one would have much the same drawbacks (only in a different form) as in pure woods of these. Hence, when mixed woods are being formed, the intention with regard to the time of utilising the different kinds of trees should be distinctly recorded, so as to assist in regulating the subsequent thinnings. Of course, such intention need not be subsequently adopted as being of the nature of instructions, because the future can be left to decide for itself whether it be advantageous to thin out one kind or the other, or to regard as the ultimate marketable crop a different tree from that originally intended, seeing that the market prices for different sorts of timber may easily undergo relative changes in the course of the years which must elapse before the trees become mature. But it is only by means of the judicious formation of mixed crops that the financial advantages of the future can be provided for in the present. The main drawback to mixed woods is that they require more careful treatment with regard to thinning than pure crops. On this account it is perhaps preferable to make the mixture in the form of small patches of the different kinds of trees on soil favourable to their growth. This is, in fact, merely following the procedure of nature. When an old tree dies, it is only to be expected that its offspring grows up close round about it; and thus "family groups" are formed, as one can see everywhere in the older forests of every description-whether Beech or Oak in Europe, or Deodar on the Himalayas, or Teak in the forests of Burma. But one can also see another law of nature simultaneously at work, and tending to bring large tracts of woodland mainly under one kind of tree. It was thus that the ancient large pure forests of Beech and Scots Pine were formed in Britain, and of Beech, Hornbeam, Silver Fir, Spruce, Pine, Birch, and Aspen on the Continent of Europe, and similar results in other continents. Hence, here again, if anything beyond mere financial advantage comes into consideration, ample justification can be found for the formation of pure crops of trees of one kind or another. On the whole, however, the growth of mixed crops is the safest and the best method with regard to the treatment of woodlands of large area.

So far as the present demand goes and the future condition of the timber market can be forecast, there seems little doubt that the greatest profit is to be found in coniferous crops. First of all, valuable crops of these can be raised on soil which is not sufficiently productive to yield a good growth of Oak, Ash, Beech, &c., and, secondly, they give the largest returns in timber per acre. Even though the price per cubic foot is nothing like so high as for Oak or Ash, yet they can often give quite as good returns as these, and often even better, on land of moderate quality, besides producing a fair yield on inferior soil and poor land where crops of hardwoods could not be grown at all with profit.

On the Continent of Europe the most profitable crops of timber are, beyond all doubt, Spruce and Silver Fir grown on fresh soil not deficient in moisture; while for inferior land, and on poor, dry, sandy stretches, the Scots Pine is the only remunerative crop. No less than 42 per cent of the total wooded area throughout Germany is under coniferous crops. In Britain, Larch has often shown itself one of the most profitable of crops, even despite the canker disease; but the experiences so often made with this fine tree in large pure plantations in different parts of the country, from the Highlands of Scotland to the south of England, should convince any one that Larch should be grown in admixture with other trees, and preferably with broad-leaved kinds, rather than in pure plantations of large extent.

As woodland crops Spruce and Silver Fir do not, for climatic reasons, thrive anything like so well in England as they do in France and Germany; but somewhat better results are obtainable, with regard to Spruce at least, in the Highlands of Scotland, with their harder winter and their mists more resembling the climate where Spruce is indigenous. The much lower rates given locally in Scotland for the "Baltic deals" of Spruce and the "white pine" of Silver Fir in comparison with "red" or Scots Pine and Larch will, however, naturally and very reasonably lead to the two latter species receiving the preference in plantations and natural regenerations. And in many cases, particularly on sandy soil in the south of England, Corsican Pine will yield a fairly good wood and a larger crop per acre than Scots Pine, while creosoting must tend to reduce future differences in price.

Where there is a good market for young stems from the size of hop-poles upwards, there is always a strong temptation to plant Larch pure. A crop of 70 years of age, consisting of about 220 trees per acre, in the south of England recently (1900) realised 20s. a-tree for the whole lot, while the plantation, originally formed at about 4 ft. by 4 ft., had always yielded a fair return in the way of thinnings since the time the poles were large enough to be cut through the centre for rails.

