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attending such a mode of ploughing must be greatly counterbalanced by its disadvantages. It is practised in all sorts of soils. Its practice in Scotland is confined to the north of the Frith of Forth, and even there it is now abandoned on the large farms, though it may still be seen in the fields of the smaller tenants. When a field is so ploughed, it has somewhat the appearance of having been drilled.

(844.) The drilling of land being confined to summer, I shall defer any remarks on that mode of ploughing until its proper season arrives.

27. OF DRAINING.

"In grounds, by art laid dry, the aqueous bane
That marred the wholesome herbs, is turn'd to use;
And drains, while drawing noxious moisture off,
Serve also to diffuse a due supply."

GRAHAM.

(845.) It is barely possible that the farm on which you learn your profession, or the one you may occupy on your own account, may not require draining. Nevertheless, you should be made well acquainted with this essential and indispensable practice in husbandry. But the probability is, that on whatever farm you may pass your life, some part of it at least, if not the whole, will require draining of one sort or another.

(846.) Draining may be defined the art of rendering land not only so free of moisture as that no superfluous water shall remain in it, but that no water shall remain in it so long as to injure or even retard the healthy growth of plants required for the use of man and beast.

(847.) On considering this definition, you may reasonably inquire why water in the soil should injure the growth of useful plants, since botanical physiologists tell us, that the greatest bulk of the food of plants consists of, or at least is conveyed to them by, water. In what way injury should arise, is certainly not very obvious; but observation has proved that stagnant water, whether on the surface or under the ground, does injure the growth of all the useful plants. It perhaps altogether prevents or checks perspiration and introsusception; or it may neutralise the chemical decomposition of substances which largely supply the food of plants. Be it as it may, experience assures us, that draining will prevent all these bad effects. You may conceive it quite possible for an obvious excess of water to injure useful plants; because you may

have observed, that excess of water is usually indicated by the presence, in number and luxuriance, of subaquatic plants, such as rushes (Juncus acutiflorus and J. effusus), &c., which only flourish where water is too abundant for other plants; and you may even conceive that damp, darklooking spots in the soil may contain as much water as to injure plants, though in a less degree; but you cannot at once imagine why land apparently dry should require draining. Land, however, though it does not contain such a superabundance of water as to obstruct arable culture, may nevertheless, by its inherent wetness, prevent or retard the luxuriant growth of useful plants, as much as decidedly wet land. The truth is, that deficiency of crops on apparently dry land is frequently attributed to unskilful husbandry, when it really arises from the baleful influence of concealed stagnant water; and the want of skill is shewn, not so much in the management of the arable culture of the land, as in neglecting to remove the true cause of the deficiency of the crop, namely, the concealed stagnant water. Indeed, my opinion is,-and its conviction has been forced upon me by dint of long and extensive observation of the state of the agricultural soil over a large portion of the country,that this is the true cause of most of the bad farming to be seen, and that not one farm is to be found throughout the kingdom that would not be much the better for draining. Entertaining this opinion, you will not be surprised at my urging upon you to practise draining, and of lingering at some length on the subject, that I may exhibit to you the various modes of doing it, according to the peculiar circumstances in which your farm may be placed.

(848.) To the experienced eye, there is little difficulty in ascertaining the particular parts of fields which are more affected than others by superfluous water. They may be detected under whatever kind of crop the field may bear at the time; for the peculiar state of the crop in those parts, when compared with the others, assists in determining the point. There is a want of vigour in the plants-their colour is not of a healthy hue their parts do not become sufficiently developed-the plants are evidently retarded in their progress to maturity-and the soil upon which they grow feels inelastic, or saddened under the tread of the foot. There is no mistaking these symptoms when once observed. They are exhibited more obviously by the grain and green crops, than by the sown grasses. In old pasture, the coarse, hard, uninviting appearance of the herbage, is quite a sufficient indication of the moistened state of the soil.

(849.) But there are appearances of moistened land, which you may easily observe without any previous tuition; and these are most appa

rent in soil after it has been ploughed, and more apparent still in spring, in the month of March, when the winds become dry and keen. Then you may observe, in a dry day, large patches or stripes, or belts of black or dark-brown coloured soil, in the face and near the top of an acclivity, whilst the rest of the field seems quite dry, of a light-brown colour; or only small spots may be observable here and there; or the flat and hollow parts of the field may be nearly covered with dark-coloured soil. You cannot mistake these broad hints of the lurking water below; but, in a few weeks, they may all have disappeared, or be reduced very much in extent, if the weather continues dry, or have become more extended in rainy weather. In the case of their disappearance in dry weather, you may conclude that any wetness of the soil which passes off as the summer advances, can do no harm to cultivated plants, and that the land, in such cases, does not require to be drained. Such a conclusion would be very erroneous; because it is on account of the water remaining in the soil all winter that the crops receive injury in summer. The amount of wetness which you saw pass away first in spring and then in summer, would have done no injury to the crops, for it would be all absorbed, and probably more, in the wants of vegetation; but the wetness remaining in and occupying the pores of the soil and of the subsoil all winter, render the soil so cold, that most of the summer's heat is required to evaporate the superfluous moisture out of it, and, in this very process drying by evaporation, the heat is dissipated that should be employed in nourishing the crops all summer. No doubt, when the soil and subsoil are put into such a state as that the water that falls upon the soil from the heavens during the winter, on being conveyed quickly away in drains, does take away some of the heat from the soil, but it cannot render it cold or sour. In such circumstances, the natural heat of the weather in spring and summer would have nothing to do but to push forward the growth of the crops to early maturity, to fill them more fully, and make them of finer quality. You thus see how concealed water injures the soil in which it is retained, and you may easily conceive how it may injure the drier soil around it, by its imbibing the water in contact, by capillary attraction. You thus also see the kind of good that draining effects in soil so situated. Did the symptoms of wet in spring remain as obvious to your senses throughout the summer, you would have no doubt of the land requiring draining; but you may now admit that you may be deceived by land shewing even favourable symptoms of drought. For all that you yet know to the contrary, water may be lurking under what you imagine to be dry soil. Yes, and it does lurk to a very great extent in this

