CD , s, Per ct. 29.20 25.77 19.93 16.13 19.37 13.16 13.21 10.00 12.50 10.82 Per ct. 12.86 12.72 10.76 9.26 11.63 9.40 8.17 6.78 9.42 8.42 Per ct. 42.06 38.49 30.69 25.39 31.00 22.56 21.38 16.78 21.92 19.24 Per ct. 2.86 Per ct. 44.92 38.49 30.69 25.39 31.16 22.56 21.38 16.78 21.92 19.24 First "cut 15 feet 31 feet 45 feet 0.16 60 feet 66 feet. 74 feet 78 feet.. 84 feet 1 Tree 18 inches in diameter 4 feet from the ground, and 96 feet high, in northerly h'ollow, southern Hum- boldt County. Sunshine and light increase the secretion of tannin. For this reason the best bark grows on ridges, and the southern districts yield a richer product than the northern. Bark from the Santa Lucia Mountains, the southernmost of all the districts, is the richest in the market and averages as high as from 20 to 24 per cent. According to the tanners who have used bark from widely separated districts, that grown in the "Bald Hills" district in the interior, beyond the influence of the sea fogs, is richer than that from the coast, where the trees are shaded by redwoods and are in the fog belt. Bark from the coast of Oregon is low in tannin, with an average of only 12 or 14 per cent. PROLONGING THE SUPPLY. 15 Table 7 shows the results of analyses of bark of representative trees of the various districts: TABLE 7. Analyses of bark samples from different districts. Bald Hills districts. Solids soluble in cold water. Solids soluble in hot water only, reds. Total solids extract. Tannin. Nontan- nin. Total. Thick bark, commercial sample, Briceland, Hum- boldt County Per cent. 24.74 14.82 14.90 15.66 15.36 20.51 22.20 14.92 14.00 16.20 22.73 19.08 21.61 18.93 18.24 Per cent. 13.18 9.60 11.86 7.12 10.02 11.21 11.69 8.89 6.73 8.92 10.07 9.76 6.85 5.40 9.24 Per cent. 37.92 24.42 26.76 22.72 25.38 31.72 33.89 23.81 20.73 25. 12 33.80 28.84 28.46 24.33 27.48 Per cent. 3.08 1.78 2.16 2.52 1.88 3.24 2.87 1.15 1.86 3.76 1.14 7.96 2.14 2.67 3.60 Per cent. 41.00 26.20 28.92 25.24 27. 26 34.96 36. 76 24.96 22.59 28.88 34.94 36.80 30.60 27.00 30.08 Thick bark, Acorn region, llumboldt County Thin tfark, Acorn region, llumboldt County Between Low Gap and Summit, west of Ukiah: It-foot tree, sample at 3 feet from ground, ridge tree ly-foot tree within 15 feet of preceding Just east of Coast Range summit (west of Ukiah); Elk Creek, Mendocino County: Thick bark > Medium bark . Thin bark Ridge tree in open, near coast at Kenny's; 2-foot tree. Ridge tree near coast at Kenny's' 2-foot tree South slope tree exposed to sun, Halfway House, Ukiah-Mendocino Road; 2-foot tree San Vicente Creek, Santa Cruz Mountains, Redwood district: 3-foot smooth-barked tree Rough-barked tree within 10 feet of preceding; 2i-foot tree San Vicente Creek, Santa Cruz Mountains, S.Woot tree PROLONGING THE SUPPLY. With the disappearance of the bodies of tanbark oak which have furnished the chief tanning material for the leather manufacturing industry on the Pacific coast the question of the continuation of the supply becomes very important. Since the greater portion of the standing tanbark is now confined to broken and inaccessible moun- tain country, the extension of transportation facilities to those regions must exert a very marked influence on its exploitation and cost. Railroads and wagon trails are being rapidly pushed into the northern coast ranges, and it is probable that within two or three years the rich belts of Mendocino, Humboldt, and Del Norte Counties will have at least one railway line. The utilization of second growth; the introduction of more conservative methods in the woods, par- ticularly in connection with the redwood lumbering industry; the protection of the forests from fire; and the extension of the use of other products as substitutes for and supplements of the bark of this most important tree, will all have their influences on the future supply. 16 CALIFORNIA TANBARK OAK. PROVIDING FOR SECOND GROWTH. SPROUT REPRODUCTION. For the maintenance of the supply of tanbark on the Pacific coast the second growth on cut-over areas offers by far the most hope. Sprout reproduction must be encouraged, since the tree sprouts very readily and with great persistence. Sprouts grow from trees of prac- tically Siuy age and under a wide variety of conditions. Of greatest economic significance are those which spring up from the stumps of trees felled for peeling. The sprouts arise from conical woody buds which are formed under the bark at the base of the tree, and which vary in number from a scattering few to crowded thousands. The sprouts themselves vary in number; as many as 1,400 have been counted on one large stump. The practice of peeling the tree down as far as possible, often below ground level, in order to obtain all the rich and heavy rump bark, exposes the buds and prevents sprouts, but peeling can safely be carried down to the surface of the ground if the peelers ring the bottom of the first run instead of stripping off the bark as far down as it can be torn. The original number of sprouts is reduced by natural processes in 30 years to from four to eight of the most vigorous poles. The rate of height growth is about 2 feet a year. By proper thinning this rate could be accelerated. Sprouts also come up freely about the base of fire-injured and even fire-killed trees, which is a great advantage where there are frequent forest fires, as in the tanbark oak regions. They even grow vigor- ously from the stumps of old trees which have been weakened by dry rot or fire and have fallen. The Stumps of such fallen veterans may be a yard or two in diameter. Circles of sprouts about the rims of such stumps which have disappeared are often found in the woods, and the trunks of these sprouts are sometimes 2 feet in diameter at 4 feet from the ground. Sometimes sprouts will start from the base of living trees, though this habit is of slight commercial importance. Nothing can better illustrate the vitality of tanbark oak than the longevity of standing trees which have been peeled. Peeling is usually done before flowering time, and for the first year afterwards the growth of the tree is so decidedly checked that it does not fruit. The second year the tree bears a full crop of acorns often an exces- sively large crop. The woodsmen call this the "last kick" of the tree, since in the third year it usually dies. If the tree stands exposed to the full heat of the sun it will probably die the first season. Yet there is abundant testimony that it may continue to live for a long period even 10 or 15 years. The apparent anomaly of a tree con- tinuing its life functions with a complete band of bark removed from its trunk can be explained by a study of "jayhawked" trees in the field. Such trees were peeled either so early in the season or so late PROLONGING THE SUPPLY. 