plants; but now they are chiefly prepared either from potassium sulphate and chloride, or from the residual ash of molasses used in making rum. But in some parts of Austria, Russia, and S.E. Europe, it is still the only way of using with profit some of the inferior kinds of wood. Potashes are made by a simple process, in four stages—(1) burning, to reduce the wood to ash, (2) extracting the lye from the ash, (3) evaporating the lye, and (4) calcining the raw potashes. 1. The wood is reduced to ash by combustion. Unsound trees and those of little value where they stand are selected for potash-burning. Such are cut into so as to form a hollow, and fire is lighted there to gradually consume the heart of the tree, while the pure ash that collects at the base is collected from time to time, and a fresh fire is kindled, if necessary. This produces the purest kind of ash, and at the same time protects it from wind and rain. Or when trees are felled for this purpose, holes about 12 x 6 in. are notched here and there along the lower side of the stem, and fires are kindled there. And in either case, the outer shell remaining unburned and the branchwood are piled and fired to reduce them also to ash, which is stored in barrels and kept in wood-lined vaults to protect it against damp till it can be taken to the potash-factory. The amount and composition of the crude ash thus obtained varies of course with the kind of tree, and the soil, situation, and climate. But the chief constituents are lime, potash, magnesia, and phosphoric acid, all the other components occurring in much less quantity, and there being only few mineral acids. The metal oxides are mostly in the form of organic acid salts, which form carbonates during combustion; hence in wood-ash there is always a larger proportion of carbonic acid, which does not, however, directly form part of the wood itself. But it is precisely because wood-ash consists mostly of carbonates that it is suitable for making potashes (see also table on p. 307, vol. i.). Mineral con. stituents per 100 parts by weight of Crude ash 20-45 10-25 5-15 2-10 1-8 1-8 1-5 1-4 1-3 1-5 15-20 Crude ash contains, however, about 25 per cent of fine charcoal, carbonic acid, and earthy impurities, so that the pure ash gives only about three-fourths of the above quantities of each constituent. 2. The potash-lye is extracted from the crude ash in a series of vats, forming a battery and ranged one above another sideways, like the steps in stairs. These vats are filled to about two-thirds with crude ash and the rest with water (each vat taking about 2 to 24 cwt. of ash and 30 to 40 gallons of water), and after three or four hours' soaking the liquor from vat 1 is run down into vat 2, that from 2 into 3, 3 into 4, and 4 into 5, the concentrated lye being drawn off from the lowest vat. But the warmer the water used, the quicker the potash is extracted. Of course, when the process is in full work, the lye is run off from 5, and its drain-pipe closed before the lye is run in from 4, and so on. When the contents of vat 1 have been drenched five times the potash has been practically thoroughly extracted, so the contents are emptied and replaced by fresh crude ash. Vat 2 then becomes number 1 in the new battery, and from the lowest vat the liquor is pumped up into the top one (now number 5 in the series), from which the concentrated liquor is drawn off. And so on in succession, vat 5 of each series becoming vat 1 of the next series The residuum emptied from the vats forms good manure, as it consists mainly of calcium carbonate and phosphate, the latter containing when dry about 8 per cent of phosphoric acid. If intended for transport, this residual manuring product has first to be dried, as it consists of 50 to 60 per cent of water. 3. The evaporation of the lye takes place in shallow iron pans. It is first warmed in a pan usually fitted to the calcining furnace, and then allowed to trickle down into a shallow evaporator heated by its own furnace. The evaporation is here allowed to go on until tests show that the concentrated lye hardens on cooling. The further supply from the warming-pan is then interrupted and the furnace lowered, while the mass in the pan is kept continually stirred until, after further evaporation, the raw potashes are left as a loose, friable, blackish-brown substance, still containing about 6-10 per cent of water. 4. The calcining to evaporate the remaining water completely, and to burn the potashes into a white powder, takes place in a fire-proof vaulted furnace, the roof of which must be within 30 in. of the bottom in order to keep the flame from the fire low down and make it pass over the potashes. The heating may consist of one or of two fires, which are kept at great heat till the furnace is thoroughly heated, when the raw potashes are thrown in and spread over the floor with an iron crook ; and during the whole process of calcining it must be kept stirred and moved, so as to bring fresh stuff to the surface. The temperature is kept moderate at first, then gradually raised to red-heat; the potashes must not, however, be allowed to melt, as otherwise the particles of charcoal cannot be got rid of by combustion, while the sole of the furnace gets damaged and the potashes become silicated. In two to three