wide-ringed oaks, the pieces were ieft still larger. In the conifers the outer or first piece was made to contain only sapwood. Desirable as it appeared to have each piece contain a certain number of rings, and thus to represent a fixed period of growth, it proved impracticable, at least in the very narrow-ringed disks of the pines, where sometimes the width of a ring is Jess than 5 mm. (0.2 inch).

H. Doe. 181 25

386 FORESTRY INVESTIGATIONS U. 8S. DEPARTMENT OF AGRICULTURE.

Some of the disks were split to a wedge shape from center to periphery, so that each smaller piece not only represents a certain period of growth in quality, but also in quantity, thus simplify- ing the calculations for the entire piece or disk. Other pieces were left in their prismatic form, when to calculate the average density of the entire piece the density of each smaller piece is multiplied by the mean distance of this smaller piece from the center, and the sum of the products divided by the sum of the distances.

Each piece is marked, first by the number of the tree, in Arabic; second, by the number of the disk, in Roman numbers; and if split into small pieces, each smaller piece by a letter of the alphabet, the piece at the periphery in all cases bearing the letter a. Besides the number and letters mentioned, each piece bears either the letter N or 8, to indicate its orientation on the north or south side of the tree. To illustrate: 5—vi1 N a means that the piece bearing the label belongs to tree 5 and disk vir comes from the north side of the tree, and is the peripheral part of this disk piece. From the collector’s notes the exact position of this piece in the tree can readily be ascertained.

The entire prisms sent by freight are left in the original form, unless used for special purposes, and are stored in a dry room for future use.

WEIGHING AND MEASURING.

The weighing is done on an apothecary’s balance, readily sensitive to 0.1 gram with a load of more than 200 grams. Dealing with pieces of 200 to 1,000 grams in weight, the aecuracy of weigh- ing is always within 1 gram.

The measuring is done by immersion in an instrument illustrated in the following design: V is a vessel of iron; S represents one of two iron standards attached to the vessel and projecting

Fic. 104.—Apparatus for determining specifie gravity.

above its top; Bis a metal bar fastened to the cup A, which serves as guard to the cup and pre- vents it going down farther at one time than another by coming to rest on the standards 8S. The cup A dips down one-sixteenth to one-eighth of an inch below the edge of the knee-like spout. In working, the cup is lifted out by the handle which the bar B forms, mice is poured into the vessel until it overflows through the spout, then the cup is set down, replacing the mobile and fickle natural water level by a constant artificial one. Now the instrument is set, the pan P is placed under the spout, the cup is lifted out and, held over the vessel, so that the drippings fall back into the latter, the piece of wood to be measured is put into the vessel and the cup replaced, and pressed down until the bar B rests on the standards 8. This is done gently to prevent the water from rising above the rim of the vessel. This latter precaution is superfluo us where the cup fits closely, as ib

. TIMBER PHYSICS—PHYSICAL EXAMINATION. 587

does in one of the instruments thus far used. ‘lhe pan with water is then weighed, the pan itself being tared by a bag of shot. ‘Che water is poured out, the pan wiped dry, and the process begins anew. To work well it takes two persons, one to weigh and record. The water pan is a seamless tin pan, holding about 1,500 ce. of water and weighing only 144 grams. The temperature as well as density of the water are ascertained, the latter, of course, omitted when distilled water is used. To maintain the water at the same temperature it requires frequent changing.

DRYING,

After marking, the pieces are left to dry at ordinary temperature. Then they are placed in a dry kiln and dried at 100° C. ;

The drying box used is a double-walled sheet-iron case, lined with asbestus paper, and heated with gasoline. The air enters below and has two outlets on top. The temperature is indicated by a thermometer and maintained fairly constant.

After being dried, the pieces of wood are weighed and measured, in the same way as described for the fresh wood, and from the data thus gathered the density, shrinkage, and moisture per cent are derived in the usual manner.

The formule employed are:

Weight of fresh wood. Volume of fresh wood. Weight of dry wood. Volume of dry wood.

(1) Density of fresh wood= (2) Density of dry wood=

(3) Shrinkage= == ape t ee

Fresh weight—dry weight.

Fresh weight.

