necessity of being formed at different distances, to the very bottom of the declivity: these being afterwards in a great measure filled with loose stones, merely conveyed away portions of surface water, without touching the spring, the great or principal cause of the wetness. The effects of drains formed in this manner he asserts to be, that of rendering the surface of the land in some degree drier, so long as they continue to run with freedom; but as they are liable soon to be obstructed and filled up by sand or other materials, the water is often forced out in different places and directions, and thus renders the land equally wet, if not more so, than it was before. In addition to this, it is a more difficult task to drain the ground a second time in a proper method, from the natural appearance of the ground being so much changed, and the bursts of the old drains, as well as the greater difficulty of ascertaining the real situation of the springs.

3932. It may sometimes happen, however, that where the highest are the strongest outlets, they may be the main or leading springs; those which show themselves lower down in the land being merely formed by the water of the main spring overflowing, and. finding itself a passage from an opening, or the porous nature of the materials of the soil near to the surface, and from being obstructed somewhat further down in the ground by some impervious stratum. This circumstance must, therefore, it is observed, be fully ascertained before the lines for the ditches or drains are marked out.

486

3933. In cases where the banks or rising grounds are formed in an irregular manner (fig. 486.), and from the nature of the situation, or the force of the water underneath, springs abound round the bases of the protuberances, the ditches made for the purpose of draining should always be carried up to a much higher level in the side of the elevated ground than that in which the water or wetness appears; as far even as to the firm unchanged land. By this means the water of the spring may be cut off, and the ground completely drained; which would not be the case if the trench or drain were formed on the line of the loose materials lower down where the water oozes out, which is liable to mislead the operator in forming the conducting trench, or that which is

to convey the water from the cross-drain on the level of the spring to the outlet or opening by which it is discharged. But where the main or principal spring comes out of a perpendicular or very steep bank, at a great height above the level of the outlet into which it may discharge itself by means of a drain; it will neither be necessary nor of any utility to form a deep trench, or make a covered drain, all the way from such outlet up to it; as from the steepness of the descent the water would be liable, when the drain was thus cut, from the thin strata of sand, and other loose materials, always found in such cases, to insinuate itself under the bricks, stones, or other substances of which the drain was formed; to undermine and force them up by the strength of the current, or, probably, in some instances, block the drain up by the loose sand or other matters, which may be forced away and carried down by it. In situations of this kind, Johnston observes, it is always the best way to begin just so far down the bank or declivity as, by cutting in a level, the drain may be six or seven fect below the level of the spring; or of such a depth as may be requisite to bring down the water to a level suitable to convey it away without its rising to the surface, and injuring the lands around it. The rest of the drain, whether it be made in a straight or oblique direction, need not be deep, and may, in many instances, be left quite open; it should, however, be carefully secured from the treading of cattle, and, where the land is under an arable system of cultivation, also from the plough. Where it is covered, the depth of about two feet may be sufficient. There will not, in such drains, be any necessity fo the use of the auger in any part of them.

3934. Where there is a difficulty in ascertaining the line of the spring, and consequently that of the cross drain, either from its not showing itself on the surface, or from there not being any apparent outlet, it may, generally, be met with in carrying up the conducting drain for conveying away the water: as soon as the operator discovers the spring, he need not proceed any further, but form the cross drain on the level thus discovered to such a distance on each side of the tail, or terminating part of the strata, of whatever sort, that contains the water, as the nature of the land, in regard to situation or other circumstances, may demand. Where, in forming a cross-drain, the line indicated by the spirit or

other level is found to be in some places below that of the spring, and where, in boring in this direction, water is not found to follow, it will be necessary to make short drains or cuts of the same depth with the cross-drain, from it quite up to the source of the spring; for, if the drain be cut below the line of the spring, the possibility of reaching it by means of an auger is lost, as where the under stratum is clay, and there is no under water, the use of the auger cannot be effectual; and if it be made above the line of the spring, it will be requisite to cut and bore much deeper, in order to reach it, the ground being in general higher in that part: besides, the portion of porous stratum below the drain may contain a sufficient quantity of water to render the land wet, and that may readily get down underneath the trench, between the holes formed by boring, and break out lower down. 3935. In situations where the extent of bog in the valley between two banks or eminences is so narrow and limited as that the stratum of rock, sand, or other materials that contains the water, may unite below the clay at such a depth as to be readily reached by the auger (fig. 487 a), it will seldom be necessary to have more than one trench up the middle,

well perforated with holes (b) by means of the auger; cross or branching drains being unnecessary in such cases. For notwithstanding the springs, that render the land injuriously wet in these cases, burst out of the banks or eminences on every side, for the most part nearly on the same level, the reservoir from which they proceed may be discovered in the middle of the valley, by penetrating with the auger through the layer of clay, that confines and forces the water to rise up and ooze out round the superior edge of it, where it forms an union with the high porous ground. From the drain being made in the hollowest part of the land, and the porous stratum containing the water being then bored into, it is obvious that the ditch or drain thus formed being so much lower than the ordinary outlet of the springs, the pressure of water above that level, which is the bottom of the drain, must be such as to force that which is under the drain or trench through the holes made by the auger, and in many instances, until a considerable quantity of the water is evacuated, make it rise to a greater height than the level of its natural outlet. The effect of which must be, that the water forming the spring, having found by these means a fresh and more easy passage, will quickly relinquish its former openings, and thus be prevented from running over and injuring the ground, that previously lay lower down than it.

3936. But in swamps or bogs that are extensive and very wet, other drains or cuts than such as convey off the springs must be made; as, notwithstanding the higher springs which chiefly cause the wetness may be intercepted, there may be lower veins of sand, gravel, or other porous materials, from which the water must likewise be drawn off. In cases of this nature, where the land is to be divided into enclosures, the ditches may be formed in such directions as to pass through and carry off collections of water of this kind, as well as those that may be retained in the hollows and depressions on the surface of the land. There are in many places very extensive tracts of ground that are rendered wet, and become full of rushes and other coarse plants, from causes of such a nature as cannot be obviated by the making of either open or covered drains, however numerous they may be. Lands in this situation are frequently termed holms, and mostly lie on the sides of such rivers and brooks as, from the frequency of their changing and altering their courses between their opposite banks, leave depositions of sand, gravel, and other porous materials, by which land is formed, that readily admits the water to filtrate and pass through it to the level of the last-formed channels, and which preserves it constantly in such a state of moisture and wetness, as to render it productive of nothing but rushes and other aquatic plants; and if a pit or ditch be made in lands under these circumstances, it quickly fills with water to the same level as that in the watercourse. This effect is, however, more liable to be produced, as well as more complete, where the current of the

water is slow, and its surface nearly equal with that of the land, than where its descent is rapid. Under such circumstances, while the river or brook remains at the ordinary height, no advantage can be gained, whatever number of drains be formed, or in whatever direction they may be made. The chief or only means of removing the wetness of land proceeding from this cause is, that of enlarging and sinking the bed of the stream, where it can be effected at a reasonable expense: where there is only one stream, and it is very winding or serpentine in its course, much may however be effected by cutting through the different points of land, and rendering the course more straight, and thereby less liable to obstruct the passage of the water. But in cases where there are more than one, that should always be made the channel of conveyance for draining the neighboring land, which is the lowest in respect to situation and the most open and straight in its course. It may likewise, in particular instances, be advantageous to stop up and divert the waters of the others into such main channels, as by such means alone they may often be rendered deeper, and more free from obstruction: the materials removed from them may serve to embank and raise up the sides to a greater height, as while the water can rise higher than the outlets of the drains, and flow backwards into them, it must render the land as wet as it was before they were formed, and the expense of cutting them be thrown away.

3937. The collected rain-water becoming stagnant on a retentive body of clay, or some other impervious material, as it can have no outlet of the natural kind, causes such lands to become soft and spongy, thus forming bogs of a very confined kind. As such bogs

are often situated very greatly below the ground that surrounds them, the opening of a main drain, or conductor, to convey off the water collected by smaller drains, would be attended, in many instances, with an expense greater than could be compensated by the land after it had been drained. The thickness of the impervious stratum that retains and keeps up the water in such cases is often so great, that though the stratum below be of a porous and open nature, such as sand, rock, or gravel, the water cannot of itself penetrate or find a passage from the one into the other; consequently, by its continued stagnation above, all the different coarse vegetable productions that have for a great length of time been produced on its surface, and probably the upper part of the soil itself, are formed into a mass or body of peat earth, equally soft and less productive than that of any bog originating from water confined below, and which is only capable of sustaining the weight of cattle in very dry seasons, when the wind and sun have exhaled and dried up a great part of its surface moisture; but even then it is incapable of admitting the plough upon it.

3938. As the cause of these kinds of bogs is materially different from that of those which have been already noticed, their drainage must of course be accomplished in a different way. The following method of proceeding is recommended as perhaps the least expensive. In the middle, or most depending part of the ground, the first drain (fig. 488 a), may be cut, into which all the others should be made to lead; the number and direction of which must be regulated by the extent of the bog. They should be cut through the peat, or moist spongy upper soil, to the surface of the clay, or other retentive stratum of materials, which must then be perforated or bored through in order to let the water down into the pervious stratum below, by which it may be absorbed and taken up. The same effect might be produced by forming one. large well, or pit, in the middle or lowest part of the bog, by digging through into

the porous stratum below, and connecting the other drains with it, as by such a method the trouble and expense of boring along the drains would be saved. In these cases, when drains are made, they should always be cut as narrow as it is possible to make them, and after the holes have been formed in them by boring, filled up with loose stones to within about a foot and a half of the surface, which space may be made up by a portion of the earth that had been taken out, putting in turf with the green side to the stones before the earth is thrown in. By this means the water and prejudicial moisture of the peat, or upper soil, may be taken away by the drains, and pass off through the holes that have been formed in their bottoms. But where pits are employed, these should only be filled with small stones to the level of the bottom of the drain, the filling being performed as soon as possible after they are formed (Anderson's Treatise on Draining, p. 88.); where there is a chalky stratum below, after taking it out, the flints contained in it may be made use of in this way with much advantage; and where the drains can be carried into quarries, where the stone is much fissured, nothing more will be ne cessary. Where land of this sort is afterwards to be ploughed, great attention should be

given to the forming of the ridges and giving them a regular descent towards themain drain, which will contribute greatly to the assistance of the others in conveying off heavy falls of rain-water when they occur.

3939. But a necessary precaution previous to any attempt to drain lands of this kind in the way that has been described, is to ascertain whether the porous stratum under the clay be dry, and capable of receiving the water when let down into it; or already so loaded with moisture itself, as, instead of receiving more from above, to force up a large quantity to the surface, and thus increase the evil it was intended to remove. This may be the case in many instances, and the substratum contain water which affords no appearances of wetness on the surface, at the place, on account of the compact body of clay that is placed over it, but which, from its being connected with some spring that is higher, may flow up when an opening or passage is given it, either by means of a pit or the auger. In this way a greater quantity of water might be brought to the surface, which, from its being confined by the surrounding banks, would render the ground much more wet than before, and in particular situations produce very great degrees of wetness. When the surrounding high ground declines lower than the bog, though it may be at a considerable distance, by the aid of the level, and the appearance of the surface, the nature of the stratum underneath may, in some degree, be ascertained; and, notwithstanding it may already contain water, a drain may be formed into it to carry off that water, and what may likewise be let down into it from the retentive stratum that lies above it. It must be confessed, however, that cases where surface water can be let down through a retentive stratum to a porous one that will actually carry it off, are very rare. When these occur, it is chiefly in limestone or coaly districts, where the surface is hilly or rugged (fig. 489.), and more calculated for the pursuits of the mineralogist than the agricultor.

3940. Draining hilly lands is not in general attended with great expense, as the drains need seldom be covered or filled up, only in such places as may be sufficient for passages for the animals to cross by. And though, where the depth of the trench does not come to the water confined below, it may be necessary to perforate lower, there need not be any fear that the holes will fill up, even where the drain is left open; as the impetuosity of the water itself, will remove any sand or mud that may fall into them, where much flood or surface water does not get in. Small openings may, however, be made along the upper

side of the trench, in order the more effectually to secure them against any obstructions; and in these the perforations may be made, leaving the mouth of the holes about six inches higher than the bottom of the drain, which will be without the reach of the water that may be collected during the time of heavy rains.

3941. The sides or declivities of many hills, from the irregularity of the disposition of the strata that compose them, are often covered with alternate portions or patches of wet and dry ground. By the general appearance of the surface and the vegetable products that are grown upon it, the nature and direction of the internal strata may frequently be ascertained with so much certainty as to determine the line or direction of a drain without the necessity of examining below the surface of the land. As the ease or difficulty of draining such grounds depends solely on the position of the different strata of which the hill or elevation may be formed, and upon the erect or slanting direction of the rock, or other retentive body in which the water is contained; where the rock has a slanting or horizontal inclination, the whole of the different springs or outlets, that show themselves on the surface, may originate from or be connected with the same collection or body of water, and may be all drained and dried up by cutting off, or letting out, the main body of water, by which they are supplied, at the inferior part of the reservoir, or that part where the water would of its own accord readily run off if it were not confined beneath an impervious covering of clay or some other material.

3942. But in cases where the rock lies in an erect or perpendicular form, and contains only partial collections of water, in some of the more open cracks or fissures of the stone, that discharge themselves at various openings, or outlets, that have not the least connection with each other, it would be an idle and fruitless endeavor to attempt the cutting of them off by means of one drain (fig. 490 a), or by boring into any one of them in particular, without cutting a drain into each (a, b, c). In this case it is more advisable to make the main drain wholly in the clay, with small cuts made up to each outlet, than along the place where the springs burst out; as in that line of direction it would be too greatly in

490

the rock, and consequently be extremely difficult to cut, on account of the nature and disposition of the stone: when the water passing out on the line of the springs can be found by the auger in the main drain, at the point where it joins it, it will, it is

observed, be the more completely cut off; but where this is not practicable, the depth of the small cuts may reduce it to such a level as will prevent its flowing over and injuring the surface of the land below it.

3943. In such hills as are constituted of alternate strata of rock, sand, and clay, the surface of the latter may frequently be wet and swamp, while that of the former is dry, and capable of producing good crops of grass; in all such cases, in order to drain the land completely, as many cuts will be necessary as there may happen divisions of wet and dry soil: the summit, or most elevated part of such hills, being mostly formed of loose porous materials, through which the rain and other water descends, till its passage becomes obstructed by some impervious bed or stratum, such as clay, when it is forced up to the surface, and runs or oozes over the obstructing stratum; and after having overflowed, the upper clay surface is immediately absorbed and taken up by the succeeding porous one, and, sinking into it in the same way as before, passes out again at the lower side of it, and renders the surface of the next clayey bed prejudicially wet as it had done in the first. In this way the same spring may affect all the other strata of the same kind of which the hill consists, from the highest part down the whole of the declivity, and produce in the bason, or hollow at the bottom, a lake or bog, should there not happen to be a passage or opening to take away the water. In order effectually to drain hills of this kind, it will be the most advisable to begin by forming a trench along the upper side of the uppermost rushy soil, by which means the highest spring may be cut off; but as the rain and other water that may come upon the next portion of porous soil may sink down through it to the lowest part, and produce another spring, a second cut must be made in that part to prevent the water from affecting the surface of the succeeding clayey bed. And similar cuts must be formed so far down the declivity as the same springs continue in the same way to injure the land, and in some cases a sufficiency of water may probably be obtained to irrigate the land below, or some other useful purpose.

SECT. III. Of the Methods of draining Mixed Soils.

3944. Where the soil is of a mixed and varied nature, but the most prevailing parts of the clayey kind, the business of draining is considerably more tedious and difficult than where the superficial and internal parts have greater regularity. In such sorts of lands, as all the different collections of water are perfectly distinct from each other, by means of the beds of clay that separate them, each collection becomes so much increased, or accumulated, in the time of heavy rains, that they are filled quite to the level of the surface of the clay by which they are surrounded; when the water getting a free passage, as it would over the edges of a bowl or dish, overflows and saturates the surface of that bed of clay in such a manner, as to render it so perfectly wet and sour, that its produce becomes not only annually more and more scanty, but the soil itself more sterile and unproductive.

3945. From the sand-beds (fig. 491 a, a, a) in such cases having no communication with each other, it must evidently require as many drains (b, b, b) as there are beds of this kind, in order fully to draw off

the water from each of them. A drain or trench is therefore recommended to be cut from the nearest and lowest part of the field intended to be drained (c), up to the highest and most distant sand-bank (d), in such a line of direction as, if possible, to pass through some of the intermediate sand-beds, and

prevent the labor and expense of making longer cuts on the sides, which would otherwise be requisite.

3946. Where the different beds of sand and clay are of less extent, and lie together with greater regularity, they can be drained in a more easy manner with less cutting, and of course at less expense. Below the layers or beds of sand and clay that lie, in this manner, alternately together, and nearly parallel to each other, is generally a body