In most cases, it will be sufficient to have contour lines taken only at intervals of two feet, and, owing to the smallness of the scale on which these maps are engraved, and to avoid complication in the finished plan, where so much else must be shown, each alternate line is omitted. Of course, where drains are at once staked out on the land, by a practiced engineer, no contour lines are taken, as by the aid of the level and rod for the flatter portions, and by the eye alone for the steeper slopes, he will be able at once to strike the proper locations and directions; but for one of less experience, who desires to thoroughly mature his plan before commencing, they are indispensable; and their introduction here will enable the novice to understand, more clearly than would otherwise be possible, the principles on which the plan should be made.



Fig. 9 - WELL'S CLINOMETER.

For preliminary examinations, and for all purposes in which great accuracy is not required, the little instrument shown in Fig. 9,—"Wells' Clinometer,"—is exceedingly simple and convenient. Its essential parts are a flat side, or base, on which it stands, and a hollow disk just half filled with some heavy liquid. The glass face of the disk is surrounded by a graduated scale that marks the angle at which the surface of the liquid stands, with reference to the flat base. The line 0.——0. being parallel to the base, when the liquid stands on that line, the flat side is horizontal; the line 90.——90. being perpendicular to the base, when the liquid stands on that line, the flat side is perpendicular or plumb. In like manner, the intervening angles are marked, and, by the aid of the following tables, the instrument indicates the rate of fall per hundred feet of horizontal measurement, and per hundred feet measured upon the sloping line.(6)

Table No. 1 shows the rise of the slope for 100 feet of the horizontal measurement. Example: If the horizontal distance is 100 feet, and the slope is at an angle of 15 deg., the rise will be 17-633/1000 feet.

Table No. 2 shows the rise of the slope for 100 feet of its own length. If the sloping line, (at an angle of 15 deg.,) is 100 feet long, it rises 25.882 feet.

TABLE No. 1. DEG. FEET. 5 8.749 10 17.663 15 26.795 20 36.397 25 46.631 30 57.735 35 70.021 40 83.910 45 100.— 50 119.175 55 142.815 60 173.205 65 214.451 70 274.748 75 373.205 80 567.128 85 1143.01

TABLE No. 2 DEG. FEET. 5 8.716 10 17.365 15 25.882 20 34.202 25 42.262 30 50.— 35 57.358 40 64.279 45 70.711 50 76.604 55 81.915 60 86.602 65 90.631 70 93.969 75 96.593 80 98.481 85 99.619

With the maps before him, showing the surface features of the field, and the position of the under-ground rock, the drainer will have to consider the following points:

1. Where, and at what depth, shall the outlet be placed?

2. What shall be the location, the length and the depth of the main drain?

3. What subsidiary mains,—or collecting drains,—shall connect the minor valleys with the main?

4. What may best be done to collect the water of large springs and carry it away?

5. What provision is necessary to collect the water that flows over the surface of out-cropping rock, or along springy lines on side hills or under banks?

6. What should be the depth, the distance apart, the direction, and the rate of fall, of the lateral drains?

7. What kind and sizes of tile should be used to form the conduits?

8. What provision should be made to prevent the obstruction of the drains, by an accumulation of silt or sand, which may enter the tiles immediately after they are laid, and before the earth becomes compacted about them; and from the entrance of vermin?

1. The outlet should be at the lowest point of the boundary, unless, (for some especial reason which does not exist in the case under consideration, nor in any usual case,) it is necessary to seek some other than the natural outfall; and it should be deep enough to take the water of the main drain, and laid on a sufficient inclination for a free flow of the water. It should, where sufficient fall can be obtained without too great cost, deliver this water over a step of at least a few inches in height, so that the action of the drain may be seen, and so that it may not be liable to be clogged by the accumulation of silt, (or mud,) in the open ditch into which it flows.

2. The main drain should, usually, be run as nearly in the lowest part of the principal valley as is consistent with tolerable straightness. It is better to cut across the point of a hill, to the extent of increasing the depth for a few rods, than to go a long distance out of the direct course to keep in the valley, both because of the cost of the large tile used in the main, and of the loss of fall occasioned by the lengthening of the line. The main should be continued from the outlet to the point at which it is most convenient to collect the more remote sub-mains, which bring together the water of several sets of laterals. As is the case in the tract under consideration, the depth of the main is often restricted, in nearly level land, toward the upper end of the flat which lies next to the outlet, by the necessity for a fall and the difficulty which often exists in securing a sufficiently low outlet. In such case, the only rule is to make it as deep as possible. When the fall is sufficient, it should be placed at such depth as will allow the laterals and sub-mains which discharge into it to enter at its top, and discharge above the level of the water which flows through it.



Fig. 10 - STONE PIT TO CONNECT SPRING WITH DRAIN.

3. Subsidiary mains, or sub-mains, connecting with the main drains, should be run up the minor valleys of the land, skirting the bases of the hills. Where the valley is a flat one, with rising ground at each side, there should be a sub-main, to receive the laterals from each hill side. As a general rule, it may be stated, that the collecting drain at the foot of a slope should be placed on the line which is first reached by the water flowing directly down over its surface, before it commences its lateral movement down the valley; and it should, if possible, be so arranged that it shall have a uniform descent for its whole distance. The proper arrangement of these collecting drains requires more skill and experience than any other branch of the work, for on their disposition depends, in a great measure, the economy and success of the undertaking.

4. Where springs exist, there should be some provision made for collecting their water in pits filled with loose stone, gravel, brush or other rubbish, or furnished with several lengths of tile set on end, one above the other, or with a barrel or other vessel; and a line of tile of proper size should be run directly to a main, or sub-main drain. The manner of doing this by means of a pit filled with stone is shown in Fig. 10. The collection of spring water in a vertical tile basin is shown in Fig. 11.



Fig. 11 - STONE AND TILE BASIN FOR SPRING WITH DRAIN.

5. Where a ledge of shelving rock, of considerable size, occurs on land to be drained, it is best to make some provision for collecting, at its base, the water flowing over its surface, and taking it at once into the drains, so that it may not make the land near it unduly wet. To effect this, a ditch should be dug along the base of the rock, and quite down to it, considerably deeper than the level of the proposed drainage; and this should be filled with small stones to that level, with a line of tile laid on top of the stones, a uniform bottom for the tile to rest upon being formed of cheap strips of board. The tile and stone should then be covered with inverted sods, with wood shavings, or with other suitable material, which will prevent the entrance of earth, (from the covering of the drain,) to choke them. The water, following down the surface of the rock, will rise through the stone work and, entering the tile, will flow off. This method may be used for springy hill sides.

6. The points previously considered relate only to the collection of unusual quantities of water, (from springs and from rock surfaces,) and to the removal from the land of what is thus collected, and of that which flows from the minor or lateral drains.

