CHAPTER V.

WOODLAND INDUSTRIES: ESTATE SAW-MILLS, PREPARATION OF WOOD-PULP AND CELLULOSE, CHARCOAL-MAKING, RESINTAPPING, &c.

IN countries where there are very extensive forests, many important industries have sprung up which require woodland produce for their raw material. And even though the British forester will usually only be called on to work small saw-mills for supplying estate timber and other local requirements, or for conversion so as to reduce the cost of transport to the nearest available timber market, yet it is desirable that he should also know something about the other woodland industries, so that he may turn such knowledge to practical use should occasion perhaps offer-such as in dealing with extensive windfalls, or with large thinnings of small dimensions, &c., for which, in their rough and raw condition, no local demand exists. These woodland industries will therefore be considered in the following order :-(1) Estate Saw-mills, (2) Preparation of Wood-pulp and Cellulose, (3) Charcoal-making, (4) Utilisation of small Waste-wood and Sawdust, (5) making Potashes, and (6) Resin-tapping.

I. Estate Saw-mills.1-Wherever there are large woodlands it will usually be found profitable to reduce the bulk of the logs for transport by conversion to a greater or less extent, even if it goes no further than cross-cutting to standard lengths (e.g., as in pitwood). The right of converting on the spot, with a small temporary saw-mill worked by a portable steam-engine, is indeed sometimes made a condition of purchase by the buyer, who is thus able to get rid of comparatively useless slabs, &c. And if these latter are marketable locally, this increases the possible margin of his profit, and he can then afford to give a better price for the wood.

On most large properties it is generally found profitable to have a permanent estate saw-mill located at some convenient centre, although even on large estates there will rarely be either a sufficient supply of home-grown wood, or a sufficient demand throughout the estate itself to keep any large saw-mill at work all the year round. Such estate mills, however, often supply other than merely estate requirements in rural districts distant from ordinary commercial saw-mills. And if this combination of converting as well as growing the timber were further developed in rural districts not well served by

1 Those specially interested in timber-conversion should consult English Timber and its Economical Conversion, by "Acorn"; Handbook of Saw-Mill and Wood-Converting Machinery, by M. P. Bale; and Modern Wood-Working Machinery, by J. S. Ransome.

saw-mills, it would be to the advantage of both the landowner and his tenants, and of the whole country-side. Timber-growing landowners who establish permanent saw-mills with good modern machinery generally find their enterprise profitable and the benefits appreciated by the surrounding population, and in such cases the main inconvenience felt is that sufficient supplies of homegrown wood are not obtainable locally to keep the mill continuously at work up to its full capacity. But even simple, old-fashioned saw-mills worked by water-power, or in connection with a portable steam-engine used for other estate purposes, can be used with profit and advantage.

Whether it is better for the timber-grower to be his own manufacturer is another question, which admits of no general answer. Whether, and to what extent, conversion may prove profitable often mainly depends on the man in charge of the business; and it is therefore fairest that he should be allowed, over and above his regular salary, a bonus of a certain small percentage on the net profit earned after payment of all expenses, including a fair allowance for wear and tear of machinery. When there has been heavy windfall among Conifers, speedy conversion by one means or another is often the only way of averting a heavy loss. But, on the other hand, it will seldom prove profitable to make falls of timber in the woods simply for the express purpose of supplying the saw-mill, and merely to keep it uninterruptedly at work. It is not true economy to manage the woods in the interests of the saw-mill; and the work of conversion should be subordinated to the more important considerations affecting the capital locked up in the woodlands.

Estate saw-mills are usually worked either by water-power or by steam, as electricity is as yet neither cheap enough nor sufficiently simple. Where sufficient water-power is obtainable, this is the cheapest and simplest method of conversion. In this case, the saw-mill is located wherever the water-power can be best utilised; but otherwise it is placed, for convenience, near the home-farm workshops, where the mill can be driven either by a stationary steam-engine used for other yard-work (pumping water, generating electricity, threshing, chaff-cutting, &c.), or by a traction-engine, which can also be used to move the sawing-machinery from place to place as required, and to transport the sawn timber after conversion. Due regard has of course to be given not only to the supply of the rough logs, but also to the removal of the sawn timber after conversion.