In presenting these values they are always multiplied by 100, so that the density expresses the weight of 100 em. of wood; thus the shrinkage and the amount of moisture become the shrinkage and moisture per cent.

(4) Moisture in wood=

SHRINKAGE EXPERIMENTS,

To discover more fully the relations of weight, humidity, and shrinkage. as well as “checking” or cracking of the wood, a number of separate experiments were made. A number of the fresh specimens were weighed and measured at variable intervals until perfectly dry. Some dry pieces were placed in water and kept immersed until the maximum volume was attained. Without describing more in detail these tests and their results, it may be mentioned that in the immersed pieces studied the final maximum volume differed very little, in some cases not at all, from the original volume of the wood when fresh; and also that in a piece of white pine only 15 em. long and weighing but 97 gs. when dry, it required a week before the swelling ceased.

To determine the shrinkage in different directions a number of measurements are made in pieces of various sizes and shapes. In most cases pins were driven into the wood to furnish a firm metal point of contact for the caliper. A number of pieces of oak were cut in various ways to study the effect of size, form, and relative position of the grain on checking.

WOOD STRUCTURE.

The most time-robbing, but also the most fascinating, part of the work consists in the study of the wood as an important tissue of a living organism; a tissue where all favorable and unfavorable changes experienced by the tree during its long lifetime find a permanent record.

GENERAL APPEARANCE,

For this study all the specimens from one tree are brought together and arranged in the same order in which they occurred in the tree. This furnishes a general view of the appearance of the stem; any striking peculiarities, such as great eccentricity of growth, unusual color, abundance of resin in any part of the stem, are seen at a glance and are noted down.

A table is prepared with separate columns, indicating—

(1) Height of the disk in the tree (this being furnished by the collector’s notes) ;

(2) Radius of the section;

388 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

3) Number of rings from periphery to center; Number of rings in the sapwood;

Width of the sapwood; and

6) Remarks on color, grain, ete.

The results from each disk occupy two lines, one for the pieces from the north side and one for those of the south side. The radius is measured correct to one-half millimeter (0.02 ineh), and the figures refer to the air-dry wood.

To count the rings, the piece is smoothed with a sharp knife or plane, the cut being made oblique, i.e., not quite across the grain, nor yetlongitudinal. Beginning at the periphery, each ring is marked with a dot of ink, and each tenth one with a line to distinguish it from the rest. After counting, the rings are measured in groups of ten, twenty, thirty, rarely more, and these meas- urements entered in separate subcolumns. In this way the rate of growth of the last ten, twenty, or thirty years throughout the tree is found, also that of similar periods previous to the last; in short, a fairly complete history of the rate of growth of the tree from the time when it had reached the height of the stump to the day when felled is thus obtained. Not only do these rings furnish information concerning the growth in thickness, but indicating the age of the tree when it had grown to the height, from which the second, third, etc., disks were taken, the rate of growth in height, as well as that of thickness, is determined, any unfavorable season of growth or any series of such seasons are found faithfully recorded in these rings, and the influence of such seasons; whatever their cause, both on the quantity and on the quality or properties of the wood, can thus be ascertained,

In inany cases, especially in the specimens from the longleaf pine, and from the limbs of all pines, the study of these rings is somewhat difficult. Zones of a centimeter and more exist where the width of the rings is such that the magnifier has to be used to distinguish them. In some cases this difficulty is increased by the fact that the last cells of one year’s growth differ from the first cells of the next year’s ring only in form and not in the thickness of their walls, and therefore produce the same color effect. Such cases frequently occur in the wood of the upper half of the disks from limbs (the limb supported horizontally and inits natural position), and often the magnifier has to be reenforced by the microscope to furnish the desired information. For this purpose the wood is treated as in all microscopic work, being first soaked in water and then sectioned with a sharp knife or razor and examined on the usual slide in water or glycerin.

The reason for beginning the counting of rings at the periphery is the same which suggested the marking of all peripheral pieces by the letter a. It is convenient, almost essential, to have, for instance, the thirty-fifth ring in Section Il represent the same year’s growth as the. thirty-fifth ving in Section X. The width of the sapwood, the number of annual rings composing it, as well as the clearness and uniformity of the line separating the sapwood from the heartwood, are sarefully recorded, Inthe columns of “remarks” any peculiarities which distinguish the particular piece of wood, such as defects of any kind, the presence of knots, abundance of resin, nature of the grain, ete., are set Gown.