The lateral drains themselves constitute the real drainage of the field, for, although main lines take water from the land on each side, their action in this regard is not usually considered, in determining either their depth or their location, and they play an exceedingly small part in the more simple form of drainage,—that in which a large tract of land, of perfectly uniform slope, is drained by parallel lines of equal length, all discharging into a single main, running across the foot of the field. The land would be equally well drained, if the parallel lines were continued to an open ditch beyond its boundary,—the main tile drain is only adopted for greater convenience and security. It will simplify the question if, in treating the theory of lateral drains, it be assumed that our field is of this uniform inclination, and admits of the use of long lines of parallel drains. In fact, it is best in practice to approximate as nearly as possible to this arrangement, because deviations from it, though always necessary in broken land, are always more expensive, and present more complicated engineering problems. If all the land to be drained had a uniform fall, in a single direction, there would be but little need of engineering skill, beyond that which is required to establish the depth, fall, and distance apart, at which the drains should be laid. It is chiefly when the land pitches in different directions, and with varying inclination, that only a person skilled in the arrangement of drains, or one who will give much consideration to the subject, can effect the greatest economy by avoiding unnecessary complication, and secure the greatest efficiency by adjusting the drains to the requirements of the land.

Assuming the land to have an unbroken inclination, so as to require only parallel drains, it becomes important to know how these parallel drains, (corresponding to the lateral drains of an irregular system,) should be made.

The history of land draining is a history of the gradual progress of an improvement, from the accomplishment of a single purpose, to the accomplishment of several purposes, and most of the instruction which modern agricultural writers have given concerning it, has shown too great dependence upon the teachings of their predecessors, who considered well the single object which they sought to attain, but who had no conception that draining was to be so generally valuable as it has become. The effort, (probably an unconscious one,) to make the theories of modern thorough-draining conform to those advanced by the early practitioners, seems to have diverted attention from some more recently developed principles, which are of much importance. For example, about a hundred years ago, Joseph Elkington, of Warwickshire, discovered that, where land is made too wet by under-ground springs, a skillful tapping of these,—drawing off their water through suitable conduits,—would greatly relieve the land, and for many years the Elkington System of drainage, being a great improvement on every thing theretofore practiced, naturally occupied the attention of the agricultural world, and the Board of Agriculture appointed a Mr. Johnstone to study the process, and write a treatise on the subject.

Catch-water drains, made so as to intercept a flow of surface water, have been in use from immemorial time, and are described by the earliest writers. Before the advent of the Draining Tile, covered drains were furnished with stones, boards, brush, weeds, and various other rubbish, and their good effect, very properly, claimed the attention of all improvers of wet land. When the tile first made its appearance in general practice, it was of what is called the "horse-shoe" form, and,—imperfect though it was,—it was better than anything that had preceded it, and was received with high approval, wherever it became known. The general use of all these materials for making drains was confined to a system of partial drainage, until the publication of a pamphlet, in 1833, by Mr. Smith, of Deanston, who advocated the drainage of the whole field, without reference to springs. From this plan, but with important modifications in matters of detail, the modern system of tile draining has grown. Many able men have aided its progress, and have helped to disseminate a knowledge of its processes and its effects, yet there are few books on draining, even the most modern ones, which do not devote much attention to Elkington's discovery; to the various sorts of stone and brush drains; and to the manufacture and use of horse-shoe tile;—not treating them as matters of antiquarian interest, but repeating the instructions for their application, and allowing the reasoning on which their early use was based, to influence, often to a damaging extent, their general consideration of the modern practice of tile draining.

These processes are all of occasional use, even at this day, but they are based on no fixed rules, and are so much a matter of traditional knowledge, with all farmers, that instruction concerning them is not needed. The kind of draining which is now under consideration, has for its object the complete removal of all of the surplus water that reaches the soil, from whatever source, and the assimilation of all wet soils to a somewhat uniform condition, as to the ease with which water passes through them.

There are instances, as has been shown, where a large spring, overflowing a considerable area, or supplying the water of an annoying brook, ought to be directly connected with the under-ground drainage, and its flow neatly carried away; and, in other cases, the surface flow over large masses of rock should be given easy entrance into the tile; but, in all ordinary lands, whether swamps, springy hill sides, heavy clays, or light soils lying on retentive subsoil, all ground, in fact, which needs under-draining at all, should be laid dry above the level to which it is deemed best to place the drains;—not only secured against the wetting of springs and soakage water, but rapidly relieved of the water of heavy rains. The water table, in short, should be lowered to the proper depth, and, by permanent outlets at that depth, be prevented from ever rising, for any considerable time, to a higher level. This being accomplished, it is of no consequence to know whence the water comes, and Elkington's system need have no place in our calculations. As round pipes, with collars, are far superior to the "horse-shoe" tiles, and are equally easy to obtain, it is not necessary to consider the manner in which these latter should be used,—only to say that they ought not to be used at all.

The water which falls upon the surface is at once absorbed, settles through the ground, until it reaches a point where the soil is completely saturated, and raises the general water level. When this level reaches the floor of the drains, the water enters at the joints and is carried off. That which passes down through the land lying between the drains, bears down upon that which has already accumulated in the soil, and forces it to seek an outlet by rising into the drains.(7) For example, if a barrel, standing on end, be filled with earth which is saturated with water, and its bung be removed, the water of saturation, (that is, all which is not held by attraction in the particles of earth,) will be removed from so much of the mass as lies above the bottom of the bung-hole. If a bucket of water be now poured upon the top, it will not all run diagonally toward the opening; it will trickle down to the level of the water remaining in the barrel, and this level will rise and water will run off at the bottom of the orifice. In this manner, the water, even below the drainage level, is changed with each addition at the surface. In a barrel filled with coarse pebbles, the water of saturation would maintain a nearly level surface; if the material were more compact and retentive, a true level would be attained only after a considerable time. Toward the end of the flow, the water would stand highest at the points furthest distant from the outlet. So, in the land, after a drenching rain, the water is first removed to the full depth, near the line of the drain, and that midway between two drains settles much more slowly, meeting more resistance from below, and, for a long time, will remain some inches higher than the floor of the drain. The usual condition of the soil, (except in very dry weather,) would be somewhat as represented in the accompanying cut, (Fig. 12.)



Fig. 12 - LINE OF SATURATION BETWEEN DRAINS.

YY are the draings. The curved line b is the line of saturation, which has descended from a, and is approaching c.

To provide for this deviation of the line of saturation, in practice, drains are placed deeper than would be necessary if the water sunk at once to the level of the drain floor, the depth of the drains being increased with the increasing distance between them.

Theoretically, every drop of water which falls on a field should sink straight down to the level of the drains, and force a drop of water below that level to rise into the drain and flow off. How exactly this is true in nature cannot be known, and is not material. Drains made in pursuance of this theory will be effective for any actual condition.