hours the calcination is complete, and if test-pieces be taken out and broken after being allowed to cool, they should be white inside. The potashes are then drawn out and cooled down, to be packed closely into barrels. This should be done at once, as potashes are strongly hygroscopic, soon forming clumps, and then finally melting if freely exposed to the air. The yield of calcined potash is from 80 to 90 per cent of the raw potash treated, from 10 to 20 per cent being lost in the process. The calcined potash is a crumbly, caked mass, that is seldom pure white, but usually more or less discoloured from minute particles of charcoal, or else reddish from ferrous oxide, or bluish or greenish from manganate of potash. It has an alkaline taste, is strongly hygroscopic, and easily soluble in water, though not in alcohol. When fresh from the calcining furnace and free from water it consists of 80-85 per cent carbonate of potash (K2CO3), 6-9 per cent carbonate of soda (Na2CO3), 6-9 per cent sulphate of potash (K9SO4), 1-4 per cent chloride of potash (KCl2), and small quantities of ferrous oxide, alumina, magnesia, silica, and combinations of manganese. In chemical factories these salts can be separated by fractional crystallisation, and the carbonate of potash obtained almost pure; but this is not necessary for most of the uses to which potashes are put, such as the manufacture of crystal glass and of soft soap, and for many chemical preparations. VI. Resin-tapping and the distillation of oil of turpentine and rosin from the crude resin have also, like the production of tar and pitch, lost all the importance they once had in the Pine tracts of Scotland early in the eighteenth century (see vol. i. p. 25); and there is no part of the United Kingdom where this is now carried on. On the Continent, too, resin-tapping is nothing like so general as it used to be up to about thirty or forty years ago, partly owing to wood having risen considerably in value, and partly owing to the competition of cheaper imports from North America, which now supplies about four-fifths of the world's consumption of oil of turpentine and rosin (chiefly obtained from Pinus palustris, P. australis, and P. Tada, and from Abies balsamea for "Canada balsam" and the finer qualities of resin most of the turpentine imported into Britain now comes from America). It still, however, forms an important woodland industry in some parts of Austria and France, and in some of the Alpine and Mediterranean districts. The chief trees tapped, and which are at the same time those that yield most resin, are the Maritime or Cluster Pine (P. maritima = P. Pinaster), in South-Western France (and especially in the sandy wastes of Gascony known as the Landes), Spain, and Portugal, and on the North African coast, and the Black Pine (Pinus Laricio, embracing • both the climatic varieties distinguished as Austrian and Corsican Pine in Britain), throughout Austria, Southern France, and Corsica. Spruce is still also tapped to some extent in parts of Bohemia, and in the Thuringian and Black Forests (Central and Southern Germany), and Larch in the Alpine districts; but Scots Pine and Silver Fir are now seldom tapped. Resins are widely distributed, and are found in all plant-organs except the cambium. They either form part of the cell-wall or of the cell-contents, but are generally collected and secreted in special intercellular resin-ducts, which are found in the bark of all the Abietineæ (see vol. i. p. 193), and usually also in their wood. The resin appears to flow gradually from the upper to the lower part of the tree, so that the roots contain most, and after that the base of the stem within about 6 to 7 ft. of the ground, while the quantity gradually decreases in the branches, crown, summit, and bark; and the older the tree, the more resin it contains. The precise method in which resin is formed physiologically, by trees in a normal condition of health, is not as yet quite satisfactorily determined, although according to recent investigations it seems to be indicated that a certain part of the cell-wall becomes transformed into a sort of mucous layer (cell-mucus) secreting oil or resin. But it is also formed, by a more or less pathological process, from the cellulose and from starch, either directly by degenerative changes in the substance, or indirectly by the formation of tannic acid. The production of resin is certainly often greatly increased by many pathological conditions (e.g., where branches are broken, and after attacks of certain insects and fungi). As the resin-ducts never open spontaneously near the outer surface of the tree, any outflow of resin is a sure sign of some sort of pathological disturbance; and in resin-tapping the wounds are made near the base of the stem in such a manner as to cause the largest possible outflow. But as the resin-ducts are very minute capillary tubes, the pressure exerted on these by the surrounding tissue of the sapwood causes the resin to exude very slowly. Resins are very complicated chemical compounds, but those of coniferous trees contain abietinic acid (C19H2O2) as one of its chief constituents, which in its pure condition forms colourless crystals insoluble in water, but soluble in alcohol, æther, alkaline fluids, &c. The main substance of resin is always amorphous, but in that of Conifers there are so many crystals of abietinic acid, that the whole yellow or brownish-yellow mass often appears clouded and more or less opaque. It has a strong and pleasant aroma (especially fragrant in the Douglas Fir), and gradually darkens and becomes hard and brittle with exposure to air. Another of the main characteristics of the resin of Conifers is the large quantity of ætherial oil, and especially of oil of turpentine, which they contain. Such turpentinous resins may either be viscous and semi-fluid (in which case they are called balsams), or else partially or wholly hardened (when they are respectively called soft and hard resins). The finer balsams (e.g., Abies balsamea) are of a honey-like consistency, clear, and either colourless, or from a pale yellow to a brown colour, though sometimes clouded by air-bubbles or drops of water, while commoner sorts are always more or less 2Q VOL. II. clouded with abietinic acid crystals, and instead of clarifying, become still more opaque when heated. The resins are rich in carbon, poor in oxygen, and entirely free from nitrogen. Insoluble in water, they mostly dissolve in alcohol, æther, oil of turpentine, petroleum, benzoline, &c. The finest product of all is the aromatic, clear, colourless "Canada balsam" of Abies balsamea, afterwards turning bright yellow, which possesses strong refractive power, and is chiefly used for optical purposes. But among European Conifers the thick viscous resin of the Larch, from which "Venice turpentine" is produced, and the thinner fluid resin of the Silver Fir, producing "Strassburg turpentine," are the finest and most turpentinous resins. The latter tree, however, yields but little resin, and that is chiefly contained in pockets throughout the bark, which are only here and there (e.g., in Alsace) cut and tapped. The Maritime Pine (producing "French turpentine ") and the Black Pine give a semi-fluid resin which, on being allowed to settle quietly, precipitates crystals of abietinic acid, and leaves a yellow to reddish-brown, honey-like fluid above; and in Maritime Pine resin this clear portion predominates, whereas in the Black Pine the greater part becomes crystalline. Spruce resin is yellow to brown, tough and semihardened. The resin found caked between the bark and the wood in the roots, as well as that on wound-cicatrisations, is usually sulphury-yellow, hard and brittle. 1. The method of tapping Resin varies according as it is to be found chiefly in the sapwood and the bark, or in interstices within the heartwood. The stem may (1) simply be bored into near the ground (Alpine method, for Larch), or (2) pieces of bark may be removed, and either (a) the exuding fluid resin is collected in earthenware cups (French method, for Maritime Pine), or (b) the semi-hardened oxidised resin is scraped off (German method, for Spruce), or else (c) deep cup-like incisions are also made into the stem to collect the resin (Austrian method, for Black Pine). But it will be more convenient to describe these different methods briefly in the order of their relative importance throughout Europe, as follows:(1) Maritime Pine, (2) Black Pine, (3) Spruce, and (4) Larch. (1) The French method of tapping the Maritime or Cluster Pine in the Landes or sand-barrens around Bordeaux (see vol. i. pp. 86, 208, and vol. ii. p. 195) is that known as Hugues' system. Tapping begins when the trees girth over 3 ft., by which time they are at least 30 to 35 years old. About the end of February or early in March of the year in which tapping is to begin, the rough bark near the foot of the tree is pared with a scraping iron from a strip about 2 ft. long and 4 to 5 in. broad, only a thin, smooth, reddish skin of bark being left to cover the sapwood. During the first half of March an incision about 4 in. broad, 1-14 in. high, and not quite in. deep is made at the pared part, about 12 or 14 in. above the ground, and a bent piece of zinc is fixed into the stem to form a gutter and lead into glazed earthenware cups, also fixed to the stem, the viscous drops of resin trickling down from the wound thus made. The zinc gutters are broader than the groove incised, and protrude forwards about 14-14 in. They are fixed in the thick bark at either side, which is first indented with a sharp curved-steel cutter of the necessary shape, while the gutter is held in place in an iron casing, and hammered home into proper position. The glazed earthenware cups contain about pint, and are nailed to the stem just below the gutter. The pot is protected against rain-water and excessive evaporation of resin by means of a zinc shade attached by its ends to the tree-bark above the cup and the gutter, so that it does not interfere with the trickling down of the drops of resin (Fig. 284). At first the incised groove has to be refreshed once a week, then afterwards once every five days, during the rest of the resin-collecting season, by extending it upwards for 4-5 in. Only a very thin shaving is pared off each time, so that the depth of the groove may not be quite in. deep. Before the tapping-season ends on 15th October the grooves will have been refreshed from 40 to 45 times, and the first year's incisions will be about 22 in. long, and during the second, third, fourth, |