peeled; and (4) buff rods, which are brown rods boiled and then peeled, but the colour thus produced can be imitated by dyeing.

In the Fen country, under very favourable circumstances, the newly planted holts can be first cut over at three years; but, in general, four or five years must elapse before the first crop is mature. Well-managed holts remain from ten to fifteen years in good bearing, their duration depending mainly on the kinds of Osiers planted, and on the degree of attention paid to cleaning, filling up, coppicing low down, &c. For strong uprights some of the coarser kinds are specially grown, or else part of the holt is left growing for two or three years to produce the stouter rods wanted. The holts are usually along river-banks, to reduce the carriage of so heavy and bulky a crop.

Throughout the Fen country the Osiers are full-grown by the middle of September, with shoots from 8 or 9 even up to 12 or 13 ft. long during the season, while the harvesting of the rods commences in January if the holts are not inundated or too marshy. But the harvesting should take place at any rate before the sap begins to rise, in order to prevent "bleeding" of the stools, which prejudices the development of the following crop.

The rods are cut as close as possible to the stool with a sharp hook, like a strong reaping-hook, a clean cut being made without splitting the rod. As soon as cut, the rods are tied up with willow bands into bundles or "bunches " girthing 45 in. (an English ell) at 1 ft. from the butt end. This ell band is held in place by being joined to the breech band round the butt end, and a third band is tied higher up.

If the rods are to be peeled to increase their value, they are taken to the peeling yard and placed with their butt end in water, until its rise makes the bark strip easily. To prevent the rods drying from exposure to the air, they are couched or put in a heap, watered, covered up, and sweated. If the rods thus pitted flush too far into leaf before being stripped, peeling is difficult, and the rods are easily damaged. Peeling begins as soon as any of the rods are fit to strip. It is chiefly done by women, who draw the rods through a break or cleave, which divides the bark into strips, which are easily removed by the hand. In this latter operation the children of the peelers assist. No use seems to be made of the bark (see p. 489).

The peeled rods are at once sorted into three grades (large, Middlesboro, and small), according to thickness and length. They are then aired for a short time, either on racks or against hedges or walls. When dry they are bunched in bundles of the same dimensions as before, and then stored in sheds.

Rods suitable for the purpose are skeined or divided lengthways into three equal parts. The thick end of the rod having been notched with a knife so as to divide it into three sectors, a triple wedge is inserted, and the rod is then drawn rapidly through the hand. To reduce each of the three parts of the split rod to a flat thin strip of equal thickness, it is drawn twice under a knife fixed to a gauge, which removes the outer ring and the inner angle. These flat skeins are used for weaving bottoms of sieves and riddles, and for making basket-handles, &c. Green rods are similarly skeined for making eel-grigs, bee-hives, &c.

It is customary, however, for most growers to sell the green rods as they are cut, and to leave it to the buyer to peel, sort, and store them.

An average crop will yield about 150 bunches of rods, having a girth of 45 in. (an English ell) at 1 ft. from the thick end of the bunch, whilst a heavy crop may reach 250 bunches, weighing about 6 stones each; the weight of rods may vary thus from about 5 to 10 tons per acre. The harvesting of the rods is paid for at about 2s. 6d. per score of bunches, or about 14d. per bunch on the average. The selling price ranges from 1s. 6d. to 2s. 6d., and averages about 2s. per bunch.

If the green rods are peeled so as to command a better price and to store well, then there is a loss of fully 50 per cent in bulk, as three bunches of green rods yield only two bunches of clean or peeled rods.

Osier-holts in the Fen districts yield about £15 an acre, taking 150 bunches of green rods as the average crop; this, of course, is subject to deduction of all the cost of planting, tending, harvesting, ground-rent, taxes, supervision, &c. The cost of peeling, sorting, and handling the same so as to transform the crop into clean white rods amounts to about 8d. per bunch, or £5 per acre. Thus a crop of 150 bunches of green rods, when peeled, yields 100 bunches of white rods, having a market value of nearly £35 (see Agricultural Leaflet No. 36-Osiers).

2. The Harvesting of Bark.-The stripping and drying of Oak-bark for tanning was formerly an important part of British forestry; but it does not pay to grow bark-coppices now, and even the barking of large Oak-trees is hardly profitable.