The depth to which the water table should be withdrawn depends, not at all on the character of the soil, but on the requirements of the crops which are to be grown upon it, and these requirements are the same in all soils,—consequently the depth should be the same in all.

What, then, shall that depth be? The usual practice of the most experienced drainers seems to have fixed four feet as about the proper depth, and the arguments against anything less than this, as well as some reasons for supposing that to be sufficient, are so clearly stated by Mr. Gisborne that it has been deemed best to quote his own words on the subject:

"Take a flower-pot a foot deep, filled with dry soil. Place it in a saucer containing three inches of water. The first effect will be, that the water will rise through the hole in the bottom of the pot till the water which fills the interstices between the soil is on a level with the water in the saucer. This effect is by gravity. The upper surface of this water is our water-table. From it water will ascend by attraction through the whole body of soil till moisture is apparent at the surface. Put in your soil at 60 deg., a reasonable summer heat for nine inches in depth, your water at 47 deg., the seven inches' temperature of Mr. Parke's undrained bog; the attracted water will ascend at 47 deg., and will diligently occupy itself in attempting to reduce the 60 deg. soil to its own temperature. Moreover, no sooner will the soil hold water of attraction, than evaporation will begin to carry it off, and will produce the cold consequent thereon. This evaporated water will be replaced by water of attraction at 47 deg., and this double cooling process will go on till all the water in the water-table is exhausted. Supply water to the saucer as fast as it disappears, and then the process will be perpetual. The system of saucer-watering is reprobated by every intelligent gardener; it is found by experience to chill vegetation; besides which, scarcely any cultivated plant can dip its roots into stagnant water with impunity. Exactly the process which we have described in the flower-pot is constantly in operation on an undrained retentive soil; the water-table may not be within nine inches of the surface, but in very many instances it is within a foot or eighteen inches, at which level the cold surplus oozes into some ditch or other superficial outlet. At eighteen inches, attraction will, on the average of soils, act with considerable power. Here, then, you have two obnoxious principles at work, both producing cold, and the one administering to the other. The obvious remedy is, to destroy their united action; to break through their line of communication. Remove your water of attraction to such a depth that evaporation cannot act upon it, or but feebly. What is that depth? In ascertaining this point we are not altogether without data. No doubt depth diminishes the power of evaporation rapidly. Still, as water taken from a 30-inch drain is almost invariably two or three degrees colder than water taken from four feet, and as this latter is generally one or two degrees colder than water from a contiguous well several feet below, we can hardly avoid drawing the conclusion that the cold of evaporation has considerable influence at 30 inches, a much-diminished influence at four feet, and little or none below that depth. If the water-table is removed to the depth of four feet, when we have allowed 18 inches of attraction, we shall still have 30 inches of defence against evaporation; and we are inclined to believe that any prejudicial combined action of attraction and evaporation is thereby well guarded against. The facts stated seem to prove that less will not suffice.

"So much on the score of temperature; but this is not all. Do the roots of esculents wish to penetrate into the earth—at least, to the depth of some feet? We believe that they do. We are sure of the brassica tribe, of grass, and clover. All our experience and observation deny the doctrine that roots only ramble when they are stinted of food; that six inches well manured is quite enough, better than more. Ask the Jerseyman; he will show you a parsnip as thick as your thigh, and as long as your leg, and will tell you of the advantages of 14 feet of dry soil. You will hear of parsnips whose roots descend to unsearchable depths. We will not appeal to the Kentucky carrot, which was drawn out by its roots at the antipodes; but Mr. Mechi's, if we remember right, was a dozen feet or more. Three years ago, in a midland county, a field of good land, in good cultivation, and richly manured, produced a heavy crop of cabbages. In November of that year we saw that field broken into in several places, and at the depth of four feet the soil (a tenacious marl, fully stiff enough for brick-earth) was occupied by the roots of cabbage, not sparingly—not mere capillae—but fibres of the size of small pack-thread. A farmer manures a field of four or five inches of free soil reposing on a retentive clay, and sows it with wheat. It comes up, and between the kernel and the manure, it looks well for a time, but anon it sickens. An Irish child looks well for five or six years, but after that time potato-feeding, and filth, and hardship, begin to tell. You ask what is amiss with the wheat, and you are told that when its roots reach the clay, they are poisoned. This field is then thorough-drained, deep, at least four feet. It receives again from the cultivator the previous treatment; the wheat comes up well, maintains throughout a healthy aspect, and gives a good return. What has become of the poison? We have been told that the rain water filtered through the soil has taken it into solution or suspension, and has carried it off through the drains; and men who assume to be of authority put forward this as one of the advantages of draining. If we believed it, we could not advocate draining. We really should not have the face to tell our readers that water, passing through soils containing elements prejudicial to vegetation, would carry them off, but would leave those which are beneficial behind. We cannot make our water so discriminating; the general merit of water of deep drainage is, that it contains very little. Its perfection would be that it should contain nothing. We understand that experiments are in progress which have ascertained that water, charged with matters which are known to stimulate vegetation, when filtered through four feet of retentive soil, comes out pure. But to return to our wheat. In the first case, it shrinks before the cold of evaporation and the cold of water of attraction, and it sickens because its feet are never dry; it suffers the usual maladies of cold and wet. In the second case, the excess of cold by evaporation is withdrawn; the cold water of attraction is removed out of its way; the warm air from the surface, rushing in to supply the place of the water which the drains remove, and the warm summer rains, bearing down with them the temperature which they have acquired from the upper soil, carry a genial heat to its lowest roots. Health, vigorous growth, and early maturity are the natural consequences. * * * * * * * * *

"The practice so derided and maligned referring to deep draining has advanced with wonderful strides. We remember the days of 15 inches; then a step to 20; a stride to 30; and the last (and probably final) jump to 50, a few inches under or over. We have dabbled in them all, generally belonging to the deep section of the day. We have used the words 'probably final,' because the first advances were experimental, and, though they were justified by the results obtained, no one attempted to explain the principle on which benefit was derived from them. The principles on which the now prevailing depth is founded, and which we believe to be true, go far to show that we have attained all the advantages which can be derived from the removal of water in ordinary agriculture. We do not mean that, even in the most retentive soil, water would not get into drains which were laid somewhat deeper; but to this there must be a not very distant limit, because pure clay, lying below the depth at which wet and drought applied at surface would expand and contract it, would certainly part with its water very slowly. We find that, in coal mines and in deep quarries, a stratum of clay of only a few inches thick interposed between two strata of pervious stone will form an effectual bar to the passage of water; whereas, if it lay within a few feet of the surface, it would, in a season of heat and drought become as pervious as a cullender. But when we have got rid of the cold arising from the evaporation of free water, have given a range of several feet to the roots of grass and cereals, and have enabled retentive land to filter through itself all the rain which falls upon its surface, we are not, in our present state of knowledge, aware of any advantage which would arise from further lowering the surface of water in agricultural land. Smith, of Deanston, first called prominent attention to the fertilizing effects of rain filtered through land, and to evils produced by allowing it to flow off the surface. Any one will see how much more effectually this benefit will be attained, and this evil avoided, by a 4-foot than a 2-foot drainage. The latter can only prepare two feet of soil for the reception and retention of rain, which two feet, being saturated, will reject more, and the surplus must run off the surface, carrying whatever it can find with it. A 4-foot drainage will be constantly tending to have four feet of soil ready for the reception of rain, and it will take much more rain to saturate four feet than two. Moreover, as a gimlet-hole bored four feet from the surface of a barrel filled with water will discharge much more in a given time than a similar hole bored at the depth of two feet, so will a 4-foot drain discharge in a given time much more water than a drain of two feet. One is acted on by a 4-foot, and the other by a 2-foot pressure."