When finished, a variable number, commonly 3 to 6 small pieces, fairly representing the wood of the tree, are split off, marked with the numbers of their respective disks, and set aside for the microscopic study, which is to tell us of the cell itself, the very element of structure, and of its share in all the properties of wood.

The small pieces are soaked in water, cut with a sharp knife or razor, and examined in water, glycerin, or chloriodide of zinc. The relative amount of the thick-walled, dark-colored bands of summer wood, the resin ducts, the dimensions of the common tracheids and their walls, both tn spring and summer wood, the medullary rays, their distribution and their elements, are the principal subjects in dealing with coniferous woods; the quantitative distribution of tissues, or how much space is occupied by the thick-walled bast, how much by vessels, how much by thin- walled, pitted tracheids and parenchyma, and how much by the medullary rays; what is the relative value of each as a strength-giving element; what is the space occupied by the lumina, what by the cell walls in each of these tissues—these are among the important points in the study of the oaks. }

Continued sections from center to periphery, magnified 25 diameters, are employed in finding the relative amount of the summer wood; the limits of the entire ring and that of spring and

TIMBER PHYSICS—STATEMENT OF RESULTS. 389

_ _ VI) 74 Ries \D..36 WAS % |133— — 68)FT. 135mm \W 38%

D..36 | ___ _ | «IBS RINGS \D..36 W45%/J4az SB|FT. 155 m.m. |W 40% S.8.17, S.7.9% RWS W..82mam.

p.sa {| __-_IV|_ 205 Rives |p.37 W.46% 70mm. \W 34% S.8% ELC i ga RWS RW..83 mm.

2/8 RINGS

D.41\___ __ | _ 222 Rines_ 43 : FT. 217mm. CBI S.8.8 S.9.4% a a ee RW..76 [RW 97mm.

197 RINGS _|D..44

FT. 180m.m. \E.W.91m.m,

ae 207mm. |" g LLNS Fed S/FT. 229Fines F

Fig. 105.—Result of physical examination. (Sample.)

LONGLEAF PINE (P. palustris), tree 3. WHITE PINE (P. Strobus), tree 116.

Locality: Wallace, Ala. Locality: Marathon County, Wis.

Site: Upland forest, quite dense. Site: Grown in dense mixed forest.

Soil: Sandy. Soil: Sandy, with sandy subsoil.

Legend. D. Denotes density or specific gravity of the dry wood. | Height is given in feet from the ground; scale, 10 feet —2 inches. W. Denotes percentage of water in the fresh wood, related to its | Radius, north and south (dotted line), in millimeters; scale, 10 mm.— weight. 0.1 inch.

S. Denotes percentage of shrinkage in kiln drying. Median line represents the pith. I. W. Denotes width of ring (average) in millimeters (25mm.—1inch). | Right-hand numbers relate to north side, left-hand numbers to south S. W. Denotes percentage of summer wood as related to total wood. side.

Roman numbers refer to number of disk, placed in position of disk. | Outer lines represent outlines of trees.

390 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

summer wood are marked on paper with the aid of the camera, and thus a panorama of the entire section is brought before the eye. The histology of the wood, the resin ducts, the tracheids and medullary rays, their form and dimensions, are studied in thin sections magnified 550 diameters and even more. Any peculiarity in form or arrangement is drawn with the camera and thus graphically recorded; the dimensions are measured in the manner described for the measurement of the summer wood, or with the ocular micrometer. In measuring cell walls the entire distance between two neighboring lumina is taken as a “double wall,” the thickness of the wall of either of the two cells being one-half of this. The advantage of this way of measuring is apparent, since the two points to be marked are in all cases perfectly clear and no arbitrary positions involved. The length of the cells is found in the usual way by separating the elements with Schultze’s solution (nitric acid, chlorate of potassium). All results tabulated are averages of not less than ten, often of more than one hundred, measurements.