Where sufficient wood can be supplied from a reasonable distance a stationary saw-mill is best, because this gives the fullest opportunities of converting slabs, tops and ends, and other small refuse into small staves, boards for packing-boxes, railway keys, and any other articles of small dimensions which can be disposed of locally with profit. The best chance is here also given of disposing of firewood, or for dry distillation, or for using the sawdust as litter and manure, &c. But where the woods are distant and comparatively small, the use of a traction-engine (see p. 575) and a portable saw-bench may be the cheapest, and in fact the only profitable, way of converting. It is simply a question as to whether it is better to bring the timber to the mill, or to take the machinery to where the timber is; and that depends entirely on local circumstances in each case. In general, a stationary saw-mill worked

by water or by steam is the more profitable, if the logs can be supplied from within about 2 miles; but otherwise portable machinery is usually preferable, even though it is more liable to get out of order than fixed machinery.

The saving that can thus be effected in the haulage of the dead-weight of green timber may easily be roughly estimated from the data given elsewhere (pp. 436-439, and 511); and unless the stems can be stripped for tanningbark, the weight of the rough, thick bark of trees comes when green to from 1 to 2 cwt. per ton of gross weight, or about 10-15 per cent of the whole weight of the timber in log; while the actual wood amounts to from 17 to 18 cwt., or about 85-90 per cent, and a considerable proportion of this is sapwood, the least durable and useful part of the log. Hence the desirability of economy in transport.

As regards the question of profit on conversion, it must be recollected that the loss by wastage usually varies from about 30 to 40, and sometimes even 50 per cent.1 Thus, whatever price is obtainable for the timber on the fall, will have to be increased by about one-third or more for each cubic foot of converted timber, merely in order to avoid a loss, owing to the extra cost of transport, handling, sawing, wear and tear of machinery, &c., on the one hand, and of loss in conversion on the other-and this latter, notwithstanding the fact that log-measurement (square-of-quarter-girth) expressly allows 21 per cent for wastage, while converted wood is sold by actual cubic contents. It does not therefore follow that conversion is profitable merely because 1s. 6d. per cubic foot can be obtained, say, for converted Larch at the saw-mill, while only 1s. is obtainable for the logs on the fall. Thus, if local experience shows that every 150 cub. ft. log-measurement of timber, saleable on the fall at 1s. per cubic foot, yield, say, about 120 cub. ft. of planks, &c., converted at a total average outlay of perhaps 40s. for carting, handling, conversion, and millsundries, then 1s. 7d. per cubic foot for the converted timber will simply equalise matters, without showing any profit, and only the slabs and waste wood will be on hand for the extra trouble and expense; but anything beyond 1s. 7d. per cubic foot, as well as anything obtainable by the sale, conversion, or use of the slabs, as firewood, &c., will represent payment for the extra trouble, and profit on the transaction.

Saw-mills and saws may vary from very simple contrivances to complicated and very powerful machinery. The motive-force may either be-(1) water-power, driving (a) ordinary vertical water-wheels, or (b) horizontal water-wheels (turbines), or else (2) steam-power; and the sawing-machinery thereby set in motion may control either (a) vertical frame-saws, (b) circular saws, (c) horizontal saws, (d) continuous endless band-saws, or (e) cylindrical or barrel-shaped saws. Vertical waterwheels are called overshot or undershot, according as the water-pressure is applied above or below the middle of the wheel, while breast-wheels receive it at about the middle of the wheel. Turbines are horizontal water-wheels with vertical axes, which receive and discharge the water round their circumference. The best turbines can

1 In supplying contracts for many hundreds of thousands of narrow-gauge railway sleepers from exceptionally fine, round, large Pyingado (ironwood) logs in Burma, I found the average out-turn in sleepers to be about 66 per cent of the total actual contents (length x mean superficies), with many fair-sized slabs left on hand.

utilise the water-power up to a maximum of 80 per cent (Unwin) in normal conditions of working.