Fast as the growth of Larch often is, yet that of the Douglas Fir is even more rapid, while the quality of the timber produced in Britain is now known to be at any rate far superior to that of Spruce or Silver Fir (see vol. i. p. 250). But it is not merely the ques tion of profit that has to be carefully considered before forming pure crops of any one kind of conifer, because experience has shown in the most convincing manner possible that Scots Pine, Spruce, Silver Fir, and Larch, grown in large masses as pure woods, are each exposed to particular dangers, and have each their own special enemies among injurious insects and fungous diseases. And there are unfortunately already signs that it is not likely to be different with Douglas Fir. The greatest ultimate advantages will therefore, in conifer crops as in broad-leaved trees, be found in judicious mixtures. On good soil Douglas Fir, pure or mixed with Larch and with perhaps a sprinkling of Menzies Spruce, in which Larch is distinctly favoured in height at time of planting and specially favoured during thinning, would probably prove one of the largest crops that can be grown, and might also (given cheap plants) prove one of the most profitable. For poorer soil a sprinkling of Larch throughout a matrix of Pines can hardly fail to be profitable, even though the Larch cannot be expected to attain good dimensions on inferior land. Whenever Spruce may form the main portion of the crop an admixture of Larch is preferable to Pine, both as being more valuable in itself and as better suited to the Spruce in its particular habit of growth. A sprinkling of Spruce among Pine affords, by reason of its conical top, convenient opportunity for assisting the latter by the removal of the former during thinnings, without breaking up the canopy to any injurious extent, while it also helps to diminish the risk of heavy damage from breakage by snow during severe winters. When young plantations of Scots Pine or Spruce are being formed, a mixture of Birch is often useful as a nurse in exposed localities. But it should be mostly cut out when once it has served this purpose, otherwise it is apt to cause trouble by seeding on adjoining areas. A few Birch here and there, however, not only form a pleasant contrast to the sombre conifers, but also add to returns obtained. And it is the best kind of tree that can be grown on poor sandy soil to protect Pine-woods from fires arising through sparks from railway engines. A few rows of Birch planted along both sides of a railway line will prove about the most effective measure that is practicable to try and catch the live sparks, and prevent them from causing forest fires. In coppice, Birch, Aspen, and other softwoods should usually be cut out in favour of more valuable hardwoods, while as highwoods their canopy soon becomes so thin as to be unable to protect the soil against deterioration.

As has already been remarked, a change of crop sometimes becomes necessary in woodlands on account of the soil being deteriorated, usually through bad management in the past. But it also sometimes happens that a change of crop promises better returns from the land, and may therefore appear desirable. It is best, however, to study first of all the details of the past management, to see if improvement cannot be made therein before adopting so drastic a measure as a total change in the kind of crop grown. Any given kind of crop can, of course, only be grown in perpetuo on the same area if it is able to protect the fertility of the land; and when woodlands show signs that the soil is becoming, or has become, deteriorated, one must first carefully consider not only whether the kind of crop or the past system of management is the cause of such deterioration, but also how this can best be repaired. A good deal can often be done to remedy matters by layering, sowing and planting, and by improving the system of management in various ways; but when copse and coppice tracts have once become much deteriorated, then there can often be very little doubt that their conversion into conifer highwoods by means of planting is the best step to take. Such changes of crop,

however, will necessarily be a new investment of capital, as but few of the crops on deteriorated land of this description will, on being cleared, yield, in addition to the usual returns of the regular fellings, anything like a sufficient surplus to pay for the planting of the land. Before making any such change of crop it is therefore necessary to consider the advantages and disadvantages carefully; because once the change is made, it is an investment of capital from which one cannot withdraw except at great loss.

5. Fixing the Rotation with which the Timber - Crops should be worked. As already mentioned, the term rotation used with regard to woodland crops simply means the number of years forming one complete generation of the trees, or one full cycle of the crop-from the seedling. growth to the ultimate fall of the mature timber.

As will be explained subsequently in dealing with the practical work of forest management, the first steps to be taken are to subdivide the whole woodland area into convenient working-circles and compartments, to classify and estimate the contents of the crops found growing throughout the whole of each working-circle, and to collect the various other data upon which the scheme of management must be based. The direction in which the several annual (or periodic) falls should take place being once fixed (in the direction opposite to the prevailing dangerous winds-i.e., generally running from E., N.E., or S.E., to W., S.W., or N. W. in most parts of Britain), and the choice of the sylvicultural method of treatment and the particular kind of crop having been made, the next most important step is to fix the rotation with which the crops forming each working-circle shall be worked. As a matter of fact, the whole of the management is essentially influenced by this. If Larch- or Pine-woods are worked with a rotation of 80 or 90 years, then each annual fall will (cæteris paribus) be equal to the total area divided by 80 or 90 respectively; while Beech-woods worked with a rotation of 100 or 120 years, grouped into periods of 20 years for natural regeneration, will respectively have five or six periodic falls, each equal to what would be the area of twenty annual falls. Hence it is very clear that fixing the rotation of a crop forming any particular working-circle means nothing short of simultaneously determining (1) the size of each annual (or periodic) fall; (2) the normal growing-stock or total amount of capital in wood required; (3) the normal increment or annual rate of growth, and consequently also (4) the normal yield annually obtained as the mature fall of timber.

It is therefore impossible to overrate the importance of careful consideration in fixing the rotation of timber-crops, because, once this is fixed, one is committed, more or less definitely, to a general scheme of management in many respects. But, from the very nature of forestry, it is obviously impossible to fix a rotation for 70 or 100 years, or more, ahead. If large new plantations are to be made, who can say, at present, whether the workingplan had best be framed for 70, 80, 100 years, or any other definite term? All that can safely be said is that-so far as local conditions, existing prices, and the probable tendency of the timber market are concerned-a rotation of x, y, or z years now seems what is likely to prove most profitable. It is, of

course, a much easier matter to calculate, as regards a crop of 40 or 50 to 60 or 70 years now on the ground, whether it will pay best to clear it at once or to let it grow for 10 or 20 years more. While recognising the absolute necessity for having some standard to go by, it therefore seems advisable, in the case of forming large new plantations, to adopt, under guidance of existing and probable future market rates, some such rotation as 60 to 80 years for conifer crops, and 100 or 120 years for Beech-woods, which (as also the annual or periodic falls, of course) can easily be raised or lowered later on, by 10, 15, or 20 years, in the light of the better knowledge that will come before the crops are mature.

The rotation with which different kinds of woodland crops can be worked depends to a very great extent on the quality of the soil. It is a matter of common experience, proved also by the Continental Tables of Average Yield, that highwoods growing on good soil and in a favourable situation can be worked with profit in a longer rotation than on poor land and in hot exposed positions. For copse and coppice-woods, on the other hand, the rotation can be shorter on good soil than on inferior land, because there is then less chance of its productivity becoming deteriorated through more frequent exposure.

In fixing the rotation of timber-crops it is not sufficient merely to be guided by what may appear to be the most profitable age for cutting the crop. It is important that the rotation adopted should amply protect the productivity of the soil. If the rotation be either so short (in coppice or copse) or so long (in highwoods) that it leads to deterioration of the soil, then any temporary advantage gained with regard to the crop now growing would be dearly bought at the expense of the next crop, and of the consequent decreased capital value of the land for growing timber.

So far as any general statement can safely be ventured on, the rotation which will best suit hardwoods like Ash, Maple, Sycamore, and Elm will in most places lie between 60 to 90 years, Beech from 100 to 120 years, and Oak from 100 to 150, and that for conifer crops 50 to 80 years, so as to yield timber for building, will probably be about the most profitable future rotation. In hardwood coppices and copses it will usually vary from 10 to 15 or 20 years according to the market for the underwood, although Aldercoppices often pay better with a rotation of 25 or 30 years and Hazel with a rotation of only 7 or 8 years, while Osier-holts are cut over annually for their harvest of small rods used in basket-making.

If it were merely desired to obtain the largest crops of wood per acre from the forests, it would be easy to fix the rotation, with a fair degree of accuracy for general purposes, by means of Average Yield Tables. It would then coincide with the time at which the average increment culminates on land of the given quality, and this is when the current annual increment is equal to the average increment (see p. 321). If the total yield of the mature fall be added to all the previous thinnings, and this sum be divided by the number of years in the rotation, the quotient will show the average yield; and a comparison of the results worked out for different ages will at once give the rotation desired. Investigations have shown, however, that this point is reached at a comparatively early age (Scots Pine 30 to 40, Beech 50 to 75, Spruce 60 to 70 years), while the crops are still in vigorous growth on good classes of land, when their clearance would be less profitable than allowing them to grow on for several years. Hence this method of trying to fix a normal rotation is of little practical value, since it gives no indication as to whether such a rotation would be more profitable or less profitable than one fixed either somewhat higher or somewhat lower.

The Rotation which promises to obtain the largest annual income from woods takes into consideration not only the total quantity of wood produced per acre,

but also the dimensions attained by the timber, because its technical value, and consequently the market-rate per cubic foot obtainable for it, increase with the diameter and the greater rotundity of the stem. This rotation is found by adding together the net money-value (i.e., free from the cost of harvesting them) of all thinnings and of the mature fall of wood, subtracting from this total the cost of regenerating the crop (or replanting the area) and the sum of the annual outlay for protection, rates, and taxes for as many years as there are in the rotation, and dividing the difference by the number of years in the rotation. As the cost of regeneration or replanting is practically the same whatever be the rotation, and as the amount annually payable for protection, rates, and taxes is subject to but little variation, it therefore follows that the most favourable rotation can be directly found by adding together the value of all thinnings and of the mature fall, and dividing their sum by the number of years in the rotation. Several such calculations being made, that rotation which gives the largest result will be the one desired. As a matter of fact, the rotation thus indicated is somewhat higher than that which yields the largest percentage on the capital employed in producing the crops of wood. This method of fixing the rotation is certainly a great improvement on that which merely considers the largest out-turn in wood per acre; but its weak point is that the calculation of the largest annual income does not take into consideration, as forestry on purely business principles should, the exact relation this amount bears to the productive capital locked up in the soil and the total growing-stock of wood. Hence it is not the method which can be recommended for Britain.

The most profitable Rotation—that is to say, the rotation which promises to yield the highest percentage on the capital value of the woodland as estimated by the net monetary value of its produce-is what should, both in theory and in practice, receive most consideration in the management of woods intended to be worked on commercial lines.1 It is found (see p. 241) by making various calculations, each as if for a single crop, in accordance with Faustmann's formula (the same rate of interest being used in each case, of course), and ascertaining that particular rotation which shows the greatest profit by indicating the maximum productivity or largest capital value for land and growing-stock. Faustmann's formula is as follows:

The productivity of the woodlands (as estimated by the net value of the timber crop, Fn + (Ta × 1·0 p2-a) + (T¿ × 1·0 p”−b) + ... + (Tq × 1·0 p2−q) − (c × 1·0 p") g &c.) is = 0.0p Where

10 p" - 1

F= the net income, free from cost of harvesting, yielded by the mature fall at the year n.

Ta, T...Tq=the net income, free from cost of harvesting, yielded by the thinnings at the years a, b......q.

p the percentage or rate of interest which the woodlands are supposed to yield annually on the investment represented by their capital value.

c=the cost of forming the crop originally, or of regenerating or replanting the area on the fall of the mature crop.

g=the annual outlay for general charges (supervision, protection, rates and taxes).

1 The same principle of course also applied to British Arboriculture in olden times. What Loudon said (Arboretum et Fruticetum Britannicum, 1838, vol. iii. p. 1809) of the Oak, applies to all trees grown for selling: :

"The age at which Oak timber ought to be felled, with a view to profit, must depend on the soil and climate in which the tree is grown, as well as on other circumstances. When