17 in the season that the bark did not part readily from the wood, and a very thin portion of the inner bark and cambium layer adhered to the wood and formed a sort of film. This film after one season looks like a thin ooat of brown varnish. The wood beneath, however, is greenish and pulpy, suggesting the mesophyll layer of a leaf. This layer does not increase appreciably in thickness. REPRODUCTION BY SEED. No other oak on the Pacific coast produces so heavy a crop of acorns as tanbark oak, but seedlings, nevertheless, are not abundant. In the main, forest seedlings are found only where a fallen tree has made a break in the forest canopy and let in light. The "Bald Hills" country is filled with hogs and cattle, which prevent seedling reproduction by devouring the acorns and browsing the tender foli- age of the young growth. Attempts at artificial . propagation outside the natural range of tanbark oak have failed. The acorns germinate in open nursery beds in about five weeks. The seedlings come up a little more promptly in loam beds than in adobe, but those in the adobe seem a trifle more vigorous than the others. Sand beds germinate only 2 per cent of the Eighty per cent of the seeds planted in 1902 at the California For- estry Station at Chico germinated, but not one seedling survived the first summer, although the soil conditions are favorable. The hot, dry climate of the interior valleys does not furnish a normal environ- ment for tanbark oak, and the formation of plantations is practica- ble only where conditions are similar to those of the natural range of the tre*e. SECOND-GROWTH BARK. For several years second growth has been peeled in the Santa Cruz Mountains, and it is claimed by some owners who superintended both peelings that the yield of second growth exceeds that of the virgin stand. There is nothing to prove or disprove this assertion, but it is probable that these men did not take account of the fact that the harvesting of the crop to-day is very much closer and more careful than the peeling of the virgin timber from 30 to 50 years ago, and that "passed trees" of the virgin stand were stripped at the sec- ond peeling. Although it is improbable that the yield of second growth at the end of 30 years would equal that of the original stand, it is sufficiently heavy to make the holding of cut-over lands profitable for repeeling in 30 years, when from 1 to 5 cords per acre can be harvested. Table 8 gives the yields of a number of second-growth trees in the Santa Cruz Mountains. 89446 Bull. 7511 3 18 CALIFORNIA TANBARK OAK. TABLE 8. Amount of bark on second-growth tan oak, age 29 to 31 years, Santa Cruz Mountains. Height of tree. Diame- ter of trunk at 2 feet. Length of peeled trunk. Diame- ter of trunk at end of last coil. Thick- ness of bark at butt. Weight of bark, green. Weight of bark dry (cal- culated). Feet. Inches. Feet. Inches. Inches. Pounds. Pounds. 52 7 24 4 U 145 91 50 6 24 4 1J 143 90 62 10 24 6 li 241 152 55 7 20 4 I* 125 79 65 9 28 , 6 2 . 243 152 55 7 20 , 5 11 120 76 62 8 - 24 5 l| 158 100 62 7 24 5 I* 160 101 60 8 28 6 2 235 148 65 10 28 6 i 303 191 70 9 28 6 i 303 191 67 10 36 5 2" 321 202 68 9 36 5 | 241 152 67 9 32 5 { 208 131 65 8 32 5 177 112 QUALITY OF SECOND-GROWTH BARK. Tanners estimate that second-growth bark will average only 10 per cent tannin, and when it was first put upon the market they objected to it; but, mixed with virgin bark, it is now used to a considerable extent. It is distinguishable from virgin bark by its peculiar smooth- ness both on the outside and the inside; by its brittleness, due to lack of fiber, especially toward the inside, where virgin bark is so fibrous; and by its sappiness and light color. Table 9 shows the characteristics of samples taken from near the bases of trees. The thinner bark higher Up would, of course, lower the average. It is possible to produce a good quality of leather by tlie use of second-growth bark alone, but a large quantity is required to offset its low tannin content. The item of labor is also greater, since it costs more to handle the extra bark. TABLE 9. Analyses showing tannin content of tan-oak bark taken from thr& 'Second- growth trees. Locality. Height. Diame- ter of wood at 1 foot. Age. Solids soluble in cold water. Solids sol- uble in hot water only, reds. Total solids. Tannin. Nontan- nin. Total. Between Comptche and Low Gap, one of 16 sprouts about stump Feet. Mi '40 60 Inches. 2* 5 9 Years. 7 24 30 Per cent. 18.28 16.22 14.10 Per cent. 8.28 10.60 8.94 Per cent. 26.56 26.82 23.04 Per cent. 1.00 , -56 .52 Per cent. 27.56 27.38 23.56 Between Comptche and Low Gap San Vicente Creek, Santa Cruz Moun- tains PROLONGING THE SUPPLY. 19 CONSERVATIVE METHODS IN THE WOODS. Redwood lumbering has done much to keep the annual supply of tanbark steady and to make remote stands accessible. It is the practice of the redwood lumber companies to send tanbark crews through the woods in advance of the redwood logging crews, since the firing of the district, which always follows felling, to facilitate the get- ting out of the redwood logs by wire cable and donkey engine, badly injures all standing trees, and even if it does not actually destroy the tanbark oak it makes peeling .difficult or impossible. GUARDING AGAINST FIRE. Up to the present time no attention has been paid to the future condition of the forestf in which peeling has been carried on. Yet the introduction of conservative methods would prevent a very large waste. Fire, which always accompanies redwood logging, makes it an economical policy to take all the bark possible, whether the .tree has reached maturity or not. Under conservative methods " jay- Hawked" trees, which yield only from 10 to 60 pounds of bark with a low tannin content, would in 10 or 20 years form profitable elements in the new stand for both bark and wood. Despite the custom of taking all the bark that can be peeled without regard to whether it is mature or not, the maximum yield is never obtained under present methods. Some trees which will not for one reason or another peel readily in one season, although they would a year or two later, are sacrificed in order to chip a little bark off their trunks or to secure one or more coils because the trees are considered as doomed to fire any- way. Often from 70 to 90 per cent of the bark in such cases can not be taken from the tree. Moreover, the fires kill very young trees, kill sprouts down to the stumps, and seriously interfere with reproduction. Under conservative management the older trees would be saved for peeling in a favorable year and the younger ones permitted to develop a new stand. As tanbark oak always grows in mixed stands, the holding of redwood and