With a fall varying from 10 to 70 ft., and giving 3 to 25 cub. ft. of water per second, a wheel can be made to act by the mere weight of the water. If the variation of head-water does not exceed 2 ft., an overshot wheel can be used; but with a greater variation of head-water level, a pitch-back or high-breast wheel is better. The ordinary undershot wheel develops only about 2 per cent of the work of the water. For woodland saw-mills the choice usually lies only between overshotwheels, where there is plenty of water, and turbines, where the quantity of water is limited, but a good fall can be provided to increase its force.

The sawing of timber by hand must, like charcoal-burning, be one of the very oldest of woodland industries. Saws were run by windmill-power as early as the thirteenth century; and the use of water-power soon followed, as water-power saw-mills are known to have been employed in Germany in 1322. The first British saw-mill that is known was erected in 1634 in America (then a colony), at the falls of the Piscataqua (between Maine and New Hampshire). An attempt was made to establish one in England in 1663, but had to be abandoned owing to the opposition of the hand-sawyers; and when the first was afterwards erected at Limehouse in 1768, it was soon destroyed by a mob. As our American colonies then supplied England with much of the timber already even then required to be imported, saw-milling soon there became an important industry. The original, simple form of mill worked by water-power consisted in a single saw attached by a long arm (pitman) to a crank on the wheel-shaft at the lower end, and by a heavy frame (gate) above, running in wooden slides upon two stout posts crossed above by a beam connecting the two sides of the mill-frame. At each turn of the mill-wheel the saw made a downward and an upward stroke, each varying very slightly from the vertical. The saw was set with teeth pointing downwards, and the downward stroke, which brought the saw slightly forward, was that which cut and tore the particles of wood resisting the passage of the saw. During the upward stroke the saw was carried slightly backwards, and in the meantime the log (held firmly in position by a dog or clamp on each side) was pushed forward a little in readiness to meet the cutting-edge of the saw with a fresh point of contact. By the slope thus given to the saw, the work of cutting was distributed all over its face in place of being confined to the first teeth coming in contact with the wood, as would be the case if the saw simply moved up and down perpendicularly. The mill-carriage (travelling table) on which the log lay was moved forward towards the saw by a rack and pinion worked by a feed-wheel, and the daily conversion was 500 to 1500 superficial feet.

The first great advance was to introduce a gang of two or more saws in the frame, and after that improvements have ever since been gradually introduced into the form, size, and mechanism of the saws and mode of suspending them, and into the driving-power and cutting-capacity of the machinery. Just as the single frame- or gate-saw worked by simple machinery was a decided advance on the older pit-saw worked by hand, so too a further improvement was made by the introduction of the gang-saw or modern frame-saw fitted with multiple saws, having shorter and thinner blades, which work more quickly, though with a shorter stroke, and cause less wastage in sawdust. A later improvement was the muley-saw, suspended without strain upon a "pitman" beneath, having its upper end hung in slides pendant from a heavy beam above, thus dispensing with the heavy gate and posts of the older saw-frame. But the muley has now in turn given place to the quicker-working circular saw where very large quantities of timber have to be converted; and in many large lumbering districts the endless band-saw is preferred even to the circular saw. A great impulse was of course given towards improvements after the introduction of steam as a motive-power (about 1855) and of iron for constructive purposes. A good account of saw-mills up to 1886 is given by Hotchkiss in an article on Saws in Encyc. Brit., 9th edit., 1886, vol. xxi. p. 344; but the modern development of horizontal frame-saws and endless vertical and horizontal band-saws has taken place chiefly within these last twenty years.

Mill-saws may vary considerably in diameter, thickness, and quality. They must be strong to stand the heavy thrust they sustain, and their thickness or

gauge is classed according to the different sizes of wire; thus a 10-gauge (10 B.W.G.) is thicker than a 12-gauge (12 B.W.G.). In large saw-mills gang- or multiple-saws are seldom thicker than 14-gauge, and can even be successfully worked as thin as 18-gauge (with a saw-kerf wastage of only in.), while the best thickness for circular saws is usually from 13- to 16-gauge.

Cross-cut Saws, for cutting across the grain of the wood, belong to the reciprocating class. The cutting-edge strikes the fibres at right angles to its length, and while its pitch is slight (if any), it must sever from each side before dislodging the sawdust. Slitting- or ripping-saws have the cutting-edge at about a right angle to the wood-fibres, and sever them in one piece, which the throat of the tooth wedges out. Circular Saws, in use among watchmakers and fine metal-workers since 1790 (invented by Bennel), were only applied after the introduction of steam-power to saw-milling about 1855, though they can also quite easily be worked by waterpower; but now they are much more largely employed than any other kind of saws, although they require to be stronger and thicker, and therefore cause more wastage than either frame-saws or band-saws. In large mills circular saws of 60 in. diameter are in common use, and can per diem of 12 hours (according to the horse-power) cut out from 20,000 to 60,000 superficial feet of 1 in. boards, as compared with 5000-8000 ft. sawn by a straight muley- or gate-saw. Saws of 8 ft. diameter are sometimes in use in California. They cannot be set in gangs close together, as in frame-saws, for sawing thin boards simultaneously; but two saws of 3-6 in. diameter, or from three to five of smaller diameter, can be set on one shaft, and simultaneously used to divide or trim the planks cut from a log. Horizontal Saws, working rapidly from side to side between supports adjustable to suit the log, have recently been introduced, and prove successful even in small estate-mills, both for breaking down timber and for re-sawing the broken-down pieces into flitches of different sizes. As thin saws of 17- to 19-gauge can be used for sawing thin boards, the wastage is less than in sawing in ordinary vertical log-frames or with circular saws. Endless Band-saws, at first used for fine work, and only introduced about twenty years ago for timbersawing, but now largely used for breaking down logs into squares, consist of a continuous ribbon-like blade running over two pulleys, placed either vertically or horizontally with reference to each other, according as the cut is to be made vertically or horizontally. They vary from about 1 to 2 up to 9 in. in width, and have a cutting capacity of 30,000 to 40,000 superficial feet per diem of 12 hours, with an expenditure of from 25 to 40 per cent less driving power than is needed for the same out-turn from a circular saw. As they are usually only from 16- to 19-gauge, according to the kind of wood sawn, the wastage is smaller than with ordinary vertical or circular saws about 14- to 16-gauge. Cylindrical or barrelshaped Saws are only used for cutting rounded staves for barrels, tubs, pails, &c.

Typical illustrations of some of the higher classes of vertical, circular, and horizontal frame-saws, and of a horizontal band-saw, are shown in Figs. 269 to 272.

Vertical Frame-Saw with Gang of Multiple-Saws (Fig. 269) for sawing logs or squares into boards or planks. The logs are fed up to the saws by revolving rollers, with a rate of feed varying up to 4 ft. a minute, according to the kind of wood and the number of saws. The pressure gear is so arranged that, by turning a hand-wheel, the rollers can be raised or lowered to suit any inequalities in the log, and thus obviate overhead levers and weights, besides leaving the top of the swing frame clear for keying-up and adjusting the saws. The swing frame is connected with the crank-shaft by two rods, one on each side of the frame, to reduce the distance between the floor-line and the foundation as much as possible, and the whole machine is bolted to a massive cast-iron bed-plate, into which the bearings for the crank-shaft are fitted.

The ends of the log that is being sawn are carried on strong iron carriages running on rails, and fitted with screw dogs, which grip the timber and have a lateral motion, enabling the saws to follow the curve of a crooked log. The swing frame, connecting