If any single fact connected with tile-drainage is established, beyond all possible doubt, it is that in the stiffest clay soils ever cultivated, drains four feet deep will act effectually; the water will find its way to them, more and more freely and completely, as the drying of successive years, and the penetration and decay of the roots of successive crops, modify the character of the land, and they will eventually be practically so porous that,—so far as the ease of drainage is concerned,—no distinction need, in practice, be made between them and the less retentive loams. For a few years, the line of saturation between the drains, as shown in Fig. 11, may stand at all seasons considerably above the level of the bottom of the tile, but it will recede year by year, until it will be practically level, except immediately after rains.

Mr. Josiah Parkes recommends drains to be laid

"At a minimum depth of four feet, designed with the two-fold object of not only freeing the active soil from stagnant and injurious water, but of converting the water falling on the surface into an agent for fertilizing; no drainage being deemed efficient that did not both remove the water falling on the surface, and 'keep down the subterranean water at a depth exceeding the power of capillary attraction to elevate it near the surface.'"

Alderman Mechi says:

"Ask nineteen farmers out of twenty, who hold strong clay land, and they will tell you it is of no use placing deep four-foot drains in such soils—the water cannot get in; a horse's foot-hole (without an opening under it) will hold water like a basin; and so on. Well, five minutes after, you tell the same farmers you propose digging a cellar, well bricked, six or eight feet deep; what is their remark? 'Oh! it's of no use your making an underground cellar in our soil, you can't keep the water OUT!' Was there ever such an illustration of prejudice as this? What is a drain pipe but a small cellar full of air? Then, again, common sense tells us, you can't keep a light fluid under a heavy one. You might as well try to keep a cork under water, as to try and keep air under water. 'Oh! but then our soil isn't porous.' If not, how can it hold water so readily? I am led to these observations by the strong controversy I am having with some Essex folks, who protest that I am mad, or foolish, for placing 1-inch pipes, at four-foot depth, in strong clays. It is in vain I refer to the numerous proofs of my soundness, brought forward by Mr. Parkes, engineer to the Royal Agricultural Society, and confirmed by Mr. Pusey. They still dispute it. It is in vain I tell them I cannot keep the rainwater out of socketed pipes, twelve feet deep, that convey a spring to my farm yard. Let us try and convince this large class of doubters; for it is of national importance. Four feet of good porous clay would afford a far better meal to some strong bean, or other tap roots, than the usual six inches; and a saving of $4 to $5 per acre, in drainage, is no trifle.

"The shallow, or non-drainers, assume that tenacious subsoils are impervious or non-absorbent. This is entirely an erroneous assumption. If soils were impervious, how could they get wet?

"I assert, and pledge my agricultural reputation for the fact, that there are no earths or clays in this kingdom, be they ever so tenacious, that will not readily receive, filter, and transmit rain water to drains placed five or more feet deep.

"A neighbor of mine drained twenty inches deep in strong clay; the ground cracked widely; the contraction destroyed the tiles, and the rains washed the surface soils into the cracks and choked the drains. He has since abandoned shallow draining.

"When I first began draining, I allowed myself to be overruled by my obstinate man, Pearson, who insisted that, for top water, two feet was a sufficient depth in a veiny soil. I allowed him to try the experiment on two small fields; the result was, that nothing prospered; and I am redraining those fields at one-half the cost, five and six feet deep, at intervals of 70 and 80 feet.

"I found iron-sand rocks, strong clay, silt, iron, etc., and an enormous quantity of water, all below the 2-foot drains. This accounted at once for the sudden check the crops always met with in May, when they wanted to send their roots down, but could not, without going into stagnant water."

"There can be no doubt that it is the depth of the drain which regulates the escape of the surface water in a given time; regard being had, as respects extreme distances, to the nature of the soil, and a due capacity of the pipe. The deeper the drain, even in the strongest soils, the quicker the water escapes. This is an astounding but certain fact.

"That deep and distant drains, where a sufficient fall can be obtained, are by far the most profitable, by affording to the roots of the plants a greater range for food."

Of course, where the soil is underlaid by rock, less than four feet from the surface; and where an outlet at that depth cannot be obtained, we must, per force, drain less deeply, but where there exists no such obstacle, drains should be laid at a general depth of four-feet,—general, not uniform, because the drain should have a uniform inclination, which the surface of the land rarely has.

*The Distance between the Drains.*—Concerning this, there is less unanimity of opinion among engineers, than prevails with regard to the question of depth.

In tolerably porous soils, it is generally conceded that 40 or even 50 feet is sufficiently near for 4-foot drains, but, for the more retentive clays, all distances from 18 feet to 50 feet are recommended, though those who belong to the more narrow school are, as a rule, extending the limit, as they see, in practice, the complete manner in which drains at wider intervals perform their work. A careful consideration of the experience of the past twenty years, and of the arguments of writers on drainage, leads to the belief that there are few soils, which need draining at all, on which it will be safe to place 4-foot drains at much wider intervals than 40 feet. In the lighter loams there are many instances of the successful application of Professor Mapes' rule, that "3-foot drains should be placed 20 feet apart, and for each additional foot in depth the distance may be doubled; for instance, 4-foot drains should be 40 feet apart, and 5-foot drains 80 feet apart." But, with reference to the greater distance, (80 feet,) it is not to be recommended in stiff clays, for any depth of drain. Where it is necessary, by reason of insufficient fall, or of underground rock, to go only three feet deep, the drains should be as near together as 20 feet.

At first thought, it may seem akin to quackery to recommend a uniform depth and distance, without reference to the character of the land to be drained; and it is unquestionably true that an exact adaptation of the work to the varying requirements of different soils would be beneficial, though no system can be adopted which will make clay drain as freely as sand. The fact is, that the adjustment of the distances between drains is very far from partaking of the nature of an exact science, and there is really very little known, by any one, of the principles on which it should be based, or of the manner in which the bearing of those principles, in any particular case, is affected by several circumstances which vary with each change of soil, inclination and exposure.