of

country, and will continue to lurk in humid localities and impervious subsoils, until a vent is given to its egress.

(850.) The phenomenon of the dark spots on fields can be satisfactorily explained. Where the surface of the land is at all permeable to water, and where it rests on beds of different depths, of various lengths and breadths, and of different consistence, the water supplied from rain or snow is interrupted in its progress by the retentive beds, and becomes accumulated in them in larger or smaller quantities, according to their form and capacity; and, at length, the superfluous portion is poured from the surcharged strata, and bursts over retentive beds through the surface-soil in the form of land-springs, at a somewhat lower level. Such springs are either concentrated in one place or diffused over a large extent of surface, according as their outlet happens to be extensive or confined, and deep draining is generally required to remove these; for which purpose, deep drains are cut through alternate beds of retentive and permeable matter, and penetrate into the very seats of the springs. It may happen, however, that the surface is as retentive as the subsoil, in which case the water, not penetrating further than the surface-soil, has a free enough passage between the impervious subsoil and the loose soil; this state of soil requires mere surface-draining. Where the upper soil is pervious, and the subsoil uniformly and extensively retentive, water accumulates on the subsoil, to the injury of plants growing on the surfacesoil; and to remove water from such a situation, not deep but numerous drains are required to give sufficient opportunities for it to pass away, and such drains are usually formed in the furrows. Where the soil and subsoil are both porous, the water passes quickly through them, and no draining is required to assist it in flowing away, as the entire subsoil constitutes a universal drain. In this state of soil, water is only held in it by capillary attraction, and what is not so supported sinks down through the porous subsoil by its own gravity. Capillary attraction is quite capable of supporting and bringing as much water through a permeable soil and subsoil, from rain above and sources of water from below, as is useful to vegetation, excepting perhaps under the extraordinary occurrence of excessive drought; and of all the sources from which the soil derives its supplies of water, that from springs is the coldest, most injurious to useful plants, and most permanent in its effects; and hence it is that the abstraction of water from the soil by draining does not necessarily interfere with it as a supporter of plants, as a meliorator of the soil, as a menstruum for the food, and as a regulator of temperature to plants.

(851.) These states of water in the soil and subsoil indicate that a

knowledge of geology might confer a more perfect understanding of the principles of draining; and, fortunately, practice in this department of rural economy has always been consistent with the facts of geology. But a geological drainer is a character who has not yet made his appearance in the world; because no practical drainer or scientific geologist has yet explored that department of geology which is most useful to agriculture, in such a manner as to assist the art of draining. Most of our arable soils are contained within the newest rock-formations, the intricate relations of which present almost insurmountable obstacles to such a knowledge of them as to be useful in draining. The intricacy of their relations render the operations of draining uncertain; and this uncertainty, I fear, must continue to exist, until the relations of the alluvial rocks are discovered to be as unvarying as those of the more indurated. Perhaps a certainty in the matter is unattainable, because the members of the alluvial formation may not present a strictly relative position to one another. Until the fact, therefore, is ascertained one way or the other, draining must be conducted, in a great measure, by trial or experiment; and in all undertakings on trial, error must be expected to ensue, and unnecessary expense incurred. An unfortunate circumstance, arising from this uncertainty, is the comparative uselessness of the experience acquired in previous operations to guide the drainer himself and others, to the means of securing more certain results in their future efforts at draining. No drainer can affirm that the number and depth, and even the direction, of the drains which he chooses to adopt, are the best suited for drying the field he wishes to drain; nor can he maintain, that exactly similar arrangements will produce exactly similar effects in the adjoining or in any other field, at a greater or shorter distance. Every experienced drainer will coincide with the justness of these remarks, and deplore the uncertain nature of his operations; but, nevertheless, the satisfactory consolation is, that as long as he finds draining, even as it is pursued, do good, so long he will continue to practise it. Were geologists to make themselves acquainted with the practical details of draining, and then study that branch of geology which would be of greatest service to draining, it is reasonable to hope that they would confer lasting obligations on the drainer, not only by directing him to a well-grounded certainty in his object, but by shewing him how to execute his art with greater simplicity. Were they also to direct particular attention to the relation that subsists, if any, between the surface of the earth's crust and the strata immediately subjacent, their investigations might supply valuable materials for a correct nomenclature and classification of soils.

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