Douglas fir lands for a second crop would give the tanbark oak the necessary fire protection and would furnish a profitable element in the later harvests. During the rainless season in California, from May to October, even in the foggy coast region, fires caused by logging crews, hunters, campers, and in the far north coast ranges by thunderstorms, lead to several million dollars damage every year. These fires rarely kill tan- bark oak trees, but make long vertical wounds from 4 to 10 feet up the sides of the trunks. On young trees these injuries are often com- pletely covered by the meeting of new bark growth, but with trees more than 100 years old the sides of the' wound usually spread. The exposed wood rots, andsucli trees, called " goose pens," are difficult 20 CALIFORNIA TANBARK OAK. to lay out accurately in felling. Even a slight injury to the trunk permits the entrance of fungi which weaken the wood, and the loss of such trees in heavy snowfalls is very large. Trees on slopes or canyon sides are the greatest sufferers; 95 per cent of the tanbark oak trees in those positions are injured by fire and 80 per cent fire hollowed. In the case of ridge trees, about 80 per cent are comparatively free from fire hollows, because a fire traveling up a slope is either running high or going out when it reaches the top. The most extensive destruction by fire in the tanbark oak belt has probably been in Del Norte County, where in former days the Indians regularly fired the woods to make better feed for the deer, and the packers set fires to keep the trails open. Kidge after ridge has been wholly or partly reduced to a low chaparral growth, although there is evidence that a dense forest existed at a comparatively recent date. A conservative estimate of the loss of tanbark by fire within 15 years in this region is 60,000 cords. In the second-growth districts the accumulation of debris inside the circles of poles about the remains of the parent stumps furnishes material for flames. Forty per cent of such poles show serious injury at the bases. ("^TANNIN EXTRACT PROCESSES. .The difficulty of transportation has prevented the exploitation of some of the most productive tanbark oak regions in Humboldt and, to a smaller extent, in Mendocino County. An attempt was made to reduce this difficulty by grinding up the bark and shipping it in sacks, but this did not help in the more remote districts where the weight was the chief drawback. In the last few years attempts have been made to solve this difficulty by extracting the tannin from the bark and shipping the extract. Two methods have been tried in California, the open-pan process and the vacuum-pan process. The open-pan process was tried in southern Mendocino County hi 1900 and 1902, but was abandoned because the heat necessary to secure rapid evaporation in concen- trating the mixture of ground bark and liquid was said to scorch the fluid and start fermentation, so that the barrels containing the completed product often burst. The vacuum-pan process is used by an extract plant at Briceland, Humboldt County. The liquid from the leaching vats is pumped into settling tanks in the concentrator house, and thence fed as needed into the "pan" or evaporator, which is a copper retort about 7 feet in diameter, heated by steam pipes coiled around the base. By heating the pan under vacuum the temperature of the liquid during evaporation is kept from exceeding* about 120 or 130 F. TANNIN EXTRACT PROCESSES. 21 The vapor is condensed in a receptacle high enough above the pan to permit a 34-foot vertical waste pipe. This pipe, kept full of water, supplies a water column sufficient to offset the atmospheric pressure and maintain the vacuum. A cord of dry bark, 2,200 pounds, is reduced to 50 gallons of extract, which weighs about 550 pounds. The extractor has a capacity of 12 cords a day. SUPPLEMENTAL MATERIALS. The duration of the bark supply from tanbark oak will be extended somewhat by the use of other materials as supplements or substi- tutes. The superiority of the product of the tanbark oak over all other Pacific coast barks is due not altogether to its high percentage of tannin, but rather to the quality of the particular tannin con- tained in it, and perhaps also to the presence of certain other acids, such as gallic and acetic. The value of this combination is proved by tanning experience. Mixing imported tanning materials, such as gambier and quebracho, increases its effectiveness and counter- acts some of its undesirable qualities. As tanners have learned the use and value of these supplementary agents, methods have been more and more adapted to them, until to-day they are regarded as indispensable and the tanbark oak product is never used alone. As the accessible supply of tanbark oak grows scarcer and dearer, the bark from other species of oak is occasionally mixed with the superior material. This is especially the case in the southern dis- tricts, where the tanbark oak is more nearly exhausted. The barks of the California black oak and the coast live oak run so high in tannin that if tannin content alone were an index of tannage value they could compete with tanbark oak. They can not be used alone, because they will not produce leather of goo'd quality; the live-oak bark in particular imparts a gritty character to the leather, which ruins the knives of the cutters, but mixed in moderate quantities with the better bark they make possible a considerable saving. Alder bark is occasionally found in shipments of bark from tan- bark oak, but the tree does not grow in sufficient quantity in Cali- fornia to be a factor in bark supply. In the Mendocino woods the chinquapin is often peeled, but it contains so little tannin that it is practically worthless. Moreover, it is very fibrous and tough, which makes it difficult for the smaller tanbark mills to handle. Analyses of average bark samples from the main trunks of the important California trees are given in Table 10. Some of these have never been subjected to commercial experiment. 22 CALIFORNIA TANBARK OAK. TABLE 10. Tannin analyses of bark of the more important forest trees of the Pacific coast. Species. Locality. Soluble solids. Insoluble solids, reds. Total solids. Tannin. Xontan- nin. Total. California black oak (Quer- cus calif or nica). California black oak Vaca Mountains, So- lano County. Briceland, Humboldt County. Berkeley Per cent. 10.00 10.16 18.76 7.92 6.67 12.18 6.56 11.97 7.07 6.20 7.60 8.60 1.45 15.58 14.11 13.45 9.03 17.52 7.15 10.80 14.40 2.50 1.76 3.91 Per cent. 10.25 7.88 9.40 5.88 2.83 10.18 5.19 11.28 4.93 4.16 4.34 12.00 3.09 10.46 2.85 3.99 4.59 6.24 5.25 3.46 6.56 2.74 5.72 5.85 Per cent. 20.25 18.04 28.16 13.80 9.50 22.36 11.66 23.25 12.00 10.36 11.94 20.60 4.54 26.04 16.96 17.44 13.62 23.76 12.40 14.26 20.96 5.24 6.48 7.76 Per cent. 0.95 .32 1.48 1.20 1.64 .80 1.00 1.55 .36 1.00 .64 1.68 .00 .97 2.60 3.72 .74 1.60 .42 1.32 2.42 .10 .59 1.58 Per cent. 21.20 18.36 29.64 15.00 11.14 23.16 12.66 24.80 12.36 11.30 12. 08 22. 28 4.54 27. Gl 19. 50 21. 16 1^.36 25. 36 12. 82 15.58 23.38 5.34 7.07 9.34 California live oak (Quercus agrifolia). Highland oak (Quercus wis- lizeni). Highland oak Vaca Mountains, So- lano County. Southern Mendocino. . Vaca Mountains, So- lano County. South central Mendo- cino. Visalia Canyon live oak, maul oak (Quercus chrysolepis). Canyon live oak California white oak (Quer- cus lobata). Pacific post oak (Quercus garryana). Pacific post oak Southern Humboldt . . South central Mendo- cino, "Bald Hills." Southern Humboldt . . Mendocino coast . Western chinquapin (Cast- anopsis chrysophylla). Red alder (Alnu-s oregona)... California yellow willow; western black willow (Salix lasiandra). California laurel ( Umbel- lularia californica). Monterey pine (Pinus radi- ata). California swamp pine (Pinus muricata). Lowland fir (Abies grandis) Berkeley Briceland Berkeley (cult.) Mendocino coast ...do Sitka spruce (Picea sitchen- sis). Douglas fir (Pseudotsuga taiifolia). Western hemlock ( Tsuga heterophylla). Western hemlock do Southern Humboldt . . Mendocino coast Noyo River, Mendo- cino coast. Mendocino coast do Redwood (Sequoia semper- virens) bark. Redwood, sapwood Redwood, heartwood do POSSIBILITIES OF UTILIZING THE WOOD. The tanbark oak peeled since 1850 is equal to more than 2,000,000 cords of firewood. But, chiefly on account of the difficulty of trans- portation, little of this amount, perhaps 5 per cent, has been used as fuel. Yet the wood has such particular value for special purposes that it is quoted in San Francisco at from $12 to $18 per cord, a price much higher than that of any other California oak. The wood burns up very completely with little smoke. The United States mint at San Francisco uses it, and there is a steady demand by the bakers of that city. The full possibilities of the wood for lumber can be deter- mined only by experiments in sawing and seasoning and by strength tests, but its availability for some purposes is undoubted. About 400,000,000 feet have been utterly lost so far, and about 627,000,000 feet are still standing. To utilize the log for lumber, it must be cared for immediately after peeling. Only the redwood logging companies possess facilities for yarding and sawing the tanbark oak; yet since the peeling time comes at the height of their busy season, any proposal CONCLUSIONS. 23 to depart from the custom of abandoning the tanbark oak log as use- less does not meet with favor. Moreover, their milling machinery is not well adapted to sawing oak logs, and, for satisfactory work, the installation of special plants would be necessary. Country wagon makers in the Coast Range constantly use tanbark oak for repair work and believe it superior to all other wood for felloes. The wood, unlike some others, such as the eastern chestnut, has no value whatever as a tanning agent. CONCLUSIONS. (1) The bark of tanbark oak is one of the most valuable tanning agents known for the production of heavy leather. Bark from the interior ridges and southern districts is prized more than bark from the deep redwood belt or from northern districts, because it averages higher in tannin. (2) The Pacific coast tanbark-oak belt contains enough standing tanbark at the present time to supply the needs of California tanneries at their present rate of consumption for 47 years. (3) There should be more systematic methods in peeling and a greater proportion of the bark above the clear trunk should be taken. Bark from one-half to one-fourth inch thick ^should be saved when- ever possible. Chipped bark should be sacked before bunching the coil bark. Trees with bound bark should be temporarily passed, and not mutilated or sacrificed. Tops should be burned in the win- ter following cutting to prevent the destruction of young growth and of passed trees by wild forest fires. (4) Tanbark oak is surpassed in reproductive powers by no other forest trees in western America, except the redwood, and it stands very close to that species. A crop of sprouts will normally arise from the base of every peeled stump. In order to favor this crop, peelers should ring the trunk at base and not break the coil down below the surface of the ground. These sprouts will give rise to " second-growth" poles which are commercailly profitable to peel within 25 or 35 years. (5) Standing trees after being peeled may live on indefinitely, but they never produce a second bark which has any commercial value. (6) The wood is, for the most part, allowed to rot on the ground. Prompt care would tend to obviate its greatest weakness, checking in seasoning, and it can certainly be applied to some of the uses for which oak wood is prized, and a stupendous annual waste thereby be eliminated. (7) Forest fires are a source of great annual loss, and. cooperative measures should be taken by the State of California, the coast counties, the redwood companies, the tanbark companies, and cattle-range owners to reduce the danger from fire. A conservative treatment of the redwoods to obtain a continuous crop will be of like advantage to the tanbark oak mixed with it. PART II. UTILIZATION OF THE WOOD OF TANBARK OAK, By H. S. BETTS. TANBARK-OAK LUMBER, v While the wood of tanbark oak is sometimes used for fuel, it is more generally burned in the redwood logging operations, or left to rot in the woods. The object of this study is to bring to the atten- tion of west coast hardwood users and the owners of tanbark-oak stumpage the possibility of using tanbark-oak lumber. The largest part of the hardwoods used on the Pacific coast is imported from the eastern part of the United States. From 1899 to 1906 there was an increase in the price of hardwoods in the East of from 25 to 65 per cent. These conditions have been reflected in the western hardwood markets. Not only are the prices of most kinds of hardwood going up rapidly, but in some cases certain species are difficult to obtain at any price. This scarcity is due not to any local condition, but to the general shortage of hardwood timber. The high price is due to the eastern market price, to which must be added about 85 cents per hundredweight in freight charges, or an advance of from $24 to $36 or even $40 per thousand board feet. Yet tanbark oak furnishes a fair quantity of good material. For instance,, the average yield of bark is from 1J to 2^ cords per acre. If, as seems reasonable, there are 800 feet board measure of lumber for every cord of bark, the yield in lumber would be from 1,000 to 1,760 feet board measure per acre. Exceptionally fine stands yield as high as 8 cords of bark to the acre, which would mean 6,400 board feet of lumber. APPEARANCE AND CHARACTERISTICS OF THE WOOD. The wood of tanbark oak, like that of other oaks, is porous and has the characteristic strongly marked medullary rays. In color it is light brown, faintly tinged with red. When the wood is first cut the sap wood is somewhat lighter in color than the heartwood, but after a few weeks' exposure to the air the two become very similar in appearance. Exact knowledge of the rate of growth of tanbark oak is very limited. Seven forest-grown trees near Sherwood, Cal., showed varia- tions of from 10 to 20 rings per inch. The trees were from 14 to 27 inches in diameter 2 feet above the ground. Even on the stump the 24 Bui. 75, Forest Service, U. S. Dept. of Agriculture. PLATE VI. FIG. 1. MACHINE AND METHOD USED FOR TESTING SMALL BEAMS. FIG. 2. SEASONING CHECKS IN THE BUTT OF A TANBARK OAK LOG THAT HAS BEEN SUBJECTED TO THE SEVERE TEST OF BEING TURNED UP AND EXPOSED TO THE HOT CALIFORNIA SUN FOR Six WEEKS. Bui. 75, Forest Service, U. S. Dept. of Agriculture. PLATE VII. FIG. 1. TANBARK OAK LUMBER FOR CAR CONSTRUCTION. FIG. 2. TANBARK OAK BOARDS AIR DRYING. APPEARANCE AND CHARACTERISTICS. 25 annual rings are difficult to distinguish, since the temperature changes from season to season are not marked enough to form the distinct bands of spring and summer wood common in eastern oaks. In the case of the lumber, it becomes impracticable to attempt to obtain the rate of growth of different pieces. STRENGTH. The material used in the tanbark oak tests was divided into three classes or shipments, differing in the age of the trees and the season of cutting. The first two shipments were selected in the summer during the peeling season, and represented in the first shipment the larger and more mature trees of the stand, and in the second shipment the smaller and younger trees. The third shipment was felled in October and represented the same wood as that obtained in the first shipment, but felled in the season when the bark was tight, or when the sap was not running. The strength of the wood in several conditions of seasoning is shown in Table 11. The three shipments had practically the same strength and, therefore, were combined in the table. TABLE 11. Strength of small clear pieces of tanbark oak, green, air-dry, and kiln-dry, size 2 by 2 inches in section. GREEN. Bending. Num- ber of tests. Mois- ture con- tent. Weight per cubic foot. Fiber stress at elastic limit per square inch. Modu- lus of rupture per square inch. Modu- lus of elastic- ity per square inch. Elastic resil- ience per cubic inch. As tested. Oven dry. i Average 256 26 26 Per ct. 89.5 110.5 65.5 Pounds. 66.5 71.7 60.3 Pounds. 43.1 48.1 38.2 Pounds. 6,576 8,283 4,869 Pounds. 10, 707 12,880 8,632 1,000 pounds. 1,678 2,251 1,203 Inch pounds. 1.49 2.35 .83 High 10 per cent Low 10 per cent AIR-DRY (10 TO 20 PER CENT MOISTURE). Average 567 14.0 45.2 43.2 9,080 15, 512 2,083 2.27 High 10 per cent 57 17.4 51.7 50.5 11,901 20,342 2,771 3.45 Low 10 per cent 57 10.5 39.5 37.1 6,482 11,625 1,511 1.19 KILN-DRY (5 TO 10 PER CENT MOISTURE). Average 31 9.6 45.4 43.9 9,289 17,693 2,292 2.17 High 10 per cent 3 ' 10.0 50.2 48.8 12,287 22, 417 2,966 3.41 Low 10 per cent 3 8.8 40.9 39.5 6,600 13, 077 1,642 1.11 26 CALIFORNIA TANBARK OAK. TABLE 11. Strength of small dear pieces of tanbark oak, green, air-dry, and kiln-dry, size 2 by 2 inches in section Continued. GREEN. Compression parallel to grain. Compression perpendic- ular to grain. Shearing. Num- ber of tests. Mois- ture con- tent. Crushing strength per square inch. Num- ber of tests. Mois- ture con- tent. Strength at elastic limit, per square inch. Num- ber of tests. Mois- ture con- tent. Strength parallel to grain per square " inch. Average 237 24 24 Per ct. 86.8 105.4 64.8 Pounds. 4.845 5,819 3,711 244 24 24 Per ct. 77.9 95.3 59.7 Pounds. 1,355 1,964 926 221 22 22 Per ct. 83.1 103.. 56.1 Pounds. 1,414 1,685 1.075 High 10 percent. . Low 10 per cent AIR-DRY (10 TO 20 PER CENT MOISTURE). Average 406 14.4 8,172 316 13 4 1 656 204 13 3 1 %0 High 10 per cent 41 17 7 10 405 32 16 9 2 343 20 16 9 2 402 Low 10 per cent 41 10.7 6,265 32 10 5 1 238 20 10 6 1 585 KILN-DRY (5 TO 10 PER CENT MOISTURE). Average * 28 9.4 9,398 26 9 5 1 818 22 9 2 037 High 10 per cent 3 10 10 737 3 10 2 293 2 10 2 384 Low 10 per cent. . 3 8.2 8,047 3 8 4 l'366 2 7 3 1 669 1 The values in this column are based on a shrinkage of 18 per cent volume. The fiber saturation point is taken as 30 per cent moisture. Clear, straight-grained specimens free from defects are needed in determining the strength of the wood itself. The results of tests made on this class material can also be used for comparison with similar tests on other kinds of wood. Pieces 2 by 2 inches in section have been found weh 1 suited to tests of this kind. For bending, 1 they are cut about 30 inches long, and for compression parallel to the grain and compression perpendicular to the grain, from 6 to 10 inches long. The blocks for shear parallel to the grain are cut with a projecting lip that is sheared off under test. In making a bending test the beam is supported at the ends and loaded at the middle. The supports for the beam are on the weighing platform of the test- ing machine, so that the load on the beam can be determined at any time during the test. This load is applied by a crosshead which can be forced down on the test specimen by means of heavy screws turned by a train of gears. The deflection or bending of the beam is measured by an apparatus (PL VIII, fig. 1 ) consisting of a light steel frame on which is mounted a movable pointer. In making a test, the frame is rested on two nails driven into the beam near the ends and the pointer attached to the center of the beam in such a way 1 For a detailed description of methods used in the tests, see Forest Service Circular 38 (revised), Instruc- tions to Engineers of Timber Tests. APPEARANCE AND CHARACTERISTICS. 27 that it moves over a graduated arc when the beam bends, and thus shows the amount of bending. The test is begun by loading the beam with about one-twentieth of the probable breaking load and noting the deflection. The load is then increased by a certain increment which is recorded with the cor- responding deflection, and the process continued until the beam breaks. The results of tests on beams of various sizes are reduced to a unit basis, so that direct comparisons as to strength and stiffness can be made between pieces of different sizes of the same or of different species of wood. In computing the results, the breaking strength is represented by 11 modulus of rupture," the stiffness by " modulus of elasticity," the load the material will carry without taking a set by " fiber stress at the elastic limit," and the ability to withstand shock without taking a set by " elastic resilience." Tests in compression parallel with the grain are made by crushing the specimens endwise as they stand upright on the platform of the testing machine. In the case of compression perpendicular to the grain, the tests are made by placing a piece of metal 2 inches wide across the test specimen as it lies flat on the platform of the machine and pressing the piece of metal against the block of wood by means of the crosshead of the machine. This test is carried only slightly beyond the elastic limit of the wood under test, as loading beyond that point has at present no significance. The action is similar to that of a rail on a tie. In making a shearing test the block is clamped firmly in a frame with the lip projecting. The frame is placed on the platform of the machine and the lip sheared off by means of a sliding plate applied against the upper surface of the lip and parallel to the gram. Table 1 1 shows the oven-dry weight of tanbark oak to be about 43.2 pounds per cubic foot. Air-dry tanbark oak, containing 15 per cent moisture, weighs about 50 pounds per cubic foot, or 4,160 pounds per 1,000 board feet. This weight is about- the same as that of white oak and is somewhat higher than that of red oak. The average bending strength (modulus of rupture) of green tan- bark oak is 10,707 pounds per square inch, and the average crushing strength, 4,845 pounds per square inch. The results of similar tests on several kinds of hickory by the Forest Service, including pignut, shagbark, mockernut, big shellbark, nutmeg, and water hickory show a bending strength of from 9,200 pounds per square inch for green nutmeg hickory to 11,450 pounds per square inch for green pignut hickory. The average oven-dry weight of pignut hickory is about 51 pounds per cubic foot. Such tests as have been made on eastern white and red oaks indi- cate that tanbark oak in bending and crushing strength ranks about the same as white oak and is somewhat superior to red oak. 28 CALIFORNIA TANBARK OAK. Data are not available for a comparison of the toughness and stiff- ness of tanbark oak and the eastern oaks and hickories. Table 11 shows a considerable increase in the strength values of the air-dry material over the green, and a still further increase in these values for the kiln-dry material. In compression perpendicular to the grain, green tanbark oak has an average strength at the elastic limit of 1,355 pounds per square inch. Green Douglas fir has an average strength of 651 pounds per square inch. In shearing strength air-dry tanbark oak shows an average of 1,960 pounds per square inch. Douglas fir has an average shearing strength of 770 pounds per square inch for air-dry pieces. Douglas fir would, of course, be expected to have lower strength values than a hardwood like tanbark oak. The comparison is used because such tests on other hardwoods have not yet been made. SEASONING. A number of the logs selected for testing purposes were sawed into boards for a seasoning test. Fifty 1-inch boards were put through a commercial dry kiln of the moist-air type in San Francisco. The results, while encouraging as regards the behavior of tanbark-oak lumber in a moist-air kiln, were not satisfactory, owing to the imperfect regulation of the kiln and consequent daily variations in temperature and humidity. After 40 days in the kiln a classification of the lumber gave the following: Number. Per cent. Good boards 28 56 Boards slightly warped 12 24 Boards checked at ends ... . 4 8 Boards badly checked 6 12 The average temperature of the kiln was only 85 F. for the 40 days, whereas it should have been at least 110 F. The loss in sea- soning eastern oak for vehicle stock is placed at about 10 per cent. The method of seasoning used by a lumber company which owns considerable tanbark-oak stumpage that it is preparing to put on the market in the form of flooring is as follows : The logs as soon as con- venient after they come in from the woods are cut into IJ-inch material. This is then carefully piled in the open yard, with sticks every 18 inches, and allowed to dry from 3 to 6 months. It is finally kiln dried from 30 to 40 days at a temperature not to exceed 110 F., when the boards are ready to be made into flooring. The kiln used is of the blower type. The results obtained in drying tanbark oak by this method have been very satisfactory. It should be remembered that the trees in this case were cut during the peeling season (May to Bui. 75, Forest Service, U. S. Dept. of Agriculture. PLATE VIII, FIQ. 1. TANBARK OAK FLOORING, AND THE METHOD OF STORING AND SORTING IT. FIG. 2. TANBARK OAK FLOORING READY FOR SHIPMENT FROM THE MILL. Bui. 75, Forest Service, U. S. Dept. of Agriculture. PLATE IX. TRANSVERSE SECTION OF A 2-YEAR-OLD TWIG OF TANBARK OAK, SHOWING TANNIN (DARK STREAKS AND AREAS) IN THE PITH, PITH RAYS, AND BARK. MAGNIFIED 30 DIAMETERS. Bui. 75, Forest Service, U. S. Dept. of Agriculture. PLATE X. FIG. 1 .TRANSVERSE SECTION OF A S-YEAR-OLD TWIG OF TANBARK OAK, SHOWING THE DISTRIBUTION OF TANNIN IN THE PITH AND PITH RAYS. MAGNIFIED 30 DIAMETERS. FIG. 2. LONGITUDINAL RADIAL SECTION OF A S-YEAR-OLD TWIG OF TANBARK OAK, SHOWING THE TANNIN IN THE PITH AND PITH RAY CELLS. MAGNIFIED 30 DIAMETERS. OCT29 1914 Division of Forestry- University of California SEASONING. 29 October) . It is very probable that winter-cut lumber could be sea- soned with less loss of material. Some of the boards and planks sawed from the logs selected for testing were piled under shelter and seasoned for about two years, when they were in the same condition as regards warping and check- ing as is usually found in eastern oaks similarly handled. Some of the lumber showed a tendency to a "blue rot," apparently caused by too close piling, since this defect was remedied by a wider piling that gave more circulation of air. In the case of some 200 pieces for mechanical tests (2 by 2 by 30 inches), cut from material seasoned under shelter for two years and then kiln dried, the pieces showed practically no checking. The sides of the pieces were slightly depressed in a few instances, but on the whole their condition was excellent. All things considered, the seasoning of tanbark oak seems to offer little, if any, more difficulty than is experienced with eastern oaks. SHRINKAGE. ^) In order to determine the amount of shrinkage in tanbark oak, 62 pieces (2 by 2 by 10 inches) were dried out slowly from a green to an oven-dry condition. The pieces were selected so that two sides were tangential to the annual rings. They were weighed and measured at intervals for a period of about one year. The drying was carried on first in a warm room and finally in an oven. When a piece of green or wet wood is dried, no change in dimen- sions takes place until a point called the fiber-saturation point 1 (generally in the neighborhood of 30 per cent moisture) is passed. The wood then begins to shrink in cross-sectional area and continues to do so uniformly with the removal of moisture until it is bone dry. The longitudinal shrinkage is so small as to be negligible. Generally, the heaviest wood shrinks the most and sapwood shrinks more than heartwood of the same specific gravity. Shrinkage is greater in the circumferential than in the radial direction. The results of the shrinkage tests on tanbark oak showed an average shrinkage in volume of 18 per cent 2 when the pieces were dried from a green to an oven-dry condition. Of this amount about 6 per cent is radial shrinkage and about 12 per cent tangential. Air- dry wood generally contains about 15 per cent moisture, so that the shrinkage from the green to the air-dry state is only about half that from the green to the absolutely dry state. The average shrinkage in volume with red oak when dried from a green to an oven-dry state is about the same as with tanbark oak. Both woods vary considerably. 1 For a full discussion of the fiber-saturation point, see Forest Service Circular 108, The Strength of Wood as Influenced by Moisture, by H. D. Tiemann. 2 This figure is based on dry volume. 30 CALIFORNIA TANBARK OAK. HARDWOODS USED ON THE COAST. The hardwoods at present used in the Pacific coast States come from many foreign markets, and only a very small proportion of them are local woods. From the Eastern States are imported oak, ash, hickory, maple, cherry, basswood, black walnut, tulip poplar, birch, and elm; from Honduras, mahogany; from Mexico, Mexican mahogany, prima vera, or jenizero; from Hawaii, koa; from Aus- tralia, iron bark (one of the eucalypts) and red bean; and from Japan, Siberian oak. The hardwoods from the Eastern States come for factory use in the rough or ' i club " form; for the vehicle industry as roughly finished parts, such as spokes, hubs, bent rims, and sawed felloes; and for cooperage as rough staves and heading. The rest are in the form of 1-inch and 2-inch boards and 3 to 6 inch planks from 6 to 16 inches wide and from 10 to 30 feet long. A small proportion comes in the form of squared timbers up to 20 by 20 inches by 24 feet long. This is for special-order work. The Mexican, Australian, Hawaiian, and Japanese woods generally come in the shape of roughly hewn timbers, the sizes ranging from 14 by 14 inches up to 36 by 36 inches and from 10 to 20 feet long. These rough timbers are sawed into veneer stock, boards, and planks, as wanted. Eastern oak makes up by far the largest amount of hardwood used in California, with hickory next, followed by maple, ash, and cotton- w'ood. Some of the hardwoods have a variety of uses, while others are con- fined to special lines. Of the eastern woods, ash, maple, hickory, elm, and birch are used chiefly for wagon stock, only a small part being used as lumber. Oak is largely used for cooperage, lumber, and wagon stock, in the order named. The term "lumber" includes boards, planks, and timbers. Oak lumber is imported for such uses as flooring, inside finish, furniture, cabinet work, bank, store, and office fixtures, paneling, wainscoting, picture molding, and doors. The black walnut, cherry, and tulip poplar from the East, the prima vera, poplar, and mahogany from Mexico, the koa from Hawaii, the red bean from Australia, and the Siberian oak from Japan also go very. largely into special lumber orders like the oak. Basswood is used in the upper parts of wagons and carriages and especially for work in pyrography. A California-grown eucalypt, the blue gum, has been made into insulator pins which have proved very satisfactory. It is also used quite extensively for cordwood, to some extent for piling, and is being tried in the form of veneer for furniture and interior finish. It is very probable that the use of blue gum in California will be considerably enlarged in the near future. The black cottonwood is used princi- SUGGESTED USES. 31 pally for fruit baskets, and for this purpose is cut into veneer one- twentieth of an inch thick. Some is made also into wagon stock. The cost of all hardwoods is high. Ash and plain oak average $100 per thousand board feet, while quartered oak and hickory average $125 per thousand. Iron bark brings about $105 per thousand, and Siberian oak about $80 per thousand. This includes the cost of transportation. SUGGESTED USES FOB TANBABK OAK. Up to the present time little has been known of the possibilities of tanbark oak. The feeling has been that the wood was subject to checking and warping to such a degree as to render its use impracti- cable. All hardwoods are more or less subject to these defects, and it is believed that the difficulties encountered in seasoning tanbark will prove no greater than those which have been overcome in some of the eastern hardwoods. In fact, the experiments made by the Forest Service, which it must be remembered were conducted under unfavorable conditions, showed that the wood can be seasoned in a dry kiln in such a manner that more than half of it will be satisfactory material and only 10 per cent badly checked. The lumber company mentioned as manufacturing tanbark oak flooring has had several experimental floors laid and in all cases they have proved satisfactory under hard usage. About 200,000 feet of flooring has been made up, and about 1,000,000 feet of lumber is in process of drying. In sawing this lumber the regular equipment of a redwood mill was used. Tanbark oak seems well suited for flooring. It has a pleasing grain and color and the necessary hardness. By using short pieces of the same length, say, from 9 to 18 inches, grooved and tongued on the ends, as well as on the sides, the material can be closely utilized. In laying a floor from such pieces a pleasing effect is obtained by having each strip of flooring break joints with the strips on each side and by alternating the light and dark pieces in each strip. It is quite probable that tanbark oak will prove suitable for tight cooperage. There seems to be a feeling at present that a contained liquid would be affected by the wood, but so far as is known the wood has not yet been given a fair trial. In regard to the tannin in the wood, there is said to be a higher percentage in the case of eastern white oak (1.32 per cent) l than in the case of tanbark oak (0.63 per cent). Of course there may be other constituents that render tanbark oak unfit for use as a liquid container, but it is at least worthy of a trial. As an inside finish, tanbark oak has the beautiful figured grain of other oaks, and there is apparently no reason why it should not give i See Yearbook for 1902, U. S. Dept. of Agriculture, article entitled "Chemical Studies of Some Forest Products of Economic Importance." 32 CALIFORNIA TANBARK OAK. satisfaction. This seems to be proved by a number of finished speci- mens of the wood now in the Forest Service offices in San Francisco. The mechanical properties of tanbark oak render it suitable for wagon and car stock. In bending and crushing strength it compares favorably with eastern oak and hickory, which have for so long been used in such construction. In drying it shrinks about the same amount as red oak. Tanbark-oak bolsters for logging trucks are in use and giving satisfaction. A number of strips of tanbark oak 1J inches thick, 4 inches wide, and 6 feet long were steamed and bent at a wagon factory in Oakland, Cal., with as good results as with white oak under similar treatment. Under present methods the price of bark f. o. b. track in the regions of production averages $15 per cord. The fuel wood from the trees that furnished this cord of bark would amount to about 2 cords, worth on an average $5 per cord delivered at the nearest railroad. Bark and cord wood together, then, would be worth $25. The 2 cords of fuel would amount to about 1,600 feet board measure. If half of this is suitable for boards, it is evident that with the present price of oak lumber the returns would be greater if the tree were cut into lumber rather than cordwood. In conclusion, there seems to be no good reason why tanbark oak should not take its place in the Pacific coast hardwood market for many if not all the purposes for which eastern hardwoods are now imported; and if this is true lumber companies owning tanbark-oak stump age could profitably take up the utilization of this wood as lumber. In California, particularly, where such large quantities of hardwood are imported at a high and constantly increasing cost, a native oak with both properties and appearance that compare favor- ably with eastern oaks ought not to be allowed to go to waste, but should at least be given a commercial trial. APPENDIX. DISTRIBUTION OF TANNIN IN TANBARK OAK. By C. D. MELL. * Tannin is found in most plants and almost exclusively in the living cells, though there are some in whose cells it is not found, such as European hackberry (Celtis australis Linn.), white mulberry (Morus alba Linn.), black elder (Sambucus canadensis Linn.), honey locust (Gleditsia triacanthos Linn.), black locust (Robinia pseudacacia Linn.), and laburnum (Cytisus laburnum Linn.). It is always in the form of a solution in the cells and not in the cell membrane, nor in its primary membrane. Tannin, chlorophyll, and starch are closely associated; tannin and chlorophyll together in collenchyma and phelloderm, and tannin and starch together in the same cells in pith rays. Tannin is most abundant in the elements outside the cambium, and in a few cases it is present sparingly in wood fibers. An investigation of the tannin contents of a number of trees shows that several of the elements of tanbark oak have tannin distributed through them, as shown in Table 12. Tannin is present in such of the structural elements of each wood as are indicated by the letter x. The small circle indicates that the tannin content in the element, so marked is very small, and of no importance in connection with commercial operations. TABLE 12. Elements of pith, wood, and bark of trees containing tannin. Quercus dcnsiflora Hook, and Am. (tan- bark oak) Alnus glutinosa (L.) Gaertn. (black alder). Betula papyri/era Marsh, (paper birch) Carpinus caroliniana Walt, (blue beech)... Corylus americana Walt, (hazel) Satix purpurea Linn, (purple willow) Platanus occidentalis Linn, (sycamore) Hamamelis virginiana Linn, (witch hazel). Acer platanoides Linn. (Norway maple) ... Rhus cotinuft Linn, (young fustic) Pyrus communis Linn, (pear) Eucalyptus cordata Labill . (gum ) Ribes rubrum Linn, (currant) Syringa vulgaris Linn, (lilac) Fraxinu* americana Linn, (white ash) Structural elements containing tannin. x \ x 33 34 CALIFORNIA TANBARK OAK. To determine correctly the distribution of tannin in plant tissue, it is best to fix the tannin content in such a manner that it becomes hard, compact, and easily recognizable under the microscope in transverse and longitudinal sections. Tannin hardens into a compact mass when treated with potassium bichromate and, in transmitted light, has an intense red-brown color. The ultimate twigs, obtained from growing trees, are cut length- wise through the pith and are allowed to dry for 12 hours in a room of ordinary temperature. Then they are soaked in a solution of potassium bichromate for a week before the sections are cut. The material must be treated before it is sectioned, otherwise the tannin content will be distributed by the knife into elements where it does not naturally occur. The color does not change when the sections are mounted in glycerin, so the sections may be preserved in this way for classroom or other demonstration work. The first 8 or 10 sec- tions should be discarded, because they will include the outer cells coated by tannin that oozed out when the twigs were first cut; and they are likely to be disappointing because they will not show the undisturbed tannin content. The cells in which tannin occurs will be filled with a compact red-brown mass (Pis. IX and X) ; or there may be only a few small red-brown globules, as in the pith ray cells of European alder (Alnus glutinosa, L. Medic.). An investigation of this sort shows that tannin is present in the twigs of tanbark oak as well as in the older bark, and that tanning extract could be made from the twigs and smaller branches, as in the case of the eastern chestnut (Castanea dentata). Yet there is but little tannin in the wood-parenchyma elements of the heartwood of tanbark oak, so that tanning-extract can not be got by chipping the wood and subjecting it to tanning-extract processes, as in the case of the chestnut. o RETURN TO the circulation desk of any University of California Library or to the NORTHERN REGIONAL LIBRARY FACILITY Bldg. 400, Richmond Field Station University of California Richmond, CA 94804-4698 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS 2-month loans may be renewed by calling (415)642-6233 1-year loans may be recharged by bringing books to NRLF Renewals and recharges may be made 4 days prior to due date DUE AS STAMPED BELOW OCT8 1989 SENT ON ILL JUL 06 2000 U. C. BERKELEY Q 1 9 ~" at t KEG'D BIOS Gay lord Bros. Makers Syracuse, N. Y. PAT. JAM. 21, 1908 477598 h UNIVERSITY OF CALIFORNIA LIBRARY