In the attempt to find the quantitative relations of the different tissues, as well as the density of each tissue, various ways have been followed. In some cases drawings of magnified sections were made on good, even paper, the different parts cut out, and the paper weighed. In other cases numerous measurements and computations were resorted to. Though none of the results of these attempts can be regarded as perfectly reliable, they have done much to point out the relative importance of different constituents of the wood structure, and also the possibility and practica- bility, and even the necessity, of this line of investigation.

INSTRUCTIONS AND BLANK FORMS, WITH ILLUSTRATIVE RECORDS. INSTRUCTIONS FOR THE COLLECTION OF TEST PIECES OF PINES FOR TIMBER INVESTIGATIONS, A.—OBJECT OF WORK.

The collector should understand that the ultimate object of these investigations is, if possible, to establish the relation of quality of timber to the conditions under which it is grown. To accomplish this object he is expected to furnish a very careful description of the conditions under which the test trees have grown, from which test pieces are taken. Care in ascertaining these and minuteness and accuracy of description are all-important in assuring proper results. It is also necessary to select and prepare the test pieces exactly as described and to make the records perfect as nearly as possible, since the history of the material is of as much importance as the determination in the

laboratory. B.—LOCALITIES FOR COLLECTING.

As to the locality from which test trees are to be taken, a distinction is made into station and site.

By station is to be understood a section of country (or any places within that section) which is characterized in a general way by similar climatic conditions and geological formation. ‘‘Station,” then, refers to the general geographical situation. ‘‘Site” refers to the local conditions and surroundings within the station from which test trees are selected.

For example, the drift deposits of the Gulf Coast plain may be taken for one station; the limestone country of northern Alabama for a second. But a limestone formation in West Virginia, which differs climatically, would necessitate another station. Within the first station a rich, moist hummock may furnish one site, a sandy piece of upland another, and a wet savannah a third. Within the second or third station a valley might furnish one site, the top of a hill another, a different exposure may call for a third, a drift-capped ledge with deeper soil may warrant the selection of another.

Choice of stations.—For each species a special selection of stations from which test pieces are to be collec ted is necessary. These will be determined, in each case separately as to number and location, from this office. It is proposed to cover the field of geographical distribution of a given species in such a manner as to take in stations of climatic difference and different geological horizon, neglecting, however, for the present, stations from extreme limits of distribution. Another factor which will determine choice is character of soil, as dependent upon geological formations. Stations which promise a variety of sites will be preferably chosen.

Choice of site.—Such sites will be chosen at each station as are usually occupied by the species at any one of the stations. If unusual sites are found occupied by the species at any one of the stations it will be determined by special correspondence whether test pieces are to be collected from it. The determination of the number of sites at each station must be left to the judgment of the collector after inspection of the localities; but before determining the number of sites the reasons for their selection must be reported to this office. The sites are characterized and selected by differences of elevation, exposure, soil conditions, and forest conditions. The difference of elevation which may distinguish a site is provisionally set at 500 feet; that is, with elevation as the criterion for choice of stations the difference must be at least 500 feet. Where differences of exposure occur a site should be chosen on each of the exposures present, keeping as much as possible at the same elevation and under other similar conditions. Soil conditions may vary in a number of directions, in mineral composition, physical properties, depth, and nature of the subsoil. For the present, only extreme differences in depth or in moisture conditions (drainage) and decided difference in mineral composition will be considered in making selection of sites.

TIMBER PHYSICS—COLLECTING MATERIAL. 391

Forest conditions refer, in the first place, tc mixed or pure forest, open or close stand, and should be chosen as near as possible to the normal character prevailing in the region. If what, in the judgment of the collector, consti- tutes normal conditions are not found, the history of the forest and the points wherein it differs from normai conditions must be specially noted.

C.—CHOICE OF TREES.

On each site five trees are to be taken, one of which is to serve as ‘‘check tree.” None of these trees are to be taken from the roadside or open field, nor from the outskirts, buf all from the interior of the forest. They are to be representative average trees—neither the largest or best nor the smallest or worst, preferably old trees and such as are not overtopped by neighbors.

The ‘‘check tree,” however, should be selected with special care, and should represent the best-developed tree that can be found, judged by relative height and diameter development and perfect crown.

The distance between the selected trees is to be not less than 100 feet or thereabout, yet care | must be exercised that all are found under precisely the same conditions for which the site was chosen.

There are also to be taken six young trees as prescribed under E.

If to be had within the station, select two trees from 30 to 60 years old or older, which are known to have grown up inthe open, and two trees which are known to have grown up in the forest, but have been isolated for a known time of ten to twenty years.

D.—PROCEDURE AND OUTFIT.

The station determined upon, the collector will proceed to examine it for the selection of sites. After having selected the sites, he will at once communicate the selection, with description and justification, to this office, negotiate with the owners of the timber (which might be done conditionally during the first examination) for the purchase or donation of test trees; and. the latter arrangements completed, without waiting reply from this office, he will at once proceed to collect test pieces on one of the sites in regard to the selection of which he is not in doubt.

To properly carry out the instructions, the following assistants and outfit may be required:

(1) Two men! with ax and saw; a boy also may be of use.

(2) Team, wagon, and log trucks for moving test pieces and logs to station.

(3) Frow or sharp hacking knife for splitting disks. Heavy mallet or medium-sized “maul” to be used with frow.

(4) A handsaw.

(5) Red chalk for marking. (A special marking hammer will be substituted. )

(6) Tape line and 2-foot rule or ealipers.

(7) Tags (specially furnished).

(8) Tacks (12-ounce) to fasten tags.

(9) Wrapping paper and twine,

(10) Franks for mailing test pieces (specially furnished).

(11) Shipping tags for logs.

(12) Seales, with weight power not less than 30 pounds.

(13) Barometer for ascertaining elevations.

(14) Compass to ascertain exposures.

(15) Spade and pick to ascertain soil conditions.

(16) Bags for shipping disks.

E.—METHOD OF MAKING TEST PIECES.

(a) Mature trees.

(1) Before felling the tree, blaze and mark the north side.

(2) Fell tree with the saw as near the ground as practicable, avoiding the flare of the butt and making the usual kerf with the ax opposite to the saw, if possible, so as to avoid north and south side. If necessary, square off the butt end.

(3) Before entting off the butt log mark the north side on the second, third, and further log lengths.

(4) Measure off and cut logs of merchantable length and diameters, beginning from the butt, noting the length and diameters in the record.

Should knots or other imperfections, externally visible, oceur within 8 inches of the log mark, make the cut lower down or higher up to avoid the imperfection.

(5) Continue measuring the full length of the tree and record its length. Note also distance from the ground and position on the tree (whether to the north, south, west, east) of one large sound limb. Mark its lower side and saw it off close to the trunk and measure its length and record it, the limb to be utilized as described later.

If the tree after felling prove unsound at the butt, it will be permissible to cut off as much or as little as necessary Within the first log length. If sound timber is not found in the first log, the tree must be discarded. Only sound timber must be shipped. Any logs showing imperfections may be shortened. Be careful to note change in position of test pieces.

(6) Mark butt end of each log with a large N on north side. Saw off squarely from the bottom end of each log a disk 6 inches long, and peyend the log measure cut off disks every 10 feet up to 2-inch diameter. Place eack disk

‘Only men pene with felling and cutting timber should ihe chosen,

392 FORESTRY INVESTIGATIONS U. 8. DEPARTMENT OF AGRICULTURE.

on its bottom end, and after having ascertained and marked the north and south line on top end. Split the disk with a sharp hacking knife and mallet along this line. Split from outside of the west half of the disk enough wood to leavea prism4 inches thick. Split from the east half two wedges with one plane in the south-north line and with their wedge tine through the heart of the disk; the euter arc to be about 4 inches.

Mark each piece as split off on top side with number of the tree (Arabic), the serial number (Roman) of the disk in the tree, beginning with No. 1 at butt log, and with a distinct N or S, the north or south position of the piece as in the tree.

Write the same data on a ecard and tack it to the piece to which they belong. Whenever disk pieces are small enough for mailing, leave them entire. Whenever they can not be shipped by mail, leave disks entire, wrap in paper, and ship by express.

(7) Weigh each piece and record weight in notebook, using the same marks as appear on the pieces.

(8) Wrap each piece in two sheets of heavy wrapping paper and tie securely.

(9) Mark on the newly cut bottom end of each log with a heavy pencil a north and south line, writing N on the north and § on the south side of the log, large and distinct. Also mark centrally with an Arabic number on each log the number of the tree in the series, and with a distinct Roman number the serial number of the log in the tree, counting the butt log as first. «

Tack to the butt end of each log securely a card (centrally), on which is written name of tree, species, locality from which tree is taken, denoted by the letter corresponding to that used in the notebook, number of tree, and section. This card or tag is intended to insure a record of each log in addition to the marking already made.

(10) Limb wood.—Having, as before noted, selected a limb, measured and recorded its distance from the butt and position on the trunk, and marked its lower side and sawed it off close to the latter, now take a disk 6 inches long from the butt end and others every 5 feet up to 2-inch diameter at the top. Number these consecutively with Roman number, calling the butt disk No. 1. Note by letters L and U the lower and upper side, as the limb appeared on the tree, and place the (Arabic) number of tree from which the limb came on each. Enforce the record by cards containing the same information, as done in case of other disk pieces.

Weigh and wrap and mail in the same manner as the other pieces.

(11) Check trees.—From the “check tree,” which is to be the very best to be found, only three disks or three logs are to be secured, from the butt, middle, and top part of the tree Absolutely clear timber, free from all knots and blemishes, is to be chosen. ‘The disk pieces are to be of the same size, and to be secured in the same manner as those described before; the logs to be not necessarily more than 6 feet; less if not enough clear timber can be found.

Note the position of each piece 4in. 4in, in the tree by measuring from the butt i — cut to the butt end of the piece.

Prepare and mark all pieces in the same manner as those from other trees, adding, however, to each piece a X mark to denote it as coming from the ‘‘ check tree.”

(12) Young trees. —Select six trees from each site approximately of fol- lowing sizes: Two, 6-inch diameter, breast high; two, 4-inch diameter, breast high; two, 2-inch diameter, breast high. Mark north and south sides and chop or saw all close to the ground and cut each tree into following lengths: First stick, 2 feet long; second stick, 4 feet long; the remaining cuts 4 feet long up to a top end diameter of about 1 inch. Cut from the basal end of each log a disk 6 inches long. Mark and ticket butt end of each log as in case of large trees. Mark a north and south line on top end of each disk, with N and § at extremities to denote north and south sides; and also ticket with same data as given on large disk pieces. Weigh and wrap as before. Of these trees only the disk pieces are to be mailed.

NO T-1.

6im.

F.—SHIPPING TEST PIECES.

Ship all pieces without delay. To each log tack securely a shipping card (furnished), so as to cover the marking tag. The logs will go to J. B. Johnson, St. Louis, Mo, The disks and other pieces are to be mailed to F. Roth, Ann Arbor, Mich., using franks, securely pasted, for mailing, unless, as noted before, they must be sent by express.

Mail at once to the above addresses notice of each shipment, and a transcript of notes and full description to this office, from which copies will be forwarded to the recipients of the test pieces.

If free transportation is obtained from the railroad companies, special additional instructions will be given under this head.

G.—RECORDS.

Careful and accurate records are most essential to secure the success of this work. <A set of specially prepared record sheets will be furnished, with instructions for their use. A transcript of the record must be sent to this office at the time of making shipment; also such notes as may seem desirable to complete the record and to give additional explanations in regard to the record and suggestions respecting the work of collecting. Original records and notes must be preserved, to ayoid loss in transmission by mail.

TIMBER PHYSICS—-COLLECTING MATERIAL. 393 FORM OF FIELD RECORD. (Folder.) Name of collector: (Charles Mohr.) Species: Pinus palustris. SraTIoN (denoted by capital letter): A. State: Alabama. County: Escambia. Town: Wallace. Longitude: 86° 12’. Latitude: 31° 15’. Average altitude: 75 to 100 feet. General configuration: Plain—hills—plateau—mountainous. General trend of valleys or hills .--.......-.-.--- Climatic features: Subtropical; mean annual temperature, 65°; mean annual rainfall, 62 inches. Sire (denoted by small letter): a. 7 Aspect: Level—ravine—cove—bench—slope (angle approximately). LOSER NO Badesoos est obses aa ease se Elevation (above average station altitude): 125 feet. Soil conditions: (1) Geological formation (if known): Southern stratified drift. (2) Mineral composition: Clay—limestone—loam—marl—sandy loam—loamy sand—sand. (3) Surface cover: Bare—grassy—mossy. Leaf cover: Abundant—scanty—lacking. (4) Depth of vegetable mold (humus): Absent—moderate—plenty—or give depth in inches. (5) Grain, consistency, and admixtures: Very fine—fine—medium—coarse—p orous—light—loose—

moderately loose—compact—binding—stones OUTOCK (8120) Of 54 eee eee een eee tee (6) Moisture conditions: Wet—moist—fresh—dry—arid—well drained—liable to overflow—swampy—near streamorspringor other kind of watersup ply. = ae <e~ tere =.= leas ele e ae i (7) Color: Ashy-gray. (8) Depth to subsoil (if known): Shallow, 3 to 4 inches to 1 foot—t foot to 4 feet, deep—over 4 feet, very deep—shifting. (9) Nature of subsoil (if ascertainable): Red, ferruginous sandy loam; moderately loose, or rather slightly binding; always of some degree of dampness; of great depth. Forest conditions: Mixed timber—pure—dense growth—moderately dense to open.....-...-.-.---.--.------- Associated species: None. TEGO NOMIE NOE 11) 0) Cloe Geocemee gene Sa8e sed NHOGSD OQSoGs anno Seae SeSbIancec Sosconpecqse cean Sasseoue Giese an: Average height: 90 feet. Undergrowth: Scanty; in the original forest often none. Conditions in the open: Field—pasture—lawn—clearing (how long cleared): In natural clearings untouched by fire, dense groves of second growth of the species. Nature of soil cover (if any): Weeds—brush—sod.

(Inside of folder.) STATION: A. SITE: a. Specizs: P. palustris. TREE No. 3. POSITION of tree (if any special point notable not appearing in general description of site, exceptional exposure to

light or dense position, etc., protected by buildings, note on back of sheet): In rather dense position. ORIGIN of tree (if ascertainable): Natural seedling, sprout from stump, artificial planting.

DIAMETER breast high: 16 inches. Herraur of stump: 20 inches. HEIGHT to first limb: 53 feet. ' Lenetu of felled tree: 110 feet 4 inches. AGE (annual rings on stump): 183. Tora. height: 111 feet 8 inches. | Weight of beg Spee q : Distance | , r oe eee r - Distance | Length of | Diameter, No. of disk. trom butt. | opie: Remarks. No. of log-| som butt. log. butt end. Feet. | Pounds. Ft. In. Ft. In. Inches. 0 27 | Crown touching those Manas 8 0 12 4 16} 13 20 of nearest trees to the eae 13 8 5 4 144 19 20 N. and NE. Open Meare 19 8 12 4 14 32 18 toward SW. INY st saes $278 14 4 13% 47 16 Vie seca” 47 8 9 4 123 | 57 14 iVelismsee' a7 8 9 4 11h 67 7 WAieSe =. 67 8 9 4 93 77 14 \auetesse5 77 8 9 4 84 87 94 97 6 LIMBwoop: DisTaNCE from butt: POSITION on trunk: Tora. length:

NuMBER of disks taken:

Nore.—As much as possible make description by underscoring terms used aboye, Add other descriptive terms if necessary,

394 FORESTRY INVESTIGATIONS U. 8S. DEPARTMENT OF AGRICULTURE.

SAMPLE RECORDS OF TESTS.

CROSS BREAKING TEST.

| , | Strength of extreme fiber,

ark Thi i 3 Wl

Mark, \3 White pine; | where f=9 7, ;2=5,660 pounds per square inch. Lepgth, 60.0 inches. Modulus of elasticity = 1,320,000 pounds per square inch, Height, 3.74 inches. Total resilience = 3,460 inch-pounds. El. Res., 550. Breadth, 3.75 inches. Resilience, per cubic inch 4.11 inch-pounds. EI. Res., 0.65.

{Number annual rings per inch =19.]

spss Load. Deflection. | Micrometer. | Remarks. i | |

h. m

4-24 200 042 0.757 | 25 1, 000 211 0. 926 26 1) 600 300 1. 065 V4 27 2, 000 454 | 1.169 28 | 2, 200 511 | 1, 226 29 2,400 595 1.310 31| 2,600 690 1.405 | 33 2, 800 853 1. 568 Z| 35 3, 000 1.015 1.730 N 37 3, 200 1. 276 1.991 | 40 | 3, 300 1.521 2. 235 | Maximum load.

Deflection in inches.

TIMBER PHYSICS—METHODS.

CROSS BREAKING TEST. (3- Strength of extreme fiber; Mark, iF Longleaf pine. 3 Wl 1

Length, 60.0 inches. Height, 3.50 inches. Breadth, 3.72 inches.

Modulus of elasticity Total resilience

395

where f=5 a a 10,230 pounds per square inch.

= 1,760,000 pounds per square inch. ,110 inech-pounds. | Resilience, per cubie inch =6.54 inch-pounds.

El. Res., 1,780. El. Res., 2.28.

6000 {Number annual rings per inch = 23.] July | Deflec-| Micro- | = = 20,1891. Load.| tion. |meter.| Remarks. h. ™. | 4 ! H 2 58 200 042 | 0.958 ! 3 0/1,000| .208| 1.124 N | \ 1. 1,600 .324 | 1.240 4000 i 2 2,000 404 1.320 | 1 ' 3 2,400 481 1.397 | ' 4) 2,800) .558| 1.474 : \ 5 | 3, 200 -640 ) 1.556 | | \ 6 3,600} .721 | 1.637 “i : \ 7} 4,000] .815| 1.731 | | ' 8 4,400 -926 | 1.842 ' ! 9 | 4,800) 1.074 | 1.990 K I i 13 | 5,180 | 1.544 | 2.460 Maximumload iN ! ' Es : | ! < 2000 ' ! £ | | i ' 8 ' 8 | t 8 ' ' taal ! 1 ’ i} | | I | | Oe 4\o as; Deflection tn inches. FINAL RECORD OF TIMBER TESTS. Cross bending test. Percent- Dimensions. Pan, 4 , | Ronilienee! Mark. age of |_ Deflec- Strength | yrodnius | in inch- moisture, iB Time. | Load. | “4ion. of elas- | pounds per Length. | Height. | Breadth. i ticity. (e) cubic 8 s inch. (7) | Inches. | Inches. | Inches. | Min. | Pounds. Inches. Pounds. ° 16.8 60.0 3.50 3. 72 15 | 5,180 | 1,544 1, 760, 000 6.54 : 54.3 60.0 3.74 3.75 16 | 3,300} 1,521 1, 320, 000 4.11 Crushing endwise. Crushing across grain. Mark. Dimensions. Strength | Dimensions. | , ~ rea Crushing per. - ‘Crushing aaa Heicht,| _ Cross "| load. sanare Heieht Cross load. anal Sey i i ea tion. , i | section. inch. see r Longleaf pine: | Inches.| Inches. | Sq.in.| Pownds.| Pounds. | Inches. | Inches. | Sq.inch.| Pounds.| Po unds. 3 | q B e222 22 eee eee eee e ee eee cent eee eee f 3.46 = - f 3.47 |) 7 = BSB ROEESEREE : ; B1\f 37 \ 12.87] 77,700 6, 040 3.73 |{ 3.93 | 13-63] 10, 400 760 White pine a ab Sw Us: 3.73 | 3.72 hs 4 5 9 Le 3-73 Nas. | 48,400] 3,480 3.72 {gig |f 14-62 5,200 360 i < ‘Tension tests. Shearing tests. > Mark. Size of re- | | aking | Strength ie i: re . Gee Area. Breaking per square | shearing | Bresing | Spaheins x Z \ | = —— Longleaf pine Sq.inch. | Sq. inch. Pounds. Pounds. | Sq. inch. Pounds. Pounds. : 2.38 = | 2, 280 551 : pi} ©0076 11, 400 11, 680 { Steen 650 iblFeess Bete ehe tere atnedee tee eu eee asec SU ces ee Sas 1, 700 409 : 2 “is |} ‘1-188 11, 200 9, 880 { 1600 | 398

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