Vast quantities of tanning materials are annually used in Britain, the imports amounting to close on £1,000,000 in value, while the quantity of tanning-bark produced of home growth still probably exceeds 200,000 tons, though it is no longer so large as it once was.

Although many kinds of bark are suitable for tanning, only Oak, Larch, and Birch have ever been very largely used in Britain for this purpose. Other barks formerly used include Willow, Mountain-Ash, Spanish Chestnut, and Alder; but these were only substitutes to eke out the supplies of Oakbark; and when large quantities of Oak-bark were imported into this country free of duty from the Continent, tanners could then get plenty of good Oakbark at a moderate price, and were no longer compelled to use inferior tanning-barks. Consequently the price of bark fell heavily, and this once important branch of British forestry received its death-blow. The market for tanning-bark for many years has been very depressed in England, owing not only to large Continental imports of bark, and of Oak-galls and Sumach from the Mediterranean, but also to increasing imports of Cutch, Gambier, and Myrobalans from India, and of Quebracho wood from the Argentine, of Dividivi seed-pods from Brazil, of Wattle-, Mimosa-, and other Acacia-barks from Australia, &c., and likewise in no small degree to the introduction on a large scale of chemical preparations for tanning purposes. This last was particularly the case about twenty to twenty-five years ago, when such chemical processes as Knapp's (with iron) and Heinzerling's (with chromic acid) tried to displace tanning with bark. But such processes of tanning with metals have been far from proving successful in producing the better classes of leather, and especially of sole-leather, for which the raw skins seem to require a longer soaking in the tanning-pit than is permissible when metals are used. For sole-leather the chief rival of Oak-bark is the Quebracho wood (Schinopsis balance), which, either rasped or after being formed into an extract, tans very quickly and cheaply. Sweet-Chestnut wood is similarly treated in Savoy and Würtemberg for producing a tanning extract. Of recent years considerable quantities of Oak-branchwood have in similar manner been used in Slavonia for making bark-extract. In Hungary a tanning-extract is also made from Spruce-bark.

The export of Quebracho wood from the Argentine, either in stem-sections (rollizos), or ground-down like meal (asserin), and of the wood-extract, is a trade that has sprung up entirely within the last twenty years. In 1902 it amounted to 245,000 tons of rollizos and 9099 tons of extract, while but little asserin was exported. From Paraguay the export in 1902 was 11,359 tons of rollizos, and 5000-6000 tons of extract.

The chemical composition of bark is very complex, and is not yet thoroughly investigated. But at any rate the bark of certain kinds of trees has a special commercial value by reason of the tannin or tannic acid contained in it. Tannins form a series of weak acids widely dispersed throughout the vegetable kingdom, but usually mainly to be found in the bark and in certain pathological or abnormal conditions, such as galls on Oak-leaves and knoppern-galls on acorns, both of which are produced by gall-wasps (Cynipida), and contain, when dried, about 60 per cent of tannin. The tannin or tannic acid of Oak-bark (C14H1009) may be taken as typical of the others generally. It is a yellowish, grey-white, amorphous powder, easily soluble in water, difficult of solution in alcohol, and insoluble in æther. It has a bitter taste, which causes the skin of the mouth to contract, and gives a bluish-black or greenish precipitation when mixed with ferric salts. When brought into contact with animal skins it transforms them into leather, characterised by pliancy and great power of resisting decomposing influences.

Tannic Acid can be transformed into Gallic Acid by the addition of water (when C4H10O+H2O=2C-H ̧O¿), so that the latter is practically a hydrate of the former; and a retransformation can take place by withdrawing the additional water. Gallic acid crystallises in fine rods, is easily soluble in water, and produces a brown colour in combination with iron-vitriol. Exposed to air, this combination with iron quickly oxidises and becomes a deep black. Gallic acid is largely contained in galls, and these are therefore of special use for making ink. Gallic acid is contained, as well as tannic acid, in the bark of Oak, Sweet-Chestnut, HorseChestnut, and other trees.1

The amount of tannin contained in bark varies greatly for different kinds of trees, and also for different parts of the same tree. The European barks used for

1 Besides tannic and gallic acids, the other constituents of technical value which may be found in different kinds of bark include the following (Schwackhöfer, in Lorey's Handbuch, &c., 1903, vol. ii. p. 296) :—

(1) Other Organic acids, such as Oxalic acid and Pectinic acid. The former is often to be found in the form of crystals (mostly oxalate of lime) in the bark.

(2) Glycosides, such as Quercitrin, (C2H2O12), in the bark of Quercus tinctoria, a yellow dye-stuff of considerable commercial importance; Salicin (C13H1807), in the bark of Willows and Poplars; Esculin (C15H1609), in the bark of Horse-Chestnut; Saponin (C19H30010), in Quillajabark, which is boiled and used for cleansing wool and different textures; Populin (C2H22O8+2H2O), in Poplar-bark; Phloridzin (C21H24O10+2H2O), in the bark of fruit-trees; and a few more, including Coniferin, from which Vanillin (closely resembling vanilla in its appearance and flavouring properties) is extracted on a commercial scale in the Saxe-Weimar forests.

(3) Starch, Sugar, Gum. A certain amount of starch is desirable in tanning-bark.

(4) Etherial Oils, Resins, Balsams, such as in the pockets of aromatic resin in the Douglas Fir, or in Cinnamon-bark, &c.

(5) Bitters and Alkaloids, such as in Cinchona-bark, from which quinine is produced. (6) In addition to the above, bark of course also contains cellulose, lignin, suberin, colouring matters, nitrogenous substances, mineral constituents, and water. There is more nitrogen in bark than in wood, and more in young bark (0'6 to 0.8 per cent) than in old tree-bark (04 to 06 per cent). The mineral constituents vary from 15 to over 7 per cent; while the water contained averages from 50 to 60 per cent, and sometimes even exceeds 70 per cent. A large percentage of water depreciates the value of tanning-bark, as damp bark soon becomes overgrown by mould-fungi (especially by Pennicillium glaucum), which rapidly oxidise the tannin. Hence the necessity for seasoning and drying bark as soon as possible.

tanning contain on the average from 5 to 15 per cent of tannin, while several of the tropical and subtropical barks have from 20 to over 35 per cent.

The tannin or tannic acid is contained in the cambial layer of the bark, but decreases by about 3 to 5 per cent from the root towards the crown. This difference is occasioned, however, mainly by the changes that take place as the bark grows older on the tree; the fleshy part of old bark contains much about the same percentage of tannin as that of young bark-viz., from about 12 to 16 per cent; but the old, hard bark contains less than the half of that, so that the whole proportion of tannin is considerably less in old, hard, rough bark than in young and smooth bark. According to its exterior smoothness or roughness, Oak-bark is therefore assorted into three classes :

(1) Smooth or silver bark, from coppice-shoots up to 14 or 16 years old, of which the best sorts contain when seasoned (air-dried) from 15 to 20 per cent of tannin;

(2) Seconds or medium quality, stripped from poles and branches, the bark of which has begun to fissure, and containing from 10 to 15 per cent of tannin;

(3) Cleaned tree-bark, from the stems of older trees, which contains 8 to 10 per cent of tannin; and

(4) Coarse, rough tree-bark, as stripped from Oaks of large size, which con

tains 5 to 8 per cent of tannin.

The bark of the Sessile Oak is usually thicker and richer in tannin than that of the Pedunculate Oak; but the quality of the bark depends far more on the soil, situation, and climate than on the species grown for bark-production. A good strong mineral soil and a warm sunny situation are the two chief factors in any given locality; while districts with a warm summer climate produce the best bark. As intensity of light is favourable to good bark-production, it follows that pure Oak-coppices will give more and better bark per unit of area than coppice under standard trees of any kind whatever, no matter how light the shade they cast on the underwood. Thinning of Oak-coppices also increases bark-production, and Gayer estimates that proper thinning increases the quantity of wood produced by about 27 per cent, and of bark by about 20 per cent, while the quality of the latter is at the same time improved.

Although many other barks contain a much greater percentage of tannin, Spruce-bark is, after Oak-bark, that used in largest quantities for tanning; indeed, throughout Northern and Eastern Germany, Poland, and Western Austria, more Spruce-bark is now used than Oak-bark. But as the better kinds of bark, peeled from 50- to 80-year-old trees in high mountainous regions, only contain from 7 to 9 per cent of tannin on the average, Spruce-bark can only be used by itself in the preparatory stages of tanning, or for calf and other small skins, and not for preparing the better classes of sole-leather, for which at least a fair proportion of Oak-bark is necessary in admixture with the Spruce. The bark of trees below about 50 years old contains less tannin, while that of above 80 years, though not containing less tannin than 50- to 80-year-old bark, has at the same time so large a proportion of red colouring-matter that it darkens the leather. Spruce-bark is peeled wherever the falls take place during late spring or summer, the measure being in any case necessary as a protection against bark-beetles when large areas are being clear-felled (see Fig. 136, p. 66).

Larch-bark contains from 10 to about 15 per cent of tannin, and is used, wherever it can be had in fair quantity, for tanning sheep-skins. In the Alps and Carpathians it is preferred to Spruce-bark.

Silver Fir-bark contains only about 5 or 6 per cent of tannin, and is nowhere largely used for tanning. In the Silver Fir districts of Central Europe the bark is worth more as fuel than for tanning.

Alder-bark contains from 16 to 20 per cent of tannin, or fully as much as the best Oak-bark; but at the same time it contains so much colouring matter, that little use can be made of it for tanning.

Birch-bark contains only about 3 per cent of tannin, but is extensively used wherever there are large Birch-woods throughout Northern Europe. As it gives a pale colour to the skins, it is used for the preliminary and the final stages of tanning. Birch-oil is extracted from the white epidermis of Birch-bark.

Willow-bark contains about 5 to 7 per cent of tannin, and is very largely used in Russia for tanning. The distinctive aroma of "Russia leather" is obtained by steeping it in Birch-oil (see Chap. V. p. 603), after it has been tanned with Willow-bark. Osier-bark grown in Russia has been found to contain up to 8 to 13 per cent of tannin, and is there used to prepare "Danish kid" and "doe-skin" for glove-makers, as also in preparing salicin, and for fodder. The larger the rods, the more tannin does their bark usually contain.

In no part of Europe is much use made of the bark of Beech, Walnut, Italian Poplar, Elm, or Horse-Chestnut for tanning, though these all contain from a slight to a fair percentage of tannin.

In tanning 1 cwt. of leather about cwt. of tannin is needed, which is about the average amount contained in 6 cwt. of the best smooth Oak-bark, in about 8 cwt. of medium quality, and in about 14 cwt. of coarse Oak-bark, while other kinds of bark are required in quantities varying according to the average percentage of tannin they contain.

(1) The Harvesting of Oak-bark. The best season for bark-stripping is when the young leaves are just beginning to flush. The bark will generally peel freely throughout May, June, and even in July; but this depends on the part of the country, and on the season. In the south of England, barking operations may begin about the middle of April and be completed by the middle of May; in the central and northern parts of Scotland, it only begins in May, and can continue till July; while in Ireland, peeling is generally done from about the end of April to the middle of June. The Pedunculate Oak will strip about eight to twelve days earlier than the Sessile Oak; and in either case the bark peels best during warm damp weather, and better in the morning and evening than during the daytime. It is best to cut and strip coppices as early as possible, because this not only lets the stools shoot again sooner, but it has also been found that the earlier the bark can be harvested, the heavier it usually is.

The method of stripping adopted for coppice-woods of course differs considerably from that for trees of large size.

In coppice-woods, any other kind of wood than Oak should first of all be cut out and removed. Then the Oak-shoots should be cut by men and thrown into small heaps to be stripped at once by women and boys, each of whom should have a separate heap, as the work is then generally done better and more quickly. Each should be provided with a large, flat, smooth stone, or a big billet of wood, and a wooden mallet, the stripper sitting in front of the stone or block of wood, and keeping the heap of wood to be stripped upon the left-hand side. A branch being taken in the left hand, and laid upon the stone or billet, the branch is firmly beaten with the flat part of the mallet till the bark parts from the wood along all its length, when it will peel off easily