In the essays on drainage which have been thus far published, there is a vagueness in the arguments on this branch of the subject, which betrays a want of definite conviction in the minds of the writers; and which tends quite as much to muddle as to enlighten the ideas of the reader. In so far as the directions are given, whether fortified by argument or not, they are clearly empirical, and are usually very much qualified by considerations which weigh with unequal force in different cases.

In laying out work, any skillful drainer will be guided, in deciding the distance between the lines, by a judgment which has grown out of his former experience; and which will enable him to adapt the work, measurably, to the requirements of the particular soil under consideration; but he would probably find it impossible to so state the reasons for his decision, that they would be of any general value to others.

Probably it will be a long time before rules on this subject, based on well sustained theory, can be laid down with distinctness, and, in the mean time, we must be guided by the results of practice, and must confine ourselves to a distance which repeated trial, in various soils, has proven to be safe for all agricultural land. In the drainage of the Central Park, after a mature consideration of all that had been published on the subject, and of a considerable previous observation and experience, it was decided to adopt a general depth of four feet, and to adhere as closely as possible to a uniform distance of forty feet. No instance was known of a failure to produce good results by draining at that distance, and several cases were recalled where drains at fifty and sixty feet had proved so inefficient that intermediate lines became necessary. After from seven to ten years' trial, the Central Park drainage, by its results, has shown that,—although some of the land is of a very retentive character,—this distance is not too great; and it is adopted here for recommendation to all who have no especial reason for supposing that greater distances will be fully effective in their more porous soils.

As has been before stated, drains at that distance, (or at any distance,) will not remove all of the water of saturation from heavy clays so rapidly as from more porous soil; but, although, in some cases, the drainage may be insufficient during the first year, and not absolutely perfect during the second and third years, the increased porosity which drainage causes, (as the summer droughts make fissures in the earth, as decayed roots and other organic deposits make these fissures permanent, and as chemical action in the aerated soil changes its character,) will finally bring clay soils to as perfect a condition as they are capable of attaining, and will invariably render them excellent for cultivation.

*The Direction of the Laterals* should be right up and down the slope of the land, in the line of steepest descent. For a long time after the general adoption of thorough-draining, there was much discussion of this subject, and much variation in practice. The influence of the old rules for making surface or "catch-water" drains lasted for a long time, and there was a general tendency to make tile drains follow the same directions. An important requirement of these was that they should not take so steep an inclination as to have their bottoms cut out and their banks undermined by the rapid flow of water, and that they should arrest and carry away the water flowing down over the surface of hill sides. The arguments for the line of steepest descent were, however, so clear, and drains laid on that line were so universally successful in practice, that it was long ago adopted by all,—save those novices who preferred to gain their education in draining in the expensive school of their own experience.

The more important reasons why this direction is the best are the following: First, it is the quickest way to get the water off. Its natural tendency is to run straight down the hill, and nothing is gained by diverting it from this course. Second, if the drain runs obliquely down the hill, the water will be likely to run out at the joints of the tile and wet the ground below it; even if it do not, mainly, run past the drain from above into the land below, instead of being forced into the tile. Third, a drain lying obliquely across a hillside will not be able to draw the water from below up the hill toward it, and the water of nearly the whole interval will have to seek its outlet through the drain below it. Fourth, drains running directly down the hill will tap any porous water bearing strata, which may crop out, at regular intervals, and will thus prevent the spewing out of the water at the surface, as it might do if only oblique drains ran for a long distance just above or just below them. Very steep, and very springy hill sides, sometimes require very frequent drains to catch the water which has a tendency to flow to the surface; this, however, rarely occurs.

In laying out a plan for draining land of a broken surface, which inclines in different directions, it is impossible to make the drains follow the line of steepest descent, and at the same time to have them all parallel, and at uniform distances. In all such cases a compromise must be made between the two requirements. The more nearly the parallel arrangement can be preserved, the less costly will the work be, while the more nearly we follow the steepest slope of the ground, the more efficient will each drain be. No rule for this adjustment can be given, but a careful study of the plan of the ground, and of its contour lines, will aid in its determination. On all irregular ground it requires great skill to secure the greatest efficiency consistent with economy.

The fall required in well made tile drains is very much less than would be supposed, by an inexperienced person, to be necessary. Wherever practicable, without too great cost, it is desirable to have a fall of one foot in one hundred feet, but more than this in ordinary work is not especially to be sought, although there is, of course, no objection to very much greater inclination.

One half of that amount of fall, or six inches in one hundred feet, is quite sufficient, if the execution of the work is carefully attended to.

The least rate of fall which it is prudent to give to a drain, in using ordinary tiles, is 2.5 in 1,000, or three inches in one hundred feet, and even this requires very careful work.(8) A fall of six inches in one hundred feet is recommended whenever it can be easily obtained—not as being more effective, but as requiring less precision, and consequently less expense.

*Kinds and Sizes of Tiles.*—Agricultural drain-tiles are made of clay similar to that which is used for brick. When burned, they are from twelve inches to fourteen inches long, with an interior diameter of from one to eight inches, and with a thickness of wall, (depending on the strength of the clay, and the size of the bore,) of from one-quarter of an inch to more than an inch. They are porous, to the extent of absorbing a certain amount of water, but their porosity has nothing to do with their use for drainage,—for this purpose they might as well be of glass. The water enters them, not through their walls, but at their joints, which cannot be made so tight that they will not admit the very small amount of water that will need to enter at each space. Gisborne says:

"If an acre of land be intersected with parallel drains twelve yards apart, and if on that acre should fall the very unusual quantity of one inch of rain in twelve hours, in order that every drop of this rain may be discharged by the drains in forty-eight hours from the commencement of the rain—(and in a less period that quantity neither will, not is it desirable that it should, filter through an agricultural soil)—the interval between two pipes will be called upon to pass two-thirds of a tablespoonful of water per minute, and no more. Inch pipes, lying at a small inclination, and running only half-full, will discharge more than double this quantity of water in forty-eight hours."

Tiles may be made of any desired form of section,—the usual forms are the "horse-shoe," the "sole," the "double-sole," and the "round." The latter may be used with collars, and they constitute the "pipes and collars," frequently referred to in English books on drainage.



Fig. 13 - HORSE-SHOE TILE.

Horse-shoe tiles, Fig. 13, are condemned by all modern engineers. Mr. Gisborne disposes of them by an argument of some length, the quotation of which in these pages is probably advisable, because they form so much better conduits than stones, and to that extent have been so successfully employed, that they are still largely used in this country by "amateurs."

"We shall shock some and surprise many of our readers, when we state confidently that, in average soils, and, still more, in those which are inclined to be tender, horse shoe tiles form the weakest and most failing conduit which has ever been used for a deep drain. It is so, however; and a little thought, even if we had no experience, will tell us that it must be so. A doggrel song, quite destitute of humor, informs us that tiles of this sort were used in 1760 at Grandesburg Hall, in Suffolk, by Mr. Charles Lawrence, the owner of the estate. The earliest of which we had experience were of large area and of weak form. Constant failures resulted from their use, and the cause was investigated; many of the tiles were found to be choked up with clay, and many to be broken longitudinally through the crown. For the first evil, two remedies were adopted; a sole of slate, of wood, or of its own material, was sometimes placed under the tile, but the more usual practice was to form them with club-feet. To meet the case of longitudinal fracture, the tiles were reduced in size, and very much thickened in proportion to their area. The first of these remedies was founded on an entirely mistaken, and the second on no conception at all of the cause of the evil to which they were respectively applied. The idea was, that this tile, standing on narrow feet, and pressed by the weight of the refilled soil, sank into the floor of the drain; whereas, in fact, the floor of the drain rose into the tile. Any one at all conversant with collieries is aware that when a strait work (which is a small subterranean tunnel six feet high and four feet wide or thereabouts) is driven in coal, the rising of the floor is a more usual and far more inconvenient occurrence than the falling of the roof: the weight of the two sides squeezes up the floor. We have seen it formed into a very decided arch without fracture. Exactly a similar operation takes place in the drain. No one had till recently dreamed of forming a tile drain, the bottom of which a man was not to approach personally within twenty inches or two feet. To no one had it then occurred that width at the bottom of the drain was a great evil. For the convenience of the operator the drain was formed with nearly perpendicular sides, of a width in which he could stand and work conveniently, shovel the bottom level with his ordinary spade, and lay the tiles by his hand; the result was a drain with nearly perpendicular sides, and a wide bottom. No sort of clay, particularly when softened by water standing on it or running over it, could fail to rise under such circumstances; and the deeper the drain the greater the pressure and the more certain the rising. A horse-shoe tile, which may be a tolerable secure conduit in a drain of two feet, in one of four feet becomes an almost certain failure. As to the longitudinal fracture—not only is the tile subject to be broken by one of those slips which are so troublesome in deep draining, and to which the lightly-filled material, even when the drain is completed, offers an imperfect resistance, but the constant pressure together of the sides, even when it does not produce a fracture of the soil, catches hold of the feet of the tile, and breaks it through the crown. Consider the case of a drain formed in clay when dry, the conduit a horse-shoe tile. When the clay expands with moisture, it necessarily presses on the tile and breaks it through the crown, its weakest part.(9) When the Regent's Park was first drained, large conduits were in fashion, and they were made circular by placing one horse-shoe tile upon another. It would be difficult to invent a weaker conduit. On re-drainage, innumerable instances were found in which the upper tile was broken through the crown, and had dropped into the lower. Next came the D form, tile and sole in one, and much reduced in size—a great advance; and when some skillful operator had laid this tile bottom upwards we were evidently on the eve of pipes. For the D tile a round pipe moulded with a flat-bottomed solid sole is now generally substituted, and is an improvement; but is not equal to pipes and collars, nor generally cheaper than they are."



Fig. 14 - SOLE TILE.

One chief objection to the Sole-tiles is, that, in the drying which they undergo, preparatory to the burning, the upper side is contracted, by the more rapid drying, and they often require to be trimmed off with a hatchet before they will form even tolerable joints; another is, that they cannot be laid with collars, which form a joint so perfect and so secure, that their use, in the smaller drains, should be considered indispensable.



Fig. 15 - DOUBLE-SOLE TILE.

The double-sole tiles, which can be laid either side up give a much better joint, but they are so heavy as to make the cost of transporation considerably greater. They are also open to the grave objection that they cannot be fitted with collars.

Experience, in both public and private works in this country, and the cumulative testimony of English and French engineers, have demonstrated that the only tile which it is economical to use, is the best that can be found, and that the best,—much the best—thus far invented, is the "pipe, or round tile, and collar,"—and these are unhesitatingly recommended for use in all cases. Round tiles of small sizes should not be laid without collars, as the ability to use these constitutes their chief advantage; holding them perfectly in place, preventing the rattling in of loose dirt in laying, and giving twice the space for the entrance of water at the joints. A chief advantage of the larger sizes is, that they may be laid on any side and thus made to fit closely. The usual sizes of these tiles are 1-1/4 inches, 2-1/4 inches, and 3-1/2 inches in interior diameter. Sections of the 2-1/4 inch make collars for the 1-1/4 inch, and sections of the 3-1/2 inch make collars for the 2-1/4 inch. The 3-1/2 inch size does not need collars, as it is easily secured in place, and is only used where the flow of water would be sufficient to wash out the slight quantity of foreign matters that might enter at the joints.



Fig. 16 - ROUND TILE AND COLLAR, AND THE SAME AS LAID.

*The size of tile* to be used is a question of consequence. In England, 1-inch pipes are frequently used, but 1-1/4 inch(10) are recommended for the smallest drains. Beyond this limit, the proper size to select is, the smallest that can convey the water which will ordinarily reach it after a heavy rain. The smaller the pipe, the more concentrated the flow, and, consequently, the more thoroughly obstructions will be removed, and the occasional flushing of the pipe, when it is taxed, for a few hours, to its utmost capacity, will insure a thorough cleansing. No inconvenience can result from the fact that, on rare occasions, the drain is unable, for a short time, to discharge all the water that reaches it, and if collars are used, or if the clay be well packed about the pipes, there need be no fear of the tile being displaced by the pressure. An idea of the drying capacity of a 1-1/4-inch tile may be gained from observing its wetting capacity, by connecting a pipe of this size with a sufficient body of water, at its surface, and discharging, over a level dry field, all the water which it will carry. A 1-1/4-inch pipe will remove all the water which would fall on an acre of land in a very heavy rain, in 24 hours,—much less time than the water would occupy in getting to the tile, in any soil which required draining; and tiles of this size are ample for the draining of two acres. In like manner, 2-1/2-inch tile will suffice for eight, and 3-1/2-inch tile for twenty acres. The foregoing estimates are, of course, made on the supposition that only the water which falls on the land, (storm water,) is to be removed. For main drains, when greater capacity is required, two tiles may be laid, (side by side,) or in such cases the larger sizes of sole tiles may be used, being somewhat cheaper. Where the drains are laid 40 feet apart, about 1,000 tiles per acre will be required, and, in estimating the quantity of tiles of the different sizes to be purchased, reference should be had to the following figures; the first 2,000 feet of drains require a collecting drain of 2-1/4-inch tile, which will take the water from 7,000 feet; and for the outlet of from 7,000 to 20,000 feet 3-1/2-inch tile may be used. Collars, being more subject to breakage, should be ordered in somewhat larger quantities.

Of course, such guessing at what is required, which is especially uncertain if the surface of the ground is so irregular as to require much deviation from regular parallel lines, is obviated by the careful preparation of a plan of the work, which enables us to measure, beforehand, the length of drain requiring the different sizes of conduit, and, as tiles are usually made one or two inches more than a foot long, a thousand of them will lay a thousand feet,—leaving a sufficient allowance for breakage, and for such slight deviations of the lines as may be necessary to pass around those stones which are too large to remove. In very stony ground, the length of lines is often materially increased, but in such ground, there is usually rock enough or such accumulations of boulders in some parts, to reduce the length of drain which it is possible to lay, at least as much as the deviations will increase it.

It is always best to make a contract for tile considerably in advance. The prices which are given in the advertisements of the makers, are those at which a single thousand,—or even a few hundred,—can be purchased, and very considerable reductions of price may be secured on large orders. Especially is this the case if the land is so situated that the tile may be purchased at either one of two tile works,—for the prices of all are extravagantly high, and manufacturers will submit to large discounts rather than lose an important order.

It is especially recommended, in making the contract, to stipulate that every tile shall be hard-burned, and that those which will not give a clear ring when struck with a metallic instrument, shall be rejected, and the cost of their transportation borne by the maker. The tiles used in the Central Park drainage were all tested with the aid of a bit of steel which had, at one end, a cutting edge. With this instrument each tile was "sounded," and its hardness was tested by scraping the square edge of the bore. If it did not "ring" when struck, or if the edge was easily cut, it was rejected. From the first cargo there were many thrown out, but as soon as the maker saw that they were really inspected, he sent tile of good quality only. Care should also be taken that no over-burned tile,—such as have been melted and warped, or very much contracted in size by too great heat,—be smuggled into the count.

A little practice will enable an ordinary workman to throw out those which are imperfect, and, as a single tile which is so underdone that it will not last, or which, from over-burning, has too small an orifice, may destroy a long drain, or a whole system of drains, the inspection should be thorough.

The collars should be examined with equal care. Concerning the use of these, Gisborne says:

"To one advantage which is derived from the use of collars we have not yet adverted—the increased facility with which free water existing in the soil can find entrance into the conduit. The collar for a 1-1/2-inch pipe has a circumference of three inches. The whole space between the collar and the pipe on each side of the collar is open, and affords no resistance to the entrance of water; while at the same time the superincumbent arch of the collar protects the junction of two pipes from the intrusion of particles of soil. We confess to some original misgivings that a pipe resting only on an inch at each end, and lying hollow, might prove weak and liable to fracture by weight pressing on it from above; but the fear was illusory. Small particles of soil trickle down the sides of every drain, and the first flow of water will deposit them in the vacant space between the two collars. The bottom, if at all soft, will also swell up into any vacancy. Practically, if you reopen a drain well laid with pipes and collars, you will find them reposing in a beautiful nidus, which, when they are carefully removed, looks exactly as if it had been moulded for them."

The cost of collars should not be considered an objection to their use; because, without collars it would not be safe, (as it is difficult to make the orifices of two pieces come exactly opposite to each other,) to use less than 2-inch tiles, while, with collars, 1-1/4-inch are sufficient for the same use, and, including the cost of collars, are hardly more expensive.

It is usual, in all works on agricultural drainage, to insert tables and formulae for the guidance of those who are to determine the size of tile required to discharge the water of a certain area. The practice is not adopted here, for the reason that all such tables are without practical value. The smoothness and uniformity of the bore; the rate of fall; the depth of the drain, and consequent "head," or pressure, of the water; the different effects of different soils in retarding the flow of the water to the drain; the different degrees to which angles in the line of tile affect the flow; the degree of acceleration of the flow which is caused by greater or less additions to the stream at the junction of branch drains; and other considerations, arising at every step of the calculation, render it impossible to apply delicate mathematical rules to work which is, at best, rude and unmathematical in the extreme. In sewerage, and the water supply of towns, such tables are useful,—though, even in the most perfect of these operations, engineers always make large allowances for circumstances whose influence cannot be exactly measured,—but in land drainage, the ordinary rules of hydraulics have to be considered in so many different bearings, that the computations of the books are not at all reliable. For instance, Messrs. Shedd & Edson, of Boston, have prepared a series of tables, based on Smeaton's experiments, for the different sizes of tile, laid at different inclinations, in which they state that 1-1/2-inch tile, laid with a fall of one foot in a length of one hundred feet, will discharge 12,054.81 gallons of water in 24 hours. This is equal to a rain-fall of over 350 inches per year on an acre of land. As the average annual rain-fall in the United States is about 40 inches, at least one-half of which is removed by evaporation, it would follow, from this table, that a 1-1/2-inch pipe, with the above named fall, would serve for the drainage of about 17 acres. But the calculation is again disturbed by the fact that the rain-fall is not evenly distributed over all the days of the year,—as much as six inches having been known to fall in a single 24 hours, (amounting to about 150,000 gallons per acre,) and the removal of this water in a single day would require a tile nearly five inches in diameter, laid at the given fall, or a 3-inch tile laid at a fall of more than 7-1/2 feet in 100 feet. But, again, so much water could not reach a drain four feet from the surface, in so short a time, and the time required would depend very much on the character of the soil. Obviously, then, these tables are worthless for our purpose. Experience has fully shown that the sizes which are recommended below are ample for practical purposes, and probably the areas to be drained by the given sizes might be greatly increased, especially with reference to such soils as do not allow water to percolate very freely through them.

In connection with this subject, attention is called to the following extract from the Author's Report on the Drainage, which accompanies the "Third Annual Report of the Board of Commissioners of the Central Park:"

"In order to test the efficiency of the system of drainage employed on the Park, I have caused daily observations to be taken of the amount of water discharged from the principal drain of 'the Green,' and have compared it with the amount of rain-fall. A portion of the record of those observations is herewith presented.

"In the column headed 'Rain-Fall,' the amount of water falling on one acre during the entire storm, is given in gallons. This is computed from the record of a rain-gauge kept on the Park.

"Under the head of 'Discharge,' the number of gallons of water drained from one acre during 24 hours is given. This is computed from observations taken, once a day or oftener, and supposes the discharge during the entire day to be the same as at the time of taking the observations. It is, consequently, but approximately correct:

Date. Hour. Rain-fall. Discharge. Remarks. July 13. 10 a.m. 49,916 184 galls. Ground dry. galls. No rain since 3d inst.; 2 inches rain fell between 5.15 and 5.45 p.m. and 1-5th of an inch between 5.45 and 7.15. July 14. 6-1/2 " 4,968 " July 15. 6-1/2 " 1,325 " July 16. 8 " 1,104 " July 16. 6 p.m. 33,398 " 7,764 " Ground saturated at a depth of 2 feet when this rain commenced. July 17. 4,319 " July 18. 9 a.m. 2,208 " July 19. 7 " 1,325 " July 20. 6-1/2 " 993 " July 21. 11 " 662 " July 22. 6-1/2 " 560 " July 23. 10 " 1,698 " 515 " This slight rain only affected the ratio of decrease. July 24. 7 " 442 " Nothing worthy of note until Aug. 3. Aug. 3. 6-1/2 " 8,490 " 191 " Rain from 3 p.m. to 3.30 p.m. Aug. 4. 6-1/2 " 13,018 " 184 " " 4.45 p.m. to 12 m.n. Aug. 5. 6-1/2 " 45,288 " 368 " " 12 m. to 6 p.m. Aug. 5. 6 p.m. 8,280 " Aug. 6. 9 a.m. 3,954 " Aug. 7. 9 " 2,208 " Aug. 8. 6-1/2 " 828 " Aug. 9. 6-1/2 " 662 " Aug. 12. 6-1/2 " 368 " Rain 12 m. Aug. 12 to 7 a.m. Aug. 13. Aug. 13. 7 " 19,244 " 1,104 " Aug. 14. 9 " 736 " Aug. 24. 9 " 1,132 " 191 " " 3 a.m. to 4.15 a.m. Aug. 25. 9 " 5,547 " 9,936 " " 3.30 p.m. 24th, to 7 a.m. 25th. Aug. 25. 7 p.m. 566 " 7,740 " " 7 a.m. to 12 m. Aug. 26. 6-1/2 a.m. 3,974 " Aug. 26. 6 p.m. 2,208 " Aug. 27. 6-1/2 a.m. 566 " 1,529 " " 4 p.m. to 6 p.m. Aug. 28. 7 " 993 " Sep. 11. 7 " 566 " 165 " " 12 m.n. (10th) to 7 a.m. (11th.) Sep. 12. 9 " 5,094 " 147 " " 12 m. (11th) to 7 a.m. (12th.) Sep. 13. 9 " 566 " 132 " " 4 p.m. to 6 p.m. Sep. 16. 9 " 15,848 " 110 " " 12 m. to 12 m.n. Sep. 17. 7 " 27,552 " 1,104 " Rain continued until 12 m. Sep. 17. 5 p.m. 6,624 " Sep. 18. 8 a.m. 566 " 4,968 " Sep. 19. 6-1/2 " 2,208 " Sep. 19. 4 p.m. 1,805 " Sep. 20. 9 a.m. 566 " 1,324 " Rain f'm 12 m. (19th) to 7 a.m. (20th.) Sep. 21. 9 " 5,094 " 945 " " 3.20 p.m. (20th) to 6 a.m. (21st.) Sep. 22. 9 " 10,185 " 1,656 " " 12 m. (21st) to 7 a.m. (22d.) Sep. 23. 9 " 40,756 " 7,948 " Rain continued until 7 a.m. (23d.) Sep. 24. 9 " 4,968 " Sep. 25. 9 " 566 " 2,984 " Sep. 26. 9 " 2,484 " Oct. 1. 9 " 828 " There was not enough rain during this period to materially affect the flow of water. Nov. 18. 9 " 83 " Nov. 19. 9 " 1,132 " 184 " Rain 4.50 p.m. (18th) to 8 a.m. (19th.) Nov. 20. 9 " 119 " Nov. 22. 9 " 29,336 " 6,624 " Rain all of the previous night. Nov. 22. 2 p.m. 6,624 " Nov. 23. 9 a.m. 4,968 " Nov. 24. 9 " 1,711 " Nov. 24. 2 p.m. 1,417 " Dec. 17. 9 a.m. 552 " Dec. 18. 9 " 4,968 " Rain during the previous night. Dec. 30. 10 " 581 "

"The tract drained by this system, though very swampy, before being drained, is now dry enough to walk upon, almost immediately after a storm, except when underlaid by a stratum of frozen ground."

The area drained by the main at which these gaugings were made, is about ten acres, and, in deference to the prevailing mania for large conduits, it had been laid with 6-inch sole-tile. The greatest recorded discharge in 24 hours was (August 25th,) less than 100,000 gallons from the ten acres,—an amount of water which did not half fill the tile, but which, according to the tables referred to, would have entirely filled it.

In view of all the information that can be gathered on the subject, the following directions are given as perfectly reliable for drains four feet or more in depth, laid on a well regulated fall of even three inches in a hundred feet:

For 2 acres 1-1/4 inch pipes (with collars.)

For 8 acres 2-1/4 inch pipes (with collars.)

For 20 acres 3-1/2 inch pipes

For 40 acres 2 3-1/2 inch pipes or one 5-inch sole-tile.

For 50 acres 6 inch pipes sole-tile.

For 100 acres 8 inch pipes or two 6-inch sole-tiles.

It is not pretended that these drains will immediately remove all the water of the heaviest storms, but they will always remove it fast enough for all practical purposes, and, if the pipes are securely laid, the drains will only be benefited by the occasional cleansing they will receive when running "more than full." In illustration of this statement, the following is quoted from a paper communicated by Mr. Parkes to the Royal Agricultural Society of England in 1843:

"Mr. Thomas Hammond, of Penshurst, (Kent,) now uses no other size for the parallel drains than the inch tile in the table, (No. 5,) having commenced with No. 4,(11) and it may be here stated, that the opinion of all the farmers who have used them in the Weald, is that a bore of an inch area is abundantly large. A piece of 9 acres, now sown with wheat, was observed by the writer, 36 hours after the termination of a rain which fell heavily and incessantly during 12 hours on the 7th of November. This field was drained in March, 1842, to the depth of 30 to 36 inches, at a distance of 24 feet asunder, the length of each drain being 235 yards.

"Each, drain emptied itself through a fence bank into a running stream in a road below it; the discharge therefore was distinctly observable. Two or three of the pipes had now ceased running; and, with the exception of one which tapped a small spring and gave a stream about the size of a tobacco pipe, the run from the others did not exceed the size of a wheat straw. The greatest flow had been observed by Mr. Hammond at no time to exceed half the bore of the pipes. The fall in this field is very great, and the drains are laid in the direction of the fall, which has always been the practice in this district. The issuing water was transparently clear; and Mr. Hammond states that he has never observed cloudiness, except for a short time after very heavy flushes of rain, when the drains are quickly cleared of all sediment, in consequence of the velocity and force of the water passing through so small a channel. Infiltration through the soil and into the pipes, must, in this case, be considered to have been perfect; and their observed action is the more determinate and valuable as regards time and effect, as the land was saturated with moisture previous to this particular fall of rain, and the pipes had ceased to run when it commenced. This piