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diff --git a/26598.txt b/26598.txt new file mode 100644 index 0000000..ded2e27 --- /dev/null +++ b/26598.txt @@ -0,0 +1,14285 @@ +The Project Gutenberg EBook of Seasoning of Wood, by Joseph B. Wagner + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Seasoning of Wood + +Author: Joseph B. Wagner + +Release Date: September 12, 2008 [EBook #26598] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK SEASONING OF WOOD *** + + + + +Produced by Jason Isbell, Irma Spehar and the Online +Distributed Proofreading Team at https://www.pgdp.net + + + + + + SEASONING OF WOOD + + A TREATISE ON THE NATURAL AND ARTIFICIAL + PROCESSES EMPLOYED IN THE PREPARATION + OF LUMBER FOR MANUFACTURE, + WITH DETAILED EXPLANATIONS OF ITS + USES, CHARACTERISTICS AND PROPERTIES + + + _ILLUSTRATIONS_ + BY + JOSEPH B. WAGNER + AUTHOR OF "COOPERAGE" + + + [Illustration] + + + NEW YORK + D. VAN NOSTRAND COMPANY + 25 PARK PLACE + 1917 + + + COPYRIGHT, 1917, BY + D. VAN NOSTRAND COMPANY + + + THE.PLIMPTON.PRESS + NORWOOD.MASS.U.S.A + + + + + PREFACE + + +The seasoning and kiln-drying of wood is such an important process in +the manufacture of woods that a need for fuller information regarding +it, based upon scientific study of the behavior of various species at +different mechanical temperatures, and under different drying +processes is keenly felt. Everyone connected with the woodworking +industry, or its use in manufactured products, is well aware of the +difficulties encountered in properly seasoning or removing the +moisture content without injury to the timber, and of its +susceptibility to atmospheric conditions after it has been thoroughly +seasoned. There is perhaps no material or substance that gives up its +moisture with more resistance than wood does. It vigorously defies the +efforts of human ingenuity to take away from it, without injury or +destruction, that with which nature has so generously supplied it. + +In the past but little has been known of this matter further than the +fact that wood contained moisture which had to be removed before the +wood could be made use of for commercial purposes. Within recent +years, however, considerable interest has been awakened among +wood-users in the operation of kiln-drying. The losses occasioned in +air-drying and improper kiln-drying, and the necessity for getting the +material dry as quickly as possible after it has come from the saw, in +order to prepare it for manufacturing purposes, are bringing about a +realization of the importance of a technical knowledge of the subject. + +Since this particular subject has never before been represented by any +technical work, and appears to have been neglected, it is hoped that +the trade will appreciate the endeavor in bringing this book before +them, as well as the difficulties encountered in compiling it, as it +is the first of its kind in existence. The author trusts that his +efforts will present some information that may be applied with +advantage, or serve at least as a matter of consideration or +investigation. + +In every case the aim has been to give the facts, and wherever a +machine or appliance has been illustrated or commented upon, or the +name of the maker has been mentioned, it has not been with the +intention either of recommending or disparaging his or their work, but +has been made use of merely to illustrate the text. + +The preparation of the following pages has been a work of pleasure to +the author. If they prove beneficial and of service to his +fellow-workmen he will have been amply repaid. + + THE AUTHOR. + + September, 1917 + + + + + CONTENTS + + + SECTION I + + TIMBER + PAGES + +Characteristics and Properties of Same--Structure +of Wood--Properties of Wood--Classes of Trees 1-7 + + SECTION II + + CONIFEROUS TREES + +Wood of Coniferous Trees--Bark and Pith--Sapwood and Heartwood--The +Annual or Yearly Ring--Spring- and Summer-Wood--Anatomical +Structure--List of Important Coniferous Trees 8-30 + + SECTION III + + BROAD-LEAVED TREES + +Wood of Broad-leaved Trees--Minute Structure--List of Most +Important Broad-leaved Trees--Red Gum--Range of Red Gum--Form +of Red Gum--Tolerance of Red Gum--Its Demands upon Soil and +Moisture--Reproduction of Red Gum--Second-growth Red Gum--Tupelo +Gum--Uses of Tupelo Gum--Range of Tupelo Gum 31-85 + + SECTION IV + + GRAIN, COLOR, ODOR, WEIGHT, AND FIGURE IN WOOD + +Different Grains of Wood--Color and Odor of Wood--Weight of +Wood--Weight of Kiln-dried Wood of Different Species--Figure in +Wood 86-97 + + SECTION V + + ENEMIES OF WOOD + +General Remarks--Ambrosia or Timber Beetles--Round-headed +Borers--Flat-headed Borers--Timber Worms--Powder Post +Borers--Conditions Favorable for Insect Injury--Crude +Products--Round Timber with Bark on--How to Prevent +Injury--Saplings--Stave, Heading, and Shingle Bolts--Unseasoned +Products in the Rough--Seasoned Products in the Rough--Dry +Cooperage Stock and Wooden Truss Hoops--Staves and Heads +of Barrels Containing Alcoholic Liquids 98-113 + + SECTION VI + + WATER IN WOOD + +Distribution of Water in Wood--Seasonal Distribution of Water in +Wood--Composition of Sap--Effects of Moisture on Wood--The +Fibre-Saturation Point in Wood 114-118 + + SECTION VII + + WHAT SEASONING IS + +What Seasoning Is--Difference Between Seasoned and Unseasoned +Wood--Manner of Evaporation of Water--Absorption of Water +by Dry Wood--Rapidity of Evaporation--Physical Properties +that Influence Drying 119-127 + + SECTION VIII + + ADVANTAGES OF SEASONING + +Advantages of Seasoning--Prevention of Checking and +Splitting--Shrinkage of Wood--Expansion of Wood--Elimination of +Stain and Mildew 128-137 + + SECTION IX + + DIFFICULTIES OF DRYING WOOD + +Difficulties of Drying Wood--Changes Rendering Drying +Difficult--Losses Due to Improper Kiln-drying--Properties of +Wood that Effect Drying--Unsolved Problems in Kiln-drying 138-144 + + SECTION X + + HOW WOOD IS SEASONED + +Methods of Drying--Drying at Atmospheric Pressure--Drying Under +Pressure and Vacuum--Impregnation Methods--Preliminary +Treatments--Out-of-door Seasoning 145-155 + + SECTION XI + + KILN-DRYING OF WOOD + +Advantages of Kiln-drying over Air Drying--Physical Conditions +Governing the Drying of Wood--Theory of Kiln-drying--Requirements +in a Satisfactory Dry Kiln--Kiln-drying--Remarks--Underlying +Principles--Objects of Kiln-drying--Conditions of Success--Different +Treatments According to Kind--Temperature Depends--Air +Circulation--Humidity--Kiln-drying--Pounds of Water Lost in Drying +100 Pounds of Green Wood in the Kiln--Kiln-drying Gum--Preliminary +Steaming--Final Steaming--Kiln-drying of Green Red Gum 156-184 + + SECTION XII + + TYPES OF DRY KILNS + +Different types of Dry Kilns--The "Blower" or "Hot Blast" Dry +Kiln--Operating the "Blower" or "Hot Blast" Dry Kiln--The +"Pipe" or "Moist-Air" Dry Kiln--Operating the "Pipe" or +"Moist-Air" Dry Kiln--Choice of Drying Method--Kilns of +Different Types--The "Progressive" Dry Kiln--The "Apartment" +Dry Kiln--The "Pocket" Dry Kiln--The "Tower" Dry Kiln--The +"Box" Dry Kiln 185-205 + + SECTION XIII + + DRY KILN SPECIALTIES + +Kiln Cars and Method of Loading Same--The "Cross-wise" Piling +Method--The "End-wise" Piling Method--The "Edge-wise" +Piling Method--The Automatic Lumber Stacker--The Unstacker +Car--Stave Piling--Shingle Piling--Stave Bolt Trucks--Different +Types of Kiln Cars--Different Types of Transfer Cars--Dry Kiln +Doors--Different Types of Kiln Door Carriers 206-236 + + SECTION XIV + + HELPFUL APPLIANCES IN KILN DRYING + +The Humidity Diagram--Examples of Use--The Hygrodeik--The +Recording Hygrometer--The Registering Hygrometer--The +Recording Thermometer--The Registering Thermometer--The +Recording Steam Gauge--The Troemroid Scalometer--Test +Samples--Weighing--Examples of Use--Records of Moisture +Content--Saw Mills--Factories--The Electric Heater 237-250 + + SECTION XV + +Bibliography--Glossary--Index of Latin Names--Index of Common +Names 251-257 + + + + + LIST OF ILLUSTRATIONS + + FIG. PAGE + + 1. Board of pine 13 + 2. Wood of spruce 14 + 3. Group of fibres from pine wood 15 + 4. Block of oak 31 + 5. Board of oak 32 + 6. Cross-section of oak highly magnified 32 + 7. Highly magnified fibres of wood 33 + 8. Isolated fibres and cells of wood 34 + 9. Cross-section of basswood 35 +10. A large red gum 52 +11. A tupelo gum slough 53 +12. Second growth red gum 57 +13. A cypress slough in dry season 58 +14. A large cottonwood 78 +15. Spiral grain in wood 87 +16. Alternating spiral grain in cypress 87 +17. Wavy grain in beech 88 +18. Section of wood showing position of the grain at base of limb 89 +19. Cross-section of a group of wood fibres 91 +20. Isolated fibres of wood 91 +21. Orientation of wood samples 93 +22. Work of ambrosia beetles in tulip or yellow poplar 100 +23. Work of ambrosia beetles in oak 100 +24. Work of round-headed and flat-headed borers in pine 102 +25. Work of timber worms in oak 103 +26. Work of powder post borers in hickory poles 104 +27. Work of powder post borers in hickory poles 104 +28. Work of powder post borers in hickory handles 105 +29. Work of round-headed borers in white pine staves 111 +30. U. S. Forest Service humidity controlled dry kiln 161 +31. Section through moist-air dry kiln 189 +32. Live steam single pipe heating apparatus 190 +33. Live steam double pipe heating apparatus 191 +34. Vertical Pipe heating apparatus 193 +35. Progressive dry kilns 197 +36. Apartment dry kilns 199 +37. Pocket dry kilns 201 +38. Tower dry kiln 203 +39. Box dry kiln 205 +40. Edge-wise method of piling 206 +41. Edge-wise method of piling 207 +42. Automatic lumber stacker 208 +43. Automatic lumber stacker 208 +44. Battery of three automatic lumber stackers 209 +45. Battery of three automatic lumber stackers 209 +46. Lumber loaded edge-wise on kiln truck 210 +47. The lumber unstacker 211 +48. The lumber unstacker car 211 +49. Method of piling veneer on edge 212 +50. Kiln truck loaded cross-wise of kiln 213 +51. Kiln truck loaded cross-wise of kiln 214 +52. Kiln truck loaded end-wise of kiln 214 +53. Kiln truck loaded end-wise of kiln 215 +54. Method of piling staves on kiln truck 216 +55. Method of piling staves on kiln truck 216 +56. Method of piling tub or pail staves on kiln truck 217 +57. Method of piling bundled staves on kiln truck 217 +58. Method of piling shingles on kiln truck 218 +59. Method of piling shingles on kiln truck 218 +60. Method of piling shingles on kiln truck 219 +61. Kiln truck designed for loose pail staves 219 +62. Kiln truck designed for handling short stock 221 +63. Stave bolt truck 221 +64. Stave bolt truck 222 +65. Stave bolt truck 222 +66. Stave bolt truck 223 +67. Stave bolt truck 223 +68. Stave bolt truck 224 +69. Regular 3-rail transfer car 224 +70. Regular 3-rail transfer car 225 +71. Special 4-rail transfer car 225 +72. Regular 2-rail transfer car 225 +73. Regular 2-rail transfer car 226 +74. Underslung type 3-rail transfer car 226 +75. Underslung type 2-rail transfer car 226 +76. Flexible type 2-rail transfer car 227 +77. Regular transfer car for stave bolt trucks 228 +78. Regular transfer car for stave bolt trucks 228 +79. Special transfer car for stave bolt trucks 228 +80. Regular channel iron kiln truck for cross-wise piling 229 +81. Regular channel iron kiln truck for cross-wise piling 229 +82. Regular channel iron kiln truck for end-wise piling 230 +83. Special channel iron kiln truck for end-wise piling 230 +84. Regular dolly kiln truck for end-wise piling 230 +85. Asbestos-lined kiln door 231 +86. Twin door carrier with door loaded 232 +87. Twin door carrier for doors 18 to 35 feet wide 232 +88. Kiln door carrier 233 +89. Kiln door construction 234 +90. Kiln door construction 235 +91. Kiln door construction 235 +92. Kiln door construction 236 +93. The Humidity diagram _facing_ 237 +94. The hygrodeik 242 +95. The recording hygrometer 243 +96. The registering hygrometer 244 +97. The recording thermometer 245 +98. The registering thermometer 246 +99. The recording steam gauge 246 +100. The troemroid scalometer 247 +101. The electric heater 250 + + + + + SEASONING OF WOOD + + + + + SECTION I + + TIMBER + + Characteristics and Properties + + +Timber was probably one of the earliest, if not the earliest, of +materials used by man for constructional purposes. With it he built +for himself a shelter from the elements; it provided him with fuel and +oft-times food, and the tree cut down and let across a stream formed +the first bridge. From it, too, he made his "dug-out" to travel along +and across the rivers of the district in which he dwelt; so on down +through the ages, for shipbuilding and constructive purposes, timber +has continued to our own time to be one of the most largely used of +nature's products. + +Although wood has been in use so long and so universally, there still +exists a remarkable lack of knowledge regarding its nature, not only +among ordinary workmen, but among those who might be expected to know +its properties. Consequently it is often used in a faulty and wasteful +manner. Experience has been almost the only teacher, and +theories--sometimes right, sometimes wrong--rather than well +substantiated facts, lead the workman. + +One reason for this imperfect knowledge lies in the fact that wood is +not a homogeneous material, but a complicated structure, and so +variable, that one piece will behave very differently from another, +although cut from the same tree. Not only does the wood of one species +differ from that of another, but the butt cut differs from that of the +top log, the heartwood from the sapwood; the wood of quickly-grown +sapling of the abandoned field, from that of the slowly-grown, old +monarch of the forest. Even the manner in which the tree was cut and +kept influences its behavior and quality. It is therefore extremely +difficult to study the material for the purpose of establishing +general laws. + +The experienced woodsman will look for straight-grained, long-fibred +woods, with the absence of disturbing resinous and coloring matter, +knots, etc., and will quickly distinguish the more porous red or black +oaks from the less porous white species, _Quercus alba_. That the +inspection should have regard to defects and unhealthy conditions +(often indicated by color) goes without saying, and such inspection is +usually practised. That knots, even the smallest, are defects, which +for some uses condemn the material entirely, need hardly be mentioned. +But that "season-checks," even those that have closed by subsequent +shrinkage, remain elements of weakness is not so readily appreciated; +yet there cannot be any doubt of this, since these, the intimate +connections of the wood fibres, when once interrupted are never +reestablished. + +Careful woods-foremen and manufacturers, therefore, are concerned as +to the manner in which their timber is treated after the felling, for, +according to the more or less careful seasoning of it, the season +checks--not altogether avoidable--are more or less abundant. + +There is no country where wood is more lavishly used or criminally +neglected than in the United States, and none in which nature has more +bountifully provided for all reasonable requirements. + +In the absence of proper efforts to secure reproduction, the most +valuable kinds are rapidly being decimated, and the necessity of a +more rational and careful use of what remains is clearly apparent. By +greater care in selection, however, not only will the duration of the +supply be extended, but more satisfactory results will accrue from its +practice. + +There are few more extensive and wide-reaching subjects on which to +treat than timber, which in this book refers to dead timber--the +timber of commerce--as distinct from the living tree. Such a great +number of different kinds of wood are now being brought from various +parts of the world, so many new kinds are continually being added, and +the subject is more difficult to explain because timber of practically +the same character which comes from different localities goes under +different names, that if one were always to adhere to the botanical +name there would be less confusion, although even botanists differ in +some cases as to names. Except in the cases of the older and better +known timbers, one rarely takes up two books dealing with timber and +finds the botanical names the same; moreover, trees of the same +species may produce a much poorer quality of timber when obtained from +different localities in the same country, so that botanical knowledge +will not always allow us to dispense with other tests. + +The structure of wood affords the only reliable means of +distinguishing the different kinds. Color, weight, smell, and other +appearances, which are often direct or indirect results of structure, +may be helpful in this distinction, but cannot be relied upon +entirely. Furthermore, structure underlies nearly all the technical +properties of this important product, and furnishes an explanation why +one piece differs in these properties from another. Structure explains +why oak is heavier, stronger, and tougher than pine; why it is harder +to saw and plane, and why it is so much more difficult to season +without injury. From its less porous structure alone it is evident +that a piece of young and thrifty oak is stronger than the porous wood +of an old or stunted tree, or that a Georgia or long-leaf pine excels +white pine in weight and strength. + +Keeping especially in mind the arrangement and direction of the fibres +of wood, it is clear at once why knots and "cross-grain" interfere +with the strength of timber. It is due to the structural peculiarities +that "honeycombing" occurs in rapid seasoning, that checks or cracks +extend radially and follow pith rays, that tangent or "bastard" cut +stock shrinks and warps more than that which is quarter-sawn. These +same peculiarities enable oak to take a better finish than basswood or +coarse-grained pine. + + + Structure of Wood + +The softwoods are made up chiefly of tracheids, or vertical cells +closed at the ends, and of the relatively short parenchyma cells of +the medullary rays which extend radially from the heart of the tree. +The course of the tracheids and the rays are at right angles to each +other. Although the tracheids have their permeable portions or pits in +their walls, liquids cannot pass through them with the greatest ease. +The softwoods do not contain "pores" or vessels and are therefore +called "non-porous" woods. + +The hardwoods are not so simple in structure as softwoods. They +contain not only rays, and in many cases tracheids, but also +thick-walled cells called fibres and wood parenchyma for the storage +of such foods as starches and sugars. The principal structural +features of the hardwoods are the pores or vessels. These are long +tubes, the segments of which are made up of cells which have lost +their end walls and joined end to end, forming continuous "pipe lines" +from the roots to the leaves in the tree. Since they possess pores or +vessels, the hardwoods are called "porous" woods. + +Red oak is an excellent example of a porous wood. In white oak the +vessels of the heartwood especially are closed, very generally by +ingrowths called tyloses. This probably explains why red oak dries +more easily and rapidly than white oak. + +The red and black gums are perhaps the simplest of the hardwoods in +structure. They are termed "diffuse porous" woods because of the +numerous scattered pores they contain. They have only vessels, wood +fibres, and a few parenchyma cells. The medullary rays, although +present, are scarcely visible in most instances. The vessels are in +many cases open, and might be expected to offer relatively little +resistance to drying. + + + Properties of Wood + +Certain general properties of wood may be discussed briefly. We know +that wood substance has the property of taking in moisture from the +air until some balance is reached between the humidity of the air and +the moisture in the wood. This moisture which goes into the cell walls +hygroscopic moisture, and the property which the wood substance has of +taking on hygroscopic moisture is termed hygroscopicity. Usually wood +contains not only hygroscopic moisture but also more or less free +water in the cell cavities. Especially is this true of sapwood. The +free water usually dries out quite rapidly with little or no shrinkage +or other physical change. + +In certain woods--for example, _Eucalyptus globulus_ and possibly some +oaks--shrinkage begins almost at once, thus introducing a factor at +the very start of the seasoning process which makes these woods very +refractory. + +The cell walls of some species, including the two already mentioned, +such as Western red cedar and redwood, become soft and plastic when +hot and moist. If the fibres are hot enough and very wet, they are not +strong enough to withstand the resulting force of the atmospheric +pressure and the tensile force exerted by the departing free water, +and the result is that the cells actually collapse. + +In general, however, the hygroscopic moisture necessary to saturate +the cell walls is termed the "fibre saturation point." This amount has +been found to be from 25 to 30 per cent of the dry wood weight. Unlike +_Eucalyptus globulus_ and certain oaks, the gums do not begin to +shrink until the moisture content has been reduced to about 30 per +cent of the dry wood weight. These woods are not subject to collapse, +although their fibres become very plastic while hot and moist. + +Upon the peculiar properties of each wood depends the difficulty or +ease of the seasoning process. + + + Classes of Trees + +The timber of the United States is furnished by three well-defined +classes of trees: (1) The needle-leaved, naked-seeded conifers, such +as pine, cedar, etc., (2) the broad-leaved trees such as oak poplar, +etc., and (3) to an inferior extent by the (one-seed leaf) palms, +yuccas, and their allies, which are confined to the most southern +parts of the country. + +Broad-leaved trees are also known as deciduous trees, although, +especially in warm countries, many of them are evergreen, while the +needle-leaved trees (conifers) are commonly termed "evergreens," +although the larch, bald cypress, and others shed their leaves every +fall, and even the names "broad-leaved" and "coniferous," though +perhaps the most satisfactory, are not at all exact, for the conifer +"ginkgo" has broad leaves and bears no cones. + +Among the woodsmen, the woods of broad-leaved trees are known as +"hardwoods," though poplar is as soft as pine, and the "coniferous +woods" are known as "softwoods," notwithstanding the fact that yew +ranks high in hardness even when compared with "hardwoods." + +Both in the number of different kinds of trees or species and still +more in the importance of their product, the conifers and broad-leaved +trees far excel the palms and their relatives. + +In the manner of their growth both the conifers and broad-leaved trees +behave alike, adding each year a new layer of wood, which covers the +old wood in all parts of the stem and limbs. Thus the trunk continues +to grow in thickness throughout the life of the tree by additions +(annual rings), which in temperate climates are, barring accidents, +accurate records of the tree. With the palms and their relatives the +stem remains generally of the same diameter, the tree of a hundred +years old being as thick as it was at ten years, the growth of these +being only at the top. Even where a peripheral increase takes place, +as in the yuccas, the wood is not laid on in well-defined layers for +the structure remains irregular throughout. Though alike in the manner +of their growth, and therefore similar in their general make-up, +conifers and broad-leaved trees differ markedly in the details of +their structure and the character of their wood. + +The wood of all conifers is very simple in its structure, the fibres +composing the main part of the wood all being alike and their +arrangement regular. The wood of the broad-leaved trees is complex in +structure; it is made up of different kinds of cells and fibres and +lacks the regularity of arrangement so noticeable in the conifers. +This difference is so great that in a study of wood structure it is +best to consider the two kinds separately. + +In this country the great variety of woods, and especially of useful +woods, often makes the mere distinction of the kind or species of tree +most difficult. Thus there are at least eight pines of the thirty-five +native ones in the market, some of which so closely resemble each +other in their minute structure that one can hardly tell them apart, +and yet they differ in quality and are often mixed or confounded in +the trade. Of the thirty-six oaks, of which probably not less than six +or eight are marketed, we can readily recognize by means of their +minute anatomy at least two tribes--the white and black oaks. The same +is true of the eleven kinds of hickory, the six kinds of ash, etc., +etc. + +The list of names of all trees indigenous to the United States, as +enumerated by the United States Forest Service, is 495 in number, the +designation of "tree" being applied to all woody plants which produce +naturally in their native habitat one main, erect stem, bearing a +definite crown, no matter what size they attain. + +Timber is produced only by the Spermatophyta, or seed-bearing plants, +which are subdivided into the Gymnosperms (conifers), and Angiosperms +(broad-leaved). The conifer or cone-bearing tree, to which belong the +pines, larches, and firs, is one of the three natural orders of +Gymnosperms. These are generally classed as "softwoods," and are more +extensively scattered and more generally used than any other class of +timber, and are simple and regular in structure. The so-called +"hardwoods" are "Dicotyledons" or broad-leaved trees, a subdivision of +the Angiosperms. They are generally of slower growth, and produce +harder timber than the conifers, but not necessarily so. Basswood, +poplar, sycamore, and some of the gums, though classed with the +hardwoods, are not nearly as hard as some of the pines. + + + + + SECTION II + + CONIFEROUS TREES + + WOOD OF THE CONIFEROUS TREES + + +Examining a smooth cross-section or end face of a well-grown log of +Georgia pine, we distinguish an envelope of reddish, scaly bark, a +small, whitish pith at the center, and between these the wood in a +great number of concentric rings. + + + Bark and Pith + +The bark of a pine stem is thickest and roughest near the base, +decreases rapidly in thickness from one to one-half inches at the +stump to one-tenth inch near the top of the tree, and forms in general +about ten to fifteen per cent of the entire trunk. The pith is quite +thick, usually one-eighth to one-fifth inch in southern species, +though much less so in white pine, and is very thin, one-fifteenth to +one twenty-fifth inch in cypress, cedar, and larch. + +In woods with a thick pith, the pith is finest at the stump, grows +rapidly thicker toward the top, and becomes thinner again in the crown +and limbs, the first one to five rings adjoining it behaving +similarly. + +What is called the pith was once the seedling tree, and in many of the +pines and firs, especially after they have been seasoning for a good +while, this is distinctly noticeable in the center of the log, and +detaches itself from the surrounding wood. + + + Sap and Heartwood + +Wood is composed of duramen or heartwood, and alburnum or sapwood, and +when dry consists approximately of 49 per cent by weight of carbon, 6 +per cent of hydrogen, 44 per cent of oxygen, and 1 per cent of ash, +which is fairly uniform for all species. The sapwood is the external +and youngest portion of the tree, and often constitutes a very +considerable proportion of it. It lies next the bark, and after a +course of years, sometimes many, as in the case of oaks, sometimes +few, as in the case of firs, it becomes hardened and ultimately forms +the duramen or heartwood. Sapwood is generally of a white or light +color, almost invariably lighter in color than the heartwood, and is +very conspicuous in the darker-colored woods, as for instance the +yellow sapwood of mahogany and similiar colored woods, and the reddish +brown heartwood; or the yellow sapwood of _Lignum-vitae_ and the dark +green heartwood. Sapwood forms a much larger proportion of some trees +than others, but being on the outer circumference it always forms a +large proportion of the timber, and even in sound, hard pine will be +from 40 per cent to 60 per cent of the tree and in some cases much +more. It is really imperfect wood, while the duramen or heartwood is +the perfect wood; the heartwood of the mature tree was the sapwood of +its earlier years. Young trees when cut down are almost all sapwood, +and practically useless as good, sound timber; it is, however, through +the sapwood that the life-giving juices which sustain the tree arise +from the soil, and if the sapwood be cut through, as is done when +"girdling," the tree quickly dies, as it can derive no further +nourishment from the soil. Although absolutely necessary to the +growing tree, sapwood is often objectionable to the user, as it is the +first part to decay. In this sapwood many cells are active, store up +starch, and otherwise assist in the life processes of the tree, +although only the last or outer layer of cells forms the growing part, +and the true life of the tree. + +The duramen or heartwood is the inner, darker part of the log. In the +heartwood all the cells are lifeless cases, and serve only the +mechanical function of keeping the tree from breaking under its own +great weight or from being laid low by the winds. The darker color of +the heartwood is due to infiltration of chemical substances into the +cell walls, but the cavities of the cells in pine are not filled up, +as is sometimes believed, nor do their walls grow thicker, nor are the +walls any more liquified than in the sapwood. + +Sapwood varies in width and in the number of rings which it contains +even in different parts of the same tree. The same year's growth which +is sapwood in one part of a disk may be heartwood in another. Sapwood +is widest in the main part of the stem and often varies within +considerable limits and without apparent regularity. Generally, it +becomes narrower toward the top and in the limbs, its width varying +with the diameter, and being the least in a given disk on the side +which has the shortest radius. Sapwood of old and stunted pines is +composed of more rings than that of young and thrifty specimens. Thus +in a pine two hundred and fifty years old a layer of wood or an annual +ring does not change from sapwood to heartwood until seventy or eighty +years after it is formed, while in a tree one hundred years old or +less it remains sapwood only from thirty to sixty years. + +The width of the sapwood varies considerably for different kinds of +pine. It is small for long-leaf and white pine and great for loblolly +and Norway pines. Occupying the peripheral part of the trunk, the +proportion which it forms of the entire mass of the stem is always +great. Thus even in old long-leaf pines, the sapwood forms 40 per cent +of the merchantable log, while in the loblolly and in all young trees +the sapwood forms the bulk of the wood. + + + The Annual or Yearly Rings + +The concentric annual or yearly rings which appear on the end face of +a log are cross-sections of so many thin layers of wood. Each such +layer forms an envelope around its inner neighbor, and is in turn +covered by the adjoining layer without, so that the whole stem is +built up of a series of thin, hollow cylinders, or rather cones. + +A new layer of wood is formed each season, covering the entire stem, +as well as all the living branches. The thickness of this layer or the +width of the yearly ring varies greatly in different trees, and also +in different parts of the same tree. + +In a normally-grown, thrifty pine log the rings are widest near the +pith, growing more and more narrow toward the bark. Thus the central +twenty rings in a disk of an old long-leaf pine may each be one-eighth +to one-sixth inch wide, while the twenty rings next to the bark may +average only one-thirtieth inch. + +In our forest trees, rings of one-half inch in width occur only near +the center in disks of very thrifty trees, of both conifers and +hardwoods. One-twelfth inch represents good, thrifty growth, and the +minimum width of one two hundred inch is often seen in stunted spruce +and pine. The average width of rings in well-grown, old white pine +will vary from one-twelfth to one-eighteenth inch, while in the slower +growing long-leaf pine it may be one twenty-fifth to one-thirtieth of +an inch. The same layer of wood is widest near the stump in very +thrifty young trees, especially if grown in the open park; but in old +forest trees the same year's growth is wider at the upper part of the +tree, being narrowest near the stump, and often also near the very tip +of the stem. Generally the rings are widest near the center, growing +narrower toward the bark. + +In logs from stunted trees the order is often reversed, the interior +rings being thin and the outer rings widest. Frequently, too, zones or +bands of very narrow rings, representing unfavorable periods of +growth, disturb the general regularity. + +Few trees, even among pines, furnish a log with truly circular +cross-section. Usually it is an oval, and at the stump commonly quite +an irregular figure. Moreover, even in very regular or circular disks +the pith is rarely in the center, and frequently one radius is +conspicuously longer than its opposite, the width of some rings, if +not all, being greater on one side than on the other. This is nearly +always so in the limbs, the lower radius exceeding the upper. In +extreme cases, especially in the limbs, a ring is frequently +conspicuous on one side, and almost or entirely lost to view on the +other. Where the rings are extremely narrow, the dark portion of the +ring is often wanting, the color being quite uniform and light. The +greater regularity or irregularity of the annual rings has much to do +with the technical qualities of the timber. + + + Spring- and Summer-Wood + +Examining the rings more closely, it is noticed that each ring is made +up of an inner, softer, light-colored and an outer, or peripheral, +firmer and darker-colored portion. Being formed in the forepart of the +season, the inner, light-colored part is termed spring-wood, the +outer, darker-portioned being the summer-wood of the ring. Since the +latter is very heavy and firm it determines to a very large extent the +weight and strength of the wood, and as its darker color influences +the shade of color of the entire piece of wood, this color effect +becomes a valuable aid in distinguishing heavy and strong from light +and soft pine wood. + +In most hard pines, like the long-leaf, the dark summer-wood appears +as a distinct band, so that the yearly ring is composed of two sharply +defined bands--an inner, the spring-wood, and an outer, the +summer-wood. But in some cases, even in hard pines, and normally in +the woods of white pines, the spring-wood passes gradually into the +darker summer-wood, so that a darkly defined line occurs only where +the spring-wood of one ring abuts against the summer-wood of its +neighbor. It is this clearly defined line which enables the eye to +distinguish even the very narrow lines in old pines and spruces. + +In some cases, especially in the trunks of Southern pines, and +normally on the lower side of pine limbs, there occur dark bands of +wood in the spring-wood portion of the ring, giving rise to false +rings, which mislead in a superficial counting of rings. In the disks +cut from limbs these dark bands often occupy the greater part of the +ring, and appear as "lunes," or sickle-shaped figures. The wood of +these dark bands is similar to that of the true summer-wood. The cells +have thick walls, but usually the compressed or flattened form. +Normally, the summer-wood forms a greater proportion of the rings in +the part of the tree formed during the period of thriftiest growth. In +an old tree this proportion is very small in the first two to five +rings about the pith, and also in the part next to the bark, the +intermediate part showing a greater proportion of summer-wood. It is +also greatest in a disk taken from near the stump, and decreases +upward in the stem, thus fully accounting for the difference in weight +and firmness of the wood of these different parts. + + [Illustration: Fig. 1. Board of Pine. CS, cross-section; RS, + radial section; TS, tangential section; _sw_, summer-wood; + _spw_, spring-wood.] + +In the long-leaf pine the summer-wood often forms scarcely ten per +cent of the wood in the central five rings; forty to fifty per cent of +the next one hundred rings, about thirty per cent of the next fifty, +and only about twenty per cent in the fifty rings next to the bark. It +averages forty-five per cent of the wood of the stump and only +twenty-four per cent of that of the top. + +Sawing the log into boards, the yearly rings are represented on the +board faces of the middle board (radial sections) by narrow parallel +strips (see Fig. 1), an inner, lighter stripe and its outer, darker +neighbor always corresponding to one annual ring. + +On the faces of the boards nearest the slab (tangential or bastard +boards) the several years' growth should also appear as parallel, but +much broader stripes. This they do if the log is short and very +perfect. Usually a variety of pleasing patterns is displayed on the +boards, depending on the position of the saw cut and on the regularity +of growth of the log (see Fig. 1). Where the cut passes through a +prominence (bump or crook) of the log, irregular, concentric circlets +and ovals are produced, and on almost all tangent boards arrow or +V-shaped forms occur. + + + Anatomical Structure + +Holding a well-smoothed disk or cross-section one-eighth inch thick +toward the light, it is readily seen that pine wood is a very porous +structure. If viewed with a strong magnifier, the little tubes, +especially in the spring-wood of the rings, are easily distinguished, +and their arrangement in regular, straight, radial rows is apparent. + + [Illustration: Fig. 2. Wood of Spruce. 1, natural size; 2, + small part of one ring magnified 100 times. The vertical + tubes are wood fibres, in this case all "tracheids." _m_, + medullary or pith ray; _n_, transverse tracheids of ray; _a_, + _b_, and _c_, bordered pits of the tracheids, more enlarged.] + +Scattered through the summer-wood portion of the rings, numerous +irregular grayish dots (the resin ducts) disturb the uniformity and +regularity of the structure. Magnified one hundred times, a piece of +spruce, which is similar to pine, presents a picture like that shown +in Fig. 2. Only short pieces of the tubes or cells of which the wood +is composed are represented in the picture. The total length of these +fibres is from one-twentieth to one-fifth inch, being the smallest +near the pith, and is fifty to one hundred times as great as their +width (see Fig. 3). They are tapered and closed at their ends, +polygonal or rounded and thin-walled, with large cavity, lumen or +internal space in the spring-wood, and thick-walled and flattened +radially, with the internal space or lumen much reduced in the +summer-wood (see right-hand portion of Fig. 2). This flattening, +together with the thicker walls of the cells, which reduces the lumen, +causes the greater firmness and darker color of the summer-wood. +There is more material in the same volume. As shown in the figure, the +tubes, cells or "tracheids" are decorated on their walls by +circlet-like structures, the "bordered pits," sections of which are +seen more magnified as _a_, _b_, and _c_, Fig. 2. These pits are in +the nature of pores, covered by very thin membranes, and serve as +waterways between the cells or tracheids. The dark lines on the side +of the smaller piece (1, Fig. 2) appear when magnified (in 2, Fig. 2) +as tiers of eight to ten rows of cells, which run radially (parallel +to the rows of tubes or tracheids), and are seen as bands on the +radial face and as rows of pores on the tangential face. These bands +or tiers of cell rows are the medullary rays or pith rays, and are +common to all our lumber woods. + +In the pines and other conifers they are quite small, but they can +readily be seen even without a magnifier. If a radial surface of +split-wood (not smoothed) is examined, the entire radial face will be +seen almost covered with these tiny structures, which appear as fine +but conspicuous cross-lines. As shown in Fig. 2, the cells of the +medullary or pith are smaller and very much shorter than the wood +fibre or tracheids, and their long axis is at right angles to that of +the fiber. + + [Illustration: Fig. 3. Group of Fibres from Pine Wood. Partly + schematic. The little circles are "border pits" (see Fig. 2, + _a-c_). The transverse rows of square pits indicate the + places of contact of these fibres and the cells of the + neighboring pith rays. Magnified about 25 times.] + +In pines and spruces the cells of the upper and lower rows of each +tier or pith ray have "bordered" pits, like those of the wood fibre or +tracheids proper, but the cells of the intermediate rows in the rays +of cedars, etc., have only "simple" pits, _i.e._, pits devoid of the +saucer-like "border" or rim. In pine, many of the pith rays are larger +than the majority, each containing a whitish line, the horizontal +resin duct, which, though much smaller, resembles the vertical ducts +on the cross-section. The larger vertical resin ducts are best +observed on removal of the bark from a fresh piece of white pine cut +in the winter where they appear as conspicuous white lines, extending +often for many inches up and down the stem. Neither the horizontal nor +the vertical resin ducts are vessels or cells, but are openings +between cells, _i.e._, intercellular spaces, in which the resin +accumulates, freely oozing out when the ducts of a fresh piece of +sapwood are cut. They are present only in our coniferous woods, and +even here they are restricted to pine, spruce, and larch, and are +normally absent in fir, cedar, cypress, and yew. Altogether, the +structure of coniferous woods is very simple and regular, the bulk +being made up of the small fibres called tracheids, the disturbing +elements of pith rays and resin ducts being insignificant, and hence +the great uniformity and great technical value of coniferous woods. + + + + + LIST OF IMPORTANT CONIFEROUS WOODS + + + CEDAR + +Light soft, stiff, not strong, of fine texture. Sap- and heartwood +distinct, the former lighter, the latter a dull grayish brown or red. +The wood seasons rapidly, shrinks and checks but little, and is very +durable in contact with the soil. Used like soft pine, but owing to +its great durability preferred for shingles, etc. Cedars usually occur +scattered, but they form in certain localities forests of considerable +extent. + + + (_a_) White Cedars + +=1. White Cedar= (_Thuya occidentalis_) (Arborvitae, Tree of Life). +Heartwood light yellowish brown, sapwood nearly white. Wood light, +soft, not strong, of fine texture, very durable in contact with the +soil, very fragrant. Scattered along streams and lakes, frequently +covering extensive swamps; rarely large enough for lumber, but +commonly used for fence posts, rails, railway ties, and shingles. This +species has been extensively cultivated as an ornamental tree for at +least a century. Maine to Minnesota and northward. + +=2. Canoe Cedar= (_Thuya gigantea_) (Red Cedar of the West). In Oregon +and Washington a very large tree, covering extensive swamps; in the +mountains much smaller, skirting the water courses. An important +lumber tree. The wood takes a fine polish; suitable for interior +finishing, as there is much variety of shading in the color. +Washington to northern California and eastward to Montana. + +=3. White Cedar= (_Chamaecyparis thyoides_). Medium-sized tree. Heartwood +light brown with rose tinge, sapwood paler. Wood light, soft, not +strong, close-grained, easily worked, very durable in contact with the +soil and very fragrant. Used in boatbuilding cooperage, interior +finish, fence posts, railway ties, etc. Along the coast from Maine to +Mississippi. + +=4. White Cedar= (_Chamaecyparis Lawsoniana_) (Port Orford Cedar, Oregon +Cedar, Lawson's Cypress, Ginger Pine). A very large tree. A fine, +close-grained, yellowish-white, durable timber, elastic, easily +worked, free of knots, and fragrant. Extensively cut for lumber; +heavier and stronger than any of the preceding. Along the coast line +of Oregon. + +=5. White Cedar= (_Libocedrus decurrens_) (Incense Cedar). A large tree, +abundantly scattered among pine and fir. Wood fine-grained. Cascades +and Sierra Nevada Mountains of Oregon and California. + +=6. Yellow Cedar= (_Cupressus nootkatensis_) (Alaska Cedar, Alaska +Cypress). A very large tree, much used for panelling and furniture. A +fine, close-grained, yellowish white, durable timber, easily worked. +Along the coast line of Oregon north. + + + (_b_) Red Cedars + +=7. Red Cedar= (_Juniperus Virginiana_) (Savin Juniper, Juniper, Red +Juniper, Juniper Bush, Pencil Cedar). Heartwood dull red color, thin +sapwood nearly white. Close even grain, compact structure. Wood light, +soft, weak, brittle, easily worked, durable in contact with the soil, +and fragrant. Used for ties, posts, interior finish, pencil cases, +cigar boxes, silos, tanks, and especially for lead pencils, for which +purpose alone several million feet are cut each year. A small to +medium-sized tree scattered through the forests, or in the West +sparsely covering extensive areas (cedar brakes). The red cedar is the +most widely distributed conifer of the United States, occurring from +the Atlantic to the Pacific, and from Florida to Minnesota. Attains a +suitable size for lumber only in the Southern, and more especially the +Gulf States. + +=8. Red Cedar= (_Juniperus communis_) (Ground Cedar). Small-sized tree, +its maximum height being about 25 feet. It is found widely distributed +throughout the Northern hemisphere. Wood in its quality similar to the +preceding. The fruit of this species is gathered in large quantities +and used in the manufacture of gin; whose peculiar flavor and +medicinal properties are due to the oil of Juniper berries, which is +secured by adding the crushed fruit to undistilled grain spirit, or by +allowing the vapor to pass over it before condensation. Used locally +for construction purposes, fence posts, etc. Ranges from Greenland to +Alaska, in the East, southward to Pennsylvania and northern Nebraska; +in the Rocky Mountains to Texas, Mexico, and Arizona. + +=9. Redwood= (_Sequoia sempervirens_) (Sequoia, California Redwood, +Coast Redwood). Wood in its quality and uses like white cedar. Thick, +red heartwood, changing to reddish brown when seasoned. Thin sapwood, +nearly white, coarse, straight grain, compact structure. Light, not +strong, soft, very durable in contact with the soil, not resinous, +easily worked, does not burn easily, receives high polish. Used for +timber, shingles, flumes, fence posts, coffins, railway ties, water +pipes, interior decorations, and cabinetmaking. A very large tree, +limited to the coast ranges of California, and forming considerable +forests, which are rapidly being converted into lumber. + + + CYPRESS + +=10. Cypress= (_Taxodium distinchum_) (Bald Cypress, Black, White, and +Red Cypress, Pecky Cypress). Wood in its appearance, quality, and uses +similar to white cedar. "Black" and "White Cypress" are heavy and +light forms of the same species. Heartwood brownish; sapwood nearly +white. Wood close, straight-grain, frequently full of small holes +caused by disease known as "pecky cypress." Greasy appearance and +feeling. Wood light, soft, not strong, durable in contact with the +soil, takes a fine polish. Green wood often very heavy. Used for +carpentry, building construction, shingles, cooperage, railway ties, +silos, tanks, vehicles, and washing machines. The cypress is a large, +deciduous tree, inhabiting swampy lands, and along rivers and coasts +of the Southern parts of the United States. Grows to a height of 150 +feet and 12 feet in diameter. + + + FIR + +This name is frequently applied to wood and to trees which are not +fir; most commonly to spruce, but also, especially in English markets, +to pine. It resembles spruce, but is easily distinguished from it, as +well as from pine and larch, by the absence of resin ducts. Quality, +uses, and habits similar to spruce. + +=11. Balsam Fir= (_Abies balsamea_) (Balsam, Fir Tree, Balm of Gilead +Fir). Heartwood white to brownish; sapwood lighter color; +coarse-grained, compact structure, satiny. Wood light, not durable or +strong, resinous, easily split. Used for boxes, crates, doors, +millwork, cheap lumber, paper pulp. Inferior to white pine or spruce, +yet often mixed and sold with these species in the lumber market. A +medium-sized tree scattered throughout the northern pineries, and cut +in lumber operations whenever of sufficient size. Minnesota to Maine +and northward. + +=12. White Fir= (_Abies grandis_ and _Abies concolor_). Medium-to very +large-sized tree, forming an important part of most of the Western +mountain forests, and furnishes much of the lumber of the respective +regions. The former occurs from Vancouver to California, and the +latter from Oregon to Arizona and eastward to Colorado and Mexico. The +wood is soft and light, coarse-grained, not unlike the "Swiss pine" of +Europe, but darker and firmer, and is not suitable for any purpose +requiring strength. It is used for boxes, barrels, and to a small +extent for wood pulp. + +=13. White Fir= (_Abies amabalis_). Good-sized tree, often forming +extensive mountain forests. Wood similar in quality and uses to _Abies +grandis_. Cascade Mountains of Washington and Oregon. + +=14. Red Fir= (_Abies nobilis_) (Noble Fir) (not to be confounded with +Douglas spruce. See No. 40). Large to very large-sized tree, forming +extensive forests on the slope of the mountains between 3,000 and +4,000 feet elevation. Cascade Mountains of Oregon. + +=15. Red Fir= (_Abies magnifica_). Very large-sized tree, forming +forests about the base of Mount Shasta. Sierra Nevada Mountains of +California, from Mount Shasta southward. + + + HEMLOCK + +Light to medium weight, soft, stiff, but brittle, commonly +cross-grained, rough and splintery. Sapwood and heartwood not well +defined. The wood of a light reddish-gray color, free from resin +ducts, moderately durable, shrinks and warps considerably in drying, +wears rough, retains nails firmly. Used principally for dimension +stuff and timbers. Hemlocks are medium- to large-sized trees, commonly +scattered among broad-leaved trees and conifers, but often forming +forests of almost pure growth. + +=16. Hemlock= (_Tsuga canadensis_) (Hemlock Spruce, Peruche). +Medium-sized tree, furnishes almost all the hemlock of the Eastern +market. Maine to Wisconsin, also following the Alleghanies southward +to Georgia and Alabama. + +=17. Hemlock= (_Tsuga mertensiana_). Large-sized tree, wood claimed to +be heavier and harder than the Eastern species and of superior +quality. Used for pulp wood, floors, panels, and newels. It is not +suitable for heavy construction, especially where exposed to the +weather, it is straight in grain and will take a good polish. Not +adapted for use partly in and partly out of the ground; in fresh water +as piles will last about ten years, but as it is softer than fir it is +less able to stand driving successfully. Washington to California and +eastward to Montana. + + + LARCH or TAMARACK + +Wood like the best of hard pine both in appearance, quality, and uses, +and owing to its great durability somewhat preferred in shipbuilding, +for telegraph poles, and railway ties. In its structure it resembles +spruce. The larches are deciduous trees, occasionally covering +considerable areas, but usually scattered among other conifers. + +=18. Tamarack= (_Larix laricina_ var. _Americana_) (Larch, Black Larch, +American Larch, Hacmatac). Heartwood light brown in color, sapwood +nearly white, coarse conspicuous grain, compact structure, annual +rings pronounced. Wood heavy, hard, very strong, durable in contact +with the soil. Used for railway ties, fence posts, sills, ship +timbers, telegraph poles, flagstaffs. Medium-sized tree, often +covering swamps, in which case it is smaller and of poor quality. +Maine to Minnesota, and southward to Pennsylvania. + +=19. Tamarack= (_Larix occidentalis_) (Western Larch, Larch). +Large-sized trees, scattered, locally abundant. Is little inferior to +oak in strength and durability. Heartwood of a light brown color with +lighter sapwood, has a fine, slightly satiny grain, and is fairly free +from knots; the annual rings are distant. Used for railway ties and +shipbuilding. Washington and Oregon to Montana. + + + PINE + +Very variable, very light and soft in "soft" pine, such as white pine; +of medium weight to heavy and quite hard in "hard" pine, of which the +long-leaf or Georgia pine is the extreme form. Usually it is stiff, +quite strong, of even texture, and more or less resinous. The sapwood +is yellowish white; the heartwood orange brown. Pine shrinks +moderately, seasons rapidly and without much injury; it works easily, +is never too hard to nail (unlike oak or hickory); it is mostly quite +durable when in contact with the soil, and if well seasoned is not +subject to the attacks of boring insects. The heavier the wood, the +darker, stronger, and harder it is, and the more it shrinks and checks +when seasoning. Pine is used more extensively than any other wood. It +is the principal wood in carpentry, as well as in all heavy +construction, bridges, trestles, etc. It is also used in almost every +other wood industry; for spars, masts, planks, and timbers in +shipbuilding, in car and wagon construction, in cooperage and +woodenware; for crates and boxes, in furniture work, for toys and +patterns, water pipes, excelsior, etc. Pines are usually large-sized +trees with few branches, the straight, cylindrical, useful stem +forming by far the greatest part of the tree. They occur gregariously, +forming vast forests, a fact which greatly facilitates their +exploitation. Of the many special terms applied to pine as lumber, +denoting sometimes differences in quality, the following deserve +attention: "White pine," "pumpkin pine," "soft pine," in the Eastern +markets refer to the wood of the white pine (_Pinus strobus_), and on +the Pacific Coast to that of the sugar pine (_Pinus lambertiana_). +"Yellow pine" is applied in the trade to all the Southern lumber +pines; in the Northwest it is also applied to the pitch pine (_Pinus +regida_); in the West it refers mostly to the bull pine (_Pinus +ponderosa_). "Yellow long-leaf pine" (Georgia pine), chiefly used in +advertisements, refers to the long-leaf Pine (_Pinus palustris_). + + + (_a_) Soft Pines + +=20. White Pine= (_Pinus strobus_) (Soft Pine, Pumpkin Pine, Weymouth +Pine, Yellow Deal). Large to very large-sized tree, reaching a height +of 80 to 100 feet or more, and in some instances 7 or 8 feet in +diameter. For the last fifty years the most important timber tree of +the United States, furnishing the best quality of soft pine. Heartwood +cream white; sapwood nearly white. Close straight grain, compact +structure; comparatively free from knots and resin. Soft, uniform; +seasons well; easy to work; nails without splitting; fairly durable in +contact with the soil; and shrinks less than other species of pine. +Paints well. Used for carpentry, construction, building, spars, masts, +matches, boxes, etc., etc., etc. + +=21. Sugar Pine= (_Pinus lambertiana_) (White Pine, Pumpkin Pine, Soft +Pine). A very large tree, forming extensive forests in the Rocky +Mountains and furnishing most of the timber of the western United +States. It is confined to Oregon and California, and grows at from +1,500 to 8,000 feet above sea level. Has an average height of 150 to +175 feet and a diameter of 4 to 5 feet, with a maximum height of 235 +feet and 12 feet in diameter. The wood is soft, durable, +straight-grained, easily worked, very resinous, and has a satiny +luster which makes it appreciated for interior work. It is extensively +used for doors, blinds, sashes, and interior finish, also for +druggists' drawers, owing to its freedom from odor, for oars, +mouldings, shipbuilding, cooperage, shingles, and fruit boxes. Oregon +and California. + +=22. White Pine= (_Pinus monticolo_). A large tree, at home in Montana, +Idaho, and the Pacific States. Most common and locally used in +northern Idaho. + +=23. White Pine= (_Pinus flexilis_). A small-sized tree, forming +mountain forests of considerable extent and locally used. Eastern +Rocky Mountain slopes, Montana to New Mexico. + + + (_b_) Hard Pines + +=24. Long-Leaf Pine= (_Pinus palustris_) (Georgia Pine, Southern Pine, +Yellow Pine, Southern Hard Pine, Long-straw Pine, etc.). Large-sized +tree. This species furnishes the hardest and most durable as well as +one of the strongest pine timbers in the market. Heartwood orange, +sapwood lighter color, the annual rings are strongly marked, and it is +full of resinous matter, making it very durable, but difficult to +work. It is hard, dense, and strong, fairly free from knots, +straight-grained, and one of the best timbers for heavy engineering +work where great strength, long span, and durability are required. +Used for heavy construction, shipbuilding, cars, docks, beams, ties, +flooring, and interior decoration. Coast region from North Carolina to +Texas. + +=25. Bull Pine= (_Pinus ponderosa_) (Yellow Pine, Western Yellow Pine, +Western Pine, Western White Pine, California White Pine). Medium- to +very large-sized tree, forming extensive forests in the Pacific and +Rocky Mountain regions. Heartwood reddish brown, sapwood yellowish +white, and there is often a good deal of it. The resinous smell of the +wood is very remarkable. It is extensively used for beams, flooring, +ceilings, and building work generally. + +=26. Bull Pine= (_Pinus Jeffreyi_) (Black Pine). Large-sized tree, wood +resembles _Pinus ponderosa_ and replacing same at high altitudes. Used +locally in California. + +=27. Loblolly Pine= (_Pinus taeda_) (Slash Pine, Old Field Pine, Rosemary +Pine, Sap Pine, Short-straw Pine). A large-sized tree, forms extensive +forests. Wider-ringed, coarser, lighter, softer, with more sapwood +than the long-leaf pine, but the two are often confounded in the +market. The more Northern tree produces lumber which is weak, brittle, +coarse-grained, and not durable, the Southern tree produces a better +quality wood. Both are very resinous. This is the common lumber pine +from Virginia to South Carolina, and is found extensively in Arkansas +and Texas. Southern States, Virginia to Texas and Arkansas. + +=28. Norway Pine= (_Pinus resinosa_) (American Red Pine, Canadian Pine). +Large-sized tree, never forming forests, usually scattered or in +small groves, together with white pine. Largely sapwood and hence not +durable. Heartwood reddish white, with fine, clear grain, fairly tough +and elastic, not liable to warp and split. Used for building +construction, bridges, piles, masts, and spars. Minnesota to Michigan; +also in New England to Pennsylvania. + +=29. Short-Leaf Pine= (_Pinus echinata_) (Slash Pine, Spruce Pine, +Carolina Pine, Yellow Pine, Old Field Pine, Hard Pine). A medium- to +large-sized tree, resembling loblolly pine, often approaches in its +wood the Norway pine. Heartwood orange, sapwood lighter; compact +structure, apt to be variable in appearance in cross-section. Wood +usually hard, tough, strong, durable, resinous. A valuable timber +tree, sometimes worked for turpentine. Used for heavy construction, +shipbuilding, cars, docks, beams, ties, flooring, and house trim. +_Pinus echinata_, _palustris_, and _taeda_ are very similar in +character, of thin wood and very difficult to distinguish one from +another. As a rule, however, _palustris_ (Long-leaf Pine) has the +smallest and most uniform growth rings, and _Pinus taeda_ (Loblolly +Pine) has the largest. All are apt to be bunched together in the +lumber market as Southern Hard Pine. All are used for the same +purposes. Short-leaf is the common lumber pine of Missouri and +Arkansas. North Carolina to Texas and Missouri. + +=30. Cuban Pine= (_Pinus cubensis_) (Slash Pine, Swamp Pine, Bastard +Pine, Meadow Pine). Resembles long-leaf pine, but commonly has a wider +sapwood and coarser grain. Does not enter the markets to any extent. +Along the coast from South Carolina to Louisiana. + +=31. Pitch Pine= (_Pinus rigida_) (Torch Pine). A small to medium-sized +tree. Heartwood light brown or red, sapwood yellowish white. Wood +light, soft, not strong, coarse-grained, durable, very resinous. Used +locally for lumber, fuel, and charcoal. Coast regions from New York +to Georgia, and along the mountains to Kentucky. + +=32. Black Pine= (_Pinus murryana_) (Lodge-pole Pine, Tamarack). +Small-sized tree. Rocky Mountains and Pacific regions. + +=33. Jersey Pine= (_Pinus inops_ var. _Virginiana_) (Scrub Pine). +Small-sized tree. Along the coast from New York to Georgia and along +the mountains to Kentucky. + +=34. Gray Pine= (_Pinus divaricata_ var. _banksiana_) (Scrub Pine, Jack +Pine). Medium- to large-sized tree. Heartwood pale brown, rarely +yellow; sapwood nearly white. Wood light, soft, not strong, +close-grained. Used for fuel, railway ties, and fence posts. In days +gone by the Indians preferred this species for frames of canoes. +Maine, Vermont, and Michigan to Minnesota. + + + REDWOOD (See Cedar) + + SPRUCE + +Resembles soft pine, is light, very soft, stiff, moderately strong, +less resinous than pine; has no distinct heartwood, and is of whitish +color. Used like soft pine, but also employed as resonance wood in +musical instruments and preferred for paper pulp. Spruces, like pines, +form extensive forests. They are more frugal, thrive on thinner soils, +and bear more shade, but usually require a more humid climate. "Black" +and "White" spruce as applied by lumbermen usually refer to narrow and +wide-ringed forms of black spruce (_Picea nigra_). + +=35. Black Spruce= (_Picea nigra_ var. _mariana_). Medium-sized tree, +forms extensive forests in northwestern United States and in British +America; occurs scattered or in groves, especially in low lands +throughout the northern pineries. Important lumber tree in eastern +United States. Heartwood pale, often with reddish tinge; sapwood pure +white. Wood light, soft, not strong. Chiefly used for manufacture of +paper pulp, and great quantities of this as well as _Picea alba_ are +used for this purpose. Used also for sounding boards for pianos, +violins, etc. Maine to Minnesota, British America, and in the +Alleghanies to North Carolina. + +=36. White Spruce= (_Picea canadensis_ var. _alba_). Medium- to +large-sized tree. Heartwood light yellow; sapwood nearly white. +Generally associated with the preceding. Most abundant along streams +and lakes, grows largest in Montana and forms the most important tree +of the sub-arctic forest of British America. Used largely for floors, +joists, doors, sashes, mouldings, and panel work, rapidly superceding +_Pinus strobus_ for building purposes. It is very similar to Norway +pine, excels it in toughness, is rather less durable and dense, and +more liable to warp in seasoning. Northern United States from Maine to +Minnesota, also from Montana to Pacific, British America. + +=37. White Spruce= (_Picea engelmanni_). Medium- to large-sized tree, +forming extensive forests at elevations from 5,000 to 10,000 feet +above sea level; resembles the preceding, but occupies a different +station. A very important timber tree in the central and southern +parts of the Rocky Mountains. Rocky Mountains from Mexico to Montana. + +=38. Tide-Land Spruce= (_Picea sitchensis_) (Sitka Spruce). A +large-sized tree, forming an extensive coast-belt forest. Used +extensively for all classes of cooperage and woodenware on the Pacific +Coast. Along the sea-coast from Alaska to central California. + +=39. Red Spruce= (_Picea rubens_). Medium-sized tree, generally +associated with _Picea nigra_ and occurs scattered throughout the +northern pineries. Heartwood reddish; sapwood lighter color, +straight-grained, compact structure. Wood light, soft, not strong, +elastic, resonant, not durable when exposed. Used for flooring, +carpentry, shipbuilding, piles, posts, railway ties, paddles, oars, +sounding boards, paper pulp, and musical instruments. Montana to +Pacific, British America. + + + BASTARD SPRUCE + +Spruce or fir in name, but resembling hard pine or larch in +appearance, quality and uses of its wood. + +=40. Douglas Spruce= (_Pseudotsuga douglasii_) (Yellow Fir, Red Fir, +Oregon Pine). One of the most important trees of the western United +States; grows very large in the Pacific States, to fair size in all +parts of the mountains, in Colorado up to about 10,000 feet above sea +level; forms extensive forests, often of pure growth, it is really +neither a pine nor a fir. Wood very variable, usually coarse-grained +and heavy, with very pronounced summer-wood. Hard and strong ("red" +fir), but often fine-grained and light ("yellow" fir). It is the chief +tree of Washington and Oregon, and most abundant and most valuable in +British Columbia, where it attains its greatest size. From the plains +to the Pacific Ocean, and from Mexico to British Columbia. + +=41. Red Fir= (_Pseudotsuga taxifolia_) (Oregon Pine, Puget Sound Pine, +Yellow Fir, Douglas Spruce, Red Pine). Heartwood light red or yellow +in color, sapwood narrow, nearly white, comparatively free from +resins, variable annual rings. Wood usually hard, strong, difficult to +work, durable, splinters easily. Used for heavy construction, +dimension timber, railway ties, doors, blinds, interior finish, piles, +etc. One of the most important of Western trees. From the plains to +the Pacific Ocean, and from Mexico to British America. + + + TAMARACK (See Larch) + + + YEW + +Wood heavy, hard, extremely stiff and strong, of fine texture with a +pale yellow sapwood, and an orange-red heartwood; seasons well and is +quite durable. Extensively used for archery bows, turner's ware, etc. +The yews form no forests, but occur scattered with other conifers. + +=42. Yew= (_Taxus brevifolia_). A small to medium-sized tree of the +Pacific region. + + + + + SECTION III + + BROAD-LEAVED TREES + + WOOD OF BROAD-LEAVED TREES + + + [Illustration: Fig. 4. Block of Oak. CS, cross-section; RS, + radial section; TS, tangential section; _mr_, medullary or + pith ray; _a_, height; _b_, width; and _e_, length of pith + ray.] + + [Illustration: Fig. 5. Board of Oak. CS, cross-section; RS, + radial section; TS, tangential section; _v_, vessels or + pores, cut through.; A, slight curve in log which appears in + section as an islet.] + + [Illustration: Fig. 6. Cross-section of Oak (Magnified about + 5 times).] + +On a cross-section of oak, the same arrangement of pith and bark, of +sapwood and heartwood, and the same disposition of the wood in +well-defined concentric or annual rings occur, but the rings are +marked by lines or rows of conspicuous pores or openings, which occupy +the greater part of the spring-wood for each ring (see Fig. 4, also +6), and are, in fact the hollows of vessels through which the cut has +been made. On the radial section or quarter-sawn board the several +layers appear as so many stripes (see Fig. 5); on the tangential +section or "bastard" face patterns similar to those mentioned for pine +wood are observed. But while the patterns in hard pine are marked by +the darker summer-wood, and are composed of plain, alternating stripes +of darker and lighter wood, the figures in oak (and other broad-leaved +woods) are due chiefly to the vessels, those of the spring-wood in oak +being the most conspicuous (see Fig. 5). So that in an oak table, the +darker, shaded parts are the spring-wood, the lighter unicolored parts +the summer-wood. On closer examination of the smooth cross-section of +oak, the spring-wood part of the ring is found to be formed in great +part of pores; large, round, or oval openings made by the cut through +long vessels. These are separated by a grayish and quite porous +tissue (see Fig. 6, A), which continues here and there in the form of +radial, often branched, patches (not the pith rays) into and through +the summer-wood to the spring-wood of the next ring. The large vessels +of the spring-wood, occupying six to ten per cent of the volume of a +log in very good oak, and twenty-five per cent or more in inferior and +narrow-ringed timber, are a very important feature, since it is +evident that the greater their share in the volume, the lighter and +weaker the wood. They are smallest near the pith, and grow wider +outward. They are wider in the stem than limb, and seem to be of +indefinite length, forming open channels, in some cases probably as +long as the tree itself. Scattered through the radiating gray patches +of porous wood are vessels similar to those of the spring-wood, but +decidedly smaller. These vessels are usually fewer and larger near the +outer portions of the ring. Their number and size can be utilized to +distinguish the oaks classed as white oaks from those classed as black +and red oaks. They are fewer and larger in red oaks, smaller but much +more numerous in white oaks. The summer-wood, except for these radial, +grayish patches, is dark colored and firm. This firm portion, divided +into bodies or strands by these patches of porous wood, and also by +fine, wavy, concentric lines of short, thin-walled cells (see Fig. 6, +A), consists of thin-walled fibres (see Fig. 7, B), and is the chief +element of strength in oak wood. In good white oak it forms one-half +or more of the wood, if it cuts like horn, and the cut surface is +shiny, and of a deep chocolate brown color. In very narrow-ringed wood +and in inferior red oak it is usually much reduced in quantity as well +as quality. The pith rays of the oak, unlike those of the coniferous +woods, are at least in part very large and conspicuous. (See Fig. 4; +their height indicated by the letter _a_, and their width by the +letter _b_.) The large medullary rays of oak are often twenty and more +cells wide, and several hundred cell rows in height, which amount +commonly to one or more inches. These large rays are conspicuous on +all sections. They appear as long, sharp, grayish lines on the +cross-sections; as short, thick lines, tapering at each end, on the +tangential or "bastard" face, and as broad, shiny bands, "the +mirrors," on the radial section. In addition to these coarse rays, +there is also a large number of small pith rays, which can be seen +only when magnified. On the whole, the pith rays form a much larger +part of the wood than might be supposed. In specimens of good white +oak it has been found that they form about sixteen to twenty-five per +cent of the wood. + + [Illustration: Fig. 7. Portion of the Firm Bodies of Fibres + with Two Cells of a Small Pith Ray _mr_ (Highly Magnified).] + + [Illustration: Fig. 8. Isolated Fibres and Cells, _a_, four + cells of wood, parenchyma; _b_, two cells from a pith ray; + _c_, a single joint or cell of a vessel, the openings _x_ + leading into its upper and lower neighbors; _d_, tracheid; + _e_, wood fibre proper.] + + + Minute Structure + + [Illustration: Fig. 9. Cross-section of Basswood (Magnified). + _v_, vessels; _mr_, pith rays.] + +If a well-smoothed thin disk or cross-section of oak (say +one-sixteenth inch thick) is held up to the light, it looks very much +like a sieve, the pores or vessels appearing as clean-cut holes. The +spring-wood and gray patches are seen to be quite porous, but the firm +bodies of fibres between them are dense and opaque. Examined with a +magnifier it will be noticed that there is no such regularity of +arrangement in straight rows as is conspicuous in pine. On the +contrary, great irregularity prevails. At the same time, while the +pores are as large as pin holes, the cells of the denser wood, unlike +those of pine wood, are too small to be distinguished. Studied with +the microscope, each vessel is found to be a vertical row of a great +number of short, wide tubes, joined end to end (see Fig. 8, _c_). The +porous spring-wood and radial gray tracts are partly composed of +smaller vessels, but chiefly of tracheids, like those of pine, and of +shorter cells, the "wood parenchyma," resembling the cells of the +medullary rays. These latter, as well as the fine concentric lines +mentioned as occurring in the summer-wood, are composed entirely of +short tube-like parenchyma cells, with square or oblique ends (see +Fig. 8, _a_ and _b_). The wood fibres proper, which form the dark, +firm bodies referred to, are very fine, thread-like cells, one +twenty-fifth to one-tenth inch long, with a wall commonly so thick +that scarcely any empty internal space or lumen remains (see Figs. 8, +_e_, and 7, B). If, instead of oak, a piece of poplar or basswood (see +Fig. 9) had been used in this study, the structure would have been +found to be quite different. The same kinds of cell-elements, vessels, +etc., are, to be sure, present, but their combination and arrangement +are different, and thus from the great variety of possible +combinations results the great variety of structure and, in +consequence, of the qualities which distinguish the wood of +broad-leaved trees. The sharp distinction of sap wood and heartwood is +wanting; the rings are not so clearly defined; the vessels of the +wood are small, very numerous, and rather evenly scattered through the +wood of the annual rings, so that the distinction of the ring almost +vanishes and the medullary or pith rays in poplar can be seen, without +being magnified, only on the radial section. + + + LIST OF MOST IMPORTANT BROAD-LEAVED TREES (HARDWOODS) + +Woods of complex and very variable structure, and therefore differing +widely in quality, behavior, and consequently in applicability to the +arts. + + + AILANTHUS + +=1. Ailanthus= (_Ailanthus glandulosa_). Medium to large-sized tree. +Wood pale yellow, hard, fine-grained, and satiny. This species +originally came from China, where it is known as the Tree of "Heaven," +was introduced into the United States and planted near Philadelphia +during the 18th century, and is more ornamental than useful. It is +used to some extent in cabinet work. Western Pennsylvania and Long +Island, New York. + + + ASH + +Wood heavy, hard, stiff, quite tough, not durable in contact with the +soil, straight-grained, rough on the split surfaces and coarse in +texture. The wood shrinks moderately, seasons with little injury, +stands well, and takes a good polish. In carpentry, ash is used for +stairways, panels, etc. It is used in shipbuilding, in the +construction of cars, wagons, etc., in the manufacture of all kinds of +farm implements, machinery, and especially of all kinds of furniture; +for cooperage, baskets, oars, tool handles, hoops, etc., etc. The +trees of the several species of ash are rapid growers, of small to +medium height with stout trunks. They form no forests, but occur +scattered in almost all our broad-leaved forests. + +=2. White Ash= (_Fraxinus Americana_). Medium-, sometimes large-sized +tree. Heartwood reddish brown, usually mottled; sapwood lighter color, +nearly white. Wood heavy, hard, tough, elastic, coarse-grained, +compact structure. Annual rings clearly marked by large open pores, +not durable in contact with the soil, is straight-grained, and the +best material for oars, etc. Used for agricultural implements, tool +handles, automobile (rim boards), vehicle bodies and parts, baseball +bats, interior finish, cabinet work, etc., etc. Basin of the Ohio, but +found from Maine to Minnesota and Texas. + +=3. Red Ash= (_Fraxinus pubescens_ var. _Pennsylvanica_). Medium-sized +tree, a timber very similar to, but smaller than _Fraxinus Americana_. +Heartwood light brown, sapwood lighter color. Wood heavy, hard, +strong, and coarse-grained. Ranges from New Brunswick to Florida, and +westward to Dakota, Nebraska, and Kansas. + +=4. Black Ash= (_Fraxinus nigra_ var. _sambucifolia_) (Hoop Ash, Ground +Ash). Medium-sized tree, very common, is more widely distributed than +the _Fraxinus Americana_; the wood is not so hard, but is well suited +for hoops and basketwork. Heartwood dark brown, sapwood light brown or +white. Wood heavy, rather soft, tough and coarse-grained. Used for +barrel hoops, basketwork, cabinetwork and interior of houses. Maine to +Minnesota and southward to Alabama. + +=5. Blue Ash= (_Fraxinus quadrangulata_). Small to medium-sized tree. +Heartwood yellow, streaked with brown, sapwood a lighter color. Wood +heavy, hard, and coarse-grained. Not common. Indiana and Illinois; +occurs from Michigan to Minnesota and southward to Alabama. + +=6. Green Ash= (_Fraxinus viridis_). Small-sized tree. Occurs from New +York to the Rocky Mountains, and southward to Florida and Arizona. + +=7. Oregon Ash= (_Fraxinus Oregana_). Small to medium-sized tree. Occurs +from western Washington to California. + +=8. Carolina Ash= (_Fraxinus Caroliniana_). Medium-sized tree. Occurs in +the Carolinas and the coast regions southward. + + + ASPEN (See Poplar) + + + BASSWOOD + +=9. Basswood= (_Tilia Americana_) (Linden, Lime Tree, American Linden, +Lin, Bee Tree). Medium- to large-sized tree. Wood light, soft, stiff, +but not strong, of fine texture, straight and close-grained, and white +to light brown color, but not durable in contact with the soil. The +wood shrinks considerably in drying, works well and stands well in +interior work. It is used for cooperage, in carpentry, in the +manufacture of furniture and woodenware (both turned and carved), for +toys, also for panelling of car and carriage bodies, for agricultural +implements, automobiles, sides and backs of drawers, cigar boxes, +excelsior, refrigerators, trunks, and paper pulp. It is also largely +cut for veneer and used as "three-ply" for boxes and chair seats. It +is used for sounding boards in pianos and organs. If well seasoned and +painted it stands fairly well for outside work. Common in all northern +broad-leaved forests. Found throughout the eastern United States, but +reaches its greatest size in the Valley of the Ohio, becoming often +130 feet in height, but its usual height is about 70 feet. + +=10. White Basswood= (_Tilia heterophylla_) (Whitewood). A small-sized +tree. Wood in its quality and uses similar to the preceding, only it +is lighter in color. Most abundant in the Alleghany region. + +=11. White Basswood= (_Tilia pubescens_) (Downy Linden, Small-leaved +Basswood). Small-sized tree. Wood in its quality and uses similar to +_Tilia Americana_. This is a Southern species which makes it way as +far north as Long Island. Is found at its best in South Carolina. + + + BEECH + +=12. Beech= (_Fagus ferruginea_) (Red Beech, White Beech). Medium-sized +tree, common, sometimes forming forests of pure growth. Wood heavy, +hard, stiff, strong, of rather coarse texture, white to light brown +color, not durable in contact with the soil, and subject to the +inroads of boring insects. Rather close-grained, conspicuous medullary +rays, and when quarter-sawn and well smoothed is very beautiful. The +wood shrinks and checks considerably in drying, works well and stands +well, and takes a fine polish. Beech is comparatively free from +objectionable taste, and finds a place in the manufacture of +commodities which come in contact with foodstuffs, such as lard tubs, +butter boxes and pails, and the beaters of ice cream freezers; for the +latter the persistent hardness of the wood when subjected to attrition +and abrasion, while wet gives it peculiar fitness. It is an excellent +material for churns. Sugar hogsheads are made of beech, partly because +it is a tasteless wood and partly because it has great strength. A +large class of woodenware, including veneer plates, dishes, boxes, +paddles, scoops, spoons, and beaters, which belong to the kitchen and +pantry, are made of this species of wood. Beech picnic plates are made +by the million, a single machine turning out 75,000 a day. The wood +has a long list of miscellaneous uses and enters in a great variety of +commodities. In every region where it grows in commercial quantities +it is made into boxes, baskets, and crating. Beech baskets are chiefly +employed in shipping fruit, berries, and vegetables. In Maine thin +veneer of beech is made specially for the Sicily orange and lemon +trade. This is shipped in bulk and the boxes are made abroad. Beech is +also an important handle wood, although not in the same class with +hickory. It is not selected because of toughness and resiliency, as +hickory is, and generally goes into plane, handsaw, pail, chisel, and +flatiron handles. Recent statistics show that in the production of +slack cooperage staves, only two woods, red gum and pine, stood above +beech in quantity, while for heading, pine alone exceeded it. It is +also used in turnery, for shoe lasts, butcher blocks, ladder rounds, +etc. Abroad it is very extensively used by the carpenter, millwright, +and wagon maker, in turnery and wood carving. Most abundant in the +Ohio and Mississippi basin, but found from Maine to Wisconsin and +southward to Florida. + + + BIRCH + +=13. Cherry Birch= (_Betula lenta_) (Black Birch, Sweet Birch, Mahogany +Birch, Wintergreen Birch). Medium-sized tree, very common. Wood of +beautiful reddish or yellowish brown, and much of it nicely figured, +of compact structure, is straight in grain, heavy, hard, strong, takes +a fine polish, and considerably used as imitation of mahogany. The +wood shrinks considerably in drying, works well and stands well, but +is not durable in contact with the soil. The medullary rays in birch +are very fine and close and not easily seen. The sweet birch is very +handsome, with satiny luster, equalling cherry, and is too costly a +wood to be profitably used for ordinary purposes, but there are both +high and low grades of birch, the latter consisting chiefly of sapwood +and pieces too knotty for first class commodities. This cheap material +swells the supply of box lumber, and a little of it is found wherever +birch passes through sawmills. The frequent objections against sweet +birch as box lumber and crating material are that it is hard to nail +and is inclined to split. It is also used for veneer picnic plates and +butter dishes, although it is not as popular for this class of +commodity as are yellow and paper birch, maple and beech. The best +grades are largely used for furniture and cabinet work, and also for +interior finish. Maine to Michigan and to Tennessee. + +=14. White Birch= (_Betula populifolia_) (Gray Birch, Old Field Birch, +Aspen-leaved Birch). Small to medium-sized tree, least common of all +the birches. Short-lived, twenty to thirty feet high, grows very +rapidly. Heartwood light brown, sapwood lighter color. Wood light, +soft, close-grained, not strong, checks badly in drying, decays +quickly, not durable in contact with the soil, takes a good polish. +Used for spools, shoepegs, wood pulp, and barrel hoops. Fuel, value +not high, but burns with bright flame. Ranges from Nova Scotia and +lower St. Lawrence River, southward, mostly in the coast region to +Delaware, and westward through northern New England and New York to +southern shore of Lake Ontario. + +=15. Yellow Birch= (_Betula lutea_) (Gray Birch, Silver Birch). Medium- +to large-sized tree, very common. Heartwood light reddish brown, +sapwood nearly white, close-grained, compact structure, with a satiny +luster. Wood heavy, very strong, hard, tough, susceptible of high +polish, not durable when exposed. Is similar to _Betula lenta_, and +finds a place in practically all kinds of woodenware. A large +percentage of broom handles on the market are made of this species of +wood, though nearly every other birch contributes something. It is +used for veneer plates and dishes made for pies, butter, lard, and +many other commodities. Tubs and pails are sometimes made of yellow +birch provided weight is not objectionable. The wood is twice as heavy +as some of the pines and cedars. Many small handles for such articles +as flatirons, gimlets, augers, screw drivers, chisels, varnish and +paint brushes, butcher and carving knives, etc. It is also widely used +for shipping boxes, baskets, and crates, and it is one of the +stiffest, strongest woods procurable, but on account of its excessive +weight it is sometimes discriminated against. It is excellent for +veneer boxes, and that is probably one of the most important places it +fills. Citrus fruit from northern Africa and the islands and countries +of the Mediterranean is often shipped to market in boxes made of +yellow birch from veneer cut in New England. The better grades are +also used for furniture and cabinet work, and the "burls" found on +this species are highly valued for making fancy articles, gavels, etc. +It is extensively used for turnery, buttons, spools, bobbins, wheel +hubs, etc. Maine to Minnesota and southward to Tennessee. + +=16. Red Birch= (_Betula rubra_ var. _nigra_) (River Birch). Small to +medium-sized tree, very common. Lighter and less valuable than the +preceding. Heartwood light brown, sapwood pale. Wood light, fairly +strong and close-grained. Red birch is best developed in the middle +South, and usually grows near the banks of rivers. Its bark hangs in +tatters, even worse than that of paper birch, but it is darker. In +Tennessee the slack coopers have found that red birch makes excellent +barrel heads and it is sometimes employed in preference to other +woods. In eastern Maryland the manufacturers of peach baskets draw +their supplies from this wood, and substitute it for white elm in +making the hoops or bands which stiffen the top of the basket, and +provide a fastening for the veneer which forms the sides. Red birch +bends in a very satisfactory manner, which is an important point. This +wood enters pretty generally into the manufacture of woodenware within +its range, but statistics do not mention it by name. It is also used +in the manufacture of veneer picnic plates, pie plates, butter dishes, +washboards, small handles, kitchen and pantry utensils, and ironing +boards. New England to Texas and Missouri. + +=17. Canoe Birch= (_Betula paprifera_) (White Birch, Paper Birch). Small +to medium-sized tree, sometimes forming forests, very common. +Heartwood light brown tinged with red, sapwood lighter color. Wood of +good quality, but light, fairly hard and strong, tough, close-grained. +Sap flows freely in spring and by boiling can be made into syrup. Not +as valuable as any of the preceding. Canoe birch is a northern tree, +easily identified by its white trunk and its ragged bark. Large +numbers of small wooden boxes are made by boring out blocks of this +wood, shaping them in lathes, and fitting lids on them. Canoe birch is +one of the best woods for this class of commodities, because it can be +worked very thin, does not split readily, and is of pleasing color. +Such boxes, or two-piece diminutive kegs, are used as containers for +articles shipped and sold in small bulk, such as tacks, small nails, +and brads. Such containers are generally cylindrical and of +considerably greater depth than diameter. Many others of nearly +similar form are made to contain ink bottles, bottles of perfumery, +drugs, liquids, salves, lotions, and powders of many kinds. Many boxes +of this pattern are used by manufacturers of pencils and crayons for +packing and shipping their wares. Such boxes are made in numerous +numbers by automatic machinery. A single machine of the most improved +pattern will turn out 1,400 boxes an hour. After the boring and +turning are done, they are smoothed by placing them into a tumbling +barrel with soapstone. It is also used for one-piece shallow trays or +boxes, without lids, and used as card receivers, pin receptacles, +butter boxes, fruit platters, and contribution plates in churches. It +is also the principal wood used for spools, bobbins, bowls, shoe +lasts, pegs, and turnery, and is also much used in the furniture +trade. All along the northern boundary of the United States and +northward, from the Atlantic to the Pacific. + + + BLACK WALNUT (See Walnut) + + + BLUE BEECH + +=18. Blue Beech= (_Carpinus Caroliniana_) (Hornbeam, Water Beech, +Ironwood). Small-sized tree. Heartwood light brown, sapwood nearly +white. Wood very hard, heavy, strong, very stiff, of rather fine +texture, not durable in contact with the soil, shrinks and checks +considerably in drying, but works well and stands well, and takes a +fine polish. Used chiefly in turnery, for tool handles, etc. Abroad +much used by mill-and wheelwrights. A small tree, largest in the +Southwest, but found in nearly all parts of the eastern United States. + + + BOIS D'ARC (See Osage Orange) + + + BUCKEYE + +Wood light, soft, not strong, often quite tough, of fine, uniform +texture and creamy white color. It shrinks considerably in drying, but +works well and stands well. Used for woodenware, artificial limbs, +paper pulp, and locally also for building construction. + +=19. Ohio Buckeye= (_AEsculus glabra_) (Horse Chestnut, Fetid Buckeye). +Small-sized tree, scattered, never forming forests. Heartwood white, +sapwood pale brown. Wood light, soft, not strong, often quite tough +and close-grained. Alleghanies, Pennsylvania to Oklahoma. + +=20. Sweet Buckeye= (_AEsculus octandra_ var. _flava_) (Horse Chestnut). +Small-sized tree, scattered, never forming forests. Wood in its +quality and uses similar to the preceding. Alleghanies, Pennsylvania +to Texas. + + + BUCKTHORNE + +=21. Buckthorne= (_Rhanmus Caroliniana_) (Indian Cherry). Small-sized +tree. Heartwood light brown, sapwood almost white. Wood light, hard, +close-grained. Does not enter the markets to any great extent. Found +along the borders of streams in rich bottom lands. Its northern limits +is Long Island, where it is only a shrub; it becomes a tree only in +southern Arkansas and adjoining regions. + + + BUTTERNUT + +=22. Butternut= (_Juglans cinerea_) (White Walnut, White Mahogany, +Walnut). Medium-sized tree, scattered, never forming forests. Wood +very similar to black walnut, but light, quite soft, and not strong. +Heartwood light gray-brown, darkening with exposure; sapwood nearly +white, coarse-grained, compact structure, easily worked, and +susceptible to high polish. Has similar grain to black walnut and when +stained is a very good imitation. Is much used for inside work, and +very durable. Used chiefly for finishing lumber, cabinet work, boat +finish and fixtures, and for furniture. Butternut furniture is often +sold as circassian walnut. Largest and most common in the Ohio basin. +Maine to Minnesota and southward to Georgia and Alabama. + + + CATALPA + +The catalpa is a tree which was planted about 25 years ago as a +commercial speculation in Iowa, Kansas, and Nebraska. Its native +habitat was along the rivers Ohio and lower Wabash, and a century ago +it gained a reputation for rapid growth and durability, but did not +grow in large quantities. As a railway tie, experiments have left no +doubt as to its resistance to decay; it stands abrasion as well as the +white oak (_Quercus alba_), and is superior to it in longevity. +Catalpa is a tree singularly free from destructive diseases. Wood cut +from the living tree is one of the most durable timbers known. In +spite of its light porous structure it resists the weathering +influences and the attacks of wood-destroying fungi to a remarkable +degree. No fungus has yet been found which will grow in the dead +timber, and for fence posts this wood has no equal, lasting longer +than almost any other species of timber. The wood is rather soft and +coarse in texture, the tree is of slow growth, and the brown colored +heartwood, even of very young trees, forms nearly three-quarters of +their volume. There is only about one-quarter inch of sapwood in a +9-inch tree. + +=23. Catalpa= (_Catalpa speciosa_ var. _bignonioides_) (Indian Bean). +Medium-sized tree. Heartwood light brown, sapwood nearly white. Wood +light, soft, not strong, brittle, very durable in contact with the +soil, of coarse texture. Used chiefly for railway ties, telegraph +poles, and fence posts, but well suited for a great variety of uses. +Lower basin of the Ohio River, locally common. Extensively planted, +and therefore promising to become of some importance. + + + CHERRY + +=24. Cherry= (_Prunus serotina_) (Wild Cherry, Black Cherry, Rum +Cherry). Wood heavy, hard, strong, of fine texture. Sapwood yellowish +white, heartwood reddish to brown. The wood shrinks considerably in +drying, works well and stands well, has a fine satin-like luster, and +takes a fine polish which somewhat resembles mahogany, and is much +esteemed for its beauty. Cherry is chiefly used as a decorative +interior finishing lumber, for buildings, cars and boats, also for +furniture and in turnery, for musical instruments, walking sticks, +last blocks, and woodenware. It is becoming too costly for many +purposes for which it is naturally well suited. The lumber-furnishing +cherry of the United States, the wild black cherry, is a small to +medium-sized tree, scattered through many of the broad-leaved trees of +the western slope of the Alleghanies, but found from Michigan to +Florida, and west to Texas. Other species of this genus, as well as +the hawthornes (_Prunus cratoegus_) and wild apple (_Pyrus_), are not +commonly offered in the markets. Their wood is of the same character +as cherry, often finer, but in smaller dimensions. + +=25. Red Cherry= (_Prunus Pennsylvanica_) (Wild Red Cherry, Bird +Cherry). Small-sized tree. Heartwood light brown, sapwood pale yellow. +Wood light, soft, and close-grained. Uses similiar to the preceding, +common throughout the Northern States, reaching its greatest size on +the mountains of Tennessee. + + + CHESTNUT + +The chestnut is a long-lived tree, attaining an age of from 400 to 600 +years, but trees over 100 years are usually hollow. It grows quickly, +and sprouts from a chestnut stump (Coppice Chestnut) often attain a +height of 8 feet in the first year. It has a fairly cylindrical stem, +and often grows to a height of 100 feet and over. Coppice chestnut, +that is, chestnut grown on an old stump, furnishes better timber for +working than chestnut grown from the nut, it is heavier, less spongy, +straighter in grain, easier to split, and stands exposure longer. + +=26. Chestnut= (_Castanea vulgaris_ var. _Americana_). Medium-to +large-sized tree, never forming forests. Wood is light, moderately +hard, stiff, elastic, not strong, but very durable when in contact +with the soil, of coarse texture. Sapwood light, heartwood darker +brown, and is readily distinguishable from the sapwood, which very +early turns into heartwood. It shrinks and checks considerably in +drying, works easily, stands well. The annual rings are very distinct, +medullary rays very minute and not visible to the naked eye. Used in +cooperage, for cabinetwork, agricultural implements, railway ties, +telegraph poles, fence posts, sills, boxes, crates, coffins, +furniture, fixtures, foundation for veneer, and locally in heavy +construction. Very common in the Alleghanies. Occurs from Maine to +Michigan and southward to Alabama. + +=27. Chestnut= (_Castanea dentata_ var. _vesca_). Medium-sized tree, +never forming forests, not common. Heartwood brown color, sapwood +lighter shade, coarse-grained. Wood and uses similar to the preceding. +Occurs scattered along the St. Lawrence River, and even there is met +with only in small quantities. + +=28. Chinquapin= (_Castanea pumila_). Medium- to small-sized tree, with +wood slightly heavier, but otherwise similiar to the preceding. Most +common in Arkansas, but with nearly the same range as _Castanea +vulgaris_. + +=29. Chinquapin= (_Castanea chrysophylla_). A medium-sized tree of the +western ranges of California and Oregon. + + + COFFEE TREE + +=30. Coffee Tree= (_Gymnocladus dioicus_) (Coffee Nut, Stump Tree). A +medium- to large-sized tree, not common. Wood heavy, hard, strong, +very stiff, of coarse texture, and durable. Sapwood yellow, heartwood +reddish brown, shrinks and checks considerably in drying, works well +and stands well, and takes a fine polish. It is used to a limited +extent in cabinetwork and interior finish. Pennsylvania to Minnesota +and Arkansas. + + + COTTONWOOD (See Poplar) + + + CRAB APPLE + +=31. Crab Apple= (_Pyrus coronaria_) (Wild Apple, Fragrant Crab). +Small-sized tree. Heartwood reddish brown, sapwood yellow. Wood heavy, +hard, not strong, close-grained. Used principally for tool handles and +small domestic articles. Most abundant in the middle and western +states, reaches its greatest size in the valleys of the lower Ohio +basin. + + + CUCUMBER TREE (See Magnolia) + + + DOGWOOD + +=32. Dogwood= (_Cornus florida_) (American Box). Small to medium-sized +tree. Attains a height of about 30 feet and about 12 inches in +diameter. The heartwood is a red or pinkish color, the sapwood, which +is considerable, is a creamy white. The wood has a dull surface and +very fine grain. It is valuable for turnery, tool handles, and +mallets, and being so free from silex, watchmakers use small splinters +of it for cleaning out the pivot holes of watches, and opticians for +removing dust from deep-seated lenses. It is also used for butchers' +skewers, and shuttle blocks and wheel stock, and is suitable for +turnery and inlaid work. Occurs scattered in all the broad-leaved +forests of our country; very common. + + + ELM + +Wood heavy, hard, strong, elastic, very tough, moderately durable in +contact with the soil, commonly cross-grained, difficult to split and +shape, warps and checks considerably in drying, but stands well if +properly seasoned. The broad sapwood whitish, heartwood light brown, +both with shades of gray and red. On split surfaces rough, texture +coarse to fine, capable of high polish. Elm for years has been the +principal wood used in slack cooperage for barrel staves, also in the +construction of cars, wagons, etc., in boat building, agricultural +implements and machinery, in saddlery and harness work, and +particularly in the manufacture of all kinds of furniture, where the +beautiful figures, especially those of the tangential or bastard +section, are just beginning to be appreciated. The elms are medium- to +large-sized trees, of fairly rapid growth, with stout trunks; they +form no forests of pure growth, but are found scattered in all the +broad-leaved woods of our country, sometimes forming a considerable +portion of the arborescent growth. + +=33. White Elm= (_Ulmus Americana_) (American Elm, Water Elm). Medium- +to large-sized tree. Wood in its quality and uses as stated above. +Common. Maine to Minnesota, southward to Florida and Texas. + +=34. Rock Elm= (_Ulmus racemosa_) (Cork Elm, Hickory Elm, White Elm, +Cliff Elm). Medium- to large-sized tree of rapid growth. Heartwood +light brown, often tinged with red, sapwood yellowish or greenish +white, compact structure, fibres interlaced. Wood heavy, hard, very +tough, strong, elastic, difficult to split, takes a fine polish. Used +for agricultural implements, automobiles, crating, boxes, cooperage, +tool handles, wheel stock, bridge timbers, sills, interior finish, +and maul heads. Fairly free from knots and has only a small quantity +of sapwood. Michigan, Ohio, from Vermont to Iowa, and southward to +Kentucky. + +=35. Red Elm= (_Ulmus fulva_ var. _pubescens_) (Slippery Elm, Moose +Elm). The red or slippery elm is not as large a tree as the white elm +(_Ulmus Americana_), though it occasionally attains a height of 135 +feet and a diameter of 4 feet. It grows tall and straight, and thrives +in river valleys. The wood is heavy, hard, strong, tough, elastic, +commonly cross-grained, moderately durable in contact with the soil, +splits easily when green, works fairly well, and stands well if +properly handled. Careful seasoning and handling are essential for the +best results. Trees can be utilized for posts when very small. When +green the wood rots very quickly in contact with the soil. Poles for +posts should be cut in summer and peeled and dried before setting. The +wood becomes very tough and pliable when steamed, and is of value for +sleigh runners and for ribs of canoes and skiffs. Together with white +elm (_Ulmus Americana_) it is extensively used for barrel staves in +slack cooperage and also for furniture. The thick, viscous inner bark, +which gives the tree its descriptive name, is quite palatable, +slightly nutritious, and has a medicinal value. Found chiefly along +water courses. New York to Minnesota, and southward to Florida and +Texas. + +=36. Cedar Elm= (_Ulmus crassifolia_). Medium- to small-sized tree, +locally quite common. Arkansas and Texas. + +=37. Winged Elm= (_Ulmus alata_) (Wahoo). Small-sized tree, locally +quite common. Heartwood light brown, sapwood yellowish white. Wood +heavy, hard, tough, strong, and close-grained. Arkansas, Missouri, and +eastern Virginia. + + [Illustration: Fig. 10. A Large Red Gum.] + + + GUM + +This general term applies to three important species of gum in the +South, the principal one usually being distinguished as "red" or +"sweet" gum (see Fig. 10). The next in importance being the "tupelo" +or "bay poplar," and the least of the trio is designated as "black" or +"sour" gum (see Fig. 11). Up to the year 1900 little was known of gum +as a wood for cooperage purposes, but by the continued advance in +price of the woods used, a few of the most progressive manufacturers, +looking into the future, saw that the supply of the various woods in +use was limited, that new woods would have to be sought, and gum was +looked upon as a possible substitute, owing to its cheapness and +abundant supply. No doubt in the future this wood will be used to a +considerable extent in the manufacture of both "tight" and "slack" +cooperage. In the manufacture of the gum, unless the knives and saws +are kept very sharp, the wood has a tendency to break out, the corners +splitting off; and also, much difficulty has been experienced in +seasoning and kiln-drying. + + [Illustration: Fig. 11. A Tupelo Gum Slough.] + +In the past, gum, having no marketable value, has been left standing +after logging operations, or, where the land has been cleared for +farming, the trees have been "girdled" and allowed to rot, and then +felled and burned as trash. Now, however, that there is a market for +this species of timber, it will be profitable to cut the gum with the +other hardwoods, and this species of wood will come in for a greater +share of attention than ever before. + +=38. Red Gum= (_Liquidamber styraciflua_) (Sweet Gum, Hazel Pine, Satin +Walnut, Liquidamber, Bilsted). The wood is about as stiff and as +strong as chestnut, rather heavy, it splits easily and is quite brash, +commonly cross-grained, of fine texture, and has a large proportion of +whitish sapwood, which decays rapidly when exposed to the weather; but +the reddish brown heartwood is quite durable, even in the ground. The +external appearance of the wood is of fine grain and smooth, close +texture, but when broken the lines of fracture do not run with +apparent direction of the growth; possibly it is this unevenness of +grain which renders the wood so difficult to dry without twisting and +warping. It has little resiliency; can be easily bent when steamed, +and when properly dried will hold its shape. The annual rings are not +distinctly marked, medullary rays fine and numerous. The green wood +contains much water, and consequently is heavy and difficult to float, +but when dry it is as light as basswood. The great amount of water in +the green wood, particularly in the sap, makes it difficult to season +by ordinary methods without warping and twisting. It does not check +badly, is tasteless and odorless, and when once seasoned, swells and +shrinks but little unless exposed to the weather. Used for boat +finish, veneers, cabinet work, furniture, fixtures, interior +decoration, shingles, paving blocks, woodenware, cooperage, machinery +frames, refrigerators, and trunk slats. + + + Range of Red Gum + +Red gum is distributed from Fairfield County, Conn., to southeastern +Missouri, through Arkansas and Oklahoma to the valley of the Trinity +River in Texas, and eastward to the Atlantic coast. Its commercial +range is restricted, however, to the moist lands of the lower Ohio and +Mississippi basins and of the Southeastern coast. It is one of the +commonest timber trees in the hardwood bottoms and drier swamps of the +South. It grows in mixture with ash, cottonwood and oak (see Fig. 12). +It is also found to a considerable extent on the lower ridges and +slopes of the southern Appalachians, but there it does not reach +merchantable value and is of little importance. Considerable +difference is found between the growth in the upper Mississippi +bottoms and that along the rivers on the Atlantic coast and on the +Gulf. In the latter regions the bottoms are lower, and consequently +more subject to floods and to continued overflows (see Fig. 11). The +alluvial deposit is also greater, and the trees grow considerably +faster. Trees of the same diameter show a larger percentage of sapwood +there than in the upper portions of the Mississippi Valley. The +Mississippi Valley hardwood trees are for the most part considerably +older, and reach larger dimensions than the timber along the coast. + + + Form of the Red Gum + +In the best situations red gum reaches a height of 150 feet, and a +diameter of 5 feet. These dimensions, however are unusual. The stem is +straight and cylindrical, with dark, deeply-furrowed bark, and +branches often winged with corky ridges. In youth, while growing +vigorously under normal conditions, it assumes a long, regular, +conical crown, much resembling the form of a conifer (see Fig. 12). +After the tree has attained its height growth, however, the crown +becomes rounded, spreading and rather ovate in shape. When growing in +the forest the tree prunes itself readily at an early period, and +forms a good length of clear stem, but it branches strongly after +making most of its height growth. The mature tree is usually forked, +and the place where the forking commences determines the number of +logs in the tree or its merchantable length, by preventing cutting to +a small diameter in the top. On large trees the stem is often not less +than eighteen inches in diameter where the branching begins. The +over-mature tree is usually broken and dry topped, with a very +spreading crown, in consequence of new branches being sent out. + + + Tolerance of Red Gum + +Throughout its entire life red gum is intolerant in shade, there are +practically no red seedlings under the dense forest cover of the +bottom land, and while a good many may come up under the pine forest +on the drier uplands, they seldom develop into large trees. As a rule +seedlings appear only in clearings or in open spots in the forest. It +is seldom that an over-topped tree is found, for the gum dies quickly +if suppressed, and is consequently nearly always a dominant or +intermediate tree. In a hardwood bottom forest the timber trees are +all of nearly the same age over considerable areas, and there is +little young growth to be found in the older stands. The reason for +this is the intolerance of most of the swamp species. A scale of +intolerance containing the important species, and beginning with the +most light-demanding, would run as follows: Cottonwood, sycamore, red +gum, white elm, white ash, and red maple. + + + Demands upon Soil and Moisture + +While the red gum grows in various situations, it prefers the deep, +rich soil of the hardwood bottoms, and there reaches its best +development (see Fig. 10). It requires considerable soil moisture, +though it does not grow in the wetter swamps, and does not thrive on +dry pine land. Seedlings, however, are often found in large numbers on +the edges of the uplands and even on the sandy pine land, but they +seldom live beyond the pole stage. When they do, they form small, +scrubby trees that are of little value. Where the soil is dry the tree +has a long tap root. In the swamps, where the roots can obtain water +easily, the development of the tap root is poor, and it is only +moderate on the glade bottom lands, where there is considerable +moisture throughout the year, but no standing water in the summer +months. + + + Reproduction of Red Gum + + [Illustration: Fig. 12. Second Growth Red Gum, Ash, + Cottonwood, and Sycamore.] + +Red gum reproduces both by seed and by sprouts (see Fig. 12). It +produces seed fairly abundantly every year, but about once in three +years there is an extremely heavy production. The tree begins to bear +seed when twenty-five to thirty years old, and seeds vigorously up to +an age of one hundred and fifty years, when its productive power +begins to diminish. A great part of the seed, however, is abortive. +Red gum is not fastidious in regard to its germinating bed; it comes +up readily on sod in old fields and meadows, on decomposing humus in +the forest, or on bare clay-loam or loamy sand soil. It requires a +considerable degree of light, however, and prefers a moist seed bed. +The natural distribution of the seed takes place for several hundred +feet from the seed trees, the dissemination depending almost entirely +on the wind. A great part of the seed falls on the hardwood bottom +when the land is flooded, and is either washed away or, if already in +the ground and germinating, is destroyed by the long-continued +overflow. After germinating, the red gum seedling demands, above +everything else, abundant light for its survival and development. It +is for this reason that there is very little growth of red gum, either +in the unculled forest or on culled land, where, as is usually the +case, a dense undergrowth of cane, briers, and rattan is present. +Under the dense underbrush of cane and briers throughout much of the +virgin forest, reproduction of any of the merchantable species is of +course impossible. And even where the land has been logged over, the +forest is seldom open enough to allow reproduction of cottonwood and +red gum. Where, however, seed trees are contiguous to pastures or +cleared land, scattered seedlings are found springing up in the open, +and where openings occur in the forest, there are often large numbers +of red gum seedlings, the reproduction generally occurring in groups. +But over the greater part of the Southern hardwood bottom land forest +reproduction is very poor. The growth of red gum during the early part +of its life, and up to the time it reaches a diameter of eight inches +breast-high, is extremely rapid, and, like most of the intolerant +species, it attains its height growth at an early period. Gum sprouts +readily from the stump, and the sprouts surpass the seedlings in rate +of height growth for the first few years, but they seldom form large +timber trees. Those over fifty years of age seldom sprout. For this +reason sprout reproduction is of little importance in the forest. The +principal requirements of red gum, then, are a moist, fairly rich soil +and good exposure to light. Without these it will not reach its best +development. + + [Illustration: Fig. 13. A Cypress Slough in the Dry Season.] + + + Second-Growth Red Gum + +Second-growth red gum occurs to any considerable extent only on land +which has been thoroughly cleared. Throughout the South there is a +great deal of land which was in cultivation before the Civil War, but +which during the subsequent period of industrial depression was +abandoned and allowed to revert to forest. These old fields now mostly +covered with second-growth forest, of which red gum forms an +important part (see Fig. 12). Frequently over fifty per cent of the +stand consists of this species, but more often, and especially on the +Atlantic coast, the greater part is of cottonwood or ash. These stands +are very dense, and the growth is extremely rapid. Small stands of +young growth are also often found along the edges of cultivated +fields. In the Mississippi Valley the abandoned fields on which young +stands have sprung up are for the most part being rapidly cleared +again. The second growth here is considered of little value in +comparison with the value of the land for agricultural purposes. In +many cases, however, the farm value of the land is not at present +sufficient to make it profitable to clear it, unless the timber cut +will at least pay for the operation. There is considerable land upon +which the second growth will become valuable timber within a few +years. Such land should not be cleared until it is possible to utilize +the timber. + +=39. Tupelo Gum= (_Nyssa aquatica_) (Bay Poplar, Swamp Poplar, Cotton +Gum, Hazel Pine, Circassian Walnut, Pepperidge, Nyssa). The close +similarity which exists between red and tupelo gum, together with the +fact that tupelo is often cut along with red gum, and marketed with +the sapwood of the latter, makes it not out of place to give +consideration to this timber. The wood has a fine, uniform texture, is +moderately hard and strong, is stiff, not elastic, very tough and hard +to split, but easy to work with tools. Tupelo takes glue, paint, or +varnish well, and absorbs very little of the material. In this respect +it is equal to yellow poplar and superior to cottonwood. The wood is +not durable in contact with ground, and requires much care in +seasoning. The distinction between the heartwood and sapwood of this +species is marked. The former varies in color from a dull gray to a +dull brown; the latter is whitish or light yellow like that of poplar. +The wood is of medium weight, about thirty-two pounds per cubic foot +when dry, or nearly that of red gum and loblolly pine. After +seasoning it is difficult to distinguish the better grades of sapwood +from poplar. Owing to the prejudice against tupelo gum, it was until +recently marketed under such names as bay poplar, swamp poplar, nyssa, +cotton gum, circassian walnut, and hazel pine. Since it has become +evident that the properties of the wood fit it for many uses, the +demand for tupelo has largely increased, and it is now taking rank +with other standard woods under its rightful name. Heretofore the +quality and usefulness of this wood were greatly underestimated, and +the difficulty of handling it was magnified. Poor success in seasoning +and kiln-drying was laid to defects of the wood itself, when, as a +matter of fact, the failures were largely due to the absence of proper +methods in handling. The passing of this prejudice against tupelo is +due to a better understanding of the characteristics and uses of the +wood. Handled in the way in which its particular character demands, +tupelo is a wood of much value. + + + Uses of Tupelo Gum + +Tupelo gum is now used in slack cooperage, principally for heading. It +is used extensively for house flooring and inside finishing, such as +mouldings, door jambs, and casings. A great deal is now shipped to +European countries, where it is highly valued for different classes of +manufacture. Much of the wood is used in the manufacture of boxes, +since it works well upon rotary veneer machines. There is also an +increasing demand for tupelo for laths, wooden pumps, violin and organ +sounding boards, coffins, mantelwork, conduits and novelties. It is +also used in the furniture trade for backing, drawers, and panels. + + + Range of Tupelo Gum + +Tupelo occurs throughout the coastal region of the Atlantic States, +from southern Virginia to northern Florida, through the Gulf States to +the valley of the Nueces River in Texas, through Arkansas and southern +Missouri to western Kentucky and Tennessee, and to the valley of the +lower Wabash River. Tupelo is being extensively milled at present only +in the region adjacent to Mobile Ala., and in southern and central +Louisiana, where it occurs in large merchantable quantities, attaining +its best development in the former locality. The country in this +locality is very swampy (see Fig. 11), and within a radius of one +hundred miles tupelo gum is one of the principal timber trees. It +grows only in the swamps and wetter situations (see Fig. 11), often in +mixture with cypress, and in the rainy season it stands in from two to +twenty feet of water. + +=40. Black Gum= (_Nyssa sylvatica_) (Sour Gum). Black gum is not cut to +much extent, owing to its less abundant supply and poorer quality, but +is used for repair work on wagons, for boxes, crates, wagon hubs, +rollers, bowls, woodenware, and for cattle yokes and other purposes +which require a strong, non-splitting wood. Heartwood is light brown +in color, often nearly white; sapwood hardly distinguishable, fine +grain, fibres interwoven. Wood is heavy, not hard, difficult to work, +strong, very tough, checks and warps considerably in drying, not +durable. It is distributed from Maine to southern Ontario, through +central Michigan to southeastern Missouri, southward to the valley of +the Brazos River in Texas, and eastward to the Kissimmee River and +Tampa Bay in Florida. It is found in the swamps and hardwood bottoms, +but is more abundant and of better size on the slightly higher ridges +and hummocks in these swamps, and on the mountain slopes in the +southern Alleghany region. Though its range is greater than that of +either red or tupelo gum, it nowhere forms an important part of the +forest. + + + HACKBERRY + +=41. Hackberry= (_Celtis occidentalis_) (Sugar Berry, Nettle Tree). The +wood is handsome, heavy, hard, strong, quite tough, of moderately fine +texture, and greenish or yellowish color, shrinks moderately, works +well and stands well, and takes a good polish. Used to some extent in +cooperage, and in the manufacture of cheap furniture. Medium- to +large-sized tree, locally quite common, largest in the lower +Mississippi Valley. Occurs in nearly all parts of the eastern United +States. + + + HICKORY + +The hickories of commerce are exclusively North American and some of +them are large and beautiful trees of 60 to 70 feet or more in height. +They are closely allied to the walnut, and the wood is very like +walnut in grain and color, though of a somewhat darker brown. It is +one of the finest of American hardwoods in point of strength; in +toughness it is superior to ash, rather coarse in texture, smooth and +of straight grain, very heavy and strong as well as elastic and +tenacious, but decays rapidly, especially the sapwood when exposed to +damp and moisture, and is very liable to attack from worms and boring +insects. The cross-section of hickory is peculiar, the annual rings +appear like fine lines instead of like the usual pores, and the +medullary rays, which are also very fine but distinct, in crossing +these form a peculiar web-like pattern which is one of the +characteristic differences between hickory and ash. Hickory is rarely +subjected to artificial treatment, but there is this curious fact in +connection with the wood, that, contrary to most other woods, creosote +is only with difficulty injected into the sap, although there is no +difficulty in getting it into the heartwood. It dries slowly, shrinks +and checks considerably in seasoning; is not durable in contact with +the soil or if exposed. Hickory excels as wagon and carriage stock, +for hoops in cooperage, and is extensively used in the manufacture of +implements and machinery, for tool handles, timber pins, harness work, +dowel pins, golf clubs, and fishing rods. The hickories are tall trees +with slender stems, never forming forests, occasionally small groves, +but usually occur scattered among other broad-leaved trees in suitable +localities. The following species all contribute more or less to the +hickory of the markets: + +=42. Shagbark Hickory= (_Hicoria ovata_) (Shellbark Hickory, Scalybark +Hickory). A medium- to large-sized tree, quite common; the favorite +among the hickories. Heartwood light brown, sapwood ivory or +cream-colored. Wood close-grained, compact structure, annual rings +clearly marked. Very hard, heavy, strong, tough, and flexible, but not +durable in contact with the soil or when exposed. Used for +agricultural implements, wheel runners, tool handles, vehicle parts, +baskets, dowel pins, harness work, golf clubs, fishing rods, etc. Best +developed in the Ohio and Mississippi basins; from Lake Ontario to +Texas, Minnesota to Florida. + +=43. Mockernut Hickory= (_Hicoria alba_) (Black Nut Hickory, Black +Hickory, Bull Nut Hickory, Big Bud Hickory, White Heart Hickory). A +medium- to large-sized tree. Wood in its quality and uses similar to +the preceding. Its range is the same as that of _Hicoria ovata_. +Common, especially in the South. + +=44. Pignut Hickory= (_Hicoria glabra_) (Brown Hickory, Black Hickory, +Switchbud Hickory). A medium- to large-sized tree. Heavier and +stronger than any of the preceding. Heartwood light to dark brown, +sapwood nearly white. Abundant, all eastern United States. + +=45. Bitternut Hickory= (_Hicoria minima_) (Swamp Hickory). A +medium-sized tree, favoring wet localities. Heartwood light brown, +sapwood lighter color. Wood in its quality and uses not so valuable as +_Hicoria ovata_, but is used for the same purposes. Abundant, all +eastern United States. + +=46. Pecan= (_Hicoria pecan_) (Illinois Nut). A large tree, very common +in the fertile bottoms of the western streams. Indiana to Nebraska and +southward to Louisiana and Texas. + + + HOLLY + +=47. Holly= (_Ilex opaca_). Small to medium-sized tree. Wood of medium +weight, hard, strong, tough, of exceedingly fine grain, closer in +texture than most woods, of white color, sometimes almost as white as +ivory; requires great care in its treatment to preserve the whiteness +of the wood. It does not readily absorb foreign matter. Much used by +turners and for all parts of musical instruments, for handles on whips +and fancy articles, draught-boards, engraving blocks, cabinet work, +etc. The wood is often dyed black and sold as ebony; works well and +stands well. Most abundant in the lower Mississippi Valley and Gulf +States, but occurring eastward to Massachusetts and north to Indiana. + +=48. Holly= (_Ilex monticolo_) (Mountain Holly). Small-sized tree. Wood +in its quality and uses similar to the preceding, but is not very +generally known. It is found in the Catskill Mountains and extends +southward along the Alleghanies as far as Alabama. + + + HORSE CHESTNUT (See Buckeye) + + + IRONWOOD + +=49. Ironwood= (_Ostrya Virginiana_) (Hop Hornbeam, Lever Wood). +Small-sized tree, common. Heartwood light brown tinged with red, +sapwood nearly white. Wood heavy, tough, exceedingly close-grained, +very strong and hard, durable in contact with the soil, and will take +a fine polish. Used for small articles like levers, handles of tools, +mallets, etc. Ranges throughout the United States east of the Rocky +Mountains. + + + LAUREL + +=50. Laurel= (_Umbellularia Californica_) (Myrtle). A Western tree, +produces timber of light brown color of great size and beauty, and is +very valuable for cabinet and inside work, as it takes a fine polish. +California and Oregon, coast range of the Sierra Nevada Mountains. + + + LOCUST + +=51. Black Locust= (_Robinia pseudacacia_) (Locust, Yellow Locust, +Acacia). Small to medium-sized tree. Wood very heavy, hard, strong, +and tough, rivalling some of the best oak in this latter quality. The +wood has great torsional strength, excelling most of the soft woods in +this respect, of coarse texture, close-grained and compact structure, +takes a fine polish. Annual rings clearly marked, very durable in +contact with the soil, shrinks and checks considerably in drying, the +very narrow sapwood greenish yellow, the heartwood brown, with shades +of red and green. Used for wagon hubs, trenails or pins, but +especially for railway ties, fence posts, and door sills. Also used +for boat parts, turnery, ornamentations, and locally for construction. +Abroad it is much used for furniture and farming implements and also +in turnery. At home in the Alleghany Mountains, extensively planted, +especially in the West. + +=52. Honey Locust= (_Gleditschia triacanthos_) (Honey Shucks, Locust, +Black Locust, Brown Locust, Sweet Locust, False Acacia, Three-Thorned +Acacia). A medium-sized tree. Wood heavy, hard, strong, tough, durable +in contact with the soil, of coarse texture, susceptible to a good +polish. The narrow sapwood yellow, the heartwood brownish red. So far, +but little appreciated except for fences and fuel. Used to some extent +for wheel hubs, and locally in rough construction. Found from +Pennsylvania to Nebraska, and southward to Florida and Texas; locally +quite abundant. + +=53. Locust= (_Robinia viscosa_) (Clammy Locust). Usually a shrub five +or six feet high, but known to reach a height of 40 feet in the +mountains of North Carolina, with the habit of a tree. Wood light +brown, heavy, hard, and close-grained. Not used to much extent in +manufacture. Range same as the preceding. + + + MAGNOLIA + +=54. Magnolia= (_Magnolia glauca_) (Swamp Magnolia, Small Magnolia, +Sweet Bay, Beaver Wood). Small-sized tree. Heartwood reddish brown, +sap wood cream white. Sparingly used in manufacture. Ranges from Essex +County, Mass., to Long Island, N. Y., from New Jersey to Florida, and +west in the Gulf region to Texas. + +=55. Magnolia= (_Magnolia tripetala_) (Umbrella Tree). A small-sized +tree. Wood in its quality similiar to the preceding. It may be easily +recognized by its great leaves, twelve to eighteen inches long, and +five to eight inches broad. This species as well as the preceding is +an ornamental tree. Ranges from Pennsylvania southward to the Gulf. + +=56. Cucumber Tree= (_Magnolia accuminata_) (Tulip-wood, Poplar). +Medium- to large-sized tree. Heartwood yellowish brown, sapwood almost +white. Wood light, soft, satiny, close-grained, durable in contact +with the soil, resembling and sometimes confounded with tulip tree +(_Liriodendron tulipifera_) in the markets. The wood shrinks +considerably, but seasons without much injury, and works and stands +well. It bends readily when steamed, and takes stain and paint well. +Used in cooperage, for siding, for panelling and finishing lumber in +house, car and shipbuilding, etc., also in the manufacture of toys, +culinary woodenware, and backing for drawers. Most common in the +southern Alleghanies, but distributed from western New York to +southern Illinois, south through central Kentucky and Tennessee to +Alabama, and throughout Arkansas. + + + MAPLE + +Wood heavy, hard, strong, stiff, and tough, of fine texture, +frequently wavy-grained, this giving rise to "curly" and "blister" +figures which are much admired. Not durable in the ground, or when +exposed. Maple is creamy white, with shades of light brown in the +heartwood, shrinks moderately, seasons, works, and stands well, wears +smoothly, and takes a fine polish. The wood is used in cooperage, and +for ceiling, flooring, panelling, stairway, and other finishing lumber +in house, ship, and car construction. It is used for the keels of +boats and ships, in the manufacture of implements and machinery, but +especially for furniture, where entire chamber sets of maple rival +those of oak. Maple is also used for shoe lasts and other form blocks; +for shoe pegs; for piano actions, school apparatus, for wood type in +show bill printing, tool handles, in wood carving, turnery, and scroll +work, in fact it is one of our most useful woods. The maples are +medium-sized trees, of fairly rapid growth, sometimes form forests, +and frequently constitute a large proportion of the arborescent +growth. They grow freely in parts of the Northern Hemisphere, and are +particularly luxuriant in Canada and the northern portions of the +United States. + +=57. Sugar Maple= (_Acer saccharum_) (Hard Maple, Rock Maple). Medium- +to large-sized tree, very common, forms considerable forests, and is +especially esteemed. The wood is close-grained, heavy, fairly hard and +strong, of compact structure. Heartwood brownish, sapwood lighter +color; it can be worked to a satin-like surface and take a fine +polish, it is not durable if exposed, and requires a good deal of +seasoning. Medullary rays small but distinct. The "curly" or "wavy" +varieties furnish wood of much beauty, the peculiar contortions of the +grain called "bird's eye" being much sought after, and used as veneer +for panelling, etc. It is used in all good grades of furniture, +cabinetmaking, panelling, interior finish, and turnery; it is not +liable to warp and twist. It is also largely used for flooring, for +rollers for wringers and mangling machines, for which there is a large +and increasing demand. The peculiarity known as "bird's eye," and +which causes a difficulty in working the wood smooth, owing to the +little pieces like knots lifting up, is supposed to be due to the +action of boring insects. Its resistance to compression across the +grain is higher than that of most other woods. Ranges from Maine to +Minnesota, abundant, with birch, in the region of the Great Lakes. + +=58. Red Maple= (_Acer rubrum_) (Swamp Maple, Soft Maple, Water Maple). +Medium-sized tree. Like the preceding but not so valuable. Scattered +along water-courses and other moist localities. Abundant. Maine to +Minnesota, southward to northern Florida. + +=59. Silver Maple= (_Acer saccharinum_) (Soft Maple, White Maple, +Silver-Leaved Maple). Medium- to large-sized tree, common. Wood +lighter, softer, and inferior to _Acer saccharum_, and usually offered +in small quantities and held separate in the markets. Heartwood +reddish brown, sapwood ivory white, fine-grained, compact structure. +Fibres sometimes twisted, weaved, or curly. Not durable. Used in +cooperage for woodenware, turnery articles, interior decorations and +flooring. Valley of the Ohio, but occurs from Maine to Dakota and +southward to Florida. + +=60. Broad-Leaved Maple= (_Acer macrophyllum_) (Oregon Maple). +Medium-sized tree, forms considerable forests, and, like the preceding +has a lighter, softer, and less valuable wood than _Acer saccharum_. +Pacific Coast regions. + +=61. Mountain Maple= (_Acer spicatum_). Small-sized tree. Heartwood pale +reddish brown, sapwood lighter color. Wood light, soft, close-grained, +and susceptible of high polish. Ranges from lower St. Lawrence River +to northern Minnesota and regions of the Saskatchewan River; south +through the Northern States and along the Appalachian Mountains to +Georgia. + +=62. Ash-Leaved Maple= (_Acer negundo_) (Box Elder). Medium- to +large-sized tree. Heartwood creamy white, sapwood nearly white. Wood +light, soft, close-grained, not strong. Used for woodenware and paper +pulp. Distributed across the continent, abundant throughout the +Mississippi Valley along banks of streams and borders of swamps. + +=63. Striped Maple= (_Acer Pennsylvanicum_) (Moose-wood). Small-sized +tree. Produces a very white wood much sought after for inlaid and for +cabinet work. Wood is light, soft, close-grained, and takes a fine +polish. Not common. Occurs from Pennsylvania to Minnesota. + + + MULBERRY + +=64. Red Mulberry= (_Morus rubra_). A small-sized tree. Wood moderately +heavy, fairly hard and strong, rather tough, of coarse texture, very +durable in contact with the soil. The sapwood whitish, heartwood +yellow to orange brown, shrinks and checks considerably in drying, +works well and stands well. Used in cooperage and locally in +construction, and in the manufacture of farm implements. Common in the +Ohio and Mississippi Valleys, but widely distributed in the eastern +United States. + + + MYRTLE (See Laurel) + + + OAK + +Wood very variable, usually very heavy and hard, very strong and +tough, porous, and of coarse texture. The sapwood whitish, the +heartwood "oak" to reddish brown. It shrinks and checks badly, giving +trouble in seasoning, but stands well, is durable, and little subject +to the attacks of boring insects. Oak is used for many purposes, and +is the chief wood used for tight cooperage; it is used in +shipbuilding, for heavy construction, in carpentry, in furniture, car +and wagon work, turnery, and even in woodcarving. It is also used in +all kinds of farm implements, mill machinery, for piles and wharves, +railway ties, etc., etc. The oaks are medium- to large-sized trees, +forming the predominant part of a large proportion of our +broad-leaved forests, so that these are generally termed "oak +forests," though they always contain considerable proportion of other +kinds of trees. Three well-marked kinds--white, red, and live oak--are +distinguished and kept separate in the markets. Of the two principal +kinds "white oak" is the stronger, tougher, less porous, and more +durable. "Red oak" is usually of coarser texture, more porous, often +brittle, less durable, and even more troublesome in seasoning than +white oak. In carpentry and furniture work red oak brings the same +price at present as white oak. The red oaks everywhere accompany the +white oaks, and, like the latter, are usually represented by several +species in any given locality. "Live oak," once largely employed in +shipbuilding, possesses all the good qualities, except that of size, +of white oak, even to a greater degree. It is one of the heaviest, +hardest, toughest, and most durable woods of this country. In +structure it resembles the red oak, but is less porous. + +=65. White Oak= (_Quercus alba_) (American Oak). Medium-to large-sized +tree. Heartwood light brown, sapwood lighter color. Annual rings well +marked, medullary rays broad and prominent. Wood tough, strong, heavy, +hard, liable to check in seasoning, durable in contact with the soil, +takes a high polish, very elastic, does not shrink much, and can be +bent to any form when steamed. Used for agricultural implements, tool +handles, furniture, fixtures, interior finish, car and wagon +construction, beams, cabinet work, tight cooperage, railway ties, +etc., etc. Because of the broad medullary rays, it is generally +"quarter-sawn" for cabinet work and furniture. Common in the Eastern +States, Ohio and Mississippi Valleys. Occurs throughout the eastern +United States. + +=66. White Oak= (_Quercus durandii_). Medium- to small-sized tree. Wood +in its quality and uses similiar to the preceding. Texas, eastward to +Alabama. + +=67. White Oak= (_Quercus garryana_) (Western White Oak). Medium- to +large-sized tree. Stronger, more durable, and wood more compact than +_Quercus alba_. Washington to California. + +=68. White Oak= (_Quercus lobata_). Medium- to large-sized tree. Largest +oak on the Pacific Coast. Wood in its quality and uses similar to +_Quercus alba_, only it is finer-grained. California. + +=69. Bur Oak= (_Quercus macrocarpa_) (Mossy-Cup Oak, Over-Cup Oak). +Large-sized tree. Heartwood "oak" brown, sapwood lighter color. Wood +heavy, strong, close-grained, durable in contact with the soil. Used +in ship- and boatbuilding, all sorts of construction, interior finish +of houses, cabinet work, tight cooperage, carriage and wagon work, +agricultural implements, railway ties, etc., etc. One of the most +valuable and most widely distributed of American oaks, 60 to 80 feet +in height, and, unlike most of the other oaks, adapts itself to +varying climatic conditions. It is one of the most durable woods when +in contact with the soil. Common, locally abundant. Ranges from +Manitoba to Texas, and from the foot hills of the Rocky Mountains to +the Atlantic Coast. It is the most abundant oak of Kansas and +Nebraska, and forms the scattered forests known as "The oak openings" +of Minnesota. + +=70. Willow Oak= (_Quercus phellos_) (Peach oak). Small to medium-sized +tree. Heartwood pale reddish brown, sapwood lighter color. Wood heavy, +hard, strong, coarse-grained. Occasionally used in construction. New +York to Texas, and northward to Kentucky. + +=71. Swamp White Oak= (_Quercus bicolor_ var. _platanoides_). +Large-sized tree. Heartwood pale brown, sapwood the same color. Wood +heavy, hard, strong, tough, coarse-grained, checks considerably in +seasoning. Used in construction, interior finish of houses, +carriage-and boatbuilding, agricultural implements, in cooperage, +railway ties, fencing, etc., etc. Ranges from Quebec to Georgia and +westward to Arkansas. Never abundant. Most abundant in the Lake +States. + +=72. Over-Cup Oak= (_Quercus lyrata_) (Swamp White Oak, Swamp Post Oak). +Medium to large-sized tree, rather restricted, as it grows in the +swampy districts of Carolina and Georgia. Is a larger tree than most +of the other oaks, and produces an excellent timber, but grows in +districts difficult of access, and is not much used. Lower Mississippi +and eastward to Delaware. + +=73. Pin Oak= (_Quercus palustris_) (Swamp Spanish Oak, Water Oak). +Medium- to large-sized tree. Heartwood pale brown with dark-colored +sap wood. Wood heavy, strong, and coarse-grained. Common along the +borders of streams and swamps, attains its greatest size in the valley +of the Ohio. Arkansas to Wisconsin, and eastward to the Alleghanies. + +=74. Water Oak= (_Quercus aquatica_) (Duck Oak, Possum Oak). Medium- to +large-sized tree, of extremely rapid growth. Eastern Gulf States, +eastward to Delaware and northward to Missouri and Kentucky. + +=75. Chestnut Oak= (_Quercus prinus_) (Yellow Oak, Rock Oak, Rock +Chestnut Oak). Heartwood dark brown, sapwood lighter color. Wood +heavy, hard, strong, tough, close-grained, durable in contact with the +soil. Used for railway ties, fencing, fuel, and locally for +construction. Ranges from Maine to Georgia and Alabama, westward +through Ohio, and southward to Kentucky and Tennessee. + +=76. Yellow Oak= (_Quercus acuminata_) (Chestnut Oak, Chinquapin Oak). +Medium- to large-sized tree. Heartwood dark brown, sapwood pale brown. +Wood heavy, hard, strong, close-grained, durable in contact with the +soil. Used in the manufacture of wheel stock, in cooperage, for +railway ties, fencing, etc., etc. Ranges from New York to Nebraska and +eastern Kansas, southward in the Atlantic region to the District of +Columbia, and west of the Alleghanies southward to the Gulf States. + +=77. Chinquapin Oak= (_Quercus prinoides_) (Dwarf Chinquapin Oak, Scrub +Chestnut Oak). Small-sized tree. Heartwood light brown, sapwood darker +color. Does not enter the markets to any great extent. Ranges from +Massachusetts to North Carolina, westward to Missouri, Nebraska, +Kansas, and eastern Texas. Reaches its best form in Missouri and +Kansas. + +=78. Basket Oak= (_Quercus michauxii_) (Cow Oak). Large-sized tree. +Locally abundant. Lower Mississippi and eastward to Delaware. + +=79. Scrub Oak= (_Quercus ilicifolia_ var. _pumila_) (Bear Oak). +Small-sized tree. Heartwood light brown, sapwood darker color. Wood +heavy, hard, strong, and coarse-grained. Found in New England and +along the Alleghanies. + +=80. Post Oak= (_Quercus obtusiloda_ var. _minor_) (Iron Oak). Medium- +to large-sized tree, gives timber of great strength. The color is of a +brownish yellow hue, close-grained, and often superior to the white +oak (_Quercus alba_) in strength and durability. It is used for posts +and fencing, and locally for construction. Arkansas to Texas, eastward +to New England and northward to Michigan. + +=81. Red Oak= (_Quercus rubra_) (Black Oak). Medium- to large-sized +tree. Heartwood light brown to red, sapwood lighter color. Wood +coarse-grained, well-marked annual rings, medullary rays few but +broad. Wood heavy, hard, strong, liable to check in seasoning. It is +found over the same range as white oak, and is more plentiful. Wood is +spongy in grain, moderately durable, but unfit for work requiring +strength. Used for agricultural implements, furniture, bob sleds, +vehicle parts, boxes, cooperage, woodenware, fixtures, interior +finish, railway ties, etc., etc. Common in all parts of its range. +Maine to Minnesota, and southward to the Gulf. + +=82. Black Oak= (_Quercus tinctoria_ var. _velutina_) (Yellow Oak). +Medium- to large-sized tree. Heartwood bright brown tinged with red, +sapwood lighter color. Wood heavy, hard, strong, coarse-grained, +checks considerably in seasoning. Very common in the Southern States, +but occurring North as far as Minnesota, and eastward to Maine. + +=83. Barren Oak= (_Quercus nigra_ var. _marilandica_) (Black Jack, Jack +Oak). Small-sized tree. Heartwood dark brown, sapwood lighter color. +Wood heavy, hard, strong, coarse-grained, not valuable. Used in the +manufacture of charcoal and for fuel. New York to Kansas and Nebraska, +and southward to Florida. Rare in the North, but abundant in the +South. + +=84. Shingle Oak= (_Quercus imbricaria_) (Laurel Oak). Small to +medium-sized tree. Heartwood pale reddish brown, sapwood lighter +color. Wood heavy, hard, strong, coarse-grained, checks considerably +in drying. Used for shingles and locally for construction. Rare in the +east, most abundant in the lower Ohio Valley. From New York to +Illinois and southward. Reaches its greatest size in southern Illinois +and Indiana. + +=85. Spanish Oak= (_Quercus digitata_ var. _falcata_) (Red Oak). +Medium-sized tree. Heartwood light reddish brown, sapwood much +lighter. Wood heavy, hard, strong, coarse-grained, and checks +considerably in seasoning. Used locally for construction, and has high +fuel value. Common in south Atlantic and Gulf region, but found from +Texas to New York, and northward to Missouri and Kentucky. + +=86. Scarlet Oak= (_Quercus coccinea_). Medium- to large-sized tree. +Heartwood light reddish-brown, sapwood darker color. Wood heavy, hard, +strong, and coarse-grained. Best developed in the lower basin of the +Ohio, but found from Minnesota to Florida. + +=87. Live Oak= (_Quercus virens_) (Maul Oak). Medium- to large-sized +tree. Grows from Maryland to the Gulf of Mexico, and often attains a +height of 60 feet and 4 feet in diameter. The wood is hard, strong, +and durable, but of rather rapid growth, therefore not as good quality +as _Quercus alba_. The live oak of Florida is now reserved by the +United States Government for Naval purposes. Used for mauls and +mallets, tool handles, etc., and locally for construction. Scattered +along the coast from Maryland to Texas. + +=88. Live Oak= (_Quercus chrysolepis_) (Maul Oak, Valparaiso Oak). +Medium- to small-sized tree. California. + + + OSAGE ORANGE + +=89. Osage Orange= (_Maclura aurantiaca_) (Bois d'Arc). A small-sized +tree of fairly rapid growth. Wood very heavy, exceedingly hard, +strong, not tough, of moderately coarse texture, and very durable and +elastic. Sapwood yellow, heartwood brown on the end face, yellow on +the longitudinal faces, soon turning grayish brown if exposed. It +shrinks considerably in drying, but once dry it stands unusually well. +Much used for wheel stock, and wagon framing; it is easily split, so +is unfit for wheel hubs, but is very suitable for wheel spokes. It is +considered one of the timbers likely to supply the place of black +locust for insulator pins on telegraph poles. Seems too little +appreciated; it is well suited for turned ware and especially for +woodcarving. Used for spokes, insulator pins, posts, railway ties, +wagon framing, turnery, and woodcarving. Scattered through the rich +bottoms of Arkansas and Texas. + + + PAPAW + +=90. Papaw= (_Asimina triloba_) (Custard Apple). Small-sized tree, often +only a shrub, Heartwood pale, yellowish green, sapwood lighter color. +Wood light, soft, coarse-grained, and spongy. Not used to any extent +in manufacture. Occurs in eastern and central Pennsylvania, west as +far as Michigan and Kansas, and south to Florida and Texas. Often +forming dense thickets in the lowlands bordering the Mississippi +River. + + + PERSIMMON + +=91. Persimmon= (_Diospyros Virginiana_). Small to medium-sized tree. +Wood very heavy, and hard, strong and tough; resembles hickory, but is +of finer texture and elastic, but liable to split in working. The +broad sapwood cream color, the heartwood brown, sometimes almost +black. The persimmon is the Virginia date plum, a tree of 30 to 50 +feet high, and 18 to 20 inches in diameter; it is noted chiefly for +its fruit, but it produces a wood of considerable value. Used in +turnery, for wood engraving, shuttles, bobbins, plane stock, shoe lasts, +and largely as a substitute for box (_Buxus sempervirens_)--especially +the black or Mexican variety,--also used for pocket rules and drawing +scales, for flutes and other wind instruments. Common, and best +developed in the lower Ohio Valley, but occurs from New York to Texas +and Missouri. + + + POPLAR (See also Tulip Wood) + +Wood light, very soft, not strong, of fine texture, and whitish, +grayish to yellowish color, usually with a satiny luster. The wood +shrinks moderately (some cross-grained forms warp excessively), but +checks very little in seasoning; is easily worked, but is not durable. +Used in cooperage, for building and furniture lumber, for crates and +boxes (especially cracker boxes), for woodenware, and paper pulp. + +=92. Cottonwood= (_Populus monilifera_, var. _angulata_) (Carolina +Poplar). Large-sized tree, forms considerable forests along many of +the Western streams, and furnishes most of the cottonwood of the +market. Heartwood dark brown, sapwood nearly white. Wood light, soft, +not strong, and close-grained (see Fig. 14). Mississippi Valley and +West. New England to the Rocky Mountains. + +=93. Cottonwood= (_Populus fremontii_ var. _wislizeni_). Medium-to +large-sized tree. Common. Wood in its quality and uses similiar to the +preceding, but not so valuable. Texas to California. + + [Illustration: Fig. 14. A Large Cottonwood. One of the + Associates of Red Gum.] + +=94. Black Cottonwood= (_Populus trichocarpa_ var. _heterophylla_) +(Swamp Cottonwood, Downy Poplar). The largest deciduous tree of +Washington. Very common. Heartwood dull brown, sapwood lighter brown. +Wood soft, close-grained. Is now manufactured into lumber in the West +and South, and used in interior finish of buildings. Northern Rocky +Mountains and Pacific region. + +=95. Poplar= (_Populus grandidentata_) (Large-Toothed Aspen). +Medium-sized tree. Heartwood light brown, sapwood nearly white. Wood +soft and close-grained, neither strong nor durable. Chiefly used for +wood pulp. Maine to Minnesota and southward along the Alleghanies. + +=96. White Poplar= (_Populus alba_) (Abele-Tree). Small to medium-sized +tree. Wood in its quality and uses similar to the preceding. Found +principally along banks of streams, never forming forests. Widely +distributed in the United States. + +=97. Lombardy Poplar= (_Populus nigra italica_). Medium-to large-sized +tree. This species is the first ornamental tree introduced into the +United States, and originated in Afghanistan. Does not enter into the +markets. Widely planted in the United States. + +=98. Balsam= (_Populus balsamifera_) (Balm of Gilead, Tacmahac). Medium- +to large-sized tree. Heartwood light brown, sapwood nearly white. Wood +light, soft, not strong, close-grained. Used extensively in the +manufacture of paper pulp. Common all along the northern boundary of +the United States. + +=99. Aspen= (_Populus tremuloides_) (Quaking Aspen). Small to +medium-sized tree, often forming extensive forests, and covering +burned areas. Heartwood light brown, sapwood nearly white. Wood light, +soft, close-grained, neither strong nor durable. Chiefly used for +woodenware, cooperage, and paper pulp. Maine to Washington and +northward, and south in the western mountains to California and New +Mexico. + + + RED GUM (See Gum) + + + SASSAFRAS + +=100. Sassafras= (_Sassafras sassafras_). Medium-sized tree, largest in +the lower Mississippi Valley. Wood light, soft, not strong, brittle, +of coarse texture, durable in contact with the soil. The sapwood +yellow, the heartwood orange brown. Used to some extent in slack +cooperage, for skiff- and boatbuilding, fencing, posts, sills, etc. +Occurs from New England to Texas and from Michigan to Florida. + + + SOUR GUM (See Gum) + + + SOURWOOD + +=101. Sourwood= (_Oxydendrum arboreum_) (Sorrel-Tree). A slender tree, +reaching the maximum height of 60 feet. Heartwood reddish brown, +sapwood lighter color. Wood heavy, hard, strong, close-grained, and +takes a fine polish. Ranges from Pennsylvania, along the Alleghanies, +to Florida and Alabama, westward through Ohio to southern Indiana and +southward through Arkansas and Louisiana to the Coast. + + + SWEET GUM (See Gum) + + + SYCAMORE + +=102. Sycamore= (_Platanus occidentalis_) (Buttonwood, Button-Ball Tree, +Plane Tree, Water Beech). A large-sized tree, of rapid growth. One of +the largest deciduous trees of the United States, sometimes attaining +a height of 100 feet. It produces a timber that is moderately heavy, +quite hard, stiff, strong, and tough, usually cross-grained; of coarse +texture, difficult to split and work, shrinks moderately, but warps +and checks considerably in seasoning, but stands well, and is not +considered durable for outside work, or in contact with the soil. It +has broad medullary rays, and much of the timber has a beautiful +figure. It is used in slack cooperage, and quite extensively for +drawers, backs, and bottoms, etc., in furniture work. It is also used +for cabinet work, for tobacco boxes, crates, desks, flooring, +furniture, ox-yokes, butcher blocks, and also for finishing lumber, +where it has too long been underrated. Common and largest in the Ohio +and Mississippi Valleys, at home in nearly all parts of the eastern +United States. + +=103. Sycamore= (_Platanus racemosa_). The California species, +resembling in its wood the Eastern form. Not used to any great extent. + + + TULIP TREE + +=104. Tulip Tree= (_Liriodendron tulipifera_) (Yellow Poplar, Tulip +Wood, White Wood, Canary Wood, Poplar, Blue Poplar, White Poplar, +Hickory Poplar). A medium- to large-sized tree, does not form forests, +but is quite common, especially in the Ohio basin. Wood usually light, +but varies in weight, it is soft, tough, but not strong, of fine +texture, and yellowish color. The wood shrinks considerably, but +seasons without much injury, and works and stands extremely well. +Heartwood light yellow or greenish brown, the sapwood is thin, nearly +white, and decays rapidly. The heartwood is fairly durable when +exposed to the weather or in contact with the soil. It bends readily +when steamed, and takes stain and paint well. The mature forest-grown +tree has a long, straight, cylindrical bole, clear of branches for at +least two thirds of its length, surmounted by a short, open, irregular +crown. When growing in the open, the tree maintains a straight stem, +but the crown extends almost to the ground, and is of conical shape. +Yellow poplar, or tulip wood, ordinarily grows to a height of from 100 +to 125 feet, with a diameter of from 3 to 6 feet, and a clear length +of about 70 feet. Trees have been found 190 feet high and ten feet in +diameter. Used in cooperage, for siding, for panelling and finishing +lumber in houses, car- and shipbuilding, for sideboards, panels of +wagons and carriages, for aeroplanes, for automobiles, also in the +manufacture of furniture farm implements, machinery, for pump logs, +and almost every kind of common woodenware, boxes shelving, drawers, +etc., etc. Also in the manufacture of toys, culinary woodenware, and +backing for veneer. It is in great demand throughout the vehicle and +implement trade, and also makes a fair grade of wood pulp. In fact the +tulip tree is one of the most useful of woods throughout the +woodworking industry of this country. Occurs from New England to +Missouri and southward to Florida. + + + TUPELO (See Gum) + + + WAAHOO + +=105. Waahoo= (_Evonymus atropurpureus_). (Burning Bush, Spindle Tree). +A small-sized tree. Wood white, tinged with orange; heavy, hard, +tough, and close-grained, works well and stands well. Used principally +for arrows and spindles. Widely distributed. Usually a shrub six to +ten feet high, becoming a tree only in southern Arkansas and Oklahoma. + + + WALNUT + +=106. Black Walnut= (_Juglans nigra_) (Walnut). A large, beautiful, and +quickly-growing tree, about 60 feet and upwards in height. Wood heavy, +hard, strong, of coarse texture, very durable in contact with the +soil. The narrow sapwood whitish, the heartwood dark, rich, chocolate +brown, sometimes almost black; aged trees of fine quality bring fancy +prices. The wood shrinks moderately in seasoning, works well and +stands well, and takes a fine polish. It is quite handsome, and has +been for a long time the favorite wood for cabinet and furniture +making. It is used for gun-stocks, fixtures, interior decoration, +veneer, panelling, stair newells, and all classes of work demanding a +high priced grade of wood. Black walnut is a large tree with stout +trunk, of rapid growth, and was formerly quite abundant throughout +the Alleghany region. Occurs from New England to Texas, and from +Michigan to Florida. Not common. + + + WHITE WALNUT (See Butternut) + + + WHITE WOOD (See Tulip and also Basswood) + + + WHITE WILLOW + +=107. White Willow= (_Salix alba_ var. _vitellina_) (Willow, Yellow +Willow, Blue Willow). The wood is very soft, light, flexible, and +fairly strong, is fairly durable in contact with the soil, works well +and stands well when seasoned. Medium-sized tree, characterized by a +short, thick trunk, and a large, rather irregular crown composed of +many branches. The size of the tree at maturity varies with the +locality. In the region where it occurs naturally, a height of 70 to +80 feet, and a diameter of three to four feet are often attained. When +planted in the Middle West, a height of from 50 to 60 feet, and a +diameter of one and one-half to two feet are all that may be expected. +When closely planted on moist soil, the tree forms a tall, slender +stem, well cleared branches. Is widely naturalized in the United +States. It is used in cooperage, for woodenware, for cricket and +baseball bats, for basket work, etc. Charcoal made from the wood is +used in the manufacture of gunpowder. It has been generally used for +fence posts on the Northwestern plains, because of scarcity of better +material. Well seasoned posts will last from four to seven years. +Widely distributed throughout the United States. + +=108. Black Willow= (_Salix nigra_). Small-sized tree. Heartwood light +reddish brown, sapwood nearly white. Wood soft, light, not strong, +close-grained, and very flexible. Used in basket making, etc. Ranges +from New York to Rocky Mountains and southward to Mexico. + +=109. Shining Willow= (_Salix lucida_). A small-sized tree. Wood in its +quality and uses similiar to the preceding. Ranges from Newfoundland +to Rocky Mountains and southward to Pennsylvania and Nebraska. + +=110. Perch Willow= (_Salix amygdaloides_) (Almond-leaf Willow). Small +to medium-sized tree. Heartwood light brown, sapwood lighter color. +Wood light, soft, flexible, not strong, close-grained. Uses similiar +to the preceding. Follows the water courses and ranges across the +continent; less abundant in New England than elsewhere. Common in the +West. + +=111. Long-Leaf Willow= (_Salix fluviatilis_) (Sand Bar Willow). A +small-sized tree. Ranges from the Arctic Circle to Northern Mexico. + +=112. Bebb Willow= (_Salix bebbiana_ var. _rostrata_). A small-sized +tree. More abundant in British America than in the United States, +where it ranges southward to Pennsylvania and westward to Minnesota. + +=113. Glaucous Willow= (_Salix discolor_) (Pussy Willow). A small-sized +tree. Common along the banks of streams, and ranges from Nova Scotia +to Manitoba, and south to Delaware; west to Indiana and northwestern +Missouri. + +=114. Crack Willow= (_Salix fragilis_). A medium to large-sized tree. +Wood is very soft, light, very flexible and fairly strong, is fairly +durable in contact with the soil, works well and stands well. Used +principally for basket making, hoops, etc., and to produce charcoal +for gunpowder. Very common, and widely distributed in the United +States. + +=115. Weeping Willow= (_Salix babylonica_). Medium- to large-sized tree. +Wood similiar to _Salix nigra_, but not so valuable. Mostly an +ornamental tree. Originally came from China. Widely planted in the +United States. + + + YELLOW WOOD + +=116. Yellow Wood= (_Cladrastis lutea_) (Virgilia). A small to +medium-sized tree. Wood yellow to pale brown, heavy, hard, +close-grained and strong. Not used to much extent in manufacturing. +Not common. Found principally on the limestone cliffs of Kentucky, +Tennessee, and North Carolina. + + + + + SECTION IV + + GRAIN, COLOR, ODOR, WEIGHT, AND FIGURE IN WOOD + + + DIFFERENT GRAINS OF WOOD + +The terms "fine-grained," "coarse-grained," "straight-grained," and +"cross-grained" are frequently applied in the trade. In common usage, +wood is coarse-grained if its annual rings are wide; fine-grained if +they are narrow. In the finer wood industries a fine-grained wood is +capable of high polish, while a coarse-grained wood is not, so that in +this latter case the distinction depends chiefly on hardness, and in +the former on an accidental case of slow or rapid growth. Generally if +the direction of the wood fibres is parallel to the axis of the stem +or limb in which they occur, the wood is straight-grained; but in many +cases the course of the fibres is spiral or twisted around the tree +(as shown in Fig. 15), and sometimes commonly in the butts of gum and +cypress, the fibres of several layers are oblique in one direction, +and those of the next series of layers are oblique in the opposite +direction. (As shown in Fig. 16 the wood is cross or twisted grain.) +Wavy-grain in a tangential plane as seen on the radial section is +illustrated in Fig. 17, which represents an extreme case observed in +beech. This same form also occurs on the radial plane, causing the +tangential section to appear wavy or in transverse folds. + +When wavy grain is fine (_i.e._, the folds or ridges small but +numerous) it gives rise to the "curly" structure frequently seen in +maple. Ordinarily, neither wavy, spiral, nor alternate grain is +visible on the cross-section; its existence often escapes the eye even +on smooth, longitudinal faces in the sawed material, so that the only +guide to their discovery lies in splitting the wood in two, in the two +normal plains. + + [Illustration: Fig. 15. Spiral Grain. Season checks, after + removal of bark, indicate the direction of the fibres or + grain of the wood.] + + [Illustration: Fig. 16. Alternating Spiral Grain in Cypress. + Side and end view of same piece. When the bark was at _o_, + the grain of this piece was straight. From that time, each + year it grew more oblique in one direction, reaching a climax + at _a_, and then turned back in the opposite direction. These + alternations were repeated periodically, the bark sharing in + these changes.] + +Generally the surface of the wood under the bark, and therefore also +that of any layer in the interior, is not uniform and smooth, but is +channelled and pitted by numerous depressions, which differ greatly in +size and form. Usually, any one depression or elevation is restricted +to one or few annual layers (_i.e._, seen only in one or few rings) +and is then lost, being compensated (the surface at the particular +spot evened up) by growth. In some woods, however, any depression or +elevation once attained grows from year to year and reaches a maximum +size, which is maintained for many years, sometimes throughout life. +In maple, where this tendency to preserve any particular contour is +very great, the depressions and elevations are usually small +(commonly less than one-eighth inch) but very numerous. + +On tangent boards of such wood, the sections, pits, and prominences +appear as circlets, and give rise to the beautiful "bird's eye" or +"landscape" structure. Similiar structures in the burls of black ash, +maple, etc., are frequently due to the presence of dormant buds, which +cause the surface of all the layers through which they pass to be +covered by small conical elevations, whose cross-sections on the sawed +board appear as irregular circlets or islets, each with a dark speck, +the section of the pith or "trace" of the dormant bud in the center. + + [Illustration: Fig. 17. Wavy Grain in Beech (_after + Nordlinger_).] + +In the wood of many broad-leaved trees the wood fibres are much longer +when full grown than when they are first formed in the cambium or +growing zone. This causes the tips of each fibre to crowd in between +the fibres above and below, and leads to an irregular interlacement of +these fibres, which adds to the toughness, but reduces the +cleavability of the wood. At the juncture of the limb and stem the +fibres on the upper and lower sides of the limb behave differently. +On the lower side they run from the stem into the limb, forming an +uninterrupted strand or tissue and a perfect union. On the upper side +the fibres bend aside, are not continuous into the limb, and hence the +connection is not perfect (see Fig. 18). Owing to this arrangement of +the fibres, the cleft made in splitting never runs into the knot if +started on the side above the limb, but is apt to enter the knot if +started below, a fact well understood in woodcraft. When limbs die, +decay, and break off, the remaining stubs are surrounded, and may +finally be covered by the growth of the trunk and thus give rise to +the annoying "dead" or "loose" knots. + + [Illustration: Fig. 18. Section of Wood showing Position of + the Grain at Base of a Limb. P, pith of both stem and limb; + 1-7, seven yearly layers of wood; _a_, _b_, knot or basal + part of a limb which lived for four years, then died and + broke off near the stem, leaving the part to the left of _a_, + _b_, a "sound" knot, the part to the right a "dead" knot, + which would soon be entirely covered by the growing stem.] + + + COLOR AND ODOR OF WOOD + +Color, like structure, lends beauty to the wood, aids in its +identification, and is of great value in the determination of its +quality. If we consider only the heartwood, the black color of the +persimmon, the dark brown of the walnut, the light brown of the white +oaks, the reddish brown of the red oaks, the yellowish white of the +tulip and poplars, the brownish red of the redwood and cedars, the +yellow of the papaw and sumac, are all reliable marks of distinction +and color. Together with luster and weight, they are only too often +the only features depended upon in practice. Newly formed wood, like +that of the outer few rings, has but little color. The sapwood +generally is light, and the wood of trees which form no heartwood +changes but little, except when stained by forerunners of disease. + +The different tints of colors, whether the brown of oak, the orange +brown of pine, the blackish tint of walnut, or the reddish cast of +cedar, are due to pigments, while the deeper shade of the summer-wood +bands in pine, cedar, oak, or walnut is due to the fact that the wood +being denser, more of the colored wood substance occurs on a given +space, _i.e._, there is more colored matter per square inch. Wood is +translucent, a thin disk of pine permitting light to pass through +quite freely. This translucency affects the luster and brightness of +lumber. + +When lumber is attacked by fungi, it becomes more opaque, loses its +brightness, and in practice is designated "dead," in distinction to +"live" or bright timber. Exposure to air darkens all wood; direct +sunlight and occasional moistening hasten this change, and cause it to +penetrate deeper. Prolonged immersion has the same effect, pine wood +becoming a dark gray, while oak changes to a blackish brown. + +Odor, like color, depends on chemical compounds, forming no part of +the wood substance itself. Exposure to weather reduces and often +changes the odor, but a piece of long-leaf pine, cedar, or camphor +wood exhales apparently as much odor as ever when a new surface is +exposed. Heartwood is more odoriferous than sapwood. Many kinds of +wood are distinguished by strong and peculiar odors. This is +especially the case with camphor, cedar, pine, oak, and mahogany, and +the list would comprise every kind of wood in use were our sense of +smell developed in keeping with its importance. + +Decomposition is usually accompanied by pronounced odors. Decaying +poplar emits a disagreeable odor, while red oak often becomes +fragrant, its smell resembling that of heliotrope. + + + WEIGHT OF WOOD + +A small cross-section of wood (as in Fig. 19) dropped into water +sinks, showing that the substance of which wood fibre or wood is built +up is heavier than water. By immersing the wood successively in +heavier liquids, until we find a liquid in which it does not sink, and +comparing the weight of the same with water, we find that wood +substance is about 1.6 times as heavy as water, and that this is as +true of poplar as of oak or pine. + + [Illustration: Fig. 19. Cross-section of a Group of Wood + Fibres (Highly Magnified.)] + +Separating a single cell (as shown in Fig. 20, _a_), drying and then +dropping it into water, it floats. The air-filled cell cavity or +interior reduces its weight, and, like an empty corked bottle, it +weighs less than the water. Soon, however, water soaks into the cell, +when it fills up and sinks. Many such cells grown together, as in a +block of wood, when all or most of them are filled with water, will +float as long as the majority of them are empty or only partially +filled. This is why a green, sappy pine pole soon sinks in "driving" +(floating down stream). Its cells are largely filled before it is +thrown in, and but little additional water suffices to make its weight +greater than that of the water. In a good-sized white pine log, +composed chiefly of empty cells (heartwood), the water requires a very +long time to fill up the cells (five years would not suffice to fill +them all), and therefore the log may float for many months. When the +wall of the wood fibre is very thick (five eighths or more of the +volume, as in Fig. 20, _b_), the fibre sinks whether empty or filled. +This applies to most of the fibres of the dark summer-wood bands in +pines, and to the compact fibres of oak or hickory, and many, +especially tropical woods, have such thick-walled cells and so little +empty or air space that they never float. + + [Illustration: Fig. 20. Isolated Fibres of Wood.] + +Here, then, are the two main factors of weight in wood; the amount of +cell wall or wood substance constant for any given piece, and the +amount of water contained in the wood, variable even in the standing +tree, and only in part eliminated in drying. + +The weight of the green wood of any species varies chiefly as a second +factor, and is entirely misleading, if the relative weight of +different kinds is sought. Thus some green sticks of the otherwise +lighter cypress and gum sink more readily than fresh oak. + +The weight of sapwood or the sappy, peripheral part of our common +lumber woods is always great, whether cut in winter or summer. It +rarely falls much below forty-five pounds, and commonly exceeds +fifty-five pounds to the cubic foot, even in our lighter wooded +species. It follows that the green wood of a sapling is heavier than +that of an old tree, the fresh wood from a disk of the upper part of a +tree is often heavier than that of the lower part, and the wood near +the bark heavier than that nearer the pith; and also that the +advantage of drying the wood before shipping is most important in +sappy and light kinds. + +When kiln-dried, the misleading moisture factor of weight is uniformly +reduced, and a fair comparison possible. For the sake of convenience +in comparison, the weight of wood is expressed either as the weight +per cubic foot, or, what is still more convenient, as specific weight +or density. If an old long-leaf pine is cut up (as shown in Fig. 21) +the wood of disk No. 1 is heavier than that of disk No. 2, the latter +heavier than that of disk No. 3, and the wood of the top disk is found +to be only about three fourths as heavy as that of disk No. 1. +Similiarly, if disk No. 2 is cut up, as in the figure, the specific +weight of the different parts is: + + _a_, about 0.52 + _b_, about 0.64 + _c_, about 0.67 + _d_, _e_, _f_, about 0.65 + +showing that in this disk at least the wood formed during the many +years' growth, represented in piece _a_, is much lighter than that of +former years. It also shows that the best wood is the middle part, +with its large proportion of dark summer bands. + + [Illustration: Fig. 21. Orientation of Wood Samples.] + +Cutting up all disks in the same way, it will be found that the piece +_a_ of the first disk is heavier than the piece _a_ of the fifth, and +that piece _c_ of the first disk excels the piece _c_ of all the other +disks. This shows that the wood grown during the same number of years +is lighter in the upper parts of the stem; and if the disks are +smoothed on the radial surfaces and set up one on top of the other in +their regular order, for the sake of comparison, this decrease in +weight will be seen to be accompanied by a decrease in the amount of +summer-wood. The color effect of the upper disks is conspicuously +lighter. If our old pine had been cut one hundred and fifty years ago, +before the outer, lighter wood was laid on, it is evident that the +weight of the wood of any one disk would have been found to increase +from the center outward, and no subsequent decrease could have been +observed. + +In a thrifty young pine, then, the wood is heavier from the center +outward, and lighter from below upward; only the wood laid on in old +age falls in weight below the average. The number of brownish bands of +summer-wood are a direct indication of these differences. If an old +oak is cut up in the same manner, the butt cut is also found heaviest +and the top lightest, but, unlike the disk of pine, the disk of oak +has its firmest wood at the center, and each successive piece from the +center outward is lighter than its neighbor. + +Examining the pieces, this difference is not as readily explained by +the appearance of each piece as in the case of pine wood. +Nevertheless, one conspicuous point appears at once. The pores, so +very distinct in oak, are very minute in the wood near the center, and +thus the wood is far less porous. + +Studying different trees, it is found that in the pines, wood with +narrow rings is just as heavy as and often heavier than the wood with +wider rings; but if the rings are unusually narrow in any part of the +disk, the wood has a lighter color; that is, there is less summer-wood +and therefore less weight. + +In oak, ash, or elm trees of thrifty growth, the rings, fairly wide +(not less than one-twelfth inch), always form the heaviest wood, while +any piece with very narrow rings is light. On the other hand, the +weight of a piece of hard maple or birch is quite independent of the +width of its rings. + +The bases of limbs (knots) are usually heavy, very heavy in conifers, +and also the wood which surrounds them, but generally the wood of the +limbs is lighter than that of the stem, and the wood of the roots is +the lightest. + +In general, it may be said that none of the native woods in common use +in this country are when dry as heavy as water, _i.e._, sixty-two +pounds to the cubic foot. Few exceed fifty pounds, while most of them +fall below forty pounds, and much of the pine and other coniferous +wood weigh less than thirty pounds per cubic foot. The weight of the +wood is in itself an important quality. Weight assists in +distinguishing maple from poplar. Lightness coupled with great +strength and stiffness recommends wood for a thousand different uses. +To a large extent weight predicates the strength of the wood, at least +in the same species, so that a heavy piece of oak will exceed in +strength a light piece of the same species, and in pine it appears +probable that, weight for weight, the strength of the wood of various +pines is nearly equal. + +WEIGHT OF KILN-DRIED WOOD OF DIFFERENT SPECIES +-----------------------------------------+---------------------------- + | Approximate + |----------+----------------- + | | Weight of + | |---------+------- + Species | Specific | 1 | 1,000 + | Weight | Cubic | Feet + | | Foot | Lumber +-----------------------------------------+----------+---------+------- +(_a_) Very Heavy Woods: | | | + Hickory, Oak, Persimmon, Osage Orange, | | | + Black Locust, Hackberry, Blue Beech, | | | + best of Elm and Ash |0.70-0.80 | 42-48 | 3,700 +(_b_) Heavy Woods | | | + Ash, Elm, Cherry, Birch, Maple, Beech, | | | + Walnut, Sour Gum, Coffee Tree, Honey | | | + Locust, best of Southern Pine and | | | + Tamarack |0.60-0.70 | 36-42 | 3,200 +(_c_) Woods of Medium Weight: | | | + Southern Pine, Pitch Pine, Tamarack, | | | + Douglas Spruce, Western Hemlock, | | | + Sweet Gum, Soft Maple, Sycamore, | | | + Sassafras, Mulberry, light grades of | | | + Birch and Cherry |0.50-0.60 | 30-36 | 2,700 +(_d_) Light Woods: | | | + Norway and Bull Pine, Red Cedar, | | | + Cypress, Hemlock, the Heavier Spruces | | | + and Firs, Redwood, Basswood, Chestnut, | | | + Butternut, Tulip, Catalpa, Buckeye, | | | + heavier grades of Poplar |0.40-0.50 | 24-30 | 2,200 +(_e_) Very Light Woods: | | | + White Pine, Spruce, Fir, White Cedar, | | | + Poplar |0.30-0.40 | 18-24 | 1,800 +-----------------------------------------+----------+---------+------- + + + "FIGURE" IN WOOD + +Many theories have been propounded as to the cause of "figure" in +timber; while it is true that all timber possesses "figure" in some +degree, which is more noticeable if it be cut in certain ways, yet +there are some woods in which it is more conspicuous than in others, +and which for cabinet or furniture work are much appreciated, as it +adds to the value of the work produced. + +The characteristic "figure" of oak is due to the broad and deep +medullary rays so conspicuous in this timber, and the same applies to +honeysuckle. Figure due to the same cause is found in sycamore and +beech, but is not so pronounced. The beautiful figure in "bird's eye +maple" is supposed to be due to the boring action of insects in the +early growth of the tree, causing pits or grooves, which in time +become filled up by being overlain by fresh layers of wood growth; +these peculiar and unique markings are found only in the older and +inner portion of the tree. + +Pitch pine has sometimes a very beautiful "figure," but it generally +does not go deep into the timber; walnut has quite a variety of +"figures," and so has the elm. It is in mahogany, however, that we +find the greatest variety of "figure," and as this timber is only used +for furniture and fancy work, a good "figure" greatly enhances its +value, as firmly figured logs bring fancy prices. + +Mahogany, unlike the oak, never draws its "figure" from its small and +almost unnoticeable medullary rays, but from the twisted condition of +its fibres; the natural growth of mahogany produces a straight wood; +what is called "figured" is unnatural and exceptional, and thus adds +to its value as an ornamental wood. These peculiarities are rarely +found in the earlier portion of the tree that is near the center, +being in this respect quite different from maple; they appear when the +tree is more fully developed, and consist of bundles of woody fibres +which, instead of being laid in straight lines, behave in an erratic +manner and are deposited in a twisted form; sometimes it may be caused +by the intersection of branches, or possibly by the crackling of the +bark pressing on the wood, and thus moving it out of its natural +straight course, causing a wavy line which in time becomes +accentuated. + +It will have been observed by most people that the outer portion of a +tree is often indented by the bark, and the outer rings often follow a +sinuous course which corresponds to this indention, but in most trees, +after a few years, this is evened up and the annual rings assume their +nearly circular form; it is supposed by some that in the case of +mahogany this is not the case, and that the indentations are even +accentuated. + +The best figured logs of timber are secured from trees which grow in +firm rocky soil; those growing on low-lying or swampy ground are +seldom figured. To the practical woodworker the figure in mahogany +causes some difficulty in planing the wood to a smooth surface; some +portions plane smooth, others are the "wrong way of the grain." + +Figure in wood is effected by the way light is thrown upon it, showing +light if seen from one direction, and dark if viewed from another, as +may easily be observed by holding a piece of figured mahogany under +artificial light and looking at it from opposite directions. The +characteristic markings on mahogany are "mottle," which is also found +in sycamore, and is conspicuous on the backs of fiddles and violins, +and is not in itself valuable; it runs the transverse way of the +fibres and is probably the effect of the wind upon the tree in its +early stages of growth. "Roe," which is said to be caused by the +contortion of the woody fibres, and takes a wavy line parallel to +them, is also found in the hollow of bent stems and in the root +structure, and when combined with "mottle" is very valuable. "Dapple" +is an exaggerated form of mottle. "Thunder shake," "wind shake," or +"tornado shake" is a rupture of the fibres across the grain, which in +mahogany does not always break them; the tree swaying in the wind only +strains its fibres, and thus produces mottle in the wood. + + + + + SECTION V + + ENEMIES OF WOOD + + +From the writer's personal investigations of this subject in different +sections of the country, the damage to forest products of various +kinds from this cause seems to be far more extensive than is generally +recognized. Allowing a loss of five per cent on the total value of the +forest products of the country, which the writer believes to be a +conservative estimate, it would amount to something over $30,000,000 +annually. This loss differs from that resulting from insect damage to +natural forest resources, in that it represents more directly a loss +of money invested in material and labor. In dealing with the insects +mentioned, as with forest insects in general, the methods which yield +the best results are those which relate directly to preventing attack, +as well as those which are unattractive or unfavorable. The insects +have two objects in their attack: one is to obtain food, the other is +to prepare for the development of their broods. Different species of +insects have special periods during the season of activity (March to +November), when the adults are on the wing in search of suitable +material in which to deposit their eggs. Some species, which fly in +April, will be attracted to the trunks of recently felled pine trees +or to piles of pine sawlogs from trees felled the previous winter. +They are not attracted to any other kind of timber, because they can +live only in the bark or wood of pine, and only in that which is in +the proper condition to favor the hatching of their eggs and the +normal development of their young. As they fly only in April, they +cannot injure the logs of trees felled during the remainder of the +year. + +There are also oak insects, which attack nothing but oak; hickory, +cypress, and spruce insects, etc., which have different habits and +different periods of flight, and require special conditions of the +bark and wood for depositing their eggs or for subsequent development +of their broods. Some of these insects have but one generation in a +year, others have two or more, while some require more than one year +for the complete development and transformation. Some species deposit +their eggs in the bark or wood of trees soon after they are felled or +before any perceptible change from the normal living tissue has taken +place; other species are attracted only to dead bark and dead wood of +trees which have been felled or girdled for several months; others are +attracted to dry and seasoned wood; while another class will attack +nothing but very old, dry bark or wood of special kinds and under +special conditions. Thus it will be seen how important it is for the +practical man to have knowledge of such of the foregoing facts as +apply to his immediate interest in the manufacture or utilization of a +given forest product, in order that he may with the least trouble and +expense adjust his business methods to meet the requirements for +preventing losses. + +The work of different kinds of insects, as represented by special +injuries to forest products, is the first thing to attract attention, +and the distinctive character of this work is easily observed, while +the insect responsible for it is seldom seen, or it is so difficult to +determine by the general observer from descriptions or illustrations +that the species is rarely recognized. Fortunately, the character of +the work is often sufficient in itself to identify the cause and +suggest a remedy, and in this section primary consideration is given +to this phase of the subject. + + + Ambrosia or Timber Beetles + + [Illustration: Fig. 22. Work of Ambrosia Beetles in Tulip or + Yellow Poplar Wood. _a_, work of _Xyleborus affinis_ and + _Xyleborus inermis_; _b_, _Xyleborus obesus_ and work; _c_, + bark; _d_, sapwood; _e_, heartwood.] + + [Illustration: Fig. 23. Work of Ambrosia Beetles in Oak. _a_, + _Monarthrum mali_ and work; _b_, _Platypus compositus_ and + work; _c_, bark; _d_, sapwood; _e_, heartwood; _f_, character + of work in wood from injured log.] + +The characteristic work of this class of wood-boring beetles is shown +in Figs. 22 and 23. The injury consists of pinhole and stained-wood +defects in the sapwood and heartwood of recently felled or girdled +trees, sawlogs, pulpwood, stave and shingle bolts, green or +unseasoned lumber, and staves and heads of barrels containing +alcoholic liquids. The holes and galleries are made by the adult +parent beetles, to serve as entrances and temporary houses or +nurseries for the development of their broods of young, which feed on +a fungus growing on the walls of the galleries. + +The growth of this ambrosia-like fungus is induced and controlled by +the parent beetles, and the young are dependent upon it for food. The +wood must be in exactly the proper condition for the growth of the +fungus in order to attract the beetles and induce them to excavate +their galleries; it must have a certain degree of moisture and other +favorable qualities, which usually prevail during the period involved +in the change from living, or normal, to dead or dry wood; such a +condition is found in recently felled trees, sawlogs, or like crude +products. + +There are two general types or classes of these galleries: one in +which the broods develop together in the main burrows (see Fig. 22), +the other in which the individuals develop in short, separate side +chambers, extending at right angles from the primary galleries (see +Fig. 23). The galleries of the latter type are usually accompanied by +a distinct staining of the wood, while those of the former are not. + +The beetles responsible for this work are cylindrical in form, +apparently with a head (the prothorax) half as long as the remainder +of the body (see Figs. 22, _a_, and 23, _a_). + +North American species vary in size from less than one-tenth to +slightly more than two-tenths of an inch, while some of the +subtropical and tropical species attain a much larger size. The +diameter of the holes made by each species corresponds closely to that +of the body, and varies from about one-twentieth to one-sixteenth of +an inch for the tropical species. + + + Round-headed Borers + + [Illustration: Fig. 24. Work of Round-headed and Flat-headed + Borers in Pine. _a_, work of round-headed borer, "sawyer," + _Monohammus spiculatus_, natural size _b_, _Ergates + spiculatus_; _c_, work of flat-headed borer, _Buprestis_, + larva and adult; _d_, bark; _e_, sapwood; _f_, heartwood.] + +The character of the work of this class of wood- and bark-boring grubs +is shown in Fig. 24. The injuries consist of irregular flattened or +nearly round wormhole defects in the wood, which sometimes result in +the destruction of valuable parts of the wood or bark material. The +sapwood and heartwood of recently felled trees, sawlogs, poles posts, +mine props, pulpwood and cordwood, also lumber or square timber, with +bark on the edges, and construction timber in new and old buildings, +are injured by wormhole defects, while the valuable parts of stored +oak and hemlock tanbark and certain kinds of wood are converted into +worm-dust. These injuries are caused by the young or larvae of +long-horned beetles. Those which infest the wood hatch from eggs +deposited in the outer bark of logs and like material, and the minute +grubs hatching therefrom bore into the inner bark, through which they +extend their irregular burrows, for the purpose of obtaining food from +the sap and other nutritive material found in the plant tissue. They +continue to extend and enlarge their burrows as they increase in size, +until they are nearly or quite full grown. They then enter the wood +and continue their excavations deep into the sapwood or heartwood +until they attain their normal size. They then excavate pupa cells in +which to transform into adults, which emerge from the wood through +exit holes in the surface. This class of borers is represented by a +large number of species. The adults, however, are seldom seen by the +general observer unless cut out of the wood before they have emerged. + + + Flat-headed Borers + +The work of the flat-headed borers (Fig. 24) is only distinguished +from that of the preceding by the broad, shallow burrows, and the much +more oblong form of the exit holes. In general, the injuries are +similiar, and effect the same class of products, but they are of much +less importance. The adult forms are flattened, metallic-colored +beetles, and represent many species, of various sizes. + + + Timber Worms + + [Illustration: Fig. 25. Work of Timber Worms in Oak. _a_, + work of oak timber worm, _Eupsalis minuta_; _b_, barked + surface; _c_, bark; _d_, sapwood timber worm, _Hylocoetus + lugubris_, and work; _e_, sapwood.] + +The character of the work done by this class is shown in Fig. 25. The +injury consists of pinhole defects in the sapwood and heartwood of +felled trees, sawlogs and like material which have been left in the +woods or in piles in the open for several months during the warmer +seasons. Stave and shingle bolts and closely piled oak lumber and +square timbers also suffer from injury of this kind. These injuries +are made by elongate, slender worms or larvae, which hatch from eggs +deposited by the adult beetles in the outer bark, or, where there is +no bark, just beneath the surface of the wood. At first the young +larvae bore almost invisible holes for a long distance through the +sapwood and heartwood, but as they increase in size the same holes are +enlarged and extended until the larvae have attained their full +growth. They then transform to adults, and emerge through the enlarged +entrance burrows. The work of these timber worms is distinguished from +that of the timber beetles by the greater variation in the size of +holes in the same piece of wood, also by the fact that they are not +branched from a single entrance or gallery, as are those made by the +beetles. + + [Illustration: Fig. 26. Work of Powder Post Beetle, + _Sinoxylon basilare_, in Hickory Poles, showing Transverse + Egg Galleries excavated by the Adult, _a_, entrance; _b_, + gallery; _c_, adult.] + + [Illustration: Fig. 27. Work of Powder + Post Beetle, _Sinoxylon basilare_, in Hickory Pole. _a_, + character of work by larvae; _b_, exit holes made by + emerging broods.] + + + Powder Post Borers + +The character of the work of this class of insects is shown in Figs. +26, 27, and 28. The injury consists of closely placed burrows, packed +with borings, or a completely destroyed or powdered condition of the +wood of seasoned products, such as lumber, crude and finished handle +and wagon stock, cooperage and wooden truss hoops, furniture, and +inside finish woodwork, in old buildings, as well as in many other +crude or finished and utilized woods. This is the work of both the +adults and young stages of some species, or of the larval stage alone +of others. In the former, the adult beetles deposit their eggs in +burrows or galleries excavated for the purpose, as in Figs. 26 and 27, +while in the latter (Fig. 28) the eggs are on or beneath the surface +of the wood. The grubs complete the destruction by boring through the +solid wood in all directions and packing their burrows with the +powdered wood. When they are full grown they transform to the adult, +and emerge from the injured material through holes in the surface. +Some of the species continue to work in the same wood until many +generations have developed and emerged or until every particle of wood +tissue has been destroyed and the available nutritive substance +extracted. + + [Illustration: Fig. 28. Work of Powder Post Beetles, _Lyctus + striatus_, in Hickory Handles and Spokes. _a_, larva; _b_, + pupa; _c_, adult; _d_, exit holes; _e_, entrance of larvae + (vents for borings are exits of parasites); _f_, work of + larvae; _g_, wood, completely destroyed; _h_, sapwood; _i_, + heartwood.] + + + Conditions Favorable for Insect + Injury--Crude Products--Round Timber with Bark on + +Newly felled trees, sawlogs, stave and heading bolts, telegraph poles, +posts, and the like material, cut in the fall and winter, and left on +the ground or in close piles during a few weeks or months in the +spring or summer, causing them to heat and sweat, are especially +liable to injury by ambrosia beetles (Figs. 22 and 23), round and +flat-headed borers (Fig. 24), and timber worms (Fig. 25), as are also +trees felled in the warm season, and left for a time before working up +into lumber. + +The proper degree of moisture found in freshly cut living or dying +wood, and the period when the insects are flying, are the conditions +most favorable for attack. This period of danger varies with the time +of the year the timber is felled and with the different kinds of +trees. Those felled in late fall and winter will generally remain +attractive to ambrosia beetles, and to the adults of round- and +flat-headed borers during March, April, and May. Those felled in April +to September may be attacked in a few days after they are felled, and +the period of danger may not extend over more than a few weeks. +Certain kinds of trees felled during certain months and seasons are +never attacked, because the danger period prevails only when the +insects are flying; on the other hand, if the same kinds of trees are +felled at a different time, the conditions may be most attractive when +the insects are active, and they will be thickly infested and ruined. + +The presence of bark is absolutely necessary for infestation by most +of the wood-boring grubs, since the eggs and young stages must occupy +the outer and inner portions before they can enter the wood. Some +ambrosia and timber worms will, however, attack barked logs, +especially those in close piles, and others shaded and protected from +rapid drying. + +The sapwood of pine, spruce, fir, cedar, cypress, and the like +softwoods is especially liable to injury by ambrosia beetles, while +the heartwood is sometimes ruined by a class of round-headed borers, +known as "sawyers." Yellow poplar, oak, chestnut, gum, hickory, and +most other hardwoods are as a rule attacked by species of ambrosia +beetles, sawyers, and timber worms, different from those infesting the +pines, there being but very few species which attack both. + +Mahogany and other rare and valuable woods imported from the tropics +to this country in the form of round logs, with or without bark on, +are commonly damaged more or less seriously by ambrosia beetles and +timber worms. + +It would appear from the writer's investigations of logs received at +the mills in this country, that the principal damage is done during a +limited period--from the time the trees are felled until they are +placed in fresh or salt water for transportation to the shipping +points. If, however, the logs are loaded on a vessel direct from the +shore, or if not left in the water long enough to kill the insects, +the latter will continue their destructive work during transportation +to other countries and after they arrive, and until cold weather +ensues or the logs are converted into lumber. + +It was also found that a thorough soaking in sea-water, while it +usually killed the insects at the time, did not prevent subsequent +attacks by both foreign and native ambrosia beetles; also, that the +removal of the bark from such logs previous to immersion did not +render them entirely immune. Those with the bark off were attacked +more than those with it on, owing to a greater amount of saline +moisture retained by the bark. + + + How to Prevent Injury + +From the foregoing it will be seen that some requisites for preventing +these insect injuries to round timber are: + + 1. To provide for as little delay as possible between the + felling of the tree and its manufacture into rough products. + This is especially necessary with trees felled from April to + September, in the region north of the Gulf States, and from + March to November in the latter, while the late fall and + winter cutting should all be worked up by March or April. + + 2. If the round timber must be left in the woods or on the + skidways during the danger period, every precaution should + be taken to facilitate rapid drying of the inner bark, by + keeping the logs off the ground in the sun, or in loose + piles; or else the opposite extreme should be adopted and + the logs kept in water. + + 3. The immediate removal of all the bark from poles, posts, + and other material which will not be seriously damaged by + checking or season checks. + + 4. To determine and utilize the proper months or seasons to + girdle or fell different kinds of trees: Bald cypress in the + swamps of the South are "girdled" in order that they may + die, and in a few weeks or months dry out and become light + enough to float. This method has been extensively adopted in + sections where it is the only practicable one by which the + timber can be transported to the sawmills. It is found, + however, that some of these "girdled" trees are especially + attractive to several species of ambrosia beetles (Figs. 22 + and 23), round-headed borers (Fig. 24) and timber worms + (Fig. 25), which cause serious injury to the sapwood or + heartwood, while other trees "girdled" at a different time + or season are not injured. This suggested to the writer the + importance of experiments to determine the proper time to + "girdle" trees to avoid losses, and they are now being + conducted on an extensive scale by the United States Forest + Service, in co-operation with prominent cypress operators in + different sections of the cypress-growing region. + + + Saplings + +Saplings, including hickory and other round hoop-poles and similiar +products, are subject to serious injuries and destruction by round- +and flat-headed borers (Fig. 24), and certain species of powder post +borers (Figs. 26 and 27) before the bark and wood are dead or dry, and +also by other powder post borers (Fig. 28) after they are dried and +seasoned. The conditions favoring attack by the former class are those +resulting from leaving the poles in piles or bundles in or near the +forest for a few weeks during the season of insect activity, and by +the latter from leaving them stored in one place for several months. + + + Stave, Heading and Shingle Bolts + +These are attacked by ambrosia beetles (Figs. 22 and 23), and the oak +timber worm (Fig. 25, _a_), which, as has been frequently reported, +cause serious losses. The conditions favoring attack by these insects +are similiar to those mentioned under "Round Timber." The insects may +enter the wood before the bolts are cut from the log or afterward, +especially if the bolts are left in moist, shady places in the woods, +in close piles during the danger period. If cut during the warm +season, the bark should be removed and the bolts converted into the +smallest practicable size and piled in such manner as to facilitate +rapid drying. + + + Unseasoned Products in the Rough + +Freshly sawn hardwood, placed in close piles during warm, damp weather +in July and September, presents especially favorable conditions for +injury by ambrosia beetles (Figs. 22, _a_, and 23, _a_). This is due +to the continued moist condition of such material. + +Heavy two-inch or three-inch stuff is also liable to attack even in +loose piles with lumber or cross sticks. An example of the latter was +found in a valuable lot of mahogany lumber of first grade, the value +of which was reduced two thirds by injury from a native ambrosia +beetle. Numerous complaints have been received from different sections +of the country of this class of injury to oak, poplar, gum, and other +hardwoods. In all cases it is the moist condition and retarded drying +of the lumber which induces attack; therefore, any method which will +provide for the rapid drying of the wood before or after piling will +tend to prevent losses. + +It is important that heavy lumber should, as far as possible, be cut +in the winter months and piled so that it will be well dried out +before the middle of March. Square timber, stave and heading bolts, +with the bark on, often suffer from injuries by flat- or round-headed +borers, hatching from eggs deposited in the bark of the logs before +they are sawed and piled. One example of serious damage and loss was +reported in which white pine staves for paint buckets and other small +wooden vessels, which had been sawed from small logs, and the bark +left on the edges, were attacked by a round-headed borer, the adults +having deposited their eggs in the bark after the stock was sawn and +piled. The character of the injury is shown in Fig. 29. Another +example was reported from a manufacturer in the South, where the +pieces of lumber which had strips of bark on one side were seriously +damaged by the same kind of borer, the eggs having been deposited in +the logs before sawing or in the bark after the lumber was piled. If +the eggs are deposited in the logs, and the borers have entered the +inner bark or the wood before sawing, they may continue their work +regardless of methods of piling, but if such lumber is cut from new +logs and placed in the pile while green, with the bark surface up, it +will be much less liable to attack than if piled with the bark edges +down. This liability of lumber with bark edges or sides to be attacked +by insects suggests the importance of the removal of the bark, to +prevent damage, or, if this is not practicable, the lumber with the +bark on the sides should be piled in open, loose piles with the bark +up, while that with the bark on the edges should be placed on the +outer edges of the piles, exposed to the light and air. + + [Illustration: Fig. 29. Work of Round-headed Borers, + _Callidium antennatum_, in White Pine Bucket Staves from New + Hampshire. _a_, where egg was deposited in bark; _b_, larval + mine; _c_, pupal cell; _d_, exit in bark; _e_, adult.] + +In the Southern States it is difficult to keep green timber in the +woods or in piles for any length of time, because of the rapidity +which wood-destroying fungi attack it. This is particularly true +during the summer season, when the humidity is greatest. There is +really no easily-applied, general specific for these summer troubles +in the handling of wood, but there are some suggestions that are worth +while that it may be well to mention. One of these, and the most +important, is to remove all the bark from the timber that has been +cut, just as soon as possible after felling. And, in this, emphasis +should be laid on the ALL, as a piece of bark no larger than a man's +little finger will furnish an entering place for insects, and once +they get in, it is a difficult matter to get rid of them, for they +seldom stop boring until they ruin the stick. And again, after the +timber has been felled and the bark removed, it is well to get it to +the mill pond or cut up into merchantable sizes and on to the pile as +soon as possible. What is wanted is to get the timber up off the +ground, to a place where it can get plenty of air, to enable the sap +to dry up before it sours; and, besides, large units of wood are more +likely to crack open on the ends from the heat than they would if cut +up into the smaller units for merchandizing. + +A moist condition of lumber and square timber, such as results from +close or solid piles, with the bottom layers on the ground or on +foundations of old decaying logs or near decaying stumps and logs, +offers especially favorable conditions for the attack of white ants. + + + Seasoned Products in the Rough + +Seasoned or dry timber in stacks or storage is liable to injury by +powder post borers (Fig. 28). The conditions favoring attack are: (1) +The presence of a large proportion of sapwood, as in hickory, ash, and +similiar woods; (2) material which is two or more years old, or that +which has been kept in one place for a long time; (3) access to old +infested material. Therefore, such stock should be frequently examined +for evidence of the presence of these insects. This is always +indicated by fine, flour-like powder on or beneath the piles, or +otherwise associated with such material. All infested material should +be at once removed and the infested parts destroyed by burning. + + + Dry Cooperage Stock and Wooden Truss Hoops + +These are especially liable to attack and serious injury by powder +post borers (Fig. 28), under the same or similiar conditions as the +preceding. + + + Staves and Heads of Barrels containing Alcoholic Liquids + +These are liable to attack by ambrosia beetles (Figs. 22, _a_, and 23, +_a_), which are attracted by the moist condition and possibly by the +peculiar odor of the wood, resembling that of dying sapwood of trees +and logs, which is their normal breeding place. + +There are many examples on record of serious losses of liquors from +leakage caused by the beetles boring through the staves and heads of +the barrels and casks in cellars and storerooms. + +The condition, in addition to the moisture of the wood, which is +favorable for the presence of the beetles, is proximity to their +breeding places, such as the trunks and stumps of recently felled or +dying oak, maple, and other hardwood or deciduous trees; lumber yards, +sawmills, freshly-cut cordwood, from living or dead trees, and forests +of hardwood timber. Under such conditions the beetles occur in great +numbers, and if the storerooms and cellars in which the barrels are +kept stored are damp, poorly ventilated, and readily accessible to +them, serious injury is almost certain to follow. + + + + + SECTION VI + + WATER IN WOOD + + DISTRIBUTION OF WATER IN WOOD + + + Local Distribution of Water in Wood + +As seasoning means essentially the more or less rapid evaporation of +water from wood, it will be necessary to discuss at the very outset +where water is found in wood, and its local seasonal distribution in a +tree. + +Water may occur in wood in three conditions: (1) It forms the greater +part (over 90 per cent) of the protoplasmic contents of the living +cells; (2) it saturates the walls of all cells; and (3) it entirely or +at least partly fills the cavities of the lifeless cells, fibres, and +vessels. + +In the sapwood of pine it occurs in all three forms; in the heartwood +only in the second form, it merely saturates the walls. + +Of 100 pounds of water associated with 100 pounds of dry wood +substance taken from 200 pounds of fresh sapwood of white pine, about +35 pounds are needed to saturate the cell walls, less than 5 pounds +are contained in the living cells, and the remaining 60 pounds partly +fill the cavities of the wood fibres. This latter forms the sap as +ordinarily understood. + +The wood next to the bark contains the most water. In the species +which do not form heartwood, the decrease toward the pith is gradual, +but where heartwood is formed the change from a more moist to a drier +condition is usually quite abrupt at the sapwood limit. + +In long-leaf pine, the wood of the outer one inch of a disk may +contain 50 per cent of water, that of the next, or the second inch, +only 35 per cent, and that of the heartwood, only 20 per cent. In +such a tree the amount of water in any one section varies with the +amount of sapwood, and is greater for the upper than the lower cuts, +greater for the limbs than the stems, and greatest of all in the +roots. + +Different trees, even of the same kind and from the same place, differ +as to the amount of water they contain. A thrifty tree contains more +water than a stunted one, and a young tree more than on old one, while +the wood of all trees varies in its moisture relations with the season +of the year. + + + Seasonal Distribution of Water in Wood + +It is generally supposed that trees contain less water in winter than +in summer. This is evidenced by the popular saying that "the sap is +down in the winter." This is probably not always the case; some trees +contain as much water in winter as in summer, if not more. Trees +normally contain the greatest amount of water during that period when +the roots are active and the leaves are not yet out. This activity +commonly begins in January, February, and March, the exact time +varying with the kind of timber and the local atmospheric conditions. +And it has been found that green wood becomes lighter or contains less +water in late spring or early summer, when transpiration through the +foliage is most rapid. The amount of water at any one season, however, +is doubtless much influenced by the amount of moisture in the soil. +The fact that the bark peels easily in the spring depends on the +presence of incomplete, soft tissue found between wood and bark during +this season, and has little to do with the total amount of water +contained in the wood of the stem. + +Even in the living tree a flow of sap from a cut occurs only in +certain kinds of trees and under special circumstances. From boards, +felled timber, etc., the water does not flow out, as is sometimes +believed, but must be evaporated. The seeming exceptions to this rule +are mostly referable to two causes; clefts or "shakes" will allow +water contained in them to flow out, and water is forced out of sound +wood, if very sappy, whenever the wood is warmed, just as water flows +from green wood when put in a stove. + + + Composition of Sap + +The term "sap" is an ambiguous expression. The sap in the tree +descends through the bark, and except in early spring is not present +in the wood of the tree except in the medullary rays and living +tissues in the "sapwood." + +What flows through the "sapwood" is chiefly water brought from the +soil. It is not pure water, but contains many substances in solution, +such as mineral salts, and in certain species--maple, birch, etc., it +also contains at certain times a small percentage of sugar and other +organic matter. + +The water rises from the roots through the sapwood to the leaves, +where it is converted into true "sap" which descends through the bark +and feeds the living tissues between the bark and the wood, which +tissues make the annual growth of the trunk. The wood itself contains +very little true sap and the heartwood none. + +The wood contains, however, mineral substances, organic acids, +volatile oils and gums, as resin, cedar oil, etc. + +All the conifers--pines, cedars, junipers, cypresses, sequoias, yews, +and spruces--contain resin. The sap of deciduous trees--those which +shed their leaves at stated seasons--is lacking in this element, and +its constituents vary greatly in the different species. But there is +one element common to all trees, and for that matter to almost all +plant growth, and that is albumen. + +Both resin and albumen, as they exist in the sap of woods, are soluble +in water; and both harden with heat, much the same as the white of an +egg, which is almost pure albumen. + +These organic substances are the dissolved reserve food, stored during +the winter in the pith rays, etc., of the wood and bark; generally but +a mere trace of them is to be found. From this it appears that the +solids contained in the sap, such as albumen, gum, sugar, etc., +cannot exercise the influence on the strength of the wood which is so +commonly claimed for them. + + + Effects of Moisture on Wood + +The question of the effect of moisture upon the strength and stiffness +of wood offers a wide scope for study, and authorities consulted +differ in conclusions. Two authorities give the tensile strength in +pounds per square inch for white oak as 10,000 and 19,500, +respectively; for spruce, 8,000 to 19,500, and other species in +similiar startling contrasts. + +Wood, we are told, is composed of organic products. The chief material +is cellulose, and this in its natural state in the living plant or +green wood contains from 25 to 35 per cent of its weight in moisture. +The moisture renders the cellulose substance pliable. What the +physical action of the water is upon the molecular structure of +organic material, to render it softer and more pliable, is largely a +matter of conjecture. + +The strength of a timber depends not only upon its relative freedom +from imperfections, such as knots, crookedness of grain, decay, +wormholes or ring-shakes, but also upon its density; upon the rate at +which it grew, and upon the arrangement of the various elements which +compose it. + +The factors effecting the strength of wood are therefore of two +classes: (1) Those inherent in the wood itself and which may cause +differences to exist between two pieces from the same species of wood +or even between the two ends of a piece, and (2) those which are +foreign to the wood itself, such as moisture, oils, and heat. + +Though the effect of moisture is generally temporary, it is far more +important than is generally realized. So great, indeed, is the effect +of moisture that under some conditions it outweighs all the other +causes which effect strength, with the exception, perhaps of decided +imperfections in the wood itself. + + + The Fibre Saturation Point in Wood + +Water exists in green wood in two forms: (1) As liquid water contained +in the cavities of the cells or pores, and (2) as "imbibed" water +intimately absorbed in the substance of which the wood is composed. +The removal of the free water from the cells or pores will evidently +have no effect upon the physical properties or shrinkage of the wood, +but as soon as any of the "imbibed" moisture is removed from the cell +walls, shrinkage begins to take place and other changes occur. The +strength also begins to increase at this time. + +The point where the cell walls or wood substance becomes saturated is +called the "fibre saturation point," and is a very significant point +in the drying of wood. + +It is easy to remove the free water from woods which will stand a high +temperature, as it is only necessary to heat the wood slightly above +the boiling point in a closed vessel, which will allow the escape of +the steam as it is formed, but will not allow dry air to come in +contact with the wood, so that the surface will not become dried below +its saturation point. This can be accomplished with most of the +softwoods, but not as a rule with the hardwoods, as they are injured +by the temperature necessary. + +The chief difficulties are encountered in evaporating the "imbibed" +moisture and also where the free water has to be removed through its +gradual transfusion instead of boiling. As soon as the imbibed +moisture begins to be extracted from any portion, shrinkage takes +place and stresses are set up in the wood which tend to cause +checking. + +The fibre saturation point lies between moisture conditions of 25 and +30 per cent of the dry weight of the wood, depending on the species. +Certain species of eucalyptus, and probably other woods, however, +appear to be exceptional in this respect, in that shrinkage begins to +take place at a moisture condition of 80 to 90 per cent of the dry +weight. + + + + + SECTION VII + + WHAT SEASONING IS + + +Seasoning is ordinarily understood to mean drying. When exposed to the +sun and air, the water in green wood rapidly evaporates. The rate of +evaporation will depend on: (1) the kind of wood; (2) the shape and +thickness of the timber; and (3) the conditions under which the wood +is placed or piled. + +Pieces of wood completely surrounded by air, exposed to the wind and +the sun, and protected by a roof from rain and snow, will dry out very +rapidly, while wood piled or packed close together so as to exclude +the air, or left in the shade and exposed to rain and snow, will dry +out very slowly and will also be subject to mould and decay. + +But seasoning implies other changes besides the evaporation of water. +Although we have as yet only a vague conception as to the exact nature +of the difference between seasoned and unseasoned wood, it is very +probable that one of these consists in changes in the albuminous +substances in the wood fibres, and possibly also in the tannins, +resins, and other incrusting substances. Whether the change in these +substances is merely a drying-out, or whether it consists in a partial +decomposition is at yet undetermined. That the change during the +seasoning process is a profound one there can be no doubt, because +experience has shown again and again that seasoned wood fibre is very +much more permeable, both for liquids and gases than the living, +unseasoned fibre. + +One can picture the albuminous substances as forming a coating which +dries out and possibly disintegrates when the wood dries. The +drying-out may result in considerable shrinkage, which may make the +wood fibre more porous. It is also possible that there are oxidizing +influences at work within these substances which result in their +disintegration. Whatever the exact nature of the change may be, one +can say without hesitation that exposure to the wind and air brings +about changes in the wood, which are of such a nature that the wood +becomes drier and more permeable. + +When seasoned by exposure to live steam, similiar changes may take +place; the water leaves the wood in the form of steam, while the +organic compounds in the walls probably coagulate or disintegrate +under the high temperature. + +The most effective seasoning is without doubt that obtained by the +uniform, slow drying which takes place in properly constructed piles +outdoors, under exposure to the winds and the sun and under cover from +the rain and snow, and is what has been termed "air-seasoning." By +air-seasoning oak and similiar hardwoods, nature performs certain +functions that cannot be duplicated by any artificial means. Because +of this, woods of this class cannot be successfully kiln-dried green +from the saw. + +In drying wood, the free water within the cells passes through the +cell walls until the cells are empty, while the cell walls remain +saturated. When all the free water has been removed, the cell walls +begin to yield up their moisture. Heat raises the absorptive power of +the fibres and so aids the passage of water from the interior of the +cells. A confusion in the word "sap" is to be found in many +discussions of kiln-drying; in some instances it means water, in other +cases it is applied to the organic substances held in a water solution +in the cell cavities. The term is best confined to the organic +substances from the living cell. These substances, for the most part +of the nature of sugar, have a strong attraction for water and water +vapor, and so retard drying and absorb moisture into dried wood. High +temperatures, especially those produced by live steam, appear to +destroy these organic compounds and therefore both to retard and to +limit the reabsorption of moisture when the wood is subsequently +exposed to the atmosphere. + +Air-dried wood, under ordinary atmospheric temperatures, retains from +10 to 20 per cent of moisture, whereas kiln-dried wood may have no +more than 5 per cent as it comes from the kiln. The exact figures for +a given species depend in the first case upon the weather conditions, +and in the second case upon the temperature in the kiln and the time +during which the wood is exposed to it. When wood that has been +kiln-dried is allowed to stand in the open, it apparently ceases to +reabsorb moisture from the air before its moisture content equals that +of wood which has merely been air-dried in the same place, and under +the same conditions, in other words kiln-dried wood will not absorb as +much moisture as air-dried wood under the same conditions. + + + Difference between Seasoned and Unseasoned Wood + +Although it has been known for a long time that there is a marked +difference in the length of life of seasoned and of unseasoned wood, +the consumers of wood have shown very little interest in its +seasoning, except for the purpose of doing away with the evils which +result from checking, warping, and shrinking. For this purpose both +kiln-drying and air-seasoning are largely in use. + +The drying of material is a subject which is extremely important to +most industries, and in no industry is it of more importance than in +the lumber trade. Timber drying means not only the extracting of so +much water, but goes very deeply into the quality of the wood, its +workability and its cell strength, etc. + +Kiln-drying, which dries the wood at a uniformly rapid rate by +artificially heating it in inclosed rooms, has become a part of almost +every woodworking industry, as without it the construction of the +finished product would often be impossible. Nevertheless much +unseasoned or imperfectly seasoned wood is used, as is evidenced by +the frequent shrinkage and warping of the finished articles. This is +explained to a certain extent by the fact that the manufacturer is +often so hard pressed for his product that he is forced to send out an +inferior article, which the consumer is willing to accept in that +condition rather than to wait several weeks or months for an article +made up of thoroughly seasoned material, and also that dry kilns are +at present constructed and operated largely without thoroughgoing +system. + +Forms of kilns and mode of operation have commonly been copied by one +woodworking plant after the example of some neighboring establishment. +In this way it has been brought about that the present practices have +many shortcomings. The most progressive operators, however, have +experimented freely in the effort to secure special results desirable +for their peculiar products. Despite the diversity of practice, it is +possible to find among the larger and more enterprising operators a +measure of agreement, as to both methods and results, and from this to +outline the essentials of a correct theory. As a result, properly +seasoned wood commands a high price, and in some cases cannot be +obtained at all. + +Wood seasoned out of doors, which by many is supposed to be much +superior to kiln-dried material, is becoming very scarce, as the +demand for any kind of wood is so great that it is thought not to pay +to hold it for the time necessary to season it properly. How long this +state of affairs is going to last it is difficult to say, but it is +believed that a reaction will come when the consumer learns that in +the long run it does not pay to use poorly seasoned material. Such a +condition has now arisen in connection with another phase of the +seasoning of wood; it is a commonly accepted fact that dry wood will +not decay nearly so fast as wet or green wood; nevertheless, the +immense superiority of seasoned over unseasoned wood for all purposes +where resistance to decay is necessary has not been sufficiently +recognized. In the times when wood of all kinds was both plentiful and +cheap, it mattered little in most cases how long it lasted or resisted +decay. Wood used for furniture, flooring, car construction, cooperage, +etc., usually got some chance to dry out before or after it was placed +in use. The wood which was exposed to decaying influences was +generally selected from those woods which, whatever their other +qualities might be, would resist decay longest. + +To-day conditions have changed, so that wood can no longer be used to +the same extent as in former years. Inferior woods with less lasting +qualities have been pressed into service. Although haphazard methods +of cutting and subsequent use are still much in vogue, there are many +signs that both lumbermen and consumers are awakening to the fact that +such carelessness and wasteful methods of handling wood will no longer +do, and must give way to more exact and economical methods. The reason +why many manufacturers and consumers of wood are still using the older +methods is perhaps because of long custom, and because they have not +yet learned that, though the saving to be obtained by the application +of good methods has at all times been appreciable, now, when wood is +more valuable, a much greater saving is possible. The increased cost +of applying economical methods is really very slight, and is many +times exceeded by the value of the increased service which can be +secured through its use. + + + Manner of Evaporation of Water + +The evaporation of water from wood takes place largely through the +ends, _i.e._, in the direction of the longitudinal axis of the wood +fibres. The evaporation from the other surfaces takes place very +slowly out of doors, and with greater rapidity in a dry kiln. The rate +of evaporation differs both with the kind of timber and its shape; +that is, thin material will dry more rapidly than heavier stock. +Sapwood dries faster than heartwood, and pine more rapidly than oak or +other hardwoods. + +Tests made show little difference in the rate of evaporation in sawn +and hewn stock, the results, however, not being conclusive. Air-drying +out of doors takes from two months to a year, the time depending on +the kind of timber, its thickness, and the climatic conditions. After +wood has reached an air-dry condition it absorbs water in small +quantities after a rain or during damp weather, much of which is +immediately lost again when a few warm, dry days follow. In this way +wood exposed to the weather will continue to absorb water and lose it +for indefinite periods. + +When soaked in water, seasoned woods absorb water rapidly. This at +first enters into the wood through the cell walls; when these are +soaked, the water will fill the cell lumen, so that if constantly +submerged the wood may become completely filled with water. + +The following figures show the gain in weight by absorption of several +coniferous woods, air-dry at the start, expressed in per cent of the +kiln-dry weight: + + ABSORPTION OF WATER BY DRY WOOD +--------------------------------------------------------------- + | White Pine | Red Cedar | Hemlock | Tamarack +--------------------------------------------------------------- +Air-dried | 108 | 109 | 111 | 108 +Kiln-dried | 100 | 100 | 100 | 100 +In water 1 day | 135 | 120 | 133 | 129 +In water 2 days | 147 | 126 | 144 | 136 +In water 3 days | 154 | 132 | 149 | 142 +In water 4 days | 162 | 137 | 154 | 147 +In water 5 days | 165 | 140 | 158 | 150 +In water 7 days | 176 | 143 | 164 | 156 +In water 9 days | 179 | 147 | 168 | 157 +In water 11 days | 184 | 149 | 173 | 159 +In water 14 days | 187 | 150 | 176 | 159 +In water 17 days | 192 | 152 | 176 | 161 +In water 25 days | 198 | 155 | 180 | 161 +In water 30 days | 207 | 158 | 183 | 166 +--------------------------------------------------------------- + + + Rapidity of Evaporation + +The rapidity with which water is evaporated, that is, the rate of +drying, depends on the size and shape of the piece and on the +structure of the wood. An inch board dries more than four times as +fast as a four-inch plank, and more than twenty times as fast as a +ten-inch timber. White pine dries faster than oak. A very moist piece +of pine or oak will, during one hour, lose more than four times as +much water per square inch from the cross-section, but only one half +as much from the tangential as from the radial section. In a long +timber, where the ends or cross-sections form but a small part of the +drying surface, this difference is not so evident. Nevertheless, the +ends dry and shrink first, and being opposed in this shrinkage by the +more moist adjoining parts, they check, the cracks largely +disappearing as seasoning progresses. + +High temperatures are very effective in evaporating the water from +wood, no matter how humid the air, and a fresh piece of sapwood may +lose weight in boiling water, and can be dried to quite an extent in +hot steam. + +In drying chemicals or fabrics, all that is required is to provide +heat enough to vaporize the moisture and circulation enough to carry +off the vapor thus secured, and the quickest and most economical means +to these ends may be used. While on the other hand, in drying wood, +whether in the form of standard stock or the finished product, the +application of the requisite heat and circulation must be carefully +regulated throughout the entire process, or warping and checking are +almost certain to result. Moreover, wood of different shapes and +thicknesses is very differently effected by the same treatment. +Finally, the tissues composing the wood, which vary in form and +physical properties, and which cross each other in regular directions, +exert their own peculiar influences upon its behavior during drying. +With our native woods, for instance, summer-wood and spring-wood show +distinct tendencies in drying, and the same is true in a less degree +of heartwood, as contrasted with sapwood. Or, again, pronounced +medullary rays further complicate the drying problem. + + + Physical Properties that influence Drying + +The principal properties which render the drying of wood peculiarly +difficult are: (1) The irregular shrinkage; (2) the different ways in +which water is contained; (3) the manner in which moisture transfuses +through the wood from the center to the surface; (4) the plasticity of +the wood substance while moist and hot; (5) the changes which take +place in the hygroscopic and chemical nature of the surface; and (6) +the difference produced in the total shrinkage by different rates of +drying. + +The shrinkage is unequal in different directions and in different +portions of the same piece. It is greatest in the circumferential +direction of the tree, being generally twice as great in this +direction as in the radial direction. In the longitudinal direction, +for most woods, it is almost negligible, being from 20 to over 100 +times as great circumferentially as longitudinally. + +There is a great variation in different species in this respect. +Consequently, it follows from necessity that large internal strains +are set up when the wood shrinks, and were it not for its plasticity +it would rupture. There is an enormous difference in the total amount +of shrinkage of different species of wood, varying from a shrinkage of +only 7 per cent in volume, based on the green dimensions, in the case +of some of the cedars to nearly 50 per cent in the case of some +species of eucalyptus. + +When the free water in the capillary spaces of the wood fibre is +evaporated it follows the laws of evaporation from capillary spaces, +except that the passages are not all free passages, and much of the +water has to pass out by a process of transfusion through the moist +cell walls. These cell walls in the green wood completely surround the +cell cavities so that there are no openings large enough to offer a +passage to water or air. + +The well-known "pits" in the cell walls extend through the secondary +thickening only, and not through the primary walls. This statement +applies to the tracheids and parenchyma cells in the conifer +(gymnosperms), and to the tracheids, parenchyma cells, and the wood +fibres in the broad-leaved trees (angiosperms); the vessels in the +latter, however, form open passages except when clogged by ingrowth +called tyloses, and the resin canals in the former sometimes form +occasional openings. + +By heating the wood above the boiling point, corresponding to the +external pressure, the free water passes through the cell walls more +readily. + +To remove the moisture from the wood substance requires heat in +addition to the latent heat of evaporation, because the molecules of +moisture are so intimately associated with the molecules, minute +particles composing the wood, that energy is required to separate them +therefrom. + +Carefully conducted experiments show this to be from 16.6 to 19.6 +calories per grain of dry wood in the case of beech, long-leaf pine, +and sugar maple. + +The difficulty imposed in drying, however, is not so much the +additional heat required as it is in the rate at which the water +transfuses through the solid wood. + + + + + SECTION VIII + + ADVANTAGES IN SEASONING + + +Three most important advantages of seasoning have already been made +apparent: + + 1. Seasoned timber lasts much longer than unseasoned. Since + the decay of timber is due to the attacks of wood-destroying + fungi, and since the most important condition of the growth + of these fungi is water, anything which lessens the amount + of water in wood aids in its preservation. + + 2. In the case of treated timber, seasoning before treatment + greatly increases the effectiveness of the ordinary methods + of treatment, and seasoning after treatment prevents the + rapid leaching out of the salts introduced to preserve the + timber. + + 3. The saving in freight where timber is shipped from one + place to another. Few persons realize how much water green + wood contains, or how much it will lose in a comparatively + short time. Experiments along this line with lodge-pole + pine, white oak, and chestnut gave results which were a + surprise to the companies owning the timber. + +Freight charges vary considerably in different parts of the country; +but a decrease of 35 to 40 per cent in weight is important enough to +deserve everywhere serious consideration from those in charge of +timber operations. + +When timber is shipped long distances over several roads, as is coming +to be more and more the case, the saving in freight will make a +material difference in the cost of lumber operations, irrespective of +any other advantages of seasoning. + + + Prevention of Checking and Splitting + +Under present methods much timber is rendered unfit for use by +improper seasoning. Green timber, particularly when cut during +January, February, and March, when the roots are most active, contains +a large amount of water. When exposed to the sun and wind or to high +temperatures in a drying room, the water will evaporate more rapidly +from the outer than from the inner parts of the piece, and more +rapidly from the ends than from the sides. As the water evaporates, +the wood shrinks, and when the shrinkage is not fairly uniform the +wood cracks and splits. + +When wet wood is piled in the sun, evaporation goes on with such +unevenness that the timbers split and crack in some cases so badly as +to become useless for the purpose for which it was intended. Such +uneven drying can be prevented by careful piling, keeping the logs +immersed in a log pond until wanted, or by piling or storing under an +open shed so that the sun cannot get at them. + +Experiments have also demonstrated that injury to stock in the way of +checking and splitting always develops immediately after the stock is +taken into the dry kiln, and is due to the degree of humidity being +too low. + +The receiving end of the kiln should always be kept moist, where the +stock has not been steamed before being put into the kiln, as when the +air is too dry it tends to dry the outside of the stock first--which +is termed "case-hardening"--and in so doing shrinks and closes up the +pores. As the material is moved down the kiln (as in the case of +"progressive kilns"), it absorbs a continually increasing amount of +heat, which tends to drive off the moisture still present in the +center of the piece, the pores on the outside having been closed up, +there is no exit for the vapor or steam that is being rapidly formed +in the center of the piece. It must find its way out in some manner, +and in doing so sets up strains, which result either in checking or +splitting. If the humidity had been kept higher, the outside of the +piece would not have dried so quickly, and the pores would have +remained open for the exit of the moisture from the interior of the +piece, and this trouble would have been avoided. (See also article +following.) + + + Shrinkage of Wood + +Since in all our woods, cells with thick walls and cells with thin +walls are more or less intermixed, and especially as the spring-wood +and summer-wood nearly always differ from each other in this respect, +strains and tendencies to warp are always active when wood dries out, +because the summer-wood shrinks more than the spring-wood, and heavier +wood in general shrinks more than light wood of the same kind. + +If a thin piece of wood after drying is placed upon a moist surface, +the cells on the under side of the piece take up moisture and swell +before the upper cells receive any moisture. This causes the under +side of the piece to become longer than the upper side, and as a +consequence warping occurs. Soon, however, the moisture penetrates to +all the cells and the piece straightens out. But while a thin board of +pine curves laterally it remains quite straight lengthwise, since in +this direction both shrinkage and swelling are small. If one side of a +green board is exposed to the sun, warping is produced by the removal +of water and consequent shrinkage of the side exposed; this may be +eliminated by the frequent turning of the topmost pieces of the piles +in order that they may be dried evenly. + +As already stated, wood loses water faster from the ends than from the +longitudinal faces. Hence the ends shrink at a different rate from the +interior parts. The faster the drying at the surface, the greater is +the difference in the moisture of the different parts, and hence the +greater the strains and consequently also the greater amount of +checking. This becomes very evident when freshly cut wood is placed in +the sun, and still more when put into a hot, dry kiln. While most of +these smaller checks are only temporary, closing up again, some large +radial checks remain and even grow larger as drying progresses. Their +cause is a different one and will presently be explained. The +temporary checks not only appear at the ends, but are developed on +the sides also, only to a much smaller degree. They become especially +annoying on the surface of thick planks of hardwoods, and also on +peeled logs when exposed to the sun. + +So far we have considered the wood as if made up only of parallel +fibres all placed longitudinally in the log. This, however, is not the +case. A large part of the wood is formed by the medullary or pith +rays. In pine over 15,000 of these occur on a square inch of a +tangential section, and even in oak the very large rays, which are +readily visible to the eye, represent scarcely a hundredth part of the +number which a microscope reveals, as the cells of these rays have +their length at right angles to the direction of the wood fibres. + +If a large pith ray of white oak is whittled out and allowed to dry, +it is found to shrink greatly in its width, while, as we have stated, +the fibres to which the ray is firmly grown in the wood do not shrink +in the same direction. Therefore, in the wood, as the cells of the +pith ray dry they pull on the longitudinal fibres and try to shorten +them, and, being opposed by the rigidity of the fibres, the pith ray +is greatly strained. But this is not the only strain it has to bear. +Since the fibres shrink as much again as the pith ray, in this its +longitudinal direction, the fibres tend to shorten the ray, and the +latter in opposing this prevents the former from shrinking as much as +they otherwise would. + +Thus the structure is subjected to two severe strains at right angles +to each other, and herein lies the greatest difficulty of wood +seasoning, for whenever the wood dries rapidly these fibres have not +the chance to "give" or accommodate themselves, and hence fibres and +pith rays separate and checking results, which, whether visible or +not, are detrimental in the use of the wood. + +The contraction of the pith rays parallel to the length of the board +is probably one of the causes of the small amount of longitudinal +shrinkage which has been observed in boards. This smaller shrinkage of +the pith rays along the radius of the log (the length of the pith +ray), opposing the shrinkage of the fibres in this direction, becomes +one of the causes of the second great trouble in wood seasoning, +namely, the difference in the shrinkage along the radius and that +along the rings or tangent. This greater tangential shrinkage appears +to be due in part to the causes just mentioned, but also to the fact +that the greatly shrinking bands of summer-wood are interrupted along +the radius by as many bands of porous spring-wood, while they are +continuous in the tangential direction. In this direction, therefore, +each such band tends to shrink, as if the entire piece were composed +of summer-wood, and since the summer-wood represents the greater part +of the wood substance, this greater tendency to tangential shrinkage +prevails. + +The effect of this greater tangential shrinkage effects every phase of +woodworking. It leads to permanent checks and causes the log or piece +to split open on drying. Sawed in two, the flat sides of the log +become convex; sawed into timber, it checks along the median line of +the four faces, and if converted into boards, the latter checks +considerably from the end through the center, all owing to the greater +tangential shrinkage of the wood. + +Briefly, then, shrinkage of wood is due to the fact that the cell +walls grow thinner on drying. The thicker cell walls and therefore the +heavier wood shrinks most, while the water in the cell cavities does +not influence the volume of the wood. + +Owing to the great difference of cells in shape, size, and thickness +of walls, and still more in their arrangement, shrinkage is not +uniform in any kind of wood. This irregularity produces strains, which +grow with the difference between adjoining cells and are greatest at +the pith rays. These strains cause warping and checking, but exist +even where no outward signs are visible. They are greater if the wood +is dried rapidly than if dried slowly, but can never be entirely +avoided. + +Temporary checks are caused by the more rapid drying of the outer +parts of any stick; permanent checks are due to the greater shrinkage, +tangentially, along the rings than along the radius. This, too, is the +cause of most of the ordinary phenomena of shrinkage, such as the +difference in behavior of the entire and quartered logs, "bastard" +(tangent) and rift (radial) boards, etc., and explains many of the +phenomena erroneously attributed to the influence of bark, or of the +greater shrinkage of outer and inner parts of any log. + +Once dry, wood may be swelled again to its original size by soaking in +water, boiling, or steaming. Soaked pieces on drying shrink again as +before; boiled and steamed pieces do the same, but to a slightly less +degree. Neither hygroscopicity, _i.e._, the capacity of taking up +water, nor shrinkage of wood can be overcome by drying at temperatures +below 200 degrees Fahrenheit. Higher temperatures, however, reduce +these qualities, but nothing short of a coaling heat robs wood of the +capacity to shrink and swell. + +Rapidly dried in a kiln, the wood of oak and other hardwoods +"case-harden," that is, the outer part dries and shrinks before the +interior has a chance to do the same, and thus forms a firm shell or +case of shrunken, commonly checked wood around the interior. This +shell does not prevent the interior from drying, but when this drying +occurs the interior is commonly checked along the medullary rays, +commonly called "honeycombing" or "hollow-horning." In practice this +occurrence can be prevented by steaming or sweating the wood in the +kiln, and still better by drying the wood in the open air or in a shed +before placing in the kiln. Since only the first shrinkage is apt to +check the wood, any kind of lumber which has once been air-dried +(three to six months for one-inch stuff) may be subjected to kiln heat +without any danger from this source. + +Kept in a bent or warped condition during the first shrinkage, the +wood retains the shape to which it has been bent and firmly opposes +any attempt at subsequent straightening. + +Sapwood, as a rule, shrinks more than heartwood of the same weight, +but very heavy heartwood may shrink more than lighter sapwood. The +amount of water in wood is no criterion of its shrinkage, since in wet +wood most of the water is held in the cavities, where it has no effect +on the volume. + +The wood of pine, spruce, cypress, etc., with its very regular +structure, dries and shrinks evenly, and suffers much less in +seasoning than the wood of broad-leaved (hardwood) trees. Among the +latter, oak is the most difficult to dry without injury. + +Desiccating the air with certain chemicals will cause the wood to dry, +but wood thus dried at 80 degrees Fahrenheit will still lose water in +the kiln. Wood dried at 120 degrees Fahrenheit loses water still if +dried at 200 degrees Fahrenheit, and this again will lose more water +if the temperature be raised, so that _absolutely dry wood_ cannot be +obtained, and chemical destruction sets in before all the water is +driven off. + +On removal from the kiln, the dry wood at once takes up moisture from +the air, even in the driest weather. At first the absorption is quite +rapid; at the end of a week a short piece of pine, 1-1/2 inches thick, +has regained two thirds of, and, in a few months, all the moisture +which it had when air-dry, 8 to 10 per cent, and also its former +dimensions. In thin boards all parts soon attain the same degree of +dryness. In heavy timbers the interior remains more moist for many +months, and even years, than the exterior parts. Finally an +equilibrium is reached, and then only the outer parts change with the +weather. + +With kiln-dried woods all parts are equally dry, and when exposed, the +moisture coming from the air must pass through the outer parts, and +thus the order is reversed. Ordinary timber requires months before it +is at its best. Kiln-dried timber, if properly handled, is prime at +once. + +Dry wood if soaked in water soon regains its original volume, and in +the heartwood portion it may even surpass it; that is to say, swell to +a larger dimension than it had when green. With the soaking it +continues to increase in weight, the cell cavities filling with water, +and if left many months all pieces sink. Yet after a year's immersion +a piece of oak 2 by 2 inches and only 6 inches long still contains +air; _i.e._, it has not taken up all the water it can. By rafting or +prolonged immersion, wood loses some of its weight, soluble materials +being leached out, but it is not impaired either as fuel or as +building material. Immersion, and still more boiling and steaming, +reduce the hygroscopicity of wood and therefore also the troublesome +"working," or shrinking and swelling. + +Exposure in dry air to a temperature of 300 degrees Fahrenheit for a +short time reduces but does not destroy the hygroscopicity, and with +it the tendency to shrink and swell. A piece of red oak which has been +subjected to a temperature of over 300 degrees Fahrenheit still swells +in hot water and shrinks in a dry kiln. + + + Expansion of Wood + +It must not be forgotten that timber, in common with every other +material, expands as well as contracts. If we extract the moisture +from a piece of wood and so cause it to shrink, it may be swelled to +its original volume by soaking it in water, but owing to the +protection given to most timber in dwelling-houses it is not much +affected by wet or damp weather. The shrinkage is more apparent, more +lasting, and of more consequence to the architect, builder, or owner +than the slight expansion which takes place, as, although the amount +of moisture contained in wood varies with the climate conditions, the +consequence of dampness or moisture on good timber used in houses only +makes itself apparent by the occasional jamming of a door or window in +wet or damp weather. + +Considerable expansion, however, takes place in the wood-paving of +streets, and when this form of paving was in its infancy much trouble +occurred owing to all allowances not having been made for this +contingency, the trouble being doubtless increased owing to the blocks +not being properly seasoned; curbing was lifted or pushed out of line +and gully grids were broken by this action. As a rule in street paving +a space of one or two inches wide is now left next to the curb, which +is filled with sand or some soft material, so that the blocks may +expand longitudinally without injuring the contour or affecting the +curbs. But even with this arrangement it is not at all unusual for an +inch or more to have to be cut off paving blocks parallel to the +channels some time after the paving has been laid, owing to the +expansion of the wood exceeding the amounts allowed. + +Considerable variation occurs in the expansion of wood blocks, and it +is noticeable in the hardwoods as well as in the softwoods, and is +often greater in the former than in the latter. + +Expansion takes place in the direction of the length of the blocks as +they are laid across the street, and causes no trouble in the other +direction, the reason being that the lengthway of a block of wood is +across the grain, of the timber, and it expands or contracts as a +plank does. On one occasion, in a roadway forty feet wide, expansion +occurred until it amounted to four inches on each side, or eight +inches in all. This continual expansion and contraction is doubtless +the cause of a considerable amount of wood street-paving bulging and +becoming filled with ridges and depressions. + + + Elimination of Stain and Mildew + +A great many manufacturers, and particularly those located in the +Southern States, experience a great amount of difficulty in their +timber becoming stained and mildewed. This is particularly true with +gum wood, as it will frequently stain and mould in twenty-four hours, +and they have experienced so much of this trouble that they have, in a +great many instances, discontinued cutting it during the summer +season. + +If this matter were given proper attention they should be able to +eliminate a great deal of this difficulty, as no doubt they will find +after investigation that the mould has been caused by the stock being +improperly piled to the weather. + +Freshly sawn wood, placed in close piles during warm, damp weather in +the months of July and August, presents especially favorable +conditions for mould and stain. In all cases it is the moist condition +and retarded drying of the wood which causes this. Therefore, any +method which will provide for the rapid drying of the wood before or +after piling will tend to prevent the difficulty, and the best method +for eliminating mould is (1) to provide for as little delay as +possible between the felling of the tree, and its manufacture into +rough products before the sap has had an opportunity of becoming sour. +This is especially necessary with trees felled from April to +September, in the region north of the Gulf States, and from March to +November in the latter, while the late fall and winter cutting should +all be worked up by March or April. (2) The material should be piled +to the weather immediately after being sawn or cut, and every +precaution should be taken in piling to facilitate rapid drying, by +keeping the piles or ricks up off the ground. (3) All weeds (and +emphasis should be placed on the ALL) and other vegetation should be +kept well clear of the piles, in order that the air may have a clear +and unobstructed passage through and around the piles, and (4) the +piles should be so constructed that each stick or piece will have as +much air space about it as it is possible to give to it. + +If the above instructions are properly carried out, there will be +little or no difficulty experienced with mould appearing on the +lumber. + + + + + SECTION IX + + DIFFICULTIES OF DRYING WOOD + + +Seasoning and kiln-drying is so important a process in the manufacture +of woods that a need is keenly felt for fuller information regarding +it, based upon scientific study of the behavior of various species at +different mechanical temperatures and under different mechanical +drying processes. The special precautions necessary to prevent loss of +strength or distortion of shape render the drying of wood especially +difficult. + +All wood when undergoing a seasoning process, either natural (by air) +or mechanical (by steam or heat in a dry kiln), checks or splits more +or less. This is due to the uneven drying-out of the wood and the +consequent strains exerted in opposite directions by the wood fibres +in shrinking. This shrinkage, it has been proven, takes place both +end-wise and across the grain of the wood. The old tradition that wood +does not shrink end-wise has long since been shattered, and it has +long been demonstrated that there is an end-wise shrinkage. + +In some woods it is very light, while in others it is easily +perceptible. It is claimed that the average end shrinkage, taking all +the woods, is only about 1-1/2 per cent. This, however, probably has +relation to the average shrinkage on ordinary lumber as it is used and +cut and dried. Now if we depart from this and take veneer, or basket +stock, or even stave bolts where they are boiled, causing swelling +both end-wise and across the grain or in dimension, after they are +thoroughly dried, there is considerably more evidence of end +shrinkage. In other words, a slack barrel stave of elm, say, 28 or 30 +inches in length, after being boiled might shrink as much in +thoroughly drying-out as compared to its length when freshly cut, as a +12-foot elm board. + +It is in cutting veneer that this end shrinkage becomes most readily +apparent. In trimming with scoring knives it is done to exact measure, +and where stock is cut to fit some specific place there has been +observed a shrinkage on some of the softer woods, like cottonwood, +amounting to fully 1/8 of an inch in 36 inches. And at times where +drying has been thorough the writer has noted a shrinkage of 1/8 of an +inch on an ordinary elm cabbage-crate strip 36 inches long, sawed from +the log without boiling. + +There are really no fixed rules of measurement or allowance, however, +because the same piece of wood may vary under different conditions, +and, again, the grain may cross a little or wind around the tree, and +this of itself has a decided effect on the amount of what is termed +"end shrinkage." + +There is more checking in the wood of the broad-leaf (hardwood) trees +than in that of the coniferous (softwood) trees, more in sapwood than +in heartwood, and more in summer-wood than in spring-wood. + +Inasmuch as under normal conditions of weather, water evaporates less +rapidly during the early seasoning of winter, wood that is cut in the +autumn and early winter is considered less subject to checking than +that which is cut in spring and summer. + +Rapid seasoning, except after wood has been thoroughly soaked or +steamed, almost invariably results in more or less serious checking. +All hardwoods which check or warp badly during the seasoning should be +reduced to the smallest practicable size before drying to avoid the +injuries involved in this process, and wood once seasoned _should +never again be exposed to the weather_, since all injuries due to +seasoning are thereby aggravated. + +Seasoning increases the strength of wood in every respect, and it is +therefore of great importance to protect the wood against moisture. + + + Changes rendering Drying difficult + +An important property rendering drying of wood peculiarly difficult is +the changes which occur in the hygroscopic properties of the surface +of a stick, and the rate at which it will allow moisture to pass +through it. If wood is dried rapidly the surface soon reaches a +condition where the transfusion is greatly hindered and sometimes +appears almost to cease. The nature of this action is not well +understood and it differs greatly in different species. Bald cypress +(_Taxodium distichum_) is an example in which this property is +particularly troublesome. The difficulty can be overcome by regulating +the humidity during the drying operation. It is one of the factors +entering into production of what is called "case-hardening" of wood, +where the surface of the piece becomes hardened in a stretched or +expanded condition, and subsequent shrinkage of the interior causes +"honeycombing," "hollow-horning," or internal checking. The outer +surface of the wood appears to undergo a chemical change in the nature +of hydrolization or oxidization, which alters the rate of absorption +and evaporation in the air. + +As the total amount of shrinkage varies with the rate at which the +wood is dried, it follows that the outer surface of a rapidly dried +board shrinks less than the interior. This sets up an internal stress, +which, if the board be afterward resawed into two thinner boards by +slicing it through the middle, causes the two halves to cup with their +convex surfaces outward. This effect may occur even though the +moisture distribution in the board has reached a uniform condition, +and the board is thoroughly dry before it is resawed. It is distinct +from the well-known "case-hardening" effect spoken of above, which is +caused by unequal moisture conditions. + +The manner in which the water passes from the interior of a piece of +wood to its surface has not as yet been fully determined, although it +is one of the most important factors which influence drying. This must +involve a transfusion of moisture through the cell walls, since, as +already mentioned, except for the open vessels in the hardwoods, free +resin ducts in the softwoods, and possibly the intercellular spaces, +the cells of green wood are enclosed by membranes and the water must +pass through the walls or the membranes of the pits. Heat appears to +increase this transfusion, but experimental data are lacking. + +It is evident that to dry wood properly a great many factors must be +taken into consideration aside from the mere evaporation of moisture. + + + Losses Due to Improper Kiln-drying + +In some cases there is practically no loss in drying, but more often +it ranges from 1 to 3 per cent, and 7 to 10 per cent in refractory +woods such as gum. In exceptional instances the losses are as high as +33 per cent. + +In air-drying there is little or no control over the process; it may +take place too rapidly on some days and too slowly on others, and it +may be very non-uniform. + +Hardwoods in large sizes almost invariably check. + +By proper kiln-drying these unfavorable circumstances may be +eliminated. However, air-drying is unquestionably to be preferred to +bad kiln-drying, and when there is any doubt in the case it is +generally safer to trust to air-drying. + +If the fundamental principles are all taken care of, green lumber can +be better dried in the dry kiln. + + + Properties of Wood that affect Drying + +It is clear, from the previous discussion of the structure of wood, +that this property is of first importance among those influencing the +seasoning of wood. The free water way usually be extracted quite +readily from porous hardwoods. The presence of tyloses in white oak +makes even this a difficult problem. On the other hand, its more +complex structure usually renders the hygroscopic moisture quite +difficult to extract. + +The lack of an open, porous structure renders the transfusion of +moisture through some woods very slow, while the reverse may be true +of other species. The point of interest is that all the different +variations in structure affect the drying rates of woods. The +structure of the gums suggests relatively easy seasoning. + +Shrinkage is a very important factor affecting the drying of woods. +Generally speaking, the greater the shrinkage the more difficult it is +to dry wood. Wood shrinks about twice as much tangentially as +radially, thus introducing very serious stresses which may cause loss +in woods whose total shrinkage is large. It has been found that the +amount of shrinkage depends, to some extent, on the rate and +temperature at which woods season. Rapid drying at high or low +temperature results in slight shrinkage, while slow drying, especially +at high temperature, increases the shrinkage. + +As some woods must be dried in one way and others in other ways, to +obtain the best general results, this effect may be for the best in +one case and the reverse in others. As an example one might cite the +case of Southern white oak. This species must be dried very slowly at +low temperatures in order to avoid the many evils to which it is heir. +It is interesting to note that this method tends to increase the +shrinkage, so that one might logically expect such treatment merely to +aggravate the evils. Such is not the case, however, as too fast drying +results in other defects much worse than that of excessive shrinkage. + +Thus we see that the shrinkage of any given species of wood depends to +a great extent on the method of drying. Just how much the shrinkage of +gum is affected by the temperature and drying rate is not known at +present. There is no doubt that the method of seasoning affects the +shrinkage of the gums, however. It is just possible that these woods +may shrink longitudinally more than is normal, thus furnishing another +cause for their peculiar action under certain circumstances. It has +been found that the properties of wood which affect the seasoning of +the gums are, in the order of their importance: (1) The indeterminate +and erratic grain; (2) the uneven shrinkage with the resultant +opposing stresses; (3) the plasticity under high temperature while +moist; and (4) the slight apparent lack of cohesion between the +fibres. The first, second, and fourth properties are clearly +detrimental, while the third may possibly be an advantage in reducing +checking and "case-hardening." + +The grain of the wood is a prominent factor also affecting the +problem. It is this factor, coupled with uneven shrinkage, which is +probably responsible, to a large extent, for the action of the gums in +drying. The grain may be said to be more or less indeterminate. It is +usually spiral, and the spiral may reverse from year to year of the +tree's growth. When a board in which this condition exists begins to +shrink, the result is the development of opposing stresses, the effect +of which is sometimes disastrous. The shrinkage around the knots seems +to be particularly uneven, so that checking at the knots is quite +common. + +Some woods, such as Western red cedar, redwood, and eucalyptus, become +very plastic when hot and moist. The result of drying-out the free +water at high temperature may be to collapse the cells. The gums are +known to be quite soft and plastic, if they are moist, at high +temperature, but they do not collapse so far as we have been able to +determine. + +The cells of certain species of wood appear to lack cohesion, +especially at the junction between the annual rings. As a result, +checks and ring shakes are very common in Western larch and hemlock. +The parenchyma cells of the medullary rays in oak do not cohere +strongly and often check open, especially when steamed too severely. + + + Unsolved Problems in Kiln-drying + + 1. Physical data of the properties of wood in relation to + heat are meagre. + + 2. Figures on the specific heat of wood are not readily + available, though upon this rests not only the exact + operation of heating coils for kilns, but the theory of + kiln-drying as a whole. + + 3. Great divergence is shown in the results of experiments + in the conductivity of wood. It remains to be seen whether + the known variation of conductivity with moisture content + will reduce these results to uniformity. + + 4. The maximum or highest temperature to which the different + species of wood may be exposed without serious loss of + strength has not yet been determined. + + 5. The optimum or absolute correct temperature for drying + the different species of wood is as yet entirely unsettled. + + 6. The inter-relation between wood and water is as + imperfectly known to dry-kiln operators as that between wood + and heat. + + 7. What moisture conditions obtain in a stick of air-dried + wood? + + 8. How is the moisture distinguished? + + 9. What is its form? + + 10. What is the meaning of the peculiar surface conditions + which even in air-dried wood appear to indicate incipient + "case-hardening"? + + 11. The manner in which the water passes from the interior + of a piece of wood to its surface has not as yet been fully + determined. + +These questions can be answered thus far only by speculation or, at +best, on the basis of incomplete data. + +Until these problems are solved, kiln-drying must necessarily remain +without the guidance of complete scientific theory. + +A correct understanding of the principles of drying is rare, and +opinions in regard to the subject are very diverse. The same lack of +knowledge exists in regard to dry kilns. The physical properties of +the wood which complicate the drying operation and render it distinct +from that of merely evaporating free water from some substance like a +piece of cloth must be studied experimentally. It cannot well be +worked out theoretically. + + + + + SECTION X + + HOW WOOD IS SEASONED + + + Methods of Drying + +The choice of a method of drying depends largely upon the object in +view. The principal objects may be grouped under three main heads, as +follows: + + 1. To reduce shipping weight. + + 2. To reduce the quantity necessary to carry in stock. + + 3. To prepare the wood for its ultimate use and improve its + qualities. + +When wood will stand the temperature without excessive checking or +undue shrinkage or loss in strength, the first object is most readily +attained by heating the wood above the boiling point in a closed +chamber, with a large circulation of air or vapor, so arranged that +the excess steam produced will escape. This process manifestly does +not apply to many of the hardwoods, but is applicable to many of the +softwoods. It is used especially in the northwestern part of the +United States, where Douglas fir boards one inch thick are dried in +from 40 to 65 hours, and sometimes in as short a time as 24 hours. In +the latter case superheated steam at 300 degrees Fahrenheit was forced +into the chamber but, of course, the lumber could not be heated +thereby much above the boiling point so long as it contained any free +water. + +This lumber, however, contained but 34 per cent moisture to start +with, and the most rapid rate was 1.6 per cent loss per hour. + +The heat of evaporation may be supplied either by superheated steam or +by steam pipes within the kiln itself. + +The quantity of wood it is necessary to carry in stock is naturally +reduced when either of the other two objects is attained and, +therefore, need not necessarily be discussed. + +In drying to prepare for use and to improve quality, careful and +scientific drying is called for. This applies more particularly to the +hardwoods, although it may be required for softwoods also. + + + Drying at Atmospheric Pressure + +Present practice of kiln-drying varies tremendously and there is no +uniformity or standard method. + +Temperatures vary anywhere from 65 to 165 degrees Fahrenheit, or even +higher, and inch boards three to six months on the sticks are being +dried in from four days to three weeks, and three-inch material in +from two to five months. + +All methods in use at atmospheric pressure may be classified under the +following headings. The kilns may be either progressive or +compartment, and preliminary steaming may or may not be used with any +one of these methods: + + 1. Dry air heated. This is generally obsolete. + 2. Moist air. + _a._ Ventilated. + _b._ Forced draft. + _c._ Condensing. + _d._ Humidity regulated. + _e._ Boiling. + 3. Superheated steam. + + + Drying under Pressure and Vacuum + +Various methods of drying wood under pressures other than atmospheric +have been tried. Only a brief mention of this subject will be made. +Where the apparatus is available probably the quickest way to dry wood +is first to heat it in saturated steam at as high a temperature as the +species can endure without serious chemical change until the heat has +penetrated to the center, then follow this with a vacuum. + +By this means the self-contained specific heat of the wood and the +water is made available for the evaporation, and the drying takes +place from the inside outwardly, just the reverse of that which occurs +by drying by means of external heat. + +When the specimen has cooled this process is then to be repeated until +it has dried down to fibre-saturation point. It cannot be dried much +below this point by this method, since the absorption during the +heating operation will then equal the evaporation during the cooling. +It may be carried further, however, by heating in partially humidified +air, proportioning the relative humidity each time it is heated to the +degree of moisture present in the wood. + +The point to be considered in this operation is that during the +heating process no evaporation shall be allowed to take place, but +only during the cooling. In this way surface drying and +"case-hardening" are prevented since the heat is from within and the +moisture passes from the inside outwardly. However, with some species, +notably oak, surface cracks appear as a network of fine checks along +the medullary rays. + +In the first place, it should be borne in mind that it is the heat +which produces evaporation and not the air nor any mysterious property +assigned to a "vacuum." + +For every pound of water evaporated at ordinary temperatures +approximately 1,000 British thermal units of heat are used up, or +"become latent," as it is called. This is true whether the evaporation +takes place in a vacuum or under a moderate air pressure. If this heat +is not supplied from an outside source it must be supplied by the +water itself (or the material being dried), the temperature of which +will consequently fall until the surrounding space becomes saturated +with vapor at a pressure corresponding to the temperature which the +water has reached; evaporation will then cease. The pressure of the +vapor in a space saturated with water vapor increases rapidly with +increase of temperature. At a so-called vacuum of 28 inches, which is +about the limit in commercial operations, and in reality signifies an +actual pressure of 2 inches of mercury column, the space will be +saturated with vapor at 101 degrees Fahrenheit. Consequently, no +evaporation will take place in such a vacuum unless the water be +warmer than 101 degrees Fahrenheit, provided there is no air leakage. +The qualification in regard to air is necessary, for the sake of +exactness, for the following reason: In any given space the total +actual pressure is made up of the combined pressures of all the gases +present. If the total pressure ("vacuum") is 2 inches, and there is no +air present, it is all produced by the water vapor (which saturates +the space at 101 degrees Fahrenheit); but if some air is present and +the total pressure is still maintained at 2 inches, then there must be +less vapor present, since the air is producing part of the pressure +and the space is no longer saturated at the given temperature. +Consequently further evaporation may occur, with a corresponding +lowering of the temperature of the water, until a balance is again +reached. Without further explanation it is easy to see that but little +water can be evaporated by a vacuum alone without addition of heat, +and that the prevalent idea that a vacuum can of itself produce +evaporation is a fallacy. If heat be supplied to the water, however, +either by conduction or radiation, evaporation will take place in +direct proportion to the amount of heat supplied, so long as the +pressure is kept down by the vacuum pump. + +At 30 inches of mercury pressure (one atmosphere) the space becomes +saturated with vapor and equilibrium is established at 212 degrees +Fahrenheit. If heat be now supplied to the water, however, evaporation +will take place in proportion to the amount of heat supplied, so long +as the pressure remains that of one atmosphere, just as in the case of +the vacuum. Evaporation in this condition, where the vapor pressure at +the temperature of the water is equal to the gas pressure on the +water, is commonly called "boiling," and the saturated vapor entirely +displaces the air under continuous operation. Whenever the space is +not saturated with vapor, whether air is present or not, evaporation +will take place, by boiling if no air be present or by diffusion under +the presence of air, until an equilibrium between temperature and +vapor pressure is resumed. + +Relative humidity is simply the ratio of the actual vapor pressure +present in a given space to the vapor pressure when the space is +saturated with vapor at the given temperature. It matters not whether +air be present or not. One hundred per cent humidity means that the +space contains all the vapor which it can hold at the given +temperature--it is saturated. Thus at 100 per cent humidity and 212 +degrees Fahrenheit the space is saturated, and since the pressure of +saturated vapor at this temperature is one atmosphere, no air can be +present under these conditions. If, however, the total pressure at +this temperature were 20 pounds (5 pounds gauge), then it would mean +that there was 5 pounds air pressure present in addition to the vapor, +yet the space would still be saturated at the given temperature. +Again, if the temperature were 101 degrees Fahrenheit, the pressure of +saturated vapor would be only 1 pound, and the additional pressure of +14 pounds, if the total pressure were atmospheric, would be made up of +air. In order to have no air present and the space still saturated at +101 degrees Fahrenheit, the total pressure must be reduced to 1 pound +by a vacuum pump. Fifty per cent relative humidity, therefore, +signifies that only half the amount of vapor required to saturate the +space at the given temperature is present. Thus at 212 degrees +Fahrenheit temperature the vapor pressure would only be 7-1/2 pounds +(vacuum of 15 inches gauge). If the total pressure were atmospheric, +then the additional 7-1/2 pounds would be simply air. + +"Live steam" is simply water-saturated vapor at a pressure usually +above atmospheric. We may just as truly have live steam at pressures +less than atmospheric, at a vacuum of 28 inches for instance. Only in +the latter case its temperature would be lower, _viz._, 101 degrees +Fahrenheit. + +Superheated steam is nothing more than water vapor at a relative +humidity less than saturation, but is usually considered at pressures +above atmospheric, and in the absence of air. The atmosphere at, say, +50 per cent relative humidity really contains superheated steam or +vapor, the only difference being that it is at a lower temperature and +pressure than we are accustomed to think of in speaking of superheated +steam, and it has air mixed with it to make up the deficiency in +pressure below the atmosphere. + +Two things should now be clear; that evaporation is produced by heat +and that the presence or absence of air does not influence the amount +of evaporation. It does, however, influence the rate of evaporation, +which is retarded by the presence of air. The main things influencing +evaporation are, first, the quantity of heat supplied and, second, the +relative humidity of the immediately surrounding space. + + + Drying by Superheated Steam + +What this term really signifies is simply water vapor in the absence +of air in a condition of less than saturation. Kilns of this type are, +properly speaking, vapor kilns, and usually operate at atmospheric +pressure, but may be used at greater pressures or at less pressures. +As stated before, the vapor present in the air at any humidity less +than saturation is really "superheated steam," only at a lower +pressure than is ordinarily understood by this term, and mixed with +air. The main argument in favor of this process seems to be based on +the idea that steam is moist heat. This is true, however, only when +the steam is near saturation. When it is superheated it is just as dry +as air containing the same relative humidity. For instance, steam at +atmospheric pressure and heated to 248 degrees Fahrenheit has a +relative humidity of only 50 per cent and is just as dry as air +containing the same humidity. If heated to 306 degrees Fahrenheit, its +relative humidity is reduced to 20 per cent; that is to say, the ratio +of its actual vapor pressure (one atmosphere) to the pressure of +saturated vapor at this temperature (five atmospheres) is 1:5, or 20 +per cent. Superheated vapor in the absence of air, however, parts with +its heat with great rapidity and finally becomes saturated when it has +lost all of its ability to cause evaporation. In this respect it is +more moist than air when it comes in contact with bodies which are at +a lower temperature. When saturated steam is used to heat the lumber +it can raise the temperature of the latter to its own temperature, but +cannot produce evaporation unless, indeed, the pressure is varied. +Only by the heat supplied above the temperature of saturation can +evaporation be produced. + + + Impregnation Methods + +Methods of partially overcoming the shrinkage by impregnation of the +cell walls with organic materials closely allied to the wood substance +itself are in use. In one of these which has been patented, sugar is +used as the impregnating material, which is subsequently hardened or +"caramelized" by heating. Experiments which the United States Forest +Service has made substantiate the claims that the sugar does greatly +reduce the shrinkage of the wood; but the use of impregnation +processes is determined rather from a financial economic standpoint +than by the physical result obtained. + +Another process consists in passing a current of electricity through +the wet boards or through the green logs before sawing. It is said +that the ligno cellulose and the sap are thus transformed by +electrolysis, and that the wood subsequently dries more rapidly. + + + Preliminary Treatments + +In many dry kiln operations, especially where the kilns are not +designed for treatments with very moist air, the wood is allowed to +air-season from several months to a year or more before running it +into the dry kiln. In this way the surface dries below its +fibre-saturation point and becomes hardened or "set" and the +subsequent shrinkage is not so great. Moreover, there is less danger +of surface checking in the kiln, since the surface has already passed +the danger point. Many woods, however, check severely in air-drying or +case-harden in the air. It is thought that such woods can be +satisfactorily handled in a humidity-regulated kiln direct from the +saw. + +Preliminary steaming is frequently used to moisten the surface if +case-hardened, and to heat the lumber through to the center before +drying begins. This is sometimes done in a separate chamber, but more +often in a compartment of the kiln itself, partitioned off by means of +a curtain which can be raised or lowered as circumstances require. +This steaming is usually conducted at atmospheric pressure and +frequently condensed steam is used at temperatures far below 212 +degrees Fahrenheit. In a humidity-regulated kiln this preliminary +treatment may be omitted, since nearly saturated conditions can be +maintained and graduated as the drying progresses. + +Recently the process of steaming at pressures up to 20 pounds gauge in +a cylinder for short periods of time, varying from 5 to 20 minutes, is +being advocated in the United States. The truck load is run into the +cylinder, steamed, and then taken directly out into the air. It may +subsequently be placed in the dry kiln if further drying is desired. +The self-contained heat of the wood evaporates considerable moisture, +and the sudden drying of the boards causes the shrinkage to be reduced +slightly in some cases. Such short periods of steaming under 20 pounds +pressure do not appear to injure the wood mechanically, although they +do darken the color appreciably, especially of the sapwood of the +species having a light-colored sap, as black walnut (_Juglans nigra_) +and red gum (_Liquidamber styraciflua_). Longer periods of steaming +have been found to weaken the wood. There is a great difference in the +effect on different species, however. + +Soaking wood for a long time before drying has been practised, but +experiments indicate that no particularly beneficial results, from the +drying standpoint, are attained thereby. In fact, in some species +containing sugars and allied substances it is probably detrimental +from the shrinkage standpoint. If soaked in boiling water some species +shrink and warp more than if dried without this treatment. + +In general, it may be said that, except possibly for short-period +steaming as described above, steaming and soaking hardwoods at +temperatures of 212 degrees Fahrenheit or over should be avoided if +possible. + +It is the old saying that wood put into water shortly after it is +felled, and left in water for a year or more, will be perfectly +seasoned after a short subsequent exposure to the air. For this reason +rivermen maintain that timber is made better by rafting. Herzenstein +says: "Floating the timber down rivers helps to wash out the sap, and +hence must be considered as favorable to its preservation, the more so +as it enables it to absorb more preservative." + +Wood which has been buried in swamps is eagerly sought after by +carpenters and joiners, because it has lost all tendency to warp and +twist. When first taken from the swamp the long-immersed logs are very +much heavier than water, but they dry with great rapidity. A cypress +log from the Mississippi Delta, which two men could barely handle at +the time it was taken out some years ago, has dried out so much since +then that to-day one man can lift it with ease. White cedar telegraph +poles are said to remain floating in the water of the Great Lakes +sometimes for several years before they are set in lines and to last +better than freshly cut poles. + +It is very probable that immersion for long periods in water does +materially hasten subsequent seasoning. The tannins, resins, +albuminous materials, etc., which are deposited in the cell walls of +the fibres of green wood, and which prevent rapid evaporation of the +water, undergo changes when under water, probably due to the action of +bacteria which live without air, and in the course of time many of +these substances are leached out of the wood. The cells thereby become +more and more permeable to water, and when the wood is finally brought +into the air the water escapes very rapidly and very evenly. +Herzenstein's statement that wood prepared by immersion and subsequent +drying will absorb more preservative, and that with greater rapidity, +is certainly borne out by experience in the United States. + +It is sometimes claimed that all seasoning preparatory to treatment +with a substance like tar oil might be done away with by putting the +green wood into a cylinder with the oil and heating to 225 degrees +Fahrenheit, thus driving the water off in the form of steam, after +which the tar oil would readily penetrate into the wood. This is the +basis of the so-called "Curtiss process" of timber treatment. Without +going into any discussion of this method of creosoting, it may be said +that the same objection made for steaming holds here. In order to get +a temperature of 212 degrees Fahrenheit in the center of the treated +wood, the outside temperature would have to be raised so high that the +strength of the wood might be seriously injured. + +A company on the Pacific coast which treats red fir piling asserts +that it avoids this danger by leaving the green timber in the tar oil +at a temperature which never exceeds 225 degrees Fahrenheit for from +five to twelve hours, until there is no further evidence of water +vapor coming out of the wood. The tar oil is then run out, and a +vacuum is created for about an hour, after which the oil is run in +again and is kept in the cylinders under 100 pounds pressure for from +ten to twelve hours, until the required amount of absorption has been +reached (about 12 pounds per cubic foot). + + + Out-of-door Seasoning + +The most effective seasoning is without doubt that obtained by the +uniform, slow drying which takes place in properly constructed piles +outdoors, under exposure to the winds and the sun. Lumber has always +been seasoned in this way, which is still the best for ordinary +purposes. + +It is probable for the sake of economy, air-drying will be eliminated +in the drying process of the future without loss to the quality of the +product, but as yet no effective method has been discovered whereby +this may be accomplished, because nature performs certain functions in +air-drying that cannot be duplicated by artificial means. Because of +this, hardwoods, as a rule, cannot be successfully kiln-dried green or +direct from the saw, and must receive a certain amount of preliminary +air-drying before being placed in a dry kiln. + +The present methods of air-seasoning in use have been determined by +long experience, and are probably as good as they could be made for +present conditions. But the same care has not up to this time been +given to the seasoning of such timber as ties, bridge material, posts, +telegraph and telephone poles, etc. These have sometimes been piled +more or less intelligently, but in the majority of cases their value +has been too low to make it seem worth while to pile with reference to +anything beyond convenience in handling. + +In piling material for air-seasoning, one should utilize high, dry +ground when possible, and see that the foundations are high enough off +the ground, so that there is proper air circulation through the bottom +of the piles, and also that the piles are far enough apart so that the +air may circulate freely through and around them. + +It is air circulation that is desired in all cases of drying, both in +dry kilns and out-of-doors, and not sunshine; that is, not the sun +shining directly upon the material. The ends also should be protected +from the sun, and everything possible done to induce a free +circulation of air, and to keep the foundations free from all plant +growth. + +Naturally, the heavier the material to be dried, the more difficulty +is experienced from checking, which has its most active time in the +spring when the sap is rising. In fact the main period of danger in +material checking comes with the March winds and the April showers, +and not infrequently in the South it occurs earlier than that. In +other words, as soon as the sap begins to rise, the timber shows signs +of checking, and that is the time to take extra precautions by careful +piling and protection from the sun. When the hot days of summer arrive +the tendency to check is not so bad, but stock will sour from the +heat, stain from the sap, mildew from moisture, and fall a prey to +wood-destroying insects. + +It has been proven in a general way that wood will season more slowly +in winter than in summer, and also that the water content during +various months varies. In the spring the drying-out of wood cut in +October and November will take place more rapidly. + + + + + SECTION XI + + KILN-DRYING OF WOOD + + + Advantages of Kiln-drying over Air-drying + +Some of the advantages of kiln-drying to be secured over air-drying in +addition to reducing the shipping weight and lessening quantity of +stock are the following: + + 1. Less material lost. + 2. Better quality of product. + 3. Prevention of sap stain and mould. + 4. Fixation of gums and resins. + 5. Reduction of hygroscopicity. + +This reduction in the tendency to take up moisture means a reduction +in the "working" of the material which, even though slight, is of +importance. + +The problem of drying wood in the best manner divides itself into two +distinct parts, one of which is entirely concerned with the behavior +of the wood itself and the physical phenomena involved, while the +other part has to do with the control of the drying process. + + + Physical Conditions governing the Drying of Wood + + 1. Wood is soft and plastic while hot and moist, and becomes + "set" in whatever shape it dries. Some species are much more + plastic than others. + + 2. Wood substance begins to shrink only when it dries below + the fibre-saturation point, at which it contains from 25 to + 30 per cent moisture based on its dry weight. Eucalyptus and + certain other species appear to be exceptions to this law. + + 3. The shrinkage of wood is about twice as great + circumferentially as in the radial direction; lengthwise, it + is very slight. + + 4. Wood shrinks most when subjected, while kept moist, to + slow drying at high temperatures. + + 5. Rapid drying produces less shrinkage than slow drying at + high temperatures, but is apt to cause case-hardening and + honeycombing, especially in dense woods. + + 6. Case-hardening, honeycombing, and cupping result directly + from conditions 1, 4, and 5, and chemical changes of the + outer surface. + + 7. Brittleness is caused by carrying the drying process too + far, or by using too high temperatures. Safe limits of + treatment vary greatly for different species. + + 8. Wood absorbs or loses moisture in proportion to the + relative humidity in the air, not according to the + temperature. This property is called its "hygroscopicity." + + 9. Hygroscopicity and "working" are reduced but not + eliminated by thorough drying. + + 10. Moisture tends to transfuse from the hot towards the + cold portion of the wood. + + 11. Collapse of the cells may occur in some species while + the wood is hot and plastic. This collapse is independent of + subsequent shrinkage. + + + Theory of Kiln-drying + +The dry kiln has long since acquired particular appreciation at the +hands of those who have witnessed its time-saving qualities, when +practically applied to the drying of timber. The science of drying is +itself of the simplest, the exposure to the air being, indeed, the +only means needed where the matter of time is not called into +question. Otherwise, where hours, even minutes, have a marked +significance, then other means must be introduced to bring about the +desired effect. In any event, however, the same simple and natural +remedy pertains,--the absorption of moisture. This moisture in green +timber is known as "sap", which is itself composed of a number of +ingredients, most important among which are water, resin, and albumen. + +All dry kilns in existence use heat to season timber; that is, to +drive out that portion of the "sap" which is volatile. + +The heat does not drive out the resin of the pines nor the albumen of +the hardwoods. It is really of no advantage in this respect. Resin in +its hardened state as produced by heat is only slowly soluble in water +and contains a large proportion of carbon, the most stable form of +matter. Therefore, its retention in the pores of the wood is a +positive advantage. + +To produce the ideal effect the drying must commence at the heart of +the piece and work outward, the moisture being removed from the +surface as fast as it exudes from the pores of the wood. To +successfully accomplish this, adjustments must be available to +regulate the temperature, circulation, and humidity according to the +variations of the atmospheric conditions, the kind and condition of +the material to be dried. + +This ideal effect is only attained by the use of a type of dry kiln in +which the surface of the lumber is kept soft, the pores being left +open until all the moisture within has been volatilized by the heat +and carried off by a free circulation of air. When the moisture has +been removed from the pores, the surface is dried without closing the +pores, resulting in timber that is clean, soft, bright, straight, and +absolutely free from stains, checks, or other imperfections. + +Now, no matter how the method of drying may be applied, it must be +remembered that vapor exists in the atmosphere at all times, its +volume being regulated by the capacity of the temperature absorbed. To +kiln-dry properly, a free current of air must be maintained, of +sufficient volume to carry off this moisture. Now, the capacity of +this air for drying depends entirely upon the ability of its +temperature to absorb or carry off a larger proportion of moisture +than that apportioned by natural means. Thus, it will be seen, a cubic +foot of air at 32 degrees Fahrenheit is capable of absorbing only two +grains of water, while at 160 degrees, it will dispose of ninety +grains. The air, therefore, should be made as dry as possible and +caused to move freely, so as to remove all moisture from the surface +of the wood as soon as it appears. Thus the heat effects a double +purpose, not only increasing the rate of evaporation, but also the +capacity of the air for absorption. Where these means are applied, +which rely on the heat alone to accomplish this purpose, only that of +the moisture which is volatile succumbs, while the albumen and resin +becoming hardened under the treatment close up the pores of the wood. +This latter result is oft-times accomplished while moisture yet +remains and which in an enforced effort to escape bursts open the +cells in which it has been confined and creates what is known as +"checks." + +Therefore, taking the above facts into consideration, the essentials +for the successful kiln-drying of wood may be enumerated as follows: + + 1. The evaporation from the surface of a stick should not + exceed the rate at which the moisture transfuses from the + interior to the surface. + + 2. Drying should proceed uniformly at all points, otherwise + extra stresses are set up in the wood, causing warping, etc. + + 3. Heat should penetrate to the interior of the piece before + drying begins. + + 4. The humidity should be suited to the condition of the + wood at the start and reduced in the proper ratio as drying + progresses. With wet or green wood it should usually be held + uniform at a degree which will prevent the surface from + drying below its saturation point until all the free water + has evaporated, then gradually reduced to remove the + hygroscopic moisture. + + 5. The temperature should be uniform and as high as the + species under treatment will stand without excessive + shrinkage, collapse, or checking. + + 6. Rate of drying should be controlled by the amount of + humidity in the air and not by the rate of circulation, + which should be made ample at all times. + + 7. In drying refractory hardwoods, such as oak, best results + are obtained at a comparatively low temperature. In more + easily dried hardwoods, such as maple, and some of the more + difficult softwoods, as cypress, the process may be hastened + by a higher temperature but not above the boiling point. In + many of the softwoods, the rate of drying may be very + greatly increased by heating above the boiling point with a + large circulation of vapor at atmospheric pressure. + + 8. Unequal shrinkage between the exterior and interior + portions of the wood and also unequal chemical changes must + be guarded against by temperatures and humidities suited to + the species in question to prevent subsequent cupping and + warping. + + 9. The degree of dryness attained should conform to the use + to which the wood is put. + + 10. Proper piling of the material and weighting to prevent + warping are of great importance. + + + Requirements in a Satisfactory Dry Kiln + +The requirements in a satisfactory dry kiln are: + + 1. Control of humidity at all times. + 2. Ample air circulation at all points. + 3. Uniform and proper temperatures. + +In order to meet these requirements the United States Forestry Service +has designed a kiln in which the humidity, temperature, and +circulation can be controlled at all times. + +Briefly, it consists of a drying chamber with a partition on either +side, making two narrow side chambers open top and bottom. + +The steam pipes are in the usual position underneath the material to +be dried. + +At the top of the side chambers is a spray; at the bottom are gutters +and an eliminator or set of baffle plates to separate the fine mist +from the air. + +The spray accomplishes two things: It induces an increased circulation +and it regulates the humidity. This is done by regulating the +temperature of the spray water. + +The air under the heating coil is saturated at whatever temperature +is required. This temperature is the dew point of the air after it +passes up into the drying chamber above the coils. Knowing the +temperature in the drying room and the dew point, the relative +humidity is thus determined. + +The relative humidity is simply the ratio of the vapor pressure at the +dew point to the pressure of saturated vapor (see Fig. 30). + + [Illustration: Fig. 30. Section through United States + Forestry Service Humidity-controlled Dry Kiln.] + + + Theory and Description of the Forestry Service Kiln + +The humidities and temperatures in the piles of lumber are largely +dependent upon the circulation of air within the kiln. The temperature +and humidity within the kiln, taken alone, are no criterion of the +conditions of drying the pile of lumber if the circulation in any +portion is deficient. It is possible to have an extremely rapid +circulation of air within the dry kiln itself and yet have stagnation +within the individual piles, the air passing chiefly through open +spaces and channels. Wherever stagnation exists or the movement of air +is too sluggish the temperature will drop and the humidity increase, +perhaps to the point of saturation. + +When in large kilns the forced circulation is in the opposite +direction from that induced by the cooling of the air by the lumber, +there is always more or less uncertainty as to the movement of the air +through the piles. Even with the boards placed edge-wise, with +stickers running vertically, and with the heating pipes beneath the +lumber, it was found that although the air passed upward through most +of the spaces it was actually descending through others, so that very +unequal drying resulted. While edge piling would at first thought seem +ideal for the freest circulation in an ordinary kiln with steam pipes +below, it in fact produces an indeterminate condition; air columns may +pass downward through some channels as well as upward through others, +and probably stagnate in still others. Nevertheless, edge piling is +greatly superior to flat piling where the heating system is below the +lumber. + +From experiments and from study of conditions in commercial kilns the +idea was developed of so arranging the parts of the kiln and the pile +of lumber that advantage might be taken of this cooling of the air to +assist the circulation. That this can be readily accomplished without +doing away with the present features of regulation of humidity by +means of a spray of water is clear from Fig. 30, which shows a +cross-section of the improved humidity-regulated dry kiln. + +In the form shown in the sketch a chamber or flue B runs through the +center near the bottom. This flue is only about 6 or 7 feet in height +and, together with the water spray F and the baffle plates DD, +constitutes the humidity-control feature of the kiln. This control of +humidity is affected by the temperature of the water used in the +spray. This spray completely saturates the air in the flue B at +whatever predetermined temperature is required. The baffle plates DD +are to separate all entrained particles of water from the air, so that +it is delivered to the heaters in a saturated condition at the +required temperature. This temperature is, therefore, the dew point of +the air when heated above, and the method of humidity control may +therefore be called the dew-point method. It is a very simple matter +by means of the humidity diagram (see Fig. 93), or by a hygrodeik +(Fig. 94), to determine what dew-point temperature is needed for any +desired humidity above the heaters. + +Besides regulating the humidity the spray F also acts as an ejector +and forces circulation of air through the flue B. The heating system H +is concentrated near the outer walls, so as to heat the rising column +of air. The temperature within the drying chamber is controlled by +means of any suitable thermostat, actuating a valve on the main steam +line. The lumber is piled in such a way that the stickers slope +downward toward the sides of the kiln. + +M is an auxiliary steam spray pointing downward for use at very high +temperatures. C is a gutter to catch the precipitation and conduct it +back to the pump, the water being recirculated through the sprays. G +is a pipe condenser for use toward the end of the drying operation. K +is a baffle plate for diverting the heated air and at the same time +shielding the under layers of boards from direct radiation of the +steam pipes. + +The operation of the kiln is simple. The heated air rises above the +pipes HH and between the piles of lumber. As it comes in contact with +the piles, portions of it are cooled and pass downward and outward +through the layers of boards into the space between the condensers GG. +Here the column of cooled air descends into the spray flue B, where +its velocity is increased by the force of the water spray. It then +passes out from the baffle plates to the heaters and repeats the +cycle. + +One of the greatest advantages of this natural circulation method is +that the colder the lumber when placed in the kiln the greater is the +movement produced, under the very conditions which call for the +greatest circulation--just the opposite of the direct-circulation +method. This is a feature of the greatest importance in winter, when +the lumber is put into the kiln in a frozen condition. One truckload +of lumber at 60 per cent moisture may easily contain over 7,000 pounds +of ice. + +In the matter of circulation the kiln is, in fact, seldom +regulatory--the colder the lumber the greater the circulation +produced, with the effect increased toward the cooler and wetter +portions of the pile. + +Preliminary steaming may be used in connection with this kiln, but +experiments indicate that ordinarily it is not desirable, since the +high humidity which can be secured gives as good results, and being at +as low a temperature as desired, much better results in the case of +certain difficult woods like oak, eucalyptus, etc., are obtained. + +This kiln has another advantage in that its operation is entirely +independent of outdoor atmospheric conditions, except that barometric +pressure will effect it slightly. + + + KILN-DRYING + + Remarks + +Drying is an essential part of the preparation of wood for +manufacture. For a long time the only drying process used or known was +air-drying, or the exposure of wood to the gradual drying influences +of the open air, and is what has now been termed "preliminary +seasoning." This method is without doubt the most successful and +effective seasoning, because nature performs certain functions in +air-drying that cannot be duplicated by artificial means. Because of +this, hardwoods, as a rule, cannot be successfully kiln-dried green or +direct from the saw. + +Within recent years, considerable interest is awakening among wood +users in the operation of kiln-drying. The losses occasioned in +air-drying and in improper kiln-drying, and the necessity for getting +material dry as quickly as possible from the saw, for shipping +purposes and also for manufacturing, are bringing about a realization +of the importance of a technical knowledge of the subject. + +The losses which occur in air-drying wood, through checking, warping, +staining, and rotting, are often greater than one would suppose. While +correct statistics of this nature are difficult to obtain, some idea +may be had of the amount of degrading of the better class of lumber. +In the case of one species of soft wood, Western larch, it is commonly +admitted that the best grades fall off sixty to seventy per cent in +air-drying, and it is probable that the same is true in the case of +Southern swamp oaks. In Western yellow pine, the loss is great, and in +the Southern red gum, it is probably as much as thirty per cent. It +may be said that in all species there is some loss in air-drying, but +in some easily dried species such as spruce, hemlock, maple, etc., it +is not so great. + +It would hardly be correct to state at the present time that this loss +could be entirely prevented by proper methods of kiln-drying the green +lumber, but it is safe to say that it can be greatly reduced. + +It is well where stock is kiln-dried direct from the saw or knife, +after having first been steamed or boiled--as in the case of veneers, +etc.,--to get them into the kiln while they are still warm, as they +are then in good condition for kiln-drying, as the fibres of the wood +are soft and the pores well opened, which will allow of forcing the +evaporation of moisture without much damage being done to the +material. + +With softwoods it is a common practice to kiln-dry direct from the +saw. This procedure, however, is ill adapted for the hardwoods, in +which it would produce such warping and checking as would greatly +reduce the value of the product. Therefore, hardwoods, as a rule, are +more or less thoroughly air-dried before being placed in the dry kiln, +where the residue of moisture may be reduced to within three or four +per cent, which is much lower than is possible by air-drying only. + +It is probable that for the sake of economy, air-drying will be +eliminated in the drying processes of the future without loss to the +quality of the product, but as yet no method has been discovered +whereby this may be accomplished. + +The dry kiln has been, and probably still is, one of the most +troublesome factors arising from the development of the timber +industry. In the earlier days, before power machinery for the +working-up of timber products came into general use, dry kilns were +unheard-of, air-drying or seasoning was then relied upon solely to +furnish the craftsman with dry stock from which to manufacture his +product. Even after machinery had made rapid and startling strides on +its way to perfection, the dry kiln remained practically an unknown +quantity, but gradually, as the industry developed and demand for dry +material increased, the necessity for some more rapid and positive +method of seasoning became apparent, and the subject of artificial +drying began to receive the serious attention of the more progressive +and energetic members of the craft. + +Kiln-drying which is an artificial method, originated in the effort to +improve or shorten the process, by subjecting the wood to a high +temperature or to a draught of heated air in a confined space or kiln. +In so doing, time is saved and a certain degree of control over the +drying operation is secured. + +The first efforts in the way of artificial drying were confined to +aiding or hastening nature in the seasoning process by exposing the +material to the direct heat from fires built in pits, over which the +lumber was piled in a way to expose it to the heat rays of the fires +below. This, of course, was a primitive, hazardous, and very +unsatisfactory method, to say the least, but it marked the first step +in the evolution of the present-day dry kiln, and in that particular +only is it deserving of mention. + + + Underlying Principles + +In addition to marking the first step in artificial drying, it +illustrated also, in the simplest manner possible, the three +underlying principles governing all drying problems: (1) The +application of heat to evaporate or volatilize the water contained in +the material; (2) with sufficient air in circulation to carry away in +suspension the vapor thus liberated; and (3) with a certain amount of +humidity present to prevent the surface from drying too rapidly while +the heat is allowed to penetrate to the interior. The last performs +two distinct functions: (a) It makes the wood more permeable to the +passage of the moisture from the interior of the wood to the surface, +and (b) it supplies the latent heat necessary to evaporate the +moisture after it reaches the surface. The air circulation is +important in removing the moisture after it has been evaporated by the +heat, and ventilation also serves the purpose of bringing the heat in +contact with the wood. If, however, plain, dry heat is applied to the +wood, the surface will become entirely dry before the interior +moisture is even heated, let alone removed. This condition causes +"case-hardening" or "hollow-horning." So it is very essential that +sufficient humidity be maintained to prevent the surface from drying +too rapidly, while the heat is allowed to penetrate to the interior. + +This humidity or moisture is originated by the evaporation from the +drying wood, or by the admission of steam into the dry kiln by the use +of steam spray pipes, and is absolutely necessary in the process of +hastening the drying of wood. With green lumber it keeps the sap near +the surface of the piece in a condition that allows the escape of the +moisture from its interior; or, in other words, it prevents the +outside from drying first, which would close the pores and cause +case-hardening. + +The great amount of latent heat necessary to evaporate the water after +it has reached the surface is shown by the fact that the evaporation +of only one pound of water will extract approximately 66 degrees from +1,000 cubic feet of air, allowing the air to drop in temperature from +154 to 84 degrees Fahrenheit. In addition to this amount of heat, the +wood and the water must also be raised to the temperature at which the +drying is to be accomplished. + +It matters not what type of dry kiln is used, source or application of +heating medium, these underlying principles remain the same, and must +be the first things considered in the design or selection of the +equipment necessary for producing the three essentials of drying: +Heat, humidity, and circulation. + +Although these principles constitute the basis of all drying problems +and must, therefore, be continually carried in mind in the +consideration of them, it is equally necessary to have a comprehensive +understanding of the characteristics of the materials to be dried, and +its action during the drying process. All failures in the past, in the +drying of timber products, can be directly attributed to either the +kiln designer's neglect of these things, or his failure to carry them +fully in mind in the consideration of his problems. + +Wood has characteristics very much different from those of other +materials, and what little knowledge we have of it and its properties +has been taken from the accumulated records of experience. The reason +for this imperfect knowledge lies in the fact that wood is not a +homogeneous material like the metals, but a complicated structure, and +so variable that one stick will behave in a manner widely different +from that of another, although it may have been cut from the same +tree. + +The great variety of woods often makes the mere distinction of the +kind or species of the tree most difficult. It is not uncommon to find +men of long experience disagree as to the kind of tree a certain piece +of lumber was cut from, and, in some cases, there is even a wide +difference in the appearance and evidently the structure of timber cut +from the same tree. + + + Objects of Kiln-drying + +The objects of kiln-drying wood may be placed under three main +headings: (1) To reduce shipping expenses; (2) to reduce the quantity +necessary to maintain in stock; and (3) to reduce losses in air-drying +and to properly prepare the wood for subsequent use. Item number 2 +naturally follows as a consequence of either 1 or 3. The reduction in +weight on account of shipping expenses is of greatest significance +with the Northwestern lumbermen in the case of Douglas fir, redwood, +Western red cedar, sugar pine, bull pine, and other softwoods. + +Very rapid methods of rough drying are possible with some of these +species, and are in use. High temperatures are used, and the water is +sometimes boiled off from the wood by heating above 212 degrees +Fahrenheit. These high-temperature methods will not apply to the +majority of hardwoods, however, nor to many of the softwoods. + +It must first of all be recognized that the drying of lumber is a +totally different operation from the drying of a fabric or of thin +material. In the latter, it is largely a matter of evaporated +moisture, but wood is not only hygroscopic and attracts moisture from +the air, but its physical behavior is very complex and renders the +extraction of moisture a very complicated process. + +An idea of its complexity may be had by mentioning some of the +conditions which must be contended with. Shrinkage is, perhaps, the +most important. This is unequal in different directions, being twice +as great tangentially as radially and fifty times as great radially as +longitudinally. Moreover, shrinkage is often unequal in different +portions of the same piece. The slowness of the transfusion of +moisture through the wood is an important factor. This varies with +different woods and greatly in different directions. Wood becomes soft +and plastic when hot and moist, and will yield more or less to +internal stresses. As some species are practically impervious to air +when wet, this plasticity of the cell walls causes them to collapse as +the water passes outward from the cell cavities. This difficulty has +given much trouble in the case of Western red cedar, and also to some +extent in redwood. The unequal shrinkage causes internal stresses in +the wood as it dries, which results in warping, checking, +case-hardening, and honeycombing. Case-hardening is one of the most +common defects in improperly dried lumber. It is clearly shown by the +cupping of the two halves when a case-hardened board is resawed. +Chemical changes also occur in the wood in drying, especially so at +higher temperatures, rendering it less hygroscopic, but more brittle. +If dried too much or at too high a temperature, the strength and +toughness is seriously reduced. + + + Conditions of Success + +Commercial success in drying therefore requires that the substance be +exposed to the air in the most efficient manner; that the temperature +of the air be as high as the substance will stand without injury, and +that the air change or movement be as rapid as is consistent with +economical installation and operation. Conditions of success therefore +require the observance of the following points, which embody the basic +principles of the process: (1) The timber should be heated through +before drying begins. (2) The air should be very humid at the +beginning of the drying process, and be made drier only gradually. (3) +The temperature of the lumber must be maintained uniformly throughout +the entire pile. (4) Control of the drying process at any given +temperature must be secured by controlling the relative humidity, not +by decreasing the circulation. (5) In general, high temperatures +permit more rapid drying than do lower temperatures. The higher the +temperature of the lumber, the more efficient is the kiln. It is +believed that temperatures as high as the boiling point are not +injurious to most woods, providing all other fundamentally important +features are taken care of. Some species, however, are not able to +stand as high temperatures as others, and (6) the degree of dryness +attained, where strength is the prime requisite, should not exceed +that at which the wood is to be used. + + + Different Treatment according to Kind + +The rapidity with which water may be evaporated, that is, the rate of +drying, depends on the size and shape of the piece and on the +structure of the wood. Thin stock can be dried much faster than thick, +under the same conditions of temperature, circulation, and humidity. +Pine can be dried, as a general thing, in about one third of the time +that would be required for oak of the same thickness, although the +former contains the more water of the two. Quarter-sawn oak usually +requires half again as long as plain oak. Mahogany requires about the +same time as plain oak; ash dries in a little less time, and maple, +according to the purpose for which it is intended, may be dried in one +fifth the time needed for oak, or may require a slightly longer +treatment. For birch, the time required is from one half to two +thirds, and for poplar and basswood, from, one fifth to one third that +required for oak. + +All kinds and thicknesses of lumber cannot be dried at the same time +in the same kiln. It is manifest that green and air-dried lumber, +dense and porous lumber, all require different treatment. For +instance, Southern yellow pine when cut green from the log will stand +a very high temperature, say 200 degrees Fahrenheit, and in fact this +high temperature is necessary together with a rapid circulation of air +in order to neutralize the acidity of the pitch which causes the wood +to blue and discolor. This lumber requires to be heated up immediately +and to be kept hot throughout the length of the kiln. Hence the kiln +must not be of such length as to allow of the air being too much +cooled before escaping. + + + Temperature depends + +While it is true that a higher temperature can be carried in the kiln +for drying pine and similar woods, this does not altogether account +for the great difference in drying time, as experience has taught us +that even when both woods are dried in the same kiln, under the same +conditions, pine will still dry much faster, proving thereby that the +structure of the wood itself affects drying. + +The aim of all kiln designers should be to dry in the shortest +possible time, without injury to the material. Experience has +demonstrated that high temperatures are very effective in evaporating +water, regardless of the degree of humidity, but great care must be +exercised in using extreme temperatures that the material to be dried +is not damaged by checking, case-hardening, or hollow-horning. + +The temperature used should depend upon the species and condition of +the material when entering the kiln. In general, it is advantageous to +have as high a temperature as possible, both for economy of operation +and speed of drying, but the physical properties of the wood will +govern this. + +Many species cannot be dried satisfactorily at high temperatures on +account of their peculiar behavior. This is particularly so with green +lumber. + +Air-dried wood will stand a relatively higher temperature, as a rule, +than wet or green wood. In drying green wood direct from the saw, it +is usually best to start with a comparatively low temperature, and not +raise the temperature until the wood is nearly dry. For example, green +maple containing about 60 per cent of its dry weight in water should +be started at about 120 degrees Fahrenheit and when it reaches a +dryness of 25 per cent, the temperature may be raised gradually up to +190 degrees. + +It is exceedingly important that the material be practically at the +same temperature throughout if perfect drying is to be secured. It +should be the same temperature in the center of a pile or car as on +the outside, and the same in the center of each individual piece of +wood as on its surface. This is the effect obtained by natural +air-drying. The outside atmosphere and breezes (natural air +circulation) are so ample that the heat extracted for drying does not +appreciably change the temperature. + +When once the wood has been raised to a high temperature through and +through and especially when the surface has been rendered most +permeable to moisture, drying may proceed as rapidly as it can be +forced by artificial circulation, provided the heat lost from the wood +through vaporization is constantly replaced by the heat of the kiln. + +It is evident that to secure an even temperature, a free circulation +of air must be brought in contact with the wood. It is also evident +that in addition to heat and a circulation of air, the air must be +charged with a certain amount of moisture to prevent surface drying or +case-hardening. + +There are some twenty-five different makes of dry kilns on the market, +which fulfill to a varying degree the fundamental requirements. +Probably none of them succeed perfectly in fulfilling all. + +It is well to have the temperature of a dry kiln controlled by a +thermostat which actuates the valve on the main steam supply pipe. It +is doubly important to maintain a uniform temperature and avoid +fluctuations in the dry kiln, since a change in temperature will +greatly alter the relative humidity. + +In artificial drying, temperatures of from 150 to 180 degrees +Fahrenheit are usually employed. Pine, spruce, cypress, cedar, etc., +are dried fresh from the saw, allowing four days for 1-inch stuff. +Hardwoods, especially oak, ash, maple, birch, sycamore, etc., are +usually air-seasoned for three to six months to allow the first +shrinkage to take place more gradually, and are then exposed to the +above temperatures in the kiln for about six to ten days for 1-inch +stuff, other dimensions in proportion. + +Freshly cut poplar and cottonwood are often dried direct from the saw +in a kiln. By employing lower temperatures, 100 to 120 degrees +Fahrenheit, green oak, ash, etc., can be seasoned in dry kilns without +much injury to the material. + +Steaming and sweating the wood is sometimes resorted to in order to +prevent checking and case-hardening, but not, as has been frequently +asserted, to enable the material to dry. + + + Air Circulation + +Air circulation is of the utmost importance, since no drying whatever +can take place when it is lacking. The evaporation of moisture +requires heat and this must be supplied by the circulating air. +Moreover, the moisture laden air must be constantly removed and fresh, +drier air substituted. Probably this is the factor which gives more +trouble in commercial operations than anything else, and the one which +causes the greatest number of failures. + +It is necessary that the air circulate through every part of the kiln +and that the moving air come in contact with every portion of the +material to be dried. In fact, the humidity is dependent upon the +circulation. If the air stagnates in any portion of the pile, then the +temperature will drop and the humidity rise to a condition of +saturation. Drying will not take place at this portion of the pile and +the material is apt to mould and rot. + +The method of piling the material on trucks or in the kiln, is +therefore, of extreme importance. Various methods are in use. Ordinary +flat piling is probably the poorest. Flat piling with open chimney +spaces in the piles is better. But neither method is suitable for a +kiln in which the circulation is mainly vertical. + +Edge piling with stickers running vertically is in use in kilns when +the heating coils are beneath. This is much better. + +Air being cooled as it comes in contact with a pile of material, +becomes denser, and consequently tends to sink. Unless the material to +be dried is so arranged that the air can pass gradually downward +through the pile as it cools, poor circulation is apt to result. + +In edge-piled lumber, with the heating system beneath the piles, the +natural tendency of the cooled air to descend is opposed by the hot +air beneath which tends to rise. An indeterminate condition is thus +brought about, resulting in non-uniform drying. It has been found that +air will rise through some layers and descend through others. + + + Humidity + +Humidity is of prime importance because the rate of drying and +prevention of checking and case-hardening are largely dependent +thereon. It is generally true that the surface of the wood should not +dry more rapidly than the moisture transfuses from the center of the +piece to its surface, otherwise disaster will result. As a sufficient +amount of moisture is removed from the wood to maintain the desired +humidity, it is not good economy to generate moisture in an outside +apparatus and force it into a kiln, unless the moisture in the wood is +not sufficient for this purpose; in that case provision should be made +for adding any additional moisture that may be required. + +The rate of evaporation may best be controlled by controlling the +amount of vapor present in the air (relative humidity); it should not +be controlled by reducing the air circulation, since a large +circulation is needed at all times to supply the necessary heat. + +The humidity should be graded from 100 per cent at the receiving end +of the kiln, to whatever humidity corresponds with the desired degree +of dryness at the delivery end. + +The kiln should be so designed that the proper degree may be +maintained at its every section. + +A fresh piece of sapwood will lose weight in boiling water and can +also be dried to quite an extent in steam. This proves conclusively +that a high degree of humidity does not have the detrimental effect on +drying that is commonly attributed to it. In fact, a proper degree of +humidity, especially in the loading or receiving end of a kiln, is +just as necessary to good results in drying as getting the proper +temperature. + +Experiments have demonstrated also that injury to stock in the way of +checking, warping, and hollow-horning always develops immediately +after the stock is taken into the kiln, and is due to the degree of +humidity being too low. The receiving end of the kiln should always be +kept moist, where the stock has not been steamed before being put into +the kiln. The reason for this is simple enough. When the air is too +dry it tends to dry the outside of the material first--which is termed +"case-hardening"--and in so doing shrinks and closes up the pores of +the wood. As the stock is moved down the kiln, it absorbs a +continually increasing amount of heat, which tends to drive off the +moisture still present in the center of the stock. The pores on the +outside having been closed up, there is no exit for the vapor or steam +that is being rapidly formed in the center. It must find its way out +some way, and in doing so sets up strains, which result either in +checking, warping, or hollow-horning. If the humidity had been kept +higher, the outside of the material would not have dried so quickly, +and the pores would have remained open for the exit of moisture from +the interior of the wood, and this trouble would have been avoided. + +Where the humidity is kept at a high point in the receiving end of the +kiln, a higher rate of temperature may also be carried, and in that +way the drying process is hastened with comparative safety. + +It is essential, therefore, to have an ample supply of heat through +the convection currents of the air; but in the case of wood the rate +of evaporation must be controlled, else checking will occur. This can +be done by means of the relative humidity, as stated before. It is +clear now that when the air--or, more properly speaking, the space--is +completely saturated no evaporation can take place at the given +temperature. By reducing the humidity, evaporation takes place more +and more rapidly. + +Another bad feature of an insufficient and non-uniform supply of heat +is that each piece of wood will be heated to the evaporating point on +the outer surface, the inside remaining cool until considerable drying +has taken place from the surface. Ordinarily in dry kilns high +humidity and large circulation of air are antitheses to one another. +To obtain the high humidity the circulation is either stopped +altogether or greatly reduced, and to reduce the humidity a greater +circulation is induced by opening the ventilators or otherwise +increasing the draft. This is evidently not good practice, but as a +rule is unavoidable in most dry kilns of present make. The humidity +should be raised to check evaporation without reducing the circulation +if possible. + +While thin stock, such as cooperage and box stuff is less inclined to +give trouble by undue checking than 1-inch and thicker, one will find +that any dry kiln will give more uniform results and, at the same +time, be more economical in the use of steam, when the humidity and +temperature is carried at as high a point as possible without injury +to the material to be dried. + +Any well-made dry kiln which will fulfill the conditions required as +to circulation and humidity control should work satisfactorily; but +each case must be studied by itself, and the various factors modified +to suit the peculiar conditions of the problem in hand. In every new +case the material should be constantly watched and studied and, if +checking begins, the humidity should be increased until it stops. It +is not reducing the circulation, but adding the necessary moisture to +the air, that should be depended on to prevent checking. For this +purpose it is well to have steam jets in the kiln so that if needed +they are ready at hand. + + + Kiln-drying + +There are two distinct ways of handling material in dry kilns. One way +is to place the load of lumber in a chamber where it remains in the +same place throughout the operation, while the conditions of the +drying medium are varied as the drying progresses. This is the +"apartment" kiln or stationary method. The other is to run the lumber +in at one end of the chamber on a wheeled truck and gradually move it +along until the drying process is completed, when it is taken out at +the opposite end of the kiln. It is the usual custom in these kilns to +maintain one end of the chamber moist and the other end dry. This is +known as the "progressive" type of kiln, and is the one most commonly +used in large operations. + +It is, however, the least satisfactory of the two where careful drying +is required, since the conditions cannot be so well regulated and the +temperatures and humidities are apt to change with any change of wind. +The apartment method can be arranged so that it will not require any +more kiln space or any more handling of lumber than the progressive +type. It does, however, require more intelligent operation, since the +conditions in the drying chamber must be changed as the drying +progresses. With the progressive type the conditions, once properly +established, remain the same. + +To obtain draft or circulation three methods are in use--by forced +draft or a blower usually placed outside the kiln, by ventilation, and +by internal circulation and condensation. A great many patents have +been taken out on different methods of ventilation, but in actual +operation few kilns work exactly as intended. Frequently the air moves +in the reverse direction for which the ventilators were planned. +Sometimes a condenser is used in connection with the blower and the +air is recirculated. It is also--and more satisfactorily--used with +the gentle internal-gravity currents of air. + +Many patents have been taken out for heating systems. The differences +among these, however, have more to do the mechanical construction than +with the process of drying. In general, the heating is either direct +or indirect. In the former steam coils are placed in the chamber with +the lumber, and in the latter the air is heated by either steam coils +or a furnace before it is introduced into the drying chamber. + +Moisture is sometimes supplied by means of free steam jets in the kiln +or in the entering air; but more often the moisture evaporated from +the lumber is relied upon to maintain the humidity necessary. + +A substance becomes dry by the evaporation of its inherent moisture +into the surrounding space. If this space be confined it soon becomes +saturated and the process stops. Hence, constant change is necessary +in order that the moisture given off may be continually carried away. + +In practice, air movement, is therefore absolutely essential to the +process of drying. Heat is merely a useful accessory which serves to +decrease the time of drying by increasing both the rate of evaporation +and the absorbing power of the surrounding space. + +It makes no difference whether this space is a vacuum or filled with +air; under either condition it will take up a stated weight of vapor. +From this it appears that the vapor molecules find sufficient space +between the molecules of air. But the converse is not true, for +somewhat less air will be contained in a given space saturated with +vapor than in one devoid of moisture. In other words the air does not +seem to find sufficient space between the molecules of vapor. + +If the temperature of the confined space be increased, opportunity +will thereby be provided for the vaporization of more water, but if it +be decreased, its capacity for moisture will be reduced and visible +water will be deposited. The temperature at which this takes place is +known as the "dew-point" and depends upon the initial degree of +saturation of the given space; the less the relative saturation the +lower the dew-point. + +Careful piling of the material to be dried, both in the yard and dry +kiln, is essential to good results in drying. + +Air-dried material is not dry, and its moisture is too unevenly +distributed to insure good behavior after manufacture. + +It is quite a difficult matter to give specific or absolute correct +weights of any species of timber when thoroughly or properly dried, in +order that one may be guided in these kiln operations, as a great deal +depends upon the species of wood to be dried, its density, and upon +the thickness which it has been cut, and its condition when entering +the drying chamber. + +Elm will naturally weigh less than beech, and where the wood is +close-grained or compact it will weigh more than coarse-grained wood +of the same species, and, therefore, no set rules can be laid down, as +good judgment only should be used, as the quality of the drying is not +purely one of time. Sometimes the comparatively slow process gives +excellent results, while to rush a lot of stock through the kiln may +be to turn it out so poorly seasoned that it will not give +satisfaction when worked into the finished product. The mistreatment +of the material in this respect results in numerous defects, chief +among which are warping and twisting, checking, case-hardening, and +honeycombing, or, as sometimes called, hollow-horning. + +Since the proportion of sap and heartwood varies with size, age, +species, and individual trees, the following figures as regards weight +must be regarded as mere approximations: + + + POUNDS OF WATER LOST IN DRYING 100 POUNDS OF GREEN WOOD IN THE KILN + +========================================================================= + |Sapwood or | Heartwood + |outer part | or interior +========================================================================= + | | +(1) Pine, cedar, spruce, and fir | 45-65 | 16-25 +(2) Cypress, extremely variable | 50-65 | 18-60 +(3) Poplar, cottonwood, and basswood | 60-65 | 40-60 +(4) Oak, beech, ash, maple, birch, elm, hickory,| | + chestnut, walnut, and sycamore | 40-50 | 30-40 +========================================================================= + +The lighter kinds have the most water in the sapwood; thus sycamore +has more water than hickory, etc. + +The efficiency of the drying operations depends a great deal upon the +way in which, the lumber is piled, especially when the humidity is not +regulated. From the theory of drying it is evident that the rate of +evaporation in dry kilns where the humidity is not regulated depends +entirely upon the rate of circulation, other things being equal. +Consequently, those portions of the wood which receive the greatest +amount of air dry the most rapidly, and vice versa. The only way, +therefore, in which anything like uniform drying can take place is +where the lumber is so piled that each portion of it comes in contact +with the same amount of air. + +In the Forestry Service kiln (Fig. 30), where the degree of relative +humidity is used to control the rate of drying, the amount of +circulation makes little difference, provided it exceeds a certain +amount. It is desirable to pile the lumber so as to offer as little +frictional resistance as possible and at the same time secure uniform +circulation. If circulation is excessive in any place it simply means +waste of energy but no other injury to the lumber. + +The best method of piling is one which permits the heated air to pass +through the pile in a somewhat downward direction. The natural +tendency of the cooled air to descend is thus taken advantage of in +assisting the circulation in the kiln. This is especially important +when cold or green lumber is first introduced into the kiln. But even +when the lumber has become warmed the cooling due to the evaporation +increases the density of the mixture of the air and vapor. + + + Kiln-drying Gum + +The following article was published by the United States Forestry +Service as to the best method of kiln-drying gum: + +=Piling.=--Perhaps the most important factor in good kiln-drying, +especially in the case of the gums, is the method of piling. It is our +opinion that proper and very careful piling will greatly reduce the +loss due to warping. A good method of piling is to place the lumber +lengthwise of the kiln and on an incline cross-wise. The warm air +should rise at the higher side of the pile and descend between the +courses of lumber. The reason for this is very simple and the +principle has been applied in the manufacture of the best ice boxes +for some time. The most efficient refrigerators are iced at the side, +the ice compartment opening to the cooling chamber at the top and +bottom. The warm air from above is cooled by melting the ice. It then +becomes denser and settles down into the main chamber. The articles in +the cooling room warm the air as they cool, so it rises to the top and +again comes in contact with the ice, thus completing the cycle. The +rate of this natural circulation is automatically regulated by the +temperature of the articles in the cooling chamber and by the amount +of ice in the icing compartment; hence the efficiency of such a box is +high. + +Now let us apply this principle to the drying of lumber. First we must +understand that as long as the lumber is moist and drying, it will +always be cooler than the surrounding air, the amount of this +difference being determined by the rate of drying and the moisture in +the wood. As the lumber dries, its temperature gradually rises until +it is equal to that of the air, when perfect dryness results. With +this fact in mind it is clear that the function of the lumber in a +kiln is exactly analogous to that of the ice in an ice box; that is, +it is the cooling agent. Similarly, the heating pipes in a dry kiln +bring about the same effect as the articles of food in the ice box in +that they serve to heat the air. Therefore, the air will be cooled by +the lumber, causing it to pass downward through the piles. If the +heating units are placed at the sides of the kiln, the action of the +air in a good ice box is duplicated in the kiln. The significant point +in this connection is that, the greener and colder the lumber, the +faster is the circulation. This is a highly desirable feature. + +A second vital point is that as the wood becomes gradually drier the +circulation automatically decreases, thus resulting in increased +efficiency, because there is no need for circulation greater than +enough to maintain the humidity of the air as it leaves the lumber +about the same as it enters. Therefore, we advocate either the +longitudinal side-wise inclined pile or edge stacking, the latter +being much preferable when possible. Of course the piles in our kiln +were small and could not be weighted properly, so the best results as +to reducing warping were not obtained. + +=Preliminary Steaming.=--Because the fibres of the gums become plastic +while moist and hot without causing defects, it is desirable to heat +the air-dried lumber to about 200 degrees Fahrenheit in saturated +steam at atmospheric pressure in order to reduce the warping. This +treatment also furnishes a means of heating the lumber very rapidly. +It is probably a good way to stop the sap-staining of green lumber, if +it is steamed while green. We have not investigated the other effects +of steaming green gum, however, so we hesitate to recommend it. + +Temperatures as high as 210 degrees Fahrenheit were used with no +apparent harm to the material. The best result was obtained with the +temperature of 180 degrees Fahrenheit, after the first preliminary +heating in steam to 200 degrees Fahrenheit. Higher temperatures may be +used with air-dried gum, however. + +The best method of humidity control proved to be to reduce the +relative humidity of the air from 100 per cent (saturated steam) very +carefully at first and then more rapidly to 30 per cent in about four +days. If the change is too marked immediately after the steaming +period, checking will invariably result. Under these temperature and +humidity conditions the stock was dried from 15 per cent moisture, +based on the dry wood weight, to 6 per cent in five days' time. The +loss due to checking was about 5 per cent, based on the actual footage +loss, not on commercial grades. + +=Final Steaming.=--From time to time during the test runs the material +was resawed to test for case-hardening. The stock dried in five days +showed slight case-hardening, so it was steamed at atmospheric +pressure for 36 minutes near the close of the run, with the result +that when dried off again the stresses were no longer present. The +material from one run was steamed for three hours at atmospheric +pressure and proved very badly case-hardened, but in the reverse +direction. It seems possible that by testing for the amount of +case-hardening one might select a final steaming period which would +eliminate all stresses in the wood. + + + Kiln-drying of Green Red Gum + +The following article was published by the United States Forestry +Service on the kiln-drying of green red gum: + +A short time ago fifteen fine, red-gum logs 16 feet long were received +from Sardis, Miss. They were in excellent condition and quite green. + +It has been our belief that if the gum could be kiln-dried directly +from the saw, a number of the difficulties in seasoning might be +avoided. Therefore, we have undertaken to find out whether or not such +a thing is feasible. The green logs now at the laboratory are to be +used in this investigation. One run of a preliminary nature has just +been made, the method and results of which I will now tell. + +This method was really adapted to the drying of Southern pine, and one +log of the green gum was cut into 1-inch stock and dried with the +pine. The heartwood contained many knots and some checks, although it +was in general of quite good quality. The sapwood was in fine +condition and almost as white as snow. + +This material was edge-stacked with one crosser at either end and one +at the center, of the 16-foot board. This is sufficient for the pine, +but was absolutely inadequate for drying green gum. A special +shrinkage take-up was applied at the three points. The results proved +very interesting in spite of the warping which was expected with but +three crossers in 16 feet. The method of circulation described was +used. It is our belief that edge piling is best for this method. + +This method of kiln-drying depends on the maintenance of a high +velocity of slightly superheated steam through the lumber. In few +words, the object is to maintain the temperature of the vapor as it +leaves the lumber at slightly above 212 degrees Fahrenheit. In order +to accomplish this result, it is necessary to maintain the high +velocity of circulation. As the wood dries, the superheat may be +increased until a temperature of 225 degrees or 230 degrees Fahrenheit +of the exit air is recorded. + +The 1-inch green gum was dried from 20.1 per cent to 11.4 per cent +moisture, based on the dry wood weight in 45 hours. The loss due to +checking was 10 per cent. Nearly every knot in the heartwood was +checked, showing that as the knots could be eliminated in any case, +this loss might not be so great. It was significant that practically +all of the checking occurred in the heartwood. The loss due to warping +was 22 per cent. Of course this was large; but not nearly enough +crossers were used for the gum. It is our opinion that this loss due +to warping can be very much reduced by using at least eight crossers +and providing for taking up of the shrinkage. A feature of this +process which is very important is that the method absolutely prevents +all sap staining. + +Another delightful surprise was the manner in which the superheated +steam method of drying changed the color of the sapwood from pure +white to a beautifully uniform, clean-looking, cherry red color which +very closely resembles that of the heartwood. This method is not new +by any means, as several patents have been granted on the steaming of +gum to render the sapwood more nearly the color of the heartwoods. The +method of application in kiln-drying green gum we believe to be new, +however. Other methods for kiln-drying this green stock are to be +tested until the proper process is developed. We expect to have +something interesting to report in the near future.[1] + + [Footnote 1: The above test was made at the United States + Forestry Service Laboratory, Madison, Wis.] + + + + + SECTION XII + + TYPES OF DRY KILNS + + DIFFERENT TYPES OF DRY KILNS + + +Dry kilns as in use to-day are divided into two classes: The "pipe" or +"moist-air" kiln, in which natural draft is relied upon for +circulation and, the "blower" or "hot blast" kiln, in which the +circulation is produced by fans or blowers. Both classes have their +adherents and either one will produce satisfactory results if properly +operated. + + + The "Blower" or "Hot Blast" Kiln + +The blower kiln in its various types has been in use so long that it +is hardly necessary to give to it a lengthy introduction. These kilns +at their inauguration were a wonderful improvement over the old style +"bake-oven" or "sweat box" kiln then employed, both on account of the +improved quality of the material and the rapidity at which it was +dried. + +These blower kilns have undergone steady improvement, not only in the +apparatus and equipment, but also in their general design, method of +introducing air, and provision for controlling the temperature and +humidity. With this type of kiln the circulation is always under +absolute control and can be adjusted to suit the conditions, which +necessarily vary with the conditions of the material to be dried and +the quantity to be put through the kiln. + +In either the blower or moist-air type of dry kiln, however, it is +absolutely essential, in order to secure satisfactory results, both as +to rapidity in drying and good quality of stock, that the kiln be so +designed that the temperature and humidity, together with circulation, +are always under convenient control. Any dry kiln in which this has +not been carefully considered will not give the desired results. + +In the old style blower kiln, while the circulation and temperature +was very largely under the operator's control, it was next to +impossible to produce conditions in the receiving end of the kiln so +that the humidity could be kept at the proper point. In fact, this was +one reason why the natural draft, or so-called moist-air kiln was +developed. + +The advent of the moist-air kiln served as an education to kiln +designers and manufacturers, in that it has shown conclusively the +value of a proper degree of humidity in the receiving end of any +progressive dry kiln, and it has been of special benefit also in that +it gave the manufacturers of blower kilns an idea as to how to improve +the design of their type of kiln to overcome the difficulty referred +to in the old style blower kilns. This has now been remedied, and in a +decidedly simple manner, as is usually the case with all things that +possess merit. + +It was found that by returning from one third to one half of the moist +air _after_ having passed through the kiln back to the fan room and by +mixing it with the fresh and more or less dry air going into the +drying room, that the humidity could be kept under convenient control. + +The amount of air that can be returned from a kiln of this class +depends upon three things: (1) The condition of the material when +entering the drying room; (2) the rapidity with which the material is +to be dried; and (3) the condition of the outside atmosphere. In the +winter season it will be found that a larger proportion of air may be +returned to the drying room than in summer, as the air during the +winter season contains considerably less moisture and as a consequence +is much drier. This is rather a fortunate coincidence, as, when the +kiln is being operated in this manner, it will be much more economical +in its steam consumption. + +In the summer season, when the outside atmosphere is saturated to a +much greater extent, it will be found that it is not possible to +return as great a quantity of air to the drying room, although there +have been instances of kilns of this class, which in operation have +had all the air returned and found to give satisfactory results. This +is an unusual condition, however, and can only be accounted for by +some special or peculiar condition surrounding the installation. + +In some instances, the desired amount of humidity in a blower type of +kiln is obtained by the addition of a steam spray in the receiving end +of the kiln, much in the same manner as that used in the moist-air +kilns. This method is not as economical as returning the +moisture-laden air from the drying room as explained in the preceding +paragraph. + +With the positive circulation that may be obtained in a blower kiln, +and with the conditions of temperature and humidity under convenient +control, this type of kiln has the elements most necessary to produce +satisfactory drying in the quickest possible elapsed time. + +It must not be inferred from this, however, that this class of dry +kiln may be installed and satisfactory results obtained regardless of +how it is handled. A great deal of the success of any dry kiln--or any +other apparatus, for that matter--depends upon intelligent operation. + + + Operation of the "Blower" Dry Kiln + +It is essential that the operator be supplied with proper facilities +to keep a record of the material as it is placed into the drying room, +and when it is taken out. An accurate record should be kept of the +temperature every two or three hours, for the different thicknesses +and species of lumber, that he may have some reliable data to guide +him in future cases. + +Any man possessing ordinary intelligence can operate dry kilns and +secure satisfactory results, providing he will use good judgment and +follow the basic instructions as outlined below: + + 1. When cold and before putting into operation, heat the + apparatus slowly until all pipes are hot, then start the fan + or blower, gradually bringing it up to its required speed. + + 2. See that _all_ steam supply valves are kept wide open, + unless you desire to lengthen the time required to dry the + material. + + 3. When using exhaust steam, the valve from the header + (which is a separate drip, independent of the trap + connection) must be kept wide open, but must be closed when + live steam is used on that part of the heater. + + 4. The engines as supplied by the manufacturers are + constructed to operate the fan or blower at a proper speed + with its throttle valve wide open, and with not less than 80 + pounds pressure of steam. + + 5. If the return steam trap does not discharge regularly, it + is important that it be opened and thoroughly cleaned and + the valve seat re-ground. + + 6. As good air circulation is as essential as the proper + degree of heat, and as the volume of air and its contact + with the material to be dried depends upon the volume + delivered by the fan or blower, it is necessary to maintain + a regular and uniform speed of the engine. + + 7. Atmospheric openings must always be maintained in the fan + or heater room for fresh air supply. + + 8. Successful drying cannot be accomplished without ample + and free circulation of air at all times. + +If the above instructions are fully carried out, and good judgment +used in the handling and operation of the blower kiln, no difficulties +should be encountered in successfully drying the materials at hand. + + + The "Pipe" or "Moist-air" Dry Kiln + +While in the blower class of dry kiln, the circulation is obtained by +forced draft with the aid of fans or blowers, in the Moist-air kilns +(see Fig. 31); the circulation is obtained by natural draft only, +aided by the manipulation of dampers installed at the receiving end of +the drying room, which lead to vertical flues through a stack to the +outside atmosphere. + +The heat in these kilns is obtained by condensing steam in coils of +pipe, which are placed underneath the material to be dried. As the +degree of heat required, and steam pressure govern the amount of +radiation, there are several types of radiating coils. In Fig. 32 will +be seen the Single Row Heating Coils for live or high pressure steam, +which are used when the low temperature is required. Figure 33 shows +the Double (or 2) Row Heating Coils for live or high pressure steam. +This apparatus is used when a medium temperature is required. In Fig. +34 will be seen the Vertical Type Heating Coils which is recommended +where exhaust or low-pressure steam is to be used, or may be used with +live or high-pressure steam when high temperatures are desired. + + [Illustration: Fig. 31. Section through a typical Moist-air + Dry Kiln.] + +These heating coils are usually installed in sections, which permit +any degree of heat from the minimum to the maximum to be maintained by +the elimination of, or the addition of, any number of heating +sections. This gives a dry kiln for the drying of green softwoods, or +by shutting off a portion of the radiating coils--thus reducing the +temperature--a dry kiln for drying hardwoods, that will not stand the +maximum degree of heat. + + [Illustration: Fig. 32. Single Pipe Heating Apparatus for Dry + Kilns, arranged for the Use of Live Steam. For Low + Temperatures.] + + [Illustration: Fig. 33. Double Pipe Heating Apparatus for Dry + Kilns, arranged for the Use of Live Steam. For Medium + Temperatures.] + +In the Moist-air or Natural Draft type of dry kiln, any degree of +humidity, from clear and dry to a dense fog may be obtained; this is +in fact, the main and most important feature of this type of dry kiln, +and the most essential one in the drying of hardwoods. + +It is not generally understood that the length of a kiln has any +effect upon the quantity of material that may be put through it, but +it is a fact nevertheless that long kilns are much more effective, and +produce a better quality of stock in less time than kilns of shorter +length. + +Experience has proven that a kiln from 80 to 125 feet in length will +produce the best results, and it should be the practice, where +possible, to keep them within these figures. The reason for this is +that in a long kiln there is a greater drop in temperature between the +discharge end and the green or receiving end of the kiln. + +It is very essential that the conditions in the receiving end of the +kiln, as far as the temperature and humidity are concerned, must go +hand in hand. + +It has also been found that in a long kiln the desired conditions may +be obtained with higher temperatures than with a shorter kiln; +consequently higher temperatures may be carried in the discharge end +of the kiln, thereby securing greater rapidity in drying. It is not +unusual to find that a temperature of 200 degrees Fahrenheit is +carried in the discharge end of a long dry kiln with safety, without +in any way injuring the quality of the material, although, it would be +better not to exceed 180 degrees in the discharge end, and about 120 +degrees in the receiving or green end in order to be on the safe side. + + + Operation of the "Moist-air" Dry Kiln + +To obtain the best results these kilns should be kept in continuous +operation when once started, that is, they should be operated +continuously day and night. When not in operation at night or on +Sundays, and the kiln is used to season green stock direct from the +saw, the large doors at both ends of the kiln should be opened wide, +or the material to be dried will "sap stain." + + [Illustration: Fig. 34. Vertical Pipe Heating Apparatus for + Dry Kilns; may be used in Connection with either Live or + Exhaust Steam for High or Low Temperatures.] + +It is highly important that the operator attending any drying +apparatus keep a minute and accurate record of the condition of the +material as it is placed into the drying room, and its final condition +when taken out. + +Records of the temperature and humidity should be taken frequently and +at stated periods for the different thicknesses and species of +material, in order that he may have reliable data to guide him in +future operations. + +The following facts should be taken into consideration when operating +the Moist-air dry kiln: + + 1. Before any material has been placed in the drying room, + the steam should be turned into the heating or radiating + coils, gradually warming them, and bringing the temperature + in the kiln up to the desired degree. + + 2. Care should be exercised that there is sufficient + humidity in the receiving or loading end of the kiln, in + order to guard against checking, case-hardening, etc. + Therefore it is essential that the steam spray at the + receiving or loading end of the kiln be properly + manipulated. + + 3. As the temperature depends principally upon the pressure + of steam carried in the boilers, maintain a steam pressure + of not less than 80 pounds at all times; it may range as + high as 100 pounds. The higher the temperature with its + relatively high humidity the more rapidly the drying will be + accomplished. + + 4. Since air circulation is as essential as the proper + degree of heat, and as its contact with the material to be + dried depends upon its free circulation, it is necessary + that the dampers for its admittance into, and its exit from, + the drying room be efficiently and properly operated. + Successful drying cannot be accomplished without ample and + free circulation of air at all times during the drying + process. + +If the above basic principles are carefully noted and followed out, +and good common sense used in the handling and operation of the kiln +apparatus, no serious difficulties should arise against the successful +drying of the materials at hand. + + + Choice of Drying Method + +At this point naturally arises the question: Which of the two classes +of dry kilns, the "Moist-air" or "Blower" kiln is the better adapted +for my particular needs? + +This must be determined entirely by the species of wood to be dried, +its condition when it goes into the kiln, and what kind of finished +product is to be manufactured from it. + +Almost any species of hardwood which has been subjected to +air-seasoning for three months or more may be dried rapidly and in the +best possible condition for glue-jointing and fine finishing with a +"Blower" kiln, but green hardwood, direct from the saw, can only be +successfully dried (if at all) in a "Moist-air" kiln. + +Most furniture factories have considerable bent stock which must of +necessity be thoroughly steamed before bending. By steaming, the +initial process of the Moist-air kiln has been consummated. Hence, the +Blower kiln is better adapted to the drying of such stock than the +Moist-air kiln would be, as the stock has been thoroughly soaked by +the preliminary steaming, and all that is required is sufficient heat +to volatilize the moisture, and a strong circulation of air to remove +it as it comes to the surface. + +The Moist-air kiln is better adapted to the drying of tight cooperage +stock, while the Blower kiln is almost universally used throughout the +slack cooperage industry for the drying of its products. + +For the drying of heavy timbers, planks, blocks, carriage stock, etc., +and for all species of hardwood thicker than one inch, the Moist-air +kiln is undoubtedly the best. + +Both types of kilns are equally well adapted to the drying of 1-inch +green Norway and white pine, elm, hemlock, and such woods as are used +in the manufacture of flooring, ceiling, siding, shingles, hoops, tub +and pail stock, etc. + +The selection of one or the other for such work is largely matter of +personal opinion. + + + Kilns of Different Types + +All dry kilns as in use to-day are divided as to method of drying into +two classes: + + The "Pipe" or "Moist-air" kiln; + The "Blower" or "Hot Blast" kiln; + +both of which have been fully explained in a previous article. + +The above two classes are again subdivided into five different types +of dry kilns as follows: + + The "Progressive" kiln; + The "Apartment" kiln; + The "Pocket" kiln; + The "Tower" kiln; + The "Box" kiln. + + + The "Progressive" Dry Kiln + +Dry kilns constructed so that the material goes in at one end and is +taken out at the opposite end are called Progressive dry kilns, from +the fact that the material gradually progresses through the kiln from +one stage to another while drying (see Fig. 31). + +In the operation of the Progressive kiln, the material is first +subjected to a sweating or steaming process at the receiving or +loading end of the kiln with a low temperature and a relative high +humidity. It then gradually progresses through the kiln into higher +temperatures and lower humidities, as well as changes of air +circulation, until it reaches the final stage at the discharge end of +the kiln. + +Progressive kilns, in order to produce the most satisfactory results, +especially in the drying of hardwoods or heavy softwood timbers, +should be not less than 100 feet in length (see Fig. 35). + +In placing this type of kiln in operation, the following instructions +should be carefully followed: + +When steam has been turned into the heating coils, and the kiln is +fairly warm, place the first car of material to be dried in the drying +room--preferably in the morning--about 25 feet from the kiln door on +the receiving or loading end of the kiln, blocking the wheels so that +it will remain stationary. + + [Illustration: Fig. 35. Exterior View of Four Progressive Dry + Kilns, each 140 Feet long by 18 Feet wide. Cross-wise piling, + fire-proof construction.] + +Five hours later, or about noon, run in the second car and stop it +about five feet from the first one placed in the drying room. Five +hours later, or in the evening push car number two up against the +first car; then run in car number three, stopping it about five feet +from car number two. + +On the morning of the second day, push car number three against the +others, and then move them all forward about 25 feet, and then run in +car number four, stopping it about five feet from the car in advance +of it. Five hours later, or about noon, run in car number five and +stop it about five feet from car number four. In the evening or about +five hours later, push these cars against the ones ahead, and run in +loaded car number six, stopping it about five feet from the preceding +car. + +On the morning of the third day, move all the cars forward about six +feet; then run in loaded car number seven stop it about four feet from +the car preceding it. Five hours later or about noon push this car +against those in advance of it, and run in loaded car number eight +moving all cars forward about six feet, and continue in this manner +until the full complement of cars have been placed in the kiln. When +the kiln has been filled, remove car number one and push all the +remaining cars forward and run in the next loaded car, and continue in +this manner as long as the kiln is in operation. + +As the temperature depends principally upon the pressure of steam, +maintain a steam pressure of not less than 80 pounds at all times; it +may range up to as high as 100 pounds. The higher the temperature with +a relatively higher humidity the more rapidly the drying will be +accomplished. + +If the above instructions are carried out, the temperatures, +humidities, and air circulation properly manipulated, there should be +complete success in the handling of this type of dry kiln. + +The Progressive type of dry kiln is adapted to such lines of +manufacture that have large quantities of material to kiln-dry where +the species to be dried is of a similiar nature or texture, and does +not vary to any great extent in its thickness, such, for instance, as: + + Oak flooring plants; + Maple flooring plants; + Cooperage plants; + Large box plants; + Furniture factories; etc. + +In the selection of this kind of dry kiln, consideration should be +given to the question of ground space of sufficient length or +dimension to accommodate a kiln of proper length for successful +drying. + + + The "Apartment" Dry Kiln + +The Apartment system of dry kilns are primarily designed for the +drying of different kinds or sizes of material at the same time, a +separate room or apartment being devoted to each species or size when +the quantity is sufficient (see Fig. 36). + +These kilns are sometimes built single or in batteries of two or more, +generally not exceeding 40 or 50 feet in length with doors and +platforms at both ends the same as the Progressive kilns; but in +operation each kiln is entirely filled at one loading and then closed, +and the entire contents dried at one time, then emptied and again +recharged. + +Any number of apartments may be built, and each apartment may be +arranged to handle any number of cars, generally about three or four, +or they may be so constructed that the material is piled directly upon +the floor of the drying room. + + [Illustration: Fig. 36. Exterior View of Six Apartment Dry + Kilns, each 10 Feet wide by 52 Feet long, End-wise Piling. + They are entirely of fire-proof construction and equipped + with double doors (Hussey asbestos outside and canvas + inside), and are also equipped with humidity and air control + dampers, which may be operated from the outside without + opening the kiln doors, which is a very good feature.] + +When cars are used, it is well to have a transfer car at each end of +the kilns, and stub tracks for holding cars of dry material, and for +the loading of the unseasoned stock, as in this manner the kilns may +be kept in full operation at all times. + +In this type of dry kiln the material receives the same treatment and +process that it would in a Progressive kiln. The advantages of +Apartment kilns is manifest where certain conditions require the +drying of numerous kinds as well as thicknesses of material at one and +the same time. This method permits of several short drying rooms or +apartments so that it is not necessary to mix hardwoods and softwoods, +or thick and thin material in the same kiln room. + +In these small kilns the circulation is under perfect control, so that +the efficiency is equal to that of the more extensive plants, and will +readily appeal to manufacturers whose output calls for the prompt and +constant seasoning of a large variety of small stock, rather than a +large volume of material of uniform size and grade. + +Apartment kilns are recommended for industries where conditions +require numerous kinds and thicknesses of material to be dried, such +as: + + Furniture factories; + Piano factories; + Interior woodwork mills; + Planing mills; etc. + + + The "Pocket" Dry Kiln + +"Pocket" dry kilns (see Fig. 37) are generally built in batteries of +several pockets. They have the tracks level and the lumber goes in and +out at the same end. Each drying room is entirely filled at one time, +the material is dried and then removed and the kiln again recharged. + +The length of "Pocket" kilns ranges generally from 14 feet to about 32 +feet. + +The interior equipment for this type of dry kiln is arranged very +similiar to that used in the Apartment kiln. The heating or radiating +coils and steam spray jets extend the whole length of the drying room, +and are arranged for the use of either live or exhaust steam, as +desired. + +Inasmuch as Pocket kilns have doors at one end only, this feature +eliminates a certain amount of door exposure, which conduces towards +economy in operation. + +In operating Pocket kilns, woods of different texture and thickness +should be separated and placed in different drying rooms, and each +kiln adjusted and operated to accommodate the peculiarities of the +species and thickness of the material to be dried. + + [Illustration: Fig. 37. Exterior View of Five Pocket Dry + Kilns, built in Two Batteries with the Front of each Set + facing the other, and a Transfer System between. They are + also equipped with the asbestos doors.] + +Naturally, the more complex the conditions of manufacturing wood +products in any industry, the more difficult will be the proper +drying of same. Pocket kilns, are, therefore, recommended for +factories having several different kinds and thicknesses of material +to dry in small quantities of each, such as: + + Planing mills; + Chair factories; + Furniture factories; + Sash and door factories; etc. + + + The "Tower" Dry Kiln + +The so-called "Tower" dry kiln (see Fig. 38) is designed for the rapid +drying of small stuff in quantities. Although the general form of +construction and the capacity of the individual bins or drying rooms +may vary, the same essential method of operation is common to all. +That is, the material itself, such as wooden novelties, loose staves, +and heading for tubs, kits, and pails, for box stuff, kindling wood, +etc., is dumped directly into the drying rooms from above, or through +the roof, in such quantities as effectually to fill the bin, from +which it is finally removed when dry, through the doors at the bottom. + +These dry kilns are usually operated as "Blower" kilns, the heating +apparatus is generally located in a separate room or building adjacent +to the main structure or drying rooms, and arranged so that the hot +air discharged through the inlet duct (see illustration) is thoroughly +distributed beneath a lattice floor upon which rests the material to +be dried. Through this floor the air passes directly upward, between +and around the stock, and finally returns to the fan or heating room. + +This return air duct is so arranged that by means of dampers, leading +from each drying room, the air may be returned in any quantity to the +fan room where it is mixed with fresh air and again used. This is one +of the main features of economy of the blower system of drying, as by +the employment of this return air system, considerable saving may be +made in the amount of steam required for drying. + + [Illustration: Fig. 38. Exterior and Sectional View of a + Battery of Tower Dry Kilns. This is a "Blower" or "Hot Blast" + type, and shows the arrangement of the fan blower, engine, + etc. This type of dry kin is used principally for the + seasoning of small, loose material.] + +The lattice floors in this type of dry kiln are built on an incline, +which arrangement materially lessens the cost, and increases the +convenience with which the dried stock may be removed from the bins or +drying rooms. + +In operation, the material is conveyed in cars or trucks on an +overhead trestle--which is inclosed--from which the material to be +dried is dumped directly into the drying rooms or bins, through +hoppers arranged for that purpose thereby creating considerable saving +in the handling of the material to be dried into the kiln. The entire +arrangement thus secures the maximum capacity, with a minimum amount +of floor space, with the least expense. Of course, the higher these +kilns are built, the less relative cost for a given result in the +amount of material dried. + +In some instances, these kilns are built less in height and up against +an embankment so that teamloads of material may be run directly onto +the roof of the kilns, and dumped through the hoppers into the drying +rooms or bins, thus again reducing to a minimum the cost of this +handling. + +The return air duct plays an important part in both of these methods +of filling, permitting the air to become saturated to the maximum +desired, and utilizing much of the heat contained therein, which would +otherwise escape to the atmosphere. + +The "Tower" kiln is especially adapted to factories of the following +class: + + Sawmills; + Novelty factories; + Woodenware factories; + Tub and pail factories; etc. + + + The "Box" Dry Kiln + +The "Box" kiln shown in Figure 39 is an exterior view of a kiln of +this type which is 20 feet wide, 19 feet deep, and 14 feet high, which +is the size generally used when the space will permit. + +Box kilns are used mostly where only a small quantity of material is +to be dried. They are not equipped with trucks or cars, the material +to be dried being piled upon a raised platform inside the drying +room. This arrangement, therefore, makes them of less cost than the +other types of dry kilns. + +They are particularly adapted to any and all species and size of +lumber to be dried in very small quantities. + + [Illustration: Fig. 39. Exterior view of the Box Dry Kiln. + This particular kiln is 20 feet wide, 19 feet deep and 14 + feet high. Box kilns are used mostly where only a small + amount of kiln-dried lumber of various sizes is required. + They are not equipped with trucks or cars, and therefore cost + less to construct than any other type of dry kiln.] + +In these small kilns the circulation is under perfect control, so that +the efficiency is equal to that of the more extensive plants. + +These special kilns will readily appeal to manufacturers, whose output +calls for the prompt and constant seasoning of a large variety of +small stock, rather than a large volume material of uniform size and +grade. + + + + + SECTION XIII + + DRY KILN SPECIALTIES + + KILN CARS AND METHOD OF LOADING + + +Within recent years, the edge-wise piling of lumber (see Figs. 40 and +41), upon kiln cars has met with considerable favor on account of its +many advantages over the older method of flat piling. It has been +proven that lumber stacked edge-wise dries more uniformly and rapidly, +and with practically no warping or twisting of the material, and that +it is finally discharged from the dry kiln in a much better and +brighter condition. This method of piling also considerably increases +the holding and consequent drying capacities of the dry kiln by reason +of the increased carrying capacities of the kiln cars, and the shorter +period of time required for drying the material. + + [Illustration: Fig. 40. Car Loaded with Lumber on its Edges + by the Automatic Stacker, to go into the Dry Kiln cross-wise. + Equipped with two edge piling kiln trucks.] + +In Figures 42 and 43 are shown different views of the automatic lumber +stacker for edge-wise piling of lumber on kiln cars. Many users of +automatic stackers report that the grade of their lumber is raised to +such an extent that the system would be profitable for this reason +alone, not taking into consideration the added saving in time and +labor, which to anyone's mind should be the most important item. + + [Illustration: Fig. 41. Car Loaded with Lumber on its Edges + by the Automatic Stacker, to go into the Dry Kiln end-wise. + The bunks on which the lumber rests are channel steel. The + end sockets are malleable iron and made for I-beam stakes.] + +In operation, the lumber is carried to these automatic stackers on +transfer chains or chain conveyors, and passes on to the stacker +table. When the table is covered with boards, the "lumber" lever is +pulled by the operator, which raises a stop, preventing any more +lumber leaving the chain conveyor. The "table" lever then operates the +friction drive and raises the table filled with the boards to a +vertical position. As the table goes up, it raises the latches, which +fall into place behind the piling strips that had been previously laid +on the table. When the table returns to the lower position, a new set +of piling strips are put in place on the table, and the stream of +boards which has been accumulating on the conveyor chain are again +permitted to flow onto the table. As each layer of lumber is added, +the kiln car is forced out against a strong tension. When the car is +loaded, binders are put on over the stakes by means of a powerful +lever arrangement. + + [Illustration: Fig. 42. The above illustration shows the + construction of the Automatic Lumber Stacker for edge piling + of lumber to go into the dry kiln end-wise.] + + [Illustration: Fig. 43. The above illustration shows the + construction of the Automatic Lumber Stacker for edge piling + of lumber to go into the dry kiln cross-wise.] + + [Illustration: Fig. 44. The above illustration shows a + battery of Three Automatic Lumber Stackers.] + + [Illustration: Fig. 45. The above illustration shows another + battery of Three Automatic Lumber Stackers.] + + [Illustration: Fig. 46. Cars Loaded with Lumber on its Edges + by the Automatic Lumber Stackers.] + +After leaving the dry kilns, the loaded car is transferred to the +unstacker (see Fig. 47). Here it is placed on the unstacker car which, +by means of a tension device, holds the load of lumber tight against +the vertical frame of the unstacker. The frame of the unstacker is +triangular and has a series of chains. Each chain has two special +links with projecting lugs. The chains all travel in unison. The lug +links engage a layer of boards, sliding the entire layer vertically, +and the boards, one at a time, fall over the top of the unstacker +frame onto the inclined table, and from there onto conveyor chains +from which they may be delivered to any point desired, depending upon +the length and direction of the chain conveyor. + +With these unstackers one man can easily unload a kiln car in twenty +minutes or less. + + [Illustration: Fig. 47. The Lumber Unstacker Car, used for + unloading cars of Lumber loaded by the Automatic Stacker.] + + [Illustration: Fig. 48. The Lumber Unstacker Car and + Unstacker, used for unloading Lumber loaded by the Automatic + Stacker.] + +The experience of many users prove that these edge stacking machines +are not alike. This is important, because there is one feature of edge +stacking that must not be overlooked. Unless each layer of boards is +forced into place by power and held under a strong pressure, much +slack will accumulate in an entire load, and the subsequent handling +of the kiln cars, and the effect of the kiln-drying will loosen up the +load until there is a tendency for the layers to telescope. And unless +the boards are held in place rigidly and with strong pressure they +will have a tendency to warp. + + [Illustration: Fig. 49. The above illustration shows method + of loading kiln cars with veneer on its edges by the use of + the Tilting Platform.] + +A kiln car of edge-stacked lumber, properly piled, is made up of +alternate solid sheets of lumber and vertical open-air spaces, so that +the hot air and vapors rise naturally and freely through the lumber, +drying both sides of the board evenly. The distribution of the heat +and moisture being even and uniform, the drying process is naturally +quickened, and there is no opportunity or tendency for the lumber to +warp. + +In Figure 49 will be seen a method of loading kiln cars with veneer on +edge by the use of a tilting platform. On the right of the +illustration is seen a partially loaded kiln car tilted to an angle of +45 degrees, to facilitate the placing of the veneer on the car. At +the left is a completely loaded car ready to enter the dry kiln. + +Gum, poplar, and pine veneers are satisfactorily dried in this manner +in from 8 to 24 hours. + +In Figure 50 will be seen method of piling lumber on the flat, +"cross-wise" of the dry kiln when same has three tracks. + + [Illustration: Fig. 50. Method of Loading lumber on its Flat, + cross-wise of the Dry Kiln when same has Three Tracks.] + +In Figure 51 will be seen another method of piling lumber on the flat, +"cross-wise" of the dry kiln when same has three tracks. + +In Figure 52 will be seen method of piling lumber on the flat, +"end-wise" of the dry kiln when same has two tracks. + +In Figure 53 will be seen another method of piling lumber on the flat, +"end-wise" of the dry kiln when same has two tracks. + +In Figure 54 will be seen method of piling slack or tight barrel +staves "cross-wise" of the kiln when same has three tracks. + +In Figure 55 will be seen another method of piling slack or tight +barrel staves "cross-wise" of the dry kiln when same has three tracks. + +In Figure 56 will be seen method of piling small tub or pail staves +"cross-wise" of the dry kiln when same has two tracks. + +In Figure 57 will be seen method of piling bundled staves "cross-wise" +of the dry kiln when same has two tracks. + + [Illustration: Fig. 51. Method of loading Lumber on its Flat, + cross-wise of the Dry Kiln when same has Three Tracks.] + + [Illustration: Fig. 52. Method of loading Lumber on its Flat, + end-wise of the Dry Kiln by the Use of the Single-sill or + Dolly Truck.] + + [Illustration: Fig. 53. Method of loading Lumber on its Flat, + end-wise of the Dry Kiln by the Use of the Double-sill + Truck.] + + [Illustration: Fig. 54. Method of loading Kiln Car with Tight + or Slack Barrel Staves cross-wise of Dry Kiln.] + + [Illustration: Fig. 55. Method of loading Kiln Car with Tight + or Slack Barrel Staves cross-wise of Dry Kiln.] + + [Illustration: Fig. 56. Method of loading Kiln Car with Tub + or Pail Staves cross-wise of Dry Kiln.] + + [Illustration: Fig. 57. Method of loading Kiln Car with + Bundled Staves cross-wise of Dry Kiln.] + +In Figure 58 will be seen method of piling shingles "cross-wise" of +dry kiln when same has three tracks. + +In Figure 59 will be seen another method of piling shingles +"cross-wise" of the dry kiln when same has three tracks. + + [Illustration: Fig. 58. Method of loading Kiln Car with + Shingles cross-wise of Dry Kiln.] + + [Illustration: Fig. 59. Method of loading Kiln Car with + Shingles cross-wise of Dry Kiln.] + +In Figure 60 will be seen method of piling shingles "end-wise" of the +dry kiln when same has two tracks. + +In Figure 61 will be seen a kiln car designed for handling short tub +or pail staves through a dry kiln. + + [Illustration: Fig. 60. Car loaded with 100,000 Shingles. + Equipped with four long end-wise piling trucks and to go into + dry kiln end-wise.] + + [Illustration: Fig. 61. Kiln Car designed for handling Short + Tub or Pail Staves through a Dry Kiln.] + +In Figure 62 will be seen a kiln car designed for short piece stock +through a dry kiln. + +In Figure 63 will be seen a type of truck designed for the handling of +stave bolts about a stave mill or through a steam box. + +In Figure 64 will be seen another type of truck designed for the +handling of stave bolts about a stave mill or through a steam box. + +In Figure 65 will be seen another type of truck designed for the +handling of stave bolts about a stave mill or through a steam box. + +In Figure 66 will be seen another type of truck designed for the +handling of stave bolts about a stave mill or through a steam box. + +In Figure 67 will be seen another type of truck designed for the +handling of stave bolts about a stave mill or through a steam box. + +In Figure 68 will be seen another type of truck designed for the +handling of stave bolts about a stave mill or through a steam box. + +In Figure 69 will be seen the Regular 3-rail Transfer Car designed for +the handling of 2-rail kiln cars which have been loaded "end-wise." + +In Figure 70 will be seen another type of Regular 3-rail Transfer Car +designed for the handling of 2-rail kiln cars which have been loaded +"end-wise." + +In Figure 71 will be seen a Specially-designed 4-rail Transfer Car for +2-rail kiln cars which have been built to accommodate extra long +material to be dried. + +In Figure 72 will be seen the Regular 2-rail Transfer Car designed for +the handling of 3-rail kiln cars which have been loaded "cross-wise." + +In Figure 73 will be seen another type of Regular 2-rail Transfer Car +designed for the handling of 3-rail kiln cars which have been loaded +"cross-wise." + +In Figure 74 will be seen the Regular 2-rail Underslung type of +Transfer Car designed for the handling of 3-rail kiln cars which have +been loaded "cross-wise." Two important features in the construction +of this transfer car make it extremely easy in its operation. It has +extra large wheels, diameter 13-1/2 inches, and being underslung, the +top of its rails are no higher than the other types of transfer cars. +Note the relative size of the wheels in the illustration, yet the car +is only about 10 inches in height. + + [Illustration: Fig. 62. Kiln Car Designed for handling Short + Piece Stock through a Dry Kiln.] + + [Illustration: Fig. 63. A Stave Bolt Truck.] + + [Illustration: Fig. 64. A Stave Bolt Truck.] + + [Illustration: Fig. 65. A Stave Bolt Truck.] + + [Illustration: Fig. 66. A Stave Bolt Truck.] + + [Illustration: Fig. 67. A Stave Bolt Truck.] + + [Illustration: Fig. 68. A Stave Bolt Truck.] + + [Illustration: Fig. 69. A Regular 3-Rail Transfer Truck.] + + [Illustration: Fig. 70. A Regular 3-Rail Transfer Truck.] + + [Illustration: Fig. 71. A Special 4-Rail Transfer Truck.] + + [Illustration: Fig. 72. A Regular 2-Rail Transfer Truck.] + + [Illustration: Fig. 73. A Regular 2-Rail Transfer Truck.] + + [Illustration: Fig. 74. A Regular 2-Rail Underslung Transfer + Truck.] + + [Illustration: Fig. 75. A Regular 3-Rail Underslung Transfer + Truck.] + +In Figure 75 will be seen the Regular 3-rail Underslung type of +Transfer Car designed for the handling of 2-rail kiln cars which have +been loaded "end-wise." This car also has the important features of +large diameter wheels and low rail construction, which make it very +easy in its operation. + + [Illustration: Fig. 76. A Special 2-Rail Flexible Transfer + Truck.] + +In Figure 76 will be seen the Special 2-rail Flexible type of Transfer +Car designed for the handling of 3-rail kiln cars which have been +loaded "cross-wise." This car is equipped with double the usual number +of wheels, and by making each set of trucks a separate unit (the front +and rear trucks being bolted to a steel beam with malleable iron +connection), a slight up-and-down movement is permitted, which enables +this transfer car to adjust itself to any unevenness in the track, +which is a very good feature. + +In Figure 77 will be seen the Regular Transfer Car designed for the +handling of stave bolt trucks. + +In Figure 78 will be seen another type of Regular Transfer Car +designed for the handling of stave bolt trucks. + +In Figure 79 will be seen a Special Transfer Car designed for the +handling of stave bolt trucks. + + [Illustration: Fig. 77. A Regular Transfer Car for handling + Stave Bolt Trucks.] + + [Illustration: Fig. 78. A Regular Transfer Car for handling + Stave Bolt Trucks.] + + [Illustration: Fig. 79. A Special Transfer Car for handling + Stave Bolt Trucks.] + +In Figure 80 will be seen the Regular Channel-iron Kiln Truck designed +for edge piling "cross-wise" of the dry kiln. + +In Figure 81 will be seen another type of Regular Channel-iron Kiln +Truck designed for edge piling "cross-wise" of the dry kiln. + + [Illustration: Fig. 80. A Regular Channel-iron Kiln Truck.] + + [Illustration: Fig. 81. A Regular Channel-iron Kiln Truck.] + +In Figure 82 will be seen the Regular Channel-iron Kiln Truck designed +for flat piling "end-wise" of the dry kiln. + + [Illustration: Fig. 82. A Regular Channel-iron Kiln Truck.] + + [Illustration: Fig. 83. A Regular Channel-iron Kiln Truck.] + + [Illustration: Fig. 84. A Regular Single-sill or Dolly Kiln + Truck.] + +In Figure 83 will be seen the Regular Channel-iron Kiln Truck with +I-Beam cross-pieces designed for flat piling "end-wise" of the dry +kiln. + +In Figure 84 will be seen the Regular Small Dolly Kiln Truck designed +for flat piling "end-wise" of the dry kiln. + + + Different Types of Kiln Doors + +In Figure 85 will be seen the Asbestos-lined Door. The construction of +this kiln door is such that it has no tendency to warp or twist. The +framework is solid and the body is made of thin slats placed so that +the slat on either side covers the open space of the other with +asbestos roofing fabric in between. This makes a comparatively light +and inexpensive door, and one that absolutely holds the heat. These +doors may be built either swinging, hoisting, or sliding. + + [Illustration: Fig. 85. An Asbestos-lined Kiln Door of the + Hinge Type.] + +In Figure 86 will be seen the Twin Carrier type of door hangers with +doors loaded and rolling clear of the opening. + + [Illustration: Fig. 86. Twin Carrier with Kiln Door loaded + and rolling clear of Opening.] + + [Illustration: Fig. 87. Twin Carriers for Kiln Doors 18 to 35 + Feet wide.] + +In Figure 87 will be seen the Twin Carrier for doors 18 to 35 feet +wide, idle on a section of the track. + +In Figure 88 will be seen another type of carrier for kiln doors. + +In Figure 89 will be seen the preceding type of kiln door carrier in +operation. + +In Figure 90 will be seen another type of carrier for kiln doors. + +In Figure 91 will be seen kiln doors seated, wood construction, +showing 3-1/2" x 5-3/4" inch-track timbers and trusses, supported on +4-inch by 6-inch jamb posts. "T" rail track, top and side, inclined +shelves on which the kiln door rests. Track timber not trussed on +openings under 12 feet wide. + + [Illustration: Fig. 88. Kiln Door Carrier engaged to Door + Ready for lifting.] + +In Figure 92 will be seen kiln doors seated, fire-proof construction, +showing 12-inch, channel, steel lintels, 2" x 2" steel angle mullions, +track brackets bolted to the steel lintels and "T" rail track. No +track timbers or trusses used. + + [Illustration: Fig. 89. Kiln Door Carrier shown on Doors of + Wood Construction.] + + [Illustration: Fig. 90. Kiln Door Construction with Door + Carrier out of Sight.] + + [Illustration: Fig. 91. Kiln Door Construction. Doors Seated. + Wood Construction.] + + [Illustration: Fig. 92. Kiln Door Construction. Doors Seated. + Fire-proof Construction.] + + + + + SECTION XIV + + HELPFUL APPLIANCES IN KILN-DRYING + + + The Humidity Diagram + + [Illustration: Fig. 93. The United States Forest Service + Humidity Diagram for determination of Absolute Humidities. + Dew Points and Vapor Pressures; also Relative Humidities by + means of Wet and Dry-Bulb Thermometer, for any temperatures + and change in temperature.] + +Some simple means of determining humidities and changes in humidity +brought about by changes in temperature in the dry kiln without the +use of tables is almost a necessity. To meet this requirement the +United States Forestry Service has devised the Humidity Diagram shown +in Figure 93. It differs in several respects from the hydrodeiks now +in use. + +The purpose of the humidity diagram is to enable the dry-kiln operator +to determine quickly the humidity conditions and vapor pressure, as +well as the changes which take place with changes of temperature. The +diagram above is adapted to the direct solution of problems of this +character without recourse to tables or mathematical calculations. + +The humidity diagram consists of two distinct sets of curves on the +same sheet. One set, the convex curves, is for the determination of +relative humidity of wet-and-dry-bulb hygrometer or psychrometer; the +other, the concave curves, is derived from the vapor pressures and +shows the amount of moisture per cubic foot at relative humidities and +temperatures when read at the dew-point. The latter curves, therefore, +are independent of all variables affecting the wet-bulb readings. They +are proportional to vapor pressures, not to density, and, therefore, +may be followed from one temperature to another with correctness. The +short dashes show the correction (increase or decrease) which is +necessary in the relative humidity, read from the convex curves, with +an increase or decrease from the normal barometric pressure of 30 +inches, for which the curves have been plotted. This correction, +except for very low temperatures, is so small that it may usually be +disregarded. + +The ordinates, or vertical distances, are relative humidity expressed +in per cent of saturation, from 0 per cent at the bottom to 100 per +cent at the top. The abscissae, or horizontal distances, are +temperatures in degrees Fahrenheit from 30 degrees below zero, at the +left, to 220 degrees above, at the right. + + + Examples of Use + +The application of the humidity diagram can best be understood by +sample problems. These problems also show the wide range of conditions +to which the diagram will apply. + + EXAMPLE 1. To find the relative humidity by use of + wet-and-dry-bulb hygrometer or psychrometer: + + Place the instrument in a strong circulation of air, or wave + it to and fro. Read the temperature of the dry bulb and the + wet, and subtract. Find on the horizontal line the + temperature shown by the dry-bulb thermometer. Follow the + vertical line from this point till it intersects with the + convex curve marked with the difference between the wet and + dry readings. The horizontal line passing through this + intersection will give the relative humidity. + + Example: Dry bulb 70 deg., wet bulb 62 deg., difference 8 deg.. Find 70 deg. + on the horizontal line of temperature. Follow up the + vertical line from 70 deg. until it intersects with the convex + curve marked 8 deg.. The horizontal line passing through this + intersection shows the relative humidity to be 64 per cent. + + EXAMPLE 2. To find how much water per cubic foot is + contained in the air: + + Find the relative humidity as in example 1. Then the nearest + concave curve gives the weight of water in grains per cubic + foot when the air is cooled to the dew-point. Using the same + quantities as in example 1, this will be slightly more than + 5 grains. + + EXAMPLE 3. To find the amount of water required to saturate + air at a given temperature: + + Find on the top line (100 per cent humidity) the given + temperature; the concave curve intersecting at or near this + point gives the number of grains per cubic foot. + (Interpolate, if great accuracy is desired.) + + EXAMPLE 4. To find the dew-point: + + Obtain the relative humidity as in example 1. Then follow up + parallel to the nearest concave curve until the top + horizontal (indicating 100 per cent relative humidity) is + reached. The temperature on this horizontal line at the + point reached will be the dew-point. + + Example: Dry bulb 70 deg., wet bulb 62 deg.. On the vertical line + for 70 deg. find the intersection with the hygrometer (convex) + curve for 8 deg.. This will be found at nearly 64 per cent + relative humidity. Then follow up parallel with the vapor + pressure (concave) curve marked 5 grains to its intersection + at the top of the chart with the 100 per cent humidity line. + This gives the dew-point as 57 deg.. + + EXAMPLE 5. To find the change in the relative humidity + produced by a change in temperature: + + Example: The air at 70 deg. Fahr. is found to contain 64 per + cent humidity; what will be its relative humidity if heated + to 150 deg. Fahr.? Starting from the intersection of the + designated humidity and temperature coordinates, follow the + vapor-pressure curve (concave) until it intersects the 150 deg. + temperature ordinate. The horizontal line then reads 6 per + cent relative humidity. The same operation applies to + reductions in temperature. In the above example what is the + humidity at 60 deg.? Following parallel to the same curve in the + opposite direction until it intersects the 60 deg. ordinate + gives 90 per cent; at 57 deg. it becomes 100 per cent, reaching + the dew-point. + + EXAMPLE 6. To find the amount of condensation produced by + lowering the temperature: + + Example: At 150 deg. the wet bulb reads 132 deg.. How much water + would be condensed if the temperature were lowered to 70 deg.? + The intersection of the hygrometer curve for 18 deg. (150 deg.-132 deg.) + with temperature line for 150 deg. shows a relative humidity of + 60 per cent. The vapor-pressure curve (concave) followed up + to the 100 per cent relative humidity line shows 45 grains + per cubic foot at the dew-point, which corresponds to a + temperature of 130 deg.. At 70 deg. it is seen that the air can + contain but 8 grains per cubic foot (saturation). + Consequently, there will be condensed 45 minus 8, or 37 + grains per cubic foot of space measured at the dew-point. + + EXAMPLE 7. To find the amount of water required to produce + saturation by a given rise in temperature: + + Example: Take the values given in example 5. The air at the + dew-point contains slightly over 5 grains per cubic foot. At + 150 deg. it is capable of containing 73 grains per cubic foot. + Consequently, 73-5=68 grains of water which can be + evaporated per cubic foot of space at the dew-point when the + temperature is raised to 150 deg.. But the latent heat necessary + to produce evaporation must be supplied in addition to the + heat required to raise the air to 150 deg.. + + EXAMPLE 8. To find the amount of water evaporated during a + given change of temperature and humidity: + + Example: At 70 deg. suppose the humidity is found to be 64 per + cent and at 150 deg. it is found to be 60 per cent. How much + water has been evaporated per cubic foot of space? At 70 deg. + temperature and 64 per cent humidity there are 5 grains of + water present per cubic foot at the dew-point (example 2). + At 150 deg. and 60 per cent humidity there are 45 grains + present. Therefore, 45-5=40 grains of water which have been + evaporated per cubic foot of space, figuring all volumes at + the dew-point. + + EXAMPLE 9. To correct readings of the hygrometer for changes + in barometric pressure: + + A change of pressure affects the reading of the wet bulb. + The chart applies at a barometric pressure of 30 inches, + and, except for great accuracy, no correction is generally + necessary. + + Find the relative humidity as usual. Then look for the + nearest barometer line (indicated by dashes). At the end of + each barometer line will be found a fraction which + represents the proportion of the relative humidity already + found, which must be added or subtracted for a change in + barometric pressure. If the barometer reading is less than + 30 inches, add; if greater than 30 inches, subtract. The + figures given are for a change of 1 inch; for other changes + use proportional amounts. Thus, for a change of 2 inches use + twice the indicated ratio; for half an inch use half, and so + on. + + Example: Dry bulb 67 deg., wet bulb 51 deg., barometer 28 inches. + The relative humidity is found, by the method given in + example 1, to equal 30 per cent. The barometric line--gives + a value of 3/100H for each inch of change. Since the + barometer is 2 inches below 30, multiply 3/100H by 2, giving + 6/100H. The correction will, therefore, be 6/100 of 30, + which equals 1.8. Since the barometer is below 30, this is + to be added, giving a corrected relative humidity of 31.8 + per cent. + + This has nothing to do with the vapor pressure (concave) + curves, which are independent of barometric pressure, and + consequently does not affect the solution of the previous + problems. + + EXAMPLE 10. At what temperature must the condenser be + maintained to produce a given humidity? + + Example: Suppose the temperature in the drying room is to be + kept at 150 deg. Fahr., and a humidity of 80 per cent is + desired. If the humidity is in excess of 80 per cent the air + must be cooled to the dew-point corresponding to this + condition (see example 4), which in this case is 141.5 deg.. + + Hence, if the condenser cools the air to this dew point the + required condition is obtained when the air is again heated + to the initial temperature. + + EXAMPLE 11. Determination of relative humidity by the + dew-point: + + The quantity of moisture present and relative humidity for + any given temperature may be determined directly and + accurately by finding the dew-point and applying the concave + (vapor-pressure) curves. This does away with the necessity + for the empirical convex curves and wet-and-dry-bulb + readings. To find the dew-point some form of apparatus, + consisting essentially of a thin glass vessel containing a + thermometer and a volatile liquid, such as ether, may be + used. The vessel is gradually cooled through the evaporation + of the liquid, accelerated by forcing air through a tube + until a haze or dimness, due to condensation from the + surrounding air, first appears upon the brighter outer + surface of the glass. The temperature at which the haze + first appears is the dew-point. Several trials should be + made for this temperature determination, using the average + temperature at which the haze appears and disappears. + + To determine the relative humidity of the surrounding air by + means of the dew-point thus determined, find the concave + curve intersecting the top horizontal (100 per cent + relative humidity) line nearest the dew-point temperature. + Follow parallel with this curve till it intersects the + vertical line representing the temperature of the + surrounding air. The horizontal line passing through this + intersection will give the relative humidity. + + Example: Temperature of surrounding air is 80; dew-point is + 61; relative humidity is 53 per cent. + + The dew-point determination is, however, not as convenient + to make as the wet-and-dry-bulb hygrometer readings. + Therefore, the hygrometer (convex) curves are ordinarily + more useful in determining relative humidities. + + + The Hygrodeik + +In Figure 94 will be seen the Hygrodeik. This instrument is used to +determine the amount of moisture in the atmosphere. It is a very +useful instrument, as the readings may be taken direct with accuracy. + +To find the relative humidity in the atmosphere, swing the index hand +to the left of the chart, and adjust the sliding pointer to that +degree of the wet-bulb thermometer scale at which the mercury stands. +Then swing the index hand to the right until the sliding pointer +intersects the curved line, which extends downwards to the left from +the degree of the dry-bulb thermometer scale, indicated by the top of +the mercury column in the dry-bulb tube. + +At that intersection, the index hand will point to the relative +humidity on scale at bottom of chart (for example see Fig. 94). Should +the temperature indicated by the wet-bulb thermometer be 60 degrees, +and that of the dry-bulb 70 degrees, the index hand will indicate +humidity 55 degrees, when the pointer rests on the intersecting line +of 60 degrees and 80 degrees. + + + The Recording Hygrometer + +In Figure 95 is shown the Recording Hygrometer complete with wet and +dry bulbs, two connecting tubes and two recording pens and special +moistening device for supplying water to the wet bulb. + +This equipment is designed particularly for use in connection with dry +rooms and dry kilns and is arranged so that the recording instrument +and the water supply bottle may be installed outside of the dry kiln +or drying room, while the wet and dry bulbs are both installed inside +the room or kiln at the point where it is desired to measure the +humidity. This instrument records on a weekly chart the humidity for +each hour of the day, during the entire week. + + [Illustration: Fig. 94. The Hygrodeik.] + + + The Registering Hygrometer + +In Figure 96 is shown the Registering Hygrometer, which consists of +two especially constructed thermometers. The special feature of the +thermometers permits placing the instrument in the dry kiln without +entering the drying room, through a small opening, where it is left +for about 20 minutes. + + [Illustration: Fig. 95. The Recording Hygrometer, Complete + with Wet and Dry Bulbs. This instrument records on a weekly + chart the humidity for each hour of the day, during the + entire week.] + +The temperature of both the dry and wet bulbs are automatically +recorded, and the outside temperature will not affect the thermometers +when removed from the kiln. From these recorded temperatures, as shown +when the instrument is removed from the kiln, the humidity can be +easily determined from a simple form of chart which is furnished free +by the makers with each instrument. + + + The Recording Thermometer + + [Illustration: Fig. 96. The Registering Hygrometer.] + + [Illustration: Fig. 97. The Recording Thermometer.] + +In Figure 97 is shown the Recording Thermometer for observing and +recording the temperatures within a dry kiln, and thus obtaining a +check upon its operation. This instrument is constructed to record +automatically, upon a circular chart, the temperatures prevailing +within the drying room at all times of the day and night, and serves +not only as a means of keeping an accurate record of the operation of +the dry kiln, but as a valuable check upon the attendant in charge of +the drying process. + + [Illustration: Fig. 98. The Registering Thermometer.] + + [Illustration: Fig. 99. The Recording Steam-Pressure Gauge.] + + + The Registering Thermometer + +In Figure 98 is shown the Registering Thermometer, which is a less +expensive instrument than that shown in Figure 97, but by its use the +maximum and minimum temperatures in the drying room during a given +period can be determined. + + + The Recording Steam Gauge + +In Figure 99 is shown the Recording Steam Pressure Gauge, which is +used for accurately recording the steam pressures kept in the boilers. +This instrument may be mounted near the boilers, or may be located at +any distance necessary, giving a true and accurate record of the +fluctuations of the steam pressure that may take place within the +boilers, and is a check upon both the day and night boiler firemen. + + + The Troemroid Scalometer + +In Figure 100 is shown the Troemroid Scalometer. This instrument is a +special scale of extreme accuracy, fitted with agate bearings with +screw adjustment for balancing. The beam is graduated from 0 to 2 +ounces, divided into 100 parts, each division representing 1-50th of +an ounce; and by using the pointer attached to the beam weight, the +1-100th part of an ounce can be weighed. + + [Illustration: Fig. 100. The Troemroid Scalometer.] + +The percentage table No. II has a range from one half of 1 per cent to +30 per cent and is designed for use where extremely fine results are +needed, or where a very small amount of moisture is present. Table +No. III ranges from 30 per cent up to 90 per cent. These instruments +are in three models as described below. + + MODEL A. (One cylinder) ranges from 1/2 of 1 per cent to 30 + per cent and is to be used for testing moisture contents in + kiln-dried and air-dried lumber. + + MODEL B. (Two cylinders) ranges from 1/2 of 1 per cent up to + 90 per cent and is to be used for testing the moisture + contents of kiln-dried, air-dried, and green lumber. + + MODEL C. (One cylinder) ranges from 30 per cent to 90 per + cent and is applicable to green lumber only. + +=Test Samples.=--The green boards and all other boards intended for +testing should be selected from boards of fair average quality. If +air-dried, select one about half way up the height of the pile of +lumber. If kiln-dried, two thirds the height of the kiln car. Do not +remove the kiln car from the kiln until after the test. Three of four +test pieces should be cut from near the middle of the cross-wise +section of the board, and 1/8 to 3/16 inch thick. Remove the +superfluous sawdust and splinters. When the test pieces are placed on +the scale pan, be sure their weight is less than two ounces and more +than 1-3/4 ounces. If necessary, use two or more broken pieces. It is +better if the test pieces can be cut off on a fine band saw. + +=Weighing.=--Set the base of the scale on a level surface and accurately +balance the scale beam. Put the test pieces on the scale pan and note +their weight on the lower edge of the beam. Set the indicator point on +the horizontal bar at a number corresponding to this weight, which may +be found on the cylinder at the top of the table. + +Dry the test pieces on the Electric Heater (Fig. 101) 30 to 40 +minutes, or on the engine cylinder two or three hours. Weigh them at +once and note the weight. Then turn the cylinder up and at the left of +it under the small pointer find the number corresponding to this +weight. The percentage of moisture lost is found directly under +pointer on the horizontal bar first mentioned. The lower portion on +the cylinder Table No. II is an extension of the upper portion, and +is manipulated in the same manner except that the bottom line of +figures is used for the first weight, and the right side of cylinder +for second weight. Turn the cylinder down instead of up when using it. + + + Examples (Test Pieces) + + MODEL A. Table No. II, Kiln-dried or Air-dried Lumber: + + If first weight is 90-1/2 and the second weight is 87, the + cylinder table will show the board from which the test + pieces were taken had a moisture content of 3.8 per cent. + + MODEL B. Tables No. II and III, Air-dried (also Green and + Kiln-dried) Lumber. + + If the first weight on lower cylinder is 97 and the second + weight is 76, the table will show 21.6 per cent of moisture. + + MODEL C. Table III, Green Lumber: + + If the first weight is 94 and the second weight is 51, the + table shows 45.8 per cent of moisture. + + + Keep Records of the Moisture Content + +=Saw Mills.=--Should test and mark each pile of lumber when first piled +in the yard, and later when sold it should be again tested and the two +records given to the purchaser. + +=Factories.=--Should test and mark the lumber when first received, and +if piled in the yard to be kiln-dried later, it should be tested +before going into the dry kiln, and again before being removed, and +these records placed on file for future reference. + +Kiln-dried lumber piled in storage rooms (without any heat) will +absorb 7 to 9 per cent of moisture, and even when so stored should be +tested for moisture before being manufactured into the finished +product. + +Never work lumber through the factory that has more than 5 or 6 per +cent of moisture or less than 3 per cent. + +Dry storage rooms should be provided with heating coils and properly +ventilated. + +Oak or any other species of wood that shows 25 or 30 per cent of +moisture when going into the dry kiln, will take longer to dry than it +would if it contained 15 to 20 per cent, therefore the importance of +testing before putting into the kiln as well as when taking it out. + + + The Electric Heater + +In Figure 101 is shown the Electric Heater. This heater is especially +designed to dry quickly the test pieces for use in connection with the +Scalometer (see Fig. 100) without charring them. It may be attached to +any electric light socket of 110 volts direct or alternating current. +A metal rack is provided to hold the test pieces vertically on edge. + + [Illustration: Fig. 101. The Electric Heater.] + +Turn the test pieces over once or twice while drying. + +It will require from 20 minutes to one hour to remove all the moisture +from the test pieces when placed on this heater, depending on whether +they are cut from green, air-dried, or kiln-dried boards. + +Test pieces cut from softwoods will dry quicker than those cut from +hardwoods. + +When the test pieces fail to show any further loss in weight, they are +then free from all moisture content. + + + + + BIBLIOGRAPHY + + +AMERICAN BLOWER COMPANY, Detroit, Mich. + +IMRE, JAMES E., "The Kiln-drying of Gum," The United States +Dept. of Agriculture, Division of Forestry. + +NATIONAL DRY KILN COMPANY, Indianapolis, Ind. + +PRICHARD, REUBEN P., "The Structure of the Common Woods," +The United States Dept. of Agriculture, Division of Forestry, +Bulletin No. 3. + +ROTH, FILIBERT, "Timber," The United States Dept. of Agriculture, +Division of Forestry, Bulletin No. 10. + +STANDARD DRY KILN COMPANY, Indianapolis, Ind. + +STURTEVANT COMPANY, B. F., Boston, Mass. + +TIEMAN, H. D., "The Effects of Moisture upon the Strength and +Stiffness of Wood," The United States Dept. of Agriculture, +Division of Forestry, Bulletin No. 70. + +TIEMAN, H. D., "Principles of Kiln-drying Lumber," The United +States Dept. of Agriculture, Division of Forestry. + +TIEMAN, H. D., "The Theory of Drying and its Application, etc.," +The United States Dept. of Agriculture, Division of Forestry, +Bulletin No. 509. + +THE UNITED STATES DEPT. OF AGRICULTURE, DIVISION OF FORESTRY, +"Check List of the Forest Trees of the United States." + +THE UNITED STATES DEPT. OF AGRICULTURE, DIVISION OF +FORESTRY, Bulletin No. 37. + +VON SCHRENK, HERMAN, "Seasoning of Timbers," The United +States Dept. of Agriculture, Division of Forestry, Bulletin +No. 41. + +WAGNER, J. B., "Cooperage," 1910. + + + + + GLOSSARY + + +=Abnormal.= Differing from the usual structure. + +=Acuminate.= Tapering at the end. + +=Adhesion.= The union of members of different floral whorls. + +=Air-seasoning.= The drying of wood in the open air. + +=Albumen.= A name applied to the food store laid up outside the +embryo in many seeds; also nitrogenous organic matter found in plants. + +=Alburnam.= Sapwood. + +=Angiosperms.= Those plants which bear their seeds within a +pericarp. + +=Annual rings.= The layers of wood which are added annually to +the tree. + +=Apartment kiln.= A drying arrangement of one or more rooms +with openings at each end. + +=Arborescent.= A tree in size and habit of growth. + + +=Baffle plate.= An obstruction to deflect air or other currents. + +=Bastard cut.= Tangential cut. Wood of inferior cut. + +=Berry.= A fruit whose entire pericarp is succulent. + +=Blower kiln.= A drying arrangement in which the air is blown +through heating coils into the drying room. + +=Box kiln.= A small square heating room with openings in one end +only. + +=Brittleness.= Aptness to break; not tough; fragility. + +=Burrow.= A shelter; insect's hole in the wood. + + +=Calorie.= Unit of heat; amount of heat which raises the +temperature. + +=Calyx.= The outer whorl of floral envelopes. + +=Capillary.= A tube or vessel extremely fine or minute. + +=Case-harden.= A condition in which the pores of the wood are +closed and the outer surface dry, while the inner portion is +still wet or unseasoned. + +=Cavity.= A hollow place; a hollow. + +=Cell.= One of the minute, elementary structures comprising the +greater part of plant tissue. + +=Cellulose.= A primary cell-wall substance. + +=Checks.= The small chinks or cracks caused by the rupture of the +wood fibres. + +=Cleft.= Opening made by splitting; divided. + +=Coarse-grained.= Wood is coarse-grained when the annual rings +are wide or far apart. + +=Cohesion.= The union of members of the same floral whorl. + +=Contorted.= Twisted together. + +=Corolla.= The inner whorl of floral envelopes. + +=Cotyledon.= One of the parts of the embryo performing in part the +function of a leaf, but usually serving as a storehouse of food +for the developing plant. + +=Crossers.= Narrow wooden strips used to separate the material on +kiln cars. + +=Cross-grained.= Wood is cross-grained when its fibres are spiral +or twisted. + + +=Dapple.= An exaggerated form of mottle. + +=Deciduous.= Not persistent; applied to leaves that fall in autumn +and to calyx and corolla when they fall off before the fruit +develops. + +=Definite.= Limited or defined. + +=Dew-point.= The point at which water is deposited from moisture-laden +air. + +=Dicotyledon.= A plant whose embryo has two opposite cotyledons. + +=Diffuse.= Widely spreading. + +=Disk.= A circular, flat, thin piece or section of the tree. + +=Duramen.= Heartwood. + + +=Embryo.= Applied in botany to the tiny plant within the seed. + +=Enchinate.= Beset with prickles. + +=Expansion.= An enlargement across the grain or lengthwise of the +wood. + + +=Fibres.= The thread-like portion of the tissue of wood. + +=Fibre-saturation point.= The amount of moisture wood will imbibe, +usually 25 to 30 per cent of its dry-wood weight. + +=Figure.= The broad and deep medullary rays as in oak showing +when the timber is cut into boards. + +=Filament.= The stalk which supports the anther. + +=Fine-grained.= Wood is fine-grained when the annual rings are +close together or narrow. + + +=Germination.= The sprouting of a seed. + +=Girdling.= To make a groove around and through the bark of a +tree, thus killing it. + +=Glands.= A secreting surface or structure; a protuberance having +the appearance of such an organ. + +=Glaucous.= Covered or whitened with a bloom. + +=Grain.= Direction or arrangement of the fibres in wood. + +=Grubs.= The larvae of wood-destroying insects. + +=Gymnosperms.= Plants bearing naked seeds; without an ovary. + + +=Habitat.= The geographical range of a plant. + +=Heartwood.= The central portion of tree. + +=Hollow-horning.= Internal checking. + +=Honeycombing.= Internal checking. + +=Hot-blast kiln.= A drying arrangement in which the air is blown +through heating coils into the drying room. + +=Humidity.= Damp, moist. + +=Hygroscopicity.= The property of readily imbibing moisture from +the atmosphere. + + +=Indefinite.= Applied to petals or other organs when too numerous +to be conveniently counted. + +=Indigenous.= Native to the country. + +=Involute.= A form of vernation in which the leaf is rolled inward +from its edges. + + +=Kiln-drying.= Drying or seasoning of wood by artificial heat in an +inclosed room. + + +=Leaflet.= A single division of a compound leaf. + +=Limb.= The spreading portion of the tree. + +=Lumen.= Internal space in the spring- and summer-wood fibres. + + +=Median.= Situated in the middle. + +=Medulla.= The pith. + +=Medullary rays.= Rays of fundamental tissue which connect the +pith with the bark. + +=Membranous.= Thin and rather soft, more or less translucent. + +=Midrib.= The central or main rib of a leaf. + +=Moist-air kiln.= A drying arrangement in which the heat is taken +from radiating coils located inside the drying room. + +=Mottle.= Figure transverse of the fibres, probably caused by the +action of wind upon the tree. + + +=Non-porous.= Without pores. + + +=Oblong.= Considerably longer than broad, with flowing outline. + +=Obtuse.= Blunt, rounded. + +=Oval.= Broadly elliptical. + +=Ovary.= The part of the pistil that contains the ovules. + + +=Parted.= Cleft nearly, but not quite to the base or midrib. + +=Parenchyma.= Short cells constituting the pith and pulp of the +tree. + +=Pericarp.= The walls of the ripened ovary, the part of the fruit +that encloses the seeds. + +=Permeable.= Capable of being penetrated. + +=Petal.= One of the leaves of the corolla. + +=Pinholes.= Small holes in the wood caused by worms or insects. + +=Pistil.= The modified leaf or leaves which bear the ovules; usually +consisting of ovary, style and stigma. + +=Plastic.= Elastic, easily bent. + +=Pocket kilns.= Small drying rooms with openings on one end only +and in which the material to be dried is piled directly on the +floor. + +=Pollen.= The fertilizing powder produced by the anther. + +=Pores.= Minute orifices in wood. + +=Porous.= Containing pores. + +=Preliminary steaming.= Subjecting wood to a steaming process +before drying or seasoning. + +=Progressive kiln.= A drying arrangement with openings at both +ends, and in which the material enters at one end and is discharged +at the other. + + +=Rick.= A pile or stack of lumber. + +=Rift.= To split; cleft. + +=Ring shake.= A large check or crack in the wood following an +annual ring. + +=Roe.= A peculiar figure caused by the contortion of the woody +fibres, and takes a wavy line parallel to them. + + +=Sapwood.= The outer portions of the tree next to the bark; +alburnam. + +=Saturate.= To cause to become completely penetrated or soaked. + +=Season checks.= Small openings in the ends of the wood caused +by the process of drying. + +=Seasoning.= The process by which wood is dried or seasoned. + +=Seedholes.= Minute holes in wood caused by wood-destroying +worms or insects. + +=Shake.= A large check or crack in wood caused by the action of +the wind on the tree. + +=Shrinkage.= A lessening or contraction of the wood substance. + +=Skidways.= Material set on an incline for transporting lumber or +logs. + +=Species.= In science, a group of existing things, associated according +to properties. + +=Spermatophyta.= Seed-bearing plants. + +=Spring-wood.= Wood that is formed in the spring of the year. + +=Stamen.= The pollen-bearing organ of the flower, usually consisting +of filament and anther. + +=Stigma.= That part of the pistil which receives the pollen. + +=Style.= That part of the pistil which connects the ovary with the +stigma. + + +=Taproot.= The main root or downward continuation of the plant +axis. + +=Temporary checks.= Checks or cracks that subsequently close. + +=Tissue.= One of the elementary fibres composing wood. + +=Thunder shake.= A rupture of the fibres of the tree across the +grain, which in some woods does not always break them. + +=Tornado shake.= (See Thunder shake.) + +=Tracheids.= The tissues of the tree which consist of vertical cells +or vessels closed at one end. + + +=Warping.= Turning or twisting out of shape. + +=Wind shake.= (See Thunder shake.) + +=Working.= The shrinking and swelling occasioned in wood. + +=Wormholes.= Small holes in wood caused by wood-destroying +worms. + + +=Vernation.= The arrangement of the leaves in the bud. + +=Whorl.= An arrangement of organs in a circle about a central axis. + + + + + INDEX OF LATIN NAMES + + +Abies amabalis, 21 +Abies balsamea, 20 +Abies concolor, 20 +Abies grandis, 20 +Abies magnifica, 21 +Abies nobilis, 21 +Acer macrophyllum, 69 +Acer negundo, 69 +Acer Pennsylvanicum, 70 +Acer rubrum, 69 +Acer saccharinum, 69 +Acer saccharum, 68 +Acer spicatum, 69 +AEsculus flava, 45 +AEsculus glabra, 45 +AEsculus octandra, 45 +Ailanthus glandulosa, 37 +Asimina triloba, 76 + + +Betula lenta, 41 +Betula lutea, 42 +Betula nigra, 43 +Betula papyrifera, 43 +Betula populifolia, 42 +Betula rubra, 43 +Buxus sempervirens, 77 + + +Carpinus Caroliana, 44 +Castanea Americana, 48 +Castanea chrysophylla, 49 +Castanea dentata, 48 +Castanea pumila, 48 +Castanea vesca, 48 +Castanea vulgaris, 48 +Catalpa bignonioides, 46 +Catalpa speciosa, 46 +Celtis occidentalis, 62 +Chamaecyparis Lawsonia, 18 +Chamaecyparis thyoides, 17 +Cladrastis lutea, 85 +Cornus florida, 49 +Cupressus nootkatensis, 18 + + +Diospyros Virginia, 77 + + +Evonymus atropurpureus, 82 + + +Fagus ferruginea, 40 +Fraxinus Americana, 37 +Fraxinus Caroliniana, 39 +Fraxinus nigra, 38 +Fraxinus Oregana, 38 +Fraxinus Pennsylvanica, 38 +Fraxinus pubescens, 38 +Fraxinus quadrangulata, 38 +Fraxinus sambucifolia, 38 +Fraxinus viridis, 38 + + +Gleditschia triacanthos, 66 +Gymnocladus dioicus, 49 + + +Hicoria alba, 64 +Hicoria glabra, 64 +Hicoria minima, 64 +Hicoria ovata, 64 +Hicoria pecan, 64 + + +Ilex monticolo, 65 +Ilex opaca, 64 + + +Juglans cinerea, 45 +Juglans nigra, 82 +Juniperus communis, 19 +Juniperus Virginiana, 18 + + +Larix Americana, 22 +Larix laricina, 22 +Larix occidentalis, 22 +Libocedrus decurrens, 18 +Liquidamber styraciflua, 54 +Liriodendron tulipfera, 81 + + +Maclura aurantiaca, 76 +Magnolia acuminata, 67 +Magnolia glauca, 67 +Magnolia tripetala, 67 +Morus rubra, 70 + + +Nyssa aquatica, 60 +Nyssa sylvatica, 62 + + +Ostrya Virginiana, 65 +Oxydendrum arboreum, 80 + + +Picea alba, 28 +Picea canadensis, 28 +Picea engelmanni, 28 +Picea mariana, 27 +Picea nigra, 27 +Picea rubens, 28 +Picea sitchensis, 28 +Pinus banksiana, 27 +Pinus cubensis, 26 +Pinus divaricata, 27 +Pinus enchinata, 26 +Pinus flexilis, 24 +Pinus inops, 27 +Pinus Jeffreyi, 25 +Pinus Lambertiana, 24 +Pinus monticolo, 24 +Pinus Murryana, 27 +Pinus palustris, 24 +Pinus ponderosa, 25 +Pinus resinosa, 25 +Pinus rigida, 26 +Pinus strobus, 23 +Pinus taeda, 25 +Pinus Virginiana, 27 +Platanus occidentalis, 80 +Platanus racemosa, 81 +Populus alba, 79 +Populus angulata, 77 +Populus balsamifera, 79 +Populus fremontii, 78 +Populus grandidentata, 79 +Populus heteropylla, 78 +Populus monilifera, 77 +Populus nigra italica, 79 +Populus tremuloides, 79 +Populus trichocarpa, 78 +Populus Wislizeni, 78 +Prunus Pennsylvanica, 47 +Prunus serotina, 47 +Pseudotsuga douglasii, 29 +Pseudotsuga taxifolia, 29 +Pyrus coronaria, 49 + + +Quercus acuminata, 73 +Quercus alba, 71 +Quercus aquatica, 73 +Quercus bicolor, 72 +Quercus chrysolepis, 76 +Quercus coccinea, 75 +Quercus digitata, 75 +Quercus durandii, 71 +Quercus falcata, 75 +Quercus garryana, 71 +Quercus ilicijolia, 74 +Quercus imbricaria, 75 +Quercus lobata, 72 +Quercus lyrata, 73 +Quercus macrocarpa, 72 +Quercus marilandica, 75 +Quercus Michauxii, 74 +Quercus minor, 74 +Quercus nigra, 75 +Quercus obtusiloda, 74 +Quercus palustris, 73 +Quercus phellos, 72 +Quercus platanoides, 72 +Quercus prinoides, 74 +Quercus prinus, 73 +Quercus pumila, 74 +Quercus rubra, 74 +Quercus tinctoria, 74 +Quercus velutina, 74 +Quercus virens, 75 + + +Rhamnus Caroliniana, 45 +Robinia pseudacacia, 66 +Robinia viscosa, 66 + + +Salix alba, 83 +Salix amygdaloides, 84 +Salix babylonica, 84 +Salix bebbiana, 84 +Salix discolor, 84 +Salix fluviatilis, 84 +Salix fragilis, 84 +Salix lucida, 84 +Salix nigra, 83 +Salix rostrata, 84 +Salix vitellina, 83 +Sassafras sassafras, 80 +Sequoia sempervirens, 19 + + +Taxodium distinchum, 19 +Taxus brevifolia, 30 +Thuya gigantea, 17 +Thuya occidentalis, 17 +Tilia Americana, 39 +Tilia heterophylla, 39 +Tilia pubescens, 39 +Tsuga canadensis, 21 +Tsuga mertensiana, 21 + + +Ulmus alata, 51 +Ulmus Americana, 50 +Ulmus crassifolia, 51 +Ulmus fulva, 51 +Ulmus pubescens, 51 +Ulmus racemosa, 50 +Umbellularia Californica, 65 + + + + + INDEX + + +Abele, Tree, 79 + +Absorption of water by dry wood, 124 + +Acacia, 66 + +Acacia, false, 66 + +Acacia, three-thorned, 66 + +According to species, different kiln drying, 170 + +Advantages in seasoning, 128 + +Advantages of kiln-drying over air-drying, 156 + +Affect drying, properties of wood that, 156 + +Ailanthus, 37 + +Air circulation, 173 + +Air-drying, advantages of kiln-drying over, 156 + +Alaska cedar, 18 + +Alaska cypress, 18 + +Alcoholic liquids, stave and heads of barrels containing, 112 + +Almond-leaf willow, 84 + +Ambrosia or timber beetles, 99 + +American box, 49 + +American elm, 50 + +American larch, 22 + +American linden, 39 + +American oak, 71 + +American red pine, 25 + +Anatomical structure, 14 + +Annual ring, the yearly or, 10 + +Apartment dry kiln, 198 + +Apple, crab, 49 + +Apple, custard, 76 + +Apple, wild, 49 + +Appliances in kiln-drying, helpful, 237 + +Arborvitae, 17 + +Ash, 37 + +Ash, black, 38 + +Ash, blue, 38 + +Ash, Carolina, 39 + +Ash, green, 38 + +Ash, ground, 38 + +Ash, hoop, 38 + +Ash-leaved maple, 69 + +Ash, Oregon, 38 + +Ash, red, 38 + +Ash, white, 37 + +Aspen, 39, 79 + +Aspen, large-toothed, 78 + +Aspen-leaved birch, 42 + +Aspen, quaking, 79 + +Atmospheric pressure, drying at, 146 + + +Bald Cypress, 19 + +Ball tree, button, 80 + +Balm of gilead, 79 + +Balm of gilead fir, 20 + +Balsam, 20, 79 + +Balsam fir, 20 + +Bark and pith, 8 + +Bark on, round timber with, 106 + +Barrels containing alcoholic liquids, staves and heads of, 112 + +Barren oak, 75 + +Bar willow, sand, 84 + +Basket oak, 74 + +Basswood, 39 + +Basswood, small-leaved, 39 + +Basswood, white, 39 + +Bastard pine, 26 + +Bastard spruce, 29 + +Bay poplar, 60 + +Bay, sweet, 67 + +Bear oak, 74 + +Beaver wood, 67 + +Bebb willow, 84 + +Bee tree, 39 + +Beech, 40 + +Beech, blue, 44 + +Beech, red, 40 + +Beech, water, 44, 80 + +Beech, white, 40 + +Berry, sugar, 62 + +Beetles, ambrosia or timber, 99 + +Big bud hickory, 64 + +Bilsted, 54 + +Birch, 41 + +Birch, aspen-leaved, 42 + +Birch, black, 41 + +Birch, canoe, 43 + +Birch, cherry, 41 + +Birch, gray, 42 + +Birch, mahogany, 41 + +Birch, old field, 42 + +Birch, paper, 43 + +Birch, red, 42 + +Birch, river, 43 + +Birch, silver, 42 + +Birch, sweet, 41 + +Birch, white, 42, 43 + +Birch, wintergreen, 41 + +Birch, yellow, 42 + +Bird cherry, 47 + +Bitternut hickory, 64 + +Black ash, 38 + +Black birch, 41 + +Black cherry, 47 + +Black cottonwood, 78 + +Black cypress, 19 + +Black gum, 62 + +Black hickory, 64 + +Black jack, 75 + +Black larch, 22 + +Black locust, 66 + +Black nut hickory, 64 + +Black oak, 74 + +Black pine, 25, 27 + +Black spruce, 27 + +Black walnut, 44, 82 + +Black willow, 83 + +Blower dry kiln, operation of, 186 + +Blower or hot blast dry kiln, 185 + +Blue ash, 38 + +Blue beech, 44 + +Blue poplar, 81 + +Blue willow, 83 + +Bois d'Arc, 45, 76 + +Bolts, stave, heading and shingle, 109 + +Borers, flat-headed, 103 + +Borers, powder post, 105 + +Borers, round-headed, 101 + +Box, American, 49 + +Box elder, 69 + +Box dry kiln, 204 + +Broad-leaved maple, 69 + +Broad-leaved trees, 31 + +Broad-leaved trees, list of most important, 37 + +Broad-leaved trees, wood of, 31 + +Brown hickory, 64 + +Brown locust, 66 + +Buckeye, 45 + +Buckeye, fetid, 45 + +Buckeye, Ohio, 45 + +Buckeye, sweet, 45 + +Buckthorne, 45 + +Bud hickory, big, 64 + +Bull nut hickory, 64 + +Bull pine, 25 + +Bur oak, 72 + +Burning bush, 82 + +Bush, burning, 82 + +Bush, juniper, 18 + +Butternut, 45 + +Button ball tree, 80 + +Button wood, 80 + + +California Redwood, 19 + +California white pine, 25 + +Canadian pine, 25 + +Canary wood, 81 + +Canoe birch, 43 + +Canoe cedar, 17 + +Carolina ash, 39 + +Carolina pine, 26 + +Carolina poplar, 77 + +Cars, method of loading kiln, 206 + +Catalpa, 46 + +Cedar, 17 + +Cedar, Alaska, 18 + +Cedar, canoe, 17 + +Cedar, elm, 51 + +Cedar, ground, 19 + +Cedar, incense, 18 + +Cedar of the West, red, 17 + +Cedar, Oregon, 18 + +Cedar, pencil, 18 + +Cedar, Port Orford, 18 + +Cedar, red, 18, 19 + +Cedar, white, 17, 18 + +Cedar, yellow, 18 + +Changes rendering drying difficult, 140 + +Characteristics and properties of wood, 1 + +Checking and splitting, prevention of, 129 + +Cherry, 47 + +Cherry birch, 41 + +Cherry, bird, 47 + +Cherry, black, 47 + +Cherry, Indian, 45 + +Cherry, red, 47 + +Cherry, rum, 47 + +Cherry, wild, 47 + +Cherry, wild red, 47 + +Chestnut, 48 + +Chestnut, horse, 45, 65 + +Chestnut oak, 73 + +Chestnut oak, rock, 73 + +Chestnut oak, scrub, 74 + +Chinquapin, 48, 49 + +Chinquapin oak, 73, 74 + +Chinquapin oak, dwarf, 74 + +Choice of drying method, 195 + +Circassian walnut, 60 + +Circulation, air, 173 + +Clammy locust, 66 + +Classes of trees, 5 + +Cliff elm, 50 + +Coast redwood, 19 + +Coffee nut, 49 + +Coffee tree, 49 + +Color and odor of wood, 89 + +Color, odor, weight, and figure in wood, grain, 86 + +Composition of sap, 116 + +Conditions and species, temperature depends on, 171 + +Conditions favorable for insect injury, 106 + +Conditions governing the drying of wood, 156 + +Conditions of success in kiln-drying, 169 + +Coniferous trees, 8 + +Coniferous trees, wood of, 8 + +Coniferous woods, list of important, 17 + +Containing alcoholic liquids, staves and heads of barrels, 112 + +Cooperage stock and wooden truss hoops, dry, 112 + +Cork elm, 50 + +Cotton gum, 60 + +Cottonwood, 49, 77, 78 + +Cottonwood, black, 78 + +Cottonwood, swamp, 78 + +Cow oak, 74 + +Crab apple, 49 + +Crab, fragrant, 49 + +Crack willow, 84 + +Crude products, 106 + +Cuban pine, 26 + +Cucumber tree, 49, 67 + +Cup oak, mossy, 72 + +Cup oak, over-, 72, 73 + +Custard apple, 76 + +Cypress, 19 + +Cypress, Alaska, 18 + +Cypress, bald, 19 + +Cypress, black, 19 + +Cypress, Lawson's, 18 + +Cypress, pecky, 19 + +Cypress, red, 19 + +Cypress, white, 19 + + +D'Arc, Bois, 45, 76 + +Deal, yellow, 23 + +Demands upon soil and moisture of red gum, 56 + +Depends on conditions and species, temperature, 171 + +Description of the forest service kiln, theory and, 161 + +Diagram, the uses of the humidity, 237 + +Difference between seasoned and unseasoned wood, 121 + +Different grains of wood, 86 + +Different kiln-drying according to species, 170 + +Different species, weight of kiln-dried wood of, 95 + +Different types, kilns of, 196 + +Different types of dry kilns, 185 + +Different types of kiln doors, 231 + +Difficult, changes rendering drying, 140 + +Difficulties of drying wood, 138 + +Distribution of water in wood, 114 + +Distribution of water in wood, local, 114 + +Distribution of water in wood seasonal, 115 + +Dogwood, 49 + +Doors, different types of kiln, 231 + +Douglas spruce, 29 + +Downy linden, 39 + +Downy poplar, 78 + +Dry cooperage stock and wooden truss hoops, 112 + +Drying according to species, different kiln, 170 + +Drying, advantages of kiln-drying over air, 156 + +Drying at atmospheric pressure, 146 + +Drying by superheated steam, 150 + +Drying, conditions of success in kiln, 169 + +Drying difficult, changes rendering, 140 + +Drying gum, kiln, 180 + +Drying, helpful appliances in kiln, 237 + +Drying, kiln, 164, 177 + +Drying, losses due to improper kiln, 141 + +Drying method, choice of, 185 + +Drying, methods of kiln, 145 + +Drying, objects of kiln, 168 + +Drying of green red gum, kiln, 183 + +Drying of wood, kiln, 156 + +Drying of wood, physical conditions governing the, 156 + +Drying, physical properties that influence, 125 + +Drying, properties of wood that effect, 141 + +Drying, theory of kiln, 157 + +Drying, underlying principles of kiln, 166 + +Drying under pressure and vacuum, 146 + +Drying, unsolved problems in kiln, 143 + +Drying wood, difficulties of, 138 + +Drying 100 lb. of green wood in the kiln, pounds of water lost, 179 + +Dry kiln, apartment, 198 + +Dry kiln, box, 204 + +Dry kiln, operation of the blower, 186 + +Dry kiln, operation of the moist-air, 192 + +Dry kiln, moist-air or pipe, 188 + +Dry kiln, pocket, 200 + +Dry kiln, progressive, 196 + +Dry kiln, requirements in a satisfactory, 160 + +Dry kilns, different types of, 185 + +Dry kiln specialties, 206 + +Dry kilns, types of, 185 + +Dry kiln, tower, 202 + +Dry wood, absorption of water by, 124 + +Duck oak, 73 + +Due to improper kiln-drying, losses, 141 + +Dwarf chinquapin oak, 74 + + +Effects of Moisture on Wood, 117 + +Elder, box, 69 + +Electric heater, the, 250 + +Elimination of stain and mildew, 136 + +Elm, 50 + +Elm, American, 50 + +Elm, cedar, 51 + +Elm, cliff, 50 + +Elm, cork, 50 + +Elm, hickory, 50 + +Elm, moose, 51 + +Elm, red, 51 + +Elm, rock, 50 + +Elm, slippery, 51 + +Elm, water, 50 + +Elm, winged, 51 + +Elm, white, 50 + +Enemies of wood, 98 + +Evaporation of water, manner of, 123 + +Evaporation, rapidity of, 124 + +Expansion of wood, 135 + + +Factories, Scalometer in, 249 + +False acacia, 66 + +Favorable for insect injury, conditions, 106 + +Fetid buckeye, 45 + +Fibre saturation point in wood, 118 + +Field birch, old, 42 + +Field pine, old, 25, 26 + +Figure in wood, 96 + +Figure in wood, grain, color, odor, weight, and, 86 + +Final steaming of gum, 182 + +Fir, 20 + +Fir, balm of gilead, 20 + +Fir balsam, 20 + +Fir, noble, 21 + +Fir, red, 21, 29 + +Fir tree, 20 + +Fir, white, 20, 21 + +Fir, yellow, 29 + +Flat-headed borers, 103 + +Forest service kiln, theory and description of, 161 + +Form of the red gum, 55 + +Fragrant crab, 49 + + +Gauge, the Recording Steam, 246 + +Georgia pine, 24 + +Gilead, balm of, 79 + +Gilead fir, balm of, 20 + +Ginger pine, 18 + +Glaucous willow, 84 + +Governing the drying of wood, physical conditions, 156 + +Grain, color, odor, weight, and figure in wood, 86 + +Grains of wood, different, 86 + +Gray birch, 42 + +Gray pine, 27 + +Green ash, 38 + +Green red gum, kiln-drying, 183 + +Green wood in the kiln, pounds of water lost in drying 100 lbs., 179 + +Ground ash, 38 + +Ground cedar, 19 + +Growth red gum, second, 59 + +Gum, 52 + +Gum, black, 62 + +Gum, cotton, 60 + +Gum, demands upon soil and moisture of red, 56 + +Gum, final steaming of, 182 + +Gum, form of red, 55 + +Gum, kiln-drying, 180 + +Gum, kiln-drying of green red, 183 + +Gum, method of piling, 180 + +Gum, preliminary steaming of, 182 + +Gum, range of red, 55 + +Gum, range of tupelo, 61 + +Gum, red, 54, 79 + +Gum, reproduction of red, 57 + +Gum, second-growth red, 59 + +Gum, sour, 62, 80 + +Gum, sweet, 54, 80 + +Gum, tolerance of the red, 56 + +Gum, tupelo, 60 + +Gum, uses of tupelo, 61 + + +Hackberry, 62 + +Hacmatac, 22 + +Hard maple, 68 + +Hard pine, 26 + +Hard pines, 24 + +Hard pine, southern, 24 + +Hardwoods, 37 + +Hazel pine, 54, 60 + +Headed borers, flat, 103 + +Headed borers, round, 101 + +Heading, stave and shingle bolts, 109 + +Heads and staves of barrels containing alcoholic liquids, 112 + +Heart hickory, white, 64 + +Heartwood, sap and, 8 + +Heater, the electric, 250 + +Helpful appliances in kiln-drying, 237 + +Hemlock, 21 + +Hemlock spruce, 21 + +Hickory, 63 + +Hickory, big bud, 64 + +Hickory, bitternut, 64 + +Hickory, black, 64 + +Hickory, black nut, 64 + +Hickory, brown, 64 + +Hickory, bull nut, 64 + +Hickory elm, 50 + +Hickory, mockernut, 64 + +Hickory, pignut, 64 + +Hickory, poplar, 81 + +Hickory, scalybark, 64 + +Hickory, shagbark, 64 + +Hickory, shellbark, 64 + +Hickory, swamp, 64 + +Hickory, switchbud, 64 + +Hickory, white heart, 64 + +Holly, 64, 65 + +Holly, mountain, 65 + +Honey locust, 66 + +Honey shucks, 66 + +Hoop ash, 38 + +Hoops, dry cooperage stock and wooden truss, 112 + +Hop hornbeam, 65 + +Hornbeam, 44 + +Hornbeam, hop, 65 + +Horse chestnut, 45, 65 + +Hot blast or blower kiln, 185 + +Humidity, 174 + +Humidity diagram, uses of the, 237 + +How to prevent insect injury, 107 + +How wood is seasoned, 145 + +Hygrodeik, the, 242 + +Hygrometer, the recording, 242 + +Hygrometer, the registering, 244 + + +Illinois Nut, 64 + +Important broad-leaved trees, list of most, 37 + +Important coniferous woods, list of, 17 + +Impregnation methods, 151 + +Improper kiln-drying, losses due to, 141 + +Incense cedar, 18 + +Indian bean, 46 + +Indian cherry, 45 + +Influence drying, physical properties that, 125 + +Injury, conditions favorable for insect, 106 + +Injury from insects, how to prevent, 107 + +Insect injury, conditions favorable for, 106 + +Insects, how to prevent injury from, 107 + +Iron oak, 74 + +Ironwood, 44, 65 + + +Jack, Black, 75 + +Jack oak, 75 + +Jack pine, 27 + +Jersey pine, 27 + +Juniper, 18 + +Juniper bush, 18 + +Juniper, red, 18 + +Juniper, savin, 18 + + +Keep Records of the Moisture Content, 249 + +Kiln, apartment dry, 198 + +Kiln, blower or hot blast, 185 + +Kiln, box dry, 204 + +Kiln cars and method of loading, 206 + +Kiln doors, different types, 231 + +Kiln-dried wood of different species, weight of, 95 + +Kiln-drying, 164, 177 + +Kiln-drying according to species, different, 170 + +Kiln-drying, conditions of success in, 169 + +Kiln-drying gum, 180 + +Kiln-drying, helpful appliances in, 237 + +Kiln-drying, losses due to improper, 141 + +Kiln-drying, objects of, 168 + +Kiln-drying of green red gum, 183 + +Kiln-drying of wood, 156 + +Kiln-drying of wood, 156 + +Kiln-drying over air-drying, advantages of, 156 + +Kiln-drying, theory of, 157 + +Kiln-drying, underlying principles of, 166 + +Kiln-drying, unsolved problems in, 143 + +Kiln, operation of the blower dry, 186 + +Kiln, operation of the moist-air dry, 192 + +Kiln, pipe or moist-air dry, 188 + +Kiln, pocket dry, 200 + +Kiln, progressive dry, 196 + +Kiln, requirements in a satisfactory dry, 160 + +Kilns, different types of dry, 185 + +Kilns of different types, 196 + +Kiln specialties, dry, 206 + +Kiln, theory and description of the forest service, 161 + +Kilns, types of dry, 185 + +Kiln, tower dry, 202 + + +Land Spruce, Tide, 28 + +Larch, 22 + +Larch, American, 22 + +Larch, black, 22 + +Larch, western, 22 + +Large-toothed aspen, 79 + +Laurel, 65 + +Laurel oak, 75 + +Lawson's cypress, 18 + +Leaf pine, long-, 24 + +Leaf pine, short-, 26 + +Leaf willow, long, 84 + +Leaved basswood, small, 39 + +Leaved birch, aspen, 42 + +Leaved maple, ash, 69 + +Leaved maple, broad, 69 + +Leaved maple, silver, 69 + +Leaved trees, broad, 31 + +Leaved trees, list of most important broad, 37 + +Leaved trees, wood of broad, 31 + +Leverwood, 65 + +Life, tree of, 17 + +Lime tree, 39 + +Lin, 39 + +Linden, 39 + +Linden, American, 39 + +Linden, downy, 39 + +Liquidamber, 54 + +Liquids, staves and heads of barrels containing alcoholic, 112 + +List of important coniferous trees, 17 + +List of most important broad-leaved trees, 37 + +Live oak, 75, 76 + +Loading, kiln cars and method of, 206 + +Loblolly pine, 25 + +Local distribution of water in wood, 114 + +Locust, 66 + +Locust, black, 66 + +Locust, brown, 66 + +Locust, clammy, 66 + +Locust, honey, 66 + +Locust, sweet, 66 + +Locust, yellow, 66 + +Lodge-pole pine, 27 + +Lombardy poplar, 79 + +Long-leaf pine, 24 + +Long-leaf willow, 84 + +Long-straw pine, 24 + +Losses due to improper kiln-drying, 141 + +Lost in kiln-drying 100 lb. green wood in the kiln, pounds of water, 179 + + +Magnolia, 67 + +Magnolia, small, 67 + +Magnolia, swamp, 67 + +Mahogany, birch, 41 + +Mahogany, white, 45 + +Manner of evaporation of water, 123 + +Maple, 67 + +Maple, ash-leaved, 69 + +Maple, broad-leaved, 69 + +Maple, hard, 68 + +Maple, mountain, 69 + +Maple, Oregon, 69 + +Maple, red, 69 + +Maple, rock, 68 + +Maple, silver, 69 + +Maple, silver-leaved, 69 + +Maple, soft, 69 + +Maple, striped, 70 + +Maple, sugar, 68 + +Maple, swamp, 69 + +Maple, water, 69 + +Maple, white, 69 + +Maul oak, 75, 76 + +Meadow pine, 26 + +Method, choice of drying, 195 + +Method of loading kiln cars, 206 + +Method of piling gum, 180 + +Methods, impregnation, 151 + +Methods of drying, 154 + +Mildew, elimination of stain and, 136 + +Minute structure, 34 + +Mockernut hickory, 64 + +Moist-air dry kiln, operation of, 192 + +Moist-air or pipe kiln, the, 188 + +Moisture content, keep records of the, 249 + +Moisture, demands upon soil and, 56 + +Moisture on wood, effects of, 117 + +Moose elm, 51 + +Moose-wood, 70 + +Mossy-cup oak, 72 + +Most important broad-leaved trees list of, 37 + +Mountain holly, 65 + +Mountain maple, 69 + +Mulberry, 70 + +Mulberry, red, 70 + +Myrtle, 65, 70 + + +Nettle Tree, 62 + +Noble fir, 21 + +Norway pine, 25 + +Nut, coffee, 49 + +Nut hickory, black, 64 + +Nut hickory, bull, 64 + +Nut, Illinois, 64 + +Nyssa, 60 + + +Oak, 70 + +Oak, American, 71 + +Oak, barren, 75 + +Oak, basket, 74 + +Oak, bear, 74 + +Oak, black, 74 + +Oak, bur, 72 + +Oak, chestnut, 73 + +Oak, chinquapin, 73, 74 + +Oak, cow, 74 + +Oak, duck, 73 + +Oak, dwarf chinquapin, 74 + +Oak, iron, 74 + +Oak, jack, 75 + +Oak, laurel, 75 + +Oak, live, 75, 76 + +Oak, maul, 75, 76 + +Oak, mossy-cup, 72 + +Oak, over-cup, 72, 73 + +Oak, peach, 72 + +Oak, pin, 73 + +Oak, possum, 73 + +Oak, post, 74 + +Oak, punk, 73 + +Oak, red, 74, 75 + +Oak, rock, 73 + +Oak, rock chestnut, 73 + +Oak, scarlet, 75 + +Oak, scrub, 74 + +Oak, scrub chestnut, 74 + +Oak, shingle, 75 + +Oak, Spanish, 75 + +Oak, swamp post, 73 + +Oak, swamp Spanish, 73 + +Oak, swamp white, 72, 73 + +Oak, water, 73 + +Oak, western white, 71 + +Oak, white, 71, 72 + +Oak, willow, 72 + +Oak, yellow, 73, 74 + +Oak, Valparaiso, 76 + +Objects of kiln-drying, 168 + +Odor and color of wood, 89 + +Odor, weight, and figure in wood, grain, color, 86 + +Ohio buckeye, 45 + +Old field birch, 42 + +Old field pine, 25, 26 + +Operation of the blower kiln, 186 + +Operation of the moist-air kiln, 192 + +Orange, osage, 76 + +Oregon ash, 38 + +Oregon cedar, 18 + +Oregon maple, 69 + +Oregon pine, 29 + +Orford cedar, Port, 18 + +Osage orange, 76 + +Out-of-door seasoning, 154 + +Over-cup oak, 72, 73 + + +Papaw, 76 + +Paper birch, 43 + +Peach oak, 72 + +Pecan, 64 + +Pecky cypress, 19 + +Pencil cedar, 18 + +Pepperidge, 60 + +Perch willow, 84 + +Persimmon, 77 + +Peruche, 21 + +Physical conditions governing the drying of wood, 156 + +Physical properties that influence drying, 125 + +Pignut hickory, 64 + +Piling gum, methods of, 180 + +Pine, American red, 25 + +Pine, bastard, 26 + +Pine, black, 25, 27 + +Pine, bull, 25 + +Pine, California white, 25 + +Pine, Canadian, 25 + +Pine, Carolina, 26 + +Pine, Cuban, 26 + +Pine, Georgia, 24 + +Pine, ginger, 18 + +Pine, gray, 27 + +Pine, hard, 26 + +Pine, hazel, 54, 60 + +Pine, jack, 27 + +Pine, Jersey, 27 + +Pine, loblolly, 25 + +Pine, lodge-pole, 27 + +Pine, long-leaf, 24 + +Pine, long-straw, 24 + +Pine, meadow, 26 + +Pine, Norway, 25 + +Pine, old field, 25, 26 + +Pine, Oregon, 29 + +Pine, pitch, 26 + +Pine, Puget Sound, 29 + +Pine, pumpkin, 23, 24 + +Pine, red, 29 + +Pine, rosemary, 25 + +Pine, sap, 25 + +Pine, scrub, 27 + +Pines, hard, 24 + +Pine, short-leaf, 26 + +Pine, short-straw, 25 + +Pine, slash, 25, 26 + +Pine, soft, 23, 24 + +Pine, southern, 24 + +Pine, southern hard, 24 + +Pine, spruce, 26 + +Pine, sugar, 24 + +Pine, swamp, 26 + +Pine, torch, 26 + +Pine, Weymouth, 23 + +Pine, western, 25 + +Pine, western white, 25 + +Pine, western yellow, 25 + +Pine, white, 23, 24 + +Pine, yellow, 24, 25, 26 + +Pin oak, 73 + +Pipe or moist-air kiln, 188 + +Pitch pine, 26 + +Pith and bark, 8 + +Plane tree, 80 + +Pocket dry kiln, the, 200 + +Point in wood, the fibre saturation, 118 + +Pole pine, lodge, 27 + +Poplar, 67, 77, 79, 81 + +Poplar, bay, 60 + +Poplar, blue, 81 + +Poplar, Carolina, 77 + +Poplar, downy, 78 + +Poplar, hickory, 81 + +Poplar, Lombardy, 79 + +Poplar, swamp, 60 + +Poplar, white, 79, 81 + +Poplar, yellow, 81 + +Port Orford cedar, 18 + +Possum oak, 73 + +Post borers, powder, 105 + +Post oak, 74 + +Post oak, swamp, 73 + +Pounds of water lost in drying 100 lb. green wood in the kiln, 179 + +Powder post borers, 105 + +Preliminary steaming of gum, 182 + +Preliminary treatments, 151 + +Pressure and vacuum, drying under, 146 + +Pressure, drying at atmospheric, 146 + +Prevent injury from insects, how to, 107 + +Prevention of checking and splitting, 129 + +Principles of kiln-drying, underlying, 166 + +Problems in kiln-drying, unsolved, 143 + +Products, crude, 106 + +Products in the rough, seasoned, 112 + +Products in the rough, unseasoned, 109 + +Progressive dry kiln, the, 196 + +Properties, characteristics and, 1 + +Properties of wood, 4 + +Properties of wood that affect drying, 141 + +Properties that influence drying, physical, 125 + +Puget Sound pine, 29 + +Pumpkin pine, 23, 24 + +Punk oak, 73 + +Pussy willow, 84 + + +Quaking Aspen, 79 + + +Range of Red Gum, 55 + +Range of tupelo gum, 61 + +Rapidity of evaporation, 124 + +Recording hygrometer, the, 242 + +Recording steam gauge, the, 246 + +Recording thermometer, the, 245 + +Records of the moisture content, keep, 249 + +Red ash, 38 + +Red beech, 40 + +Red birch, 43 + +Red cedar, 18, 19 + +Red cedar of the West, 17 + +Red cherry, 47 + +Red cherry, wild, 47 + +Red cypress, 19 + +Red elm, 51 + +Red fir, 21, 29 + +Red gum, 54, 79 + +Red gum, demands upon soil and moisture of, 56 + +Red gum, form of the, 55 + +Red gum, kiln-drying of green, 183 + +Red gum, range of, 55 + +Red gum, reproduction of, 57 + +Red gum, second-growth, 59 + +Red gum, tolerance of, 56 + +Red juniper, 18 + +Red maple, 69 + +Red mulberry, 70 + +Red oak, 74, 75 + +Red pine, 29 + +Red pine, American, 25 + +Red spruce, 28 + +Redwood, 19, 27 + +Redwood, California, 19 + +Redwood, Coast, 19 + +Registering hygrometer, the, 244 + +Registering thermometer, the, 246 + +Rendering drying difficult, changes, 140 + +Reproduction of red gum, 57 + +Requirements in a satisfactory dry kiln, 160 + +Ring, the annual or yearly, 10 + +River birch, 43 + +Rock chestnut oak, 73 + +Rock elm, 50 + +Rock maple, 68 + +Rock oak, 73 + +Rosemary pine, 25 + +Rough, seasoned products in the, 112 + +Rough, unseasoned products in the, 109 + +Round-headed borers, 101 + +Round timber with bark on, 106 + +Rum cherry, 47 + + +Samples for Scalometer Test, 248 + +Sand bar willow, 84 + +Sap and heartwood, 8 + +Sap, composition of, 116 + +Saplings, 108 + +Sap pine, 25 + +Sassafras, 80 + +Satin walnut, 54 + +Satisfactory dry kiln, requirements in a, 160 + +Saturation point in wood, fibre, 118 + +Sawmills, scalometer in, 249 + +Savin juniper, 18 + +Scalometer in factories, 249 + +Scalometer in sawmills, 249 + +Scalometer, test samples for, 248 + +Scalometer, the troemroid, 247 + +Scalometer, weighing with, 248 + +Scalybark hickory, 64 + +Scarlet oak, 75 + +Scrub chestnut oak, 74 + +Scrub oak, 74 + +Scrub pine, 27 + +Seasonal distribution of water in wood, 115 + +Seasoned and unseasoned wood, difference between, 121 + +Seasoned, how wood is, 145 + +Seasoned products in the rough, 112 + +Seasoning, advantages in, 128 + +Seasoning is, what, 119 + +Seasoning, out-of-door, 154 + +Second-growth red gum, 59 + +Sequoia, 19 + +Service kiln, theory and description of forest, 161 + +Shagbark hickory, 64 + +Shellbark hickory, 64 + +Shingle, heading and stave bolts, 109 + +Shingle oak, 75 + +Shining willow, 84 + +Short-leaf pine, 26 + +Short-straw pine, 25 + +Shrinkage of wood, 130 + +Shucks, honey, 66 + +Sitka spruce, 28 + +Silver birch, 42 + +Silver-leaved maple, 69 + +Silver maple, 69 + +Slash pine, 25, 26 + +Slippery elm, 51 + +Small-leaved basswood, 39 + +Small magnolia, 67 + +Soft maple, 69 + +Soft pine, 23, 24 + +Soil and moisture, demands upon, 56 + +Sorrel-tree, 80 + +Sound pine, Puget, 29 + +Sour gum, 62, 80 + +Sourwood, 80 + +Southern hard pine, 24 + +Southern pine, 24 + +Spanish oak, 75 + +Spanish oak, swamp, 73 + +Specialties, dry-kiln, 206 + +Species, different kiln-drying according to, 170 + +Species, temperature depends upon condition and, 171 + +Species, weight of kiln-dried wood of different, 95 + +Spindle tree, 82 + +Splitting, prevention of checking and, 129 + +Spring and summer-wood, 12 + +Spruce, 27 + +Spruce, bastard, 29 + +Spruce, black, 27 + +Spruce, Douglas, 29 + +Spruce, hemlock, 21 + +Spruce pine, 26 + +Spruce, red, 28 + +Spruce, Sitka, 28 + +Spruce, tide-land, 28 + +Spruce, white, 28 + +Stain and mildew, elimination of, 136 + +Stave, heading and shingle bolts, 109 + +Staves and heads of barrels containing alcoholic liquids, 112 + +Steam, drying by superheated, 150 + +Steam gauge, the recording, 246 + +Steaming of gum, preliminary, 182 + +Steaming of gum, final, 182 + +Stock and wooden truss hoops, dry cooperage, 112 + +Straw pine, long, 24 + +Straw pine, short, 25 + +Striped maple, 70 + +Structure, anatomical, 14 + +Structure, minute, 34 + +Structure of wood, 4 + +Stump tree, 49 + +Success in kiln-drying, conditions of, 169 + +Sugar berry, 62 + +Sugar maple, 68 + +Sugar pine, 24 + +Summerwood, spring and, 12 + +Superheated steam, drying by, 150 + +Swamp cottonwood, 78 + +Swamp hickory, 64 + +Swamp magnolia, 67 + +Swamp maple, 69 + +Swamp pine, 26 + +Swamp poplar, 60 + +Swamp post oak, 73 + +Swamp Spanish oak, 73 + +Swamp white oak, 72, 73 + +Sweet bay, 67 + +Sweet buckeye, 45 + +Sweet birch, 41 + +Sweet gum, 54, 80 + +Sweet locust, 66 + +Switchbud hickory, 64 + +Sycamore, 80, 81 + + +Tacmahac, 79 + +Tamarack, 22, 27, 29 + +Temperature depends upon conditions and species, 171 + +Test samples for scalometer, 248 + +Theory and description of the forest service kiln, 161 + +Theory of kiln-drying, 157 + +Thermometer, the recording, 245 + +Thermometer, the registering, 246 + +Thorned acacia, three, 66 + +Three-thorned acacia, 66 + +Tide-land spruce, 28 + +Timber, 1 + +Timber beetles, ambrosia or, 99 + +Timber with bark on, round, 106 + +Timber worms, 103 + +Tolerance of red gum, 56 + +Toothed aspen, large-, 79 + +Torch pine, 26 + +Tower dry kiln, the, 202 + +Treatments, preliminary, 151 + +Tree, abele, 79 + +Tree, bee, 39 + +Tree, button ball, 80 + +Tree, coffee, 49 + +Tree, cucumber, 49, 67 + +Tree, fir, 20 + +Tree, lime, 39 + +Tree, nettle, 62 + +Tree of life, 17 + +Tree, plane, 80 + +Trees, broad-leaved, 31 + +Trees, classes of, 5 + +Trees, coniferous, 8 + +Trees, list of important coniferous, 17 + +Trees, list of most important broad-leaved, 37 + +Tree, sorrel, 80 + +Tree, spindle, 82 + +Tree, stump, 49 + +Trees, wood of broad-leaved, 31 + +Trees, wood of the coniferous, 8 + +Tree, tulip, 81 + +Tree, umbrella, 67 + +Troemroid Scalometer, the, 247 + +Truss hoops, dry cooperage stock and, 112 + +Tulip tree, 81 + +Tulip wood, 67, 81 + +Tupelo, 82 + +Tupelo gum, 60 + +Tupelo gum, range of, 61 + +Tupelo gum, uses of, 61 + +Types of dry kilns, different, 185 + +Types of kiln doors, different, 231 + +Types, kilns of different, 196 + + +Umbrella Tree, 67 + +Underlying principles of kiln-drying, 166 + +Unseasoned products in the rough, 109 + +Unseasoned wood, difference between seasoned and, 121 + +Unsolved problems in kiln-drying, 143 + +Uses of the humidity diagram, 237 + +Uses of tupelo gum, 61 + + +Vacuum, Drying under Pressure and, 146 + +Valparaiso oak, 76 + +Virgilia, 85 + + +Wahoo, 51, 82 + +Walnut, 45, 82 + +Walnut, black, 44, 82 + +Walnut, circassian, 60 + +Walnut, satin, 54 + +Walnut, white, 45, 83 + +Water beech, 44, 80 + +Water by dry wood, absorption of, 124 + +Water elm, 50 + +Water in wood, 114 + +Water in wood, distribution of, 114 + +Water in wood, local distribution of, 114 + +Water in wood, seasonal distribution of, 115 + +Water lost in drying 100 lb. of green wood in the kiln, pounds of, 179 + +Water, manner of evaporation of, 123 + +Water maple, 69 + +Water oak, 73 + +Weeping willow, 84 + +Weighing with scalometer, 248 + +Weight, and figure in wood, grain, color, odor, 86 + +Weight of kiln-dried wood of different species, 95 + +Weight of wood, 91 + +Western larch, 22 + +Western pine, 25 + +Western white oak, 71 + +Western white pine, 25 + +Western yellow pine, 25 + +West, red cedar of the, 17 + +Weymouth pine, 23 + +What seasoning is, 119 + +White ash, 37 + +White basswood, 39 + +White beech, 40 + +White birch, 42, 43 + +White cedar, 17, 18 + +White cypress, 19 + +White elm, 50 + +White fir, 20, 21 + +White heart hickory, 64 + +White mahogany, 45 + +White maple, 69 + +White oak, 71, 72 + +White oak, swamp, 72, 73 + +White oak, western, 71 + +White pine, 23, 24 + +White pine, California, 25 + +White pine, western, 25 + +White poplar, 79, 81 + +White spruce, 28 + +White walnut, 45, 83 + +White willow, 83 + +Whitewood, 39, 81, 83 + +Wild apple, 49 + +Wild cherry, 47 + +Wild red cherry, 47 + +Willow, 83 + +Willow, almond-leaf, 84 + +Willow, bebb, 84 + +Willow, black, 83 + +Willow, blue, 83 + +Willow, crack, 84 + +Willow, glaucous, 84 + +Willow, long-leaf, 84 + +Willow, oak, 72 + +Willow, perch, 84 + +Willow, pussy, 84 + +Willow, sand bar, 84 + +Willow, shining, 84 + +Willow, weeping, 84 + +Willow, white, 83 + +Willow, yellow, 83 + +Winged elm, 51 + +Wintergreen birch, 41 + +Wood, absorption of water by dry, 124 + +Wood, beaver, 67 + +Wood, canary, 81 + +Wood, characteristics and properties of, 1 + +Wood, color and odor of, 89 + +Wood, different grains of, 86 + +Wood, difference between seasoned and unseasoned, 121 + +Wood, difficulties of drying, 138 + +Wood, distribution of water in, 114 + +Wood, effects of moisture on, 117 + +Wood, enemies of, 98 + +Wood, expansion of, 135 + +Wood, figure in, 96 + +Wood, grain, color, odor, weight, and figure in, 86 + +Wood, how seasoned, 145 + +Wood in the kiln, pounds of water lost in drying 100 lb. of green, 179 + +Wood, iron, 65 + +Wood, kiln-drying of, 156 + +Wood, lever, 65 + +Wood, local distribution of water in, 114 + +Wood, moose, 70 + +Wood, of broad-leaves trees, 31 + +Wood of different species, weight of kiln-dried, 95 + +Wood of coniferous trees, 8 + +Wood, physical conditions governing the drying of, 156 + +Wood, properties of, 4 + +Wood, seasonal distribution of water in, 115 + +Wood, shrinkage of, 130 + +Woods, list of important coniferous, 17 + +Wood, spring and summer, 12 + +Wood, structure of, 4 + +Wood that effect drying, properties of, 141 + +Wood, the fibre saturation point in, 118 + +Wood, tulip, 67, 81 + +Wood, water in, 114 + +Wood, weight of, 89 + +Wood, white, 81, 83 + +Wood, yellow, 85 + +Wooden truss hoops, dry cooperage, stock and, 112 + +Worms, timber, 103 + + +Yearly Ring, the Annual of, 10 + +Yellow birch, 42 + +Yellow cedar, 18 + +Yellow deal, 23 + +Yellow fir, 29 + +Yellow locust, 66 + +Yellow oak, 73, 74 + +Yellow pine, 24, 25, 26 + +Yellow pine, western, 25 + +Yellow poplar, 81 + +Yellow willow, 83 + +Yellow wood, 85 + +Yew, 29, 30 + + + + + D. VAN NOSTRAND COMPANY + 25 PARK PLACE + NEW YORK + + + SHORT-TITLE CATALOG + OF + Publications and Importations + OF + SCIENTIFIC AND ENGINEERING + BOOKS + + [Illustration] + + This list includes + the technical publications of the following English publishers: + + SCOTT, GREENWOOD & CO. JAMES MUNRO & CO., Ltd. + CONSTABLE & COMPANY, Ltd. TECHNICAL PUBLISHING CO. + ELECTRICIAN PRINTING & PUBLISHING CO. + + for whom D. Van Nostrand Company are American agents. + + + + + JULY, 1917 + + SHORT-TITLE CATALOG + OF THE + Publications and Importations + OF + D. VAN NOSTRAND COMPANY + 25 PARK PLACE, N. Y. + + _Prices marked with an asterisk (*) are NET._ + + _All bindings are in cloth unless otherwise noted._ + + +Abbott, A. V. The Electrical Transmission of Energy 8vo, *$5 00 + +---- A Treatise on Fuel. (Science Series No. 9) 16mo, 0 50 + +---- Testing Machines. (Science Series No. 74.) 16mo, 0 50 + +Adam, P. Practical Bookbinding. Trans. by T. E. Maw 12mo, *2 50 + +Adams, H. Theory and Practice in Designing 8vo, *2 50 + +Adams, H. C. Sewage of Sea Coast Towns 8vo, *2 00 + +Adams, J. W. Sewers and Drains for Populous Districts 8vo, 2 50 + +Adler, A. A. Theory of Engineering Drawing 8vo, *2 00 + +---- Principles of Parallel Projecting-line Drawing 8vo, *1 00 + +Aikman, C. M. Manures and the Principles of Manuring 8vo, 2 50 + +Aitken, W. Manual of the Telephone 8vo, *8 00 + +d'Albe, E. E. F., Contemporary Chemistry 12mo, *1 25 + +Alexander, J. H. Elementary Electrical Engineering 12mo, 2 00 + +Allan, W. Strength of Beams Under Transverse Loads. + (Science Series No. 19.) 16mo, 0 50 + +---- Theory of Arches. (Science Series No. 11) 16mo, + +Allen, H. Modern Power Gas Producer Practice and + Applications. 12mo, *2 50 + +Anderson, J. W. Prospector's Handbook 12mo, 1 50 + +Andes, L. Vegetable Fats and Oils 8vo, *4 00 + +---- Animal Fats and Oils. Trans. by C. Salter 8vo, *4 00 + +---- Drying Oils, Boiled Oil, and Solid and Liquid Driers 8vo, *5 00 + +---- Iron Corrosion, Anti-fouling and Anti-corrosive + Paints. Trans. by C. Salter 8vo, *4 00 + +---- Oil Colors, and Printers' Ink. Trans. by A. Morris + and H. Robson 8vo, *2 50 + +---- Treatment of Paper for Special Purposes. Trans. + by C. Salter 12mo, *2 50 + +Andrews, E. S. Reinforced Concrete Construction 12mo, *1 50 + +---- Theory and Design of Structures 8vo, *3 50 + +---- Further Problems in the Theory and Design + of Structures 8vo, *2 50 + +---- The Strength of Materials 8vo, *4 00 + +Andrews, E. S., and Heywood, H. B. The Calculus + for Engineers. 12mo, *1 50 + +Annual Reports on the Progress of Chemistry. Twelve + Volumes now ready. Vol. I., 1904, Vol. XII., 1914 8vo, each, *2 00 + +Argand, M. Imaginary Quantities. Translated from the + French by A. S. Hardy. (Science Series No. 52.) 16mo, 0 50 + +Armstrong, R., and Idell, F. E. Chimneys for Furnaces + and Steam Boilers. (Science Series No. 1.) 16mo, 0 50 + +Arnold, E. Armature Windings of Direct-Current Dynamos. + Trans. by F. B. DeGress 8vo, *2 00 + +Asch, W., and Asch, D. The Silicates in Chemistry + and Commerce 8vo, *6 00 + +Ashe, S. W., and Kelley, J. D. Electric Railways. + Theoretically and Practically Treated. Vol. I. + Rolling Stock 12mo, *2 50 + +Ashe, S. W. Electric Railways. Vol. II. Engineering + Preliminaries and Direct Current Sub-Stations 12mo, *2 50 + +---- Electricity: Experimentally and Practically Applied 12mo, *2 00 + +Ashley, R. H. Chemical Calculations 12mo, *2 00 + +Atkins, W. Common Battery Telephony Simplified 12mo, *1 25 + +Atkinson, A. A. Electrical and Magnetic Calculations 8vo, *1 50 + +Atkinson, J. J. Friction of Air in Mines. (Science + Series No. 14.) 16mo, 0 50 + +Atkinson, J. J., and Williams, Jr., E. H. Gases Met + with in Coal Mines. (Science Series No. 13.) 16mo, 0 50 + +Atkinson, P. The Elements of Electric Lighting 12mo, 1 00 + +---- The Elements of Dynamic Electricity and Magnetism 12mo, 2 00 + +---- Power Transmitted by Electricity 12mo, 2 00 + +Auchincloss, W. S. Link and Valve Motions Simplified 8vo, *1 50 + +Austin, E. Single Phase Electric Railways 4to, *5 00 + +Austin and Cohn. Pocketbook of Radiotelegraphy (_In Press._) + +Ayrton, H. The Electric Arc 8vo, *5 00 + + +Bacon, F. W. Treatise on the Richards Steam-Engine + Indicator 12mo, 1 00 + +Bailey, R. D. The Brewers' Analyst 8vo, *5 00 + +Baker, A. L. Quaternions 8vo, *1 25 + +---- Thick-Lens Optics 12mo, *1 50 + +Baker, Benj. Pressure of Earthwork. (Science + Series No. 56.) 16mo, + +Baker, G. S. Ship Form, Resistance and Screw Propulsion 8vo, *4 50 + +Baker, I. O. Levelling. (Science Series No. 91.) 16mo, 0 50 + +Baker, M. N. Potable Water. (Science Series No. 61.) 16mo, 0 50 + +---- Sewerage and Sewage Purification. (Science + Series No. 18.) 16mo, 0 50 + +Baker, T. T. Telegraphic Transmission of Photographs 12mo, *1 25 + +Bale, G. R. Modern Iron Foundry Practice. Two Volumes. 12mo. + Vol. I. Foundry Equipment, Materials Used *2 50 + Vol. II. Machine Moulding and Moulding Machines *1 50 + +Ball, J. W. Concrete Structures in Railways 8vo, *2 50 + +Ball, R. S. Popular Guide to the Heavens 8vo, *5 00 + +---- Natural Sources of Power. (Westminster Series.) 8vo, *2 00 + +Ball, W. V. Law Affecting Engineers 8vo, *3 50 + +Bankson, Lloyd. Slide Valve Diagrams. (Science + Series No. 108.). 16mo, 0 50 + +Barham, G. B. Development of the Incandescent Electric + Lamp 8vo, *2 00 + +Barker, A. F. Textiles and Their Manufacture. + (Westminster Series.) 8vo, 2 00 + +Barker, A. F., and Midgley, E. Analysis of Textile Fabrics 8vo, 3 00 + +Barker, A. H. Graphic Methods of Engine Design 12mo, *1 50 + +---- Heating and Ventilation 4to, *8 00 + +Barnard, J. H. The Naval Militiaman's Guide 16mo, leather, 1 00 + +Barnard, Major J. G. Rotary Motion. 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Treatise on Photographic Optics 12mo, 1 50 + +Coles-Finch, W. Water, Its Origin and Use 8vo, *5 00 + +Collins, J. E. Useful Alloys and Memoranda for + Goldsmiths, Jewelers. 16mo, 0 50 + +Collis, A. G. High and Low Tension Switch-Gear Design 8vo, *3 50 + +---- Switchgear. (Installation Manuals Series.) 12mo, *0 50 + +Comstock, D. F., and Troland, L. T. The Nature + of Electricity and Matter 8vo, *2 00 + +Coombs, H. A. Gear Teeth. (Science Series No. 120.) 16mo, 0 50 + +Cooper, W. R. Primary Batteries 8vo, *4 00 + +Copperthwaite, W. C. Tunnel Shields 4to, *9 00 + +Corfield, W. H. Dwelling Houses. (Science Series No. 50.) 16mo, 0 50 + +---- Water and Water-Supply. (Science Series No. 17.) 16mo, 0 50 + +Cornwall, H. B. Manual of Blow-pipe Analysis 8vo, *2 50 + +Cowee, G. A. Practical Safety Methods and Devices 8vo, *3 00 + +Cowell, W. B. Pure Air, Ozone, and Water 12mo, *2 00 + +Craig, J. W., and Woodward, W. P. Questions and + Answers About Electrical Apparatus 12mo, leather, 1 50 + +Craig, T. Motion of a Solid in a Fuel. (Science + Series No. 49.) 16mo, 0 50 + +---- Wave and Vortex Motion. (Science Series No. 43.) 16mo, 0 50 + +Cramp, W. Continuous Current Machine Design 8vo, *2 50 + +Crehore, A. C. Mystery of Matter and Energy 8vo, 1 00 + +Creedy, F. Single Phase Commutator Motors 8vo, *2 00 + +Crocker, F. B. Electric Lighting. Two Volumes. 8vo, + Vol. I. The Generating Plant 3 00 + Vol. II. Distributing Systems and Lamps + +Crocker, F. B., and Arendt, M. Electric Motors 8vo, *2 50 + +Crocker, F. B., and Wheeler, S. S. The Management + of Electrical Machinery 12mo, *1 00 + +Cross, C. F., Bevan, E. J., and Sindall, R. W. Wood + Pulp and Its Applications. (Westminster Series.) 8vo, *2 00 + +Crosskey, L. R. Elementary Perspective 8vo, 1 25 + +Crosskey, L. R., and Thaw, J. Advanced Perspective 8vo, 1 50 + +Culley, J. L. Theory of Arches. (Science Series No. 87.) 16mo, 0 50 + +Cushing, H. C., Jr., and Harrison, N. Central Station + Management *2 00 + + +Dadourian, H. M. Analytical Mechanics 12mo, *3 00 + +Dana, R. T. Handbook of Construction plant 12mo, leather, *5 00 + +Danby, A. Natural Rock Asphalts and Bitumens 8vo, *2 50 + +Davenport, C. The Book. (Westminster Series.) 8vo, *2 00 + +Davey, N. The Gas Turbine 8vo, *4 00 + +Davies, F. H. Electric Power and Traction 8vo, *2 00 + +---- Foundations and Machinery Fixing. (Installation + Manual Series.) 16mo, *1 00 + +Deerr, N. Sugar Cane 8vo, 8 00 + +Deite, C. Manual of Soapmaking. Trans. by S. T. King 4to, *5 00 + +De la Coux, H. The Industrial Uses of Water. Trans. + by A. Morris. 8vo, *4 50 + +Del Mar, W. A. Electric Power Conductors 8vo, *2 00 + +Denny, G. A. Deep-level Mines of the Rand 4to, *10 00 + +---- Diamond Drilling for Gold *5 00 + +De Roos, J. D. C. Linkages. (Science Series No. 47.) 16mo, 0 50 + +Derr, W. L. 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Elementary Text-book of Light, + Heat and Sound 12mo, 1 00 + +---- Heat and the Principles of Thermo-dynamics 12mo, *2 00 + +Dron, R. W. Mining Formulas 12mo, 1 00 + +Dubbel, H. High Power Gas Engines 8vo, *5 00 + +Dumesny, P., and Noyer, J. Wood Products, Distillates, + and Extracts. 8vo, *4 50 + +Duncan, W. G., and Penman, D. The Electrical Equipment + of Collieries. 8vo, *4 00 + +Dunkley, W. G. Design of Machine Elements 8vo, 1 50 + +Dunstan, A. E., and Thole, F. B. T. Textbook of + Practical Chemistry. 12mo, *1 40 + +Durham, H. W. Saws 8vo, 2 50 + +Duthie, A. L. Decorative Glass Processes. + (Westminster Series.). 8vo, *2 00 + +Dwight, H. B. Transmission Line Formulas 8vo, *2 00 + +Dyson, S. S. Practical Testing of Raw Materials 8vo, *5 00 + +Dyson, S. S., and Clarkson, S. S. Chemical Works 8vo, *7 50 + + +Eccles, W. H. Wireless Telegraphy and Telephony 12mo, *4 50 + +Eck, J. Light, Radiation and Illumination. Trans. + by Paul Hogner, 8vo, *2 50 + +Eddy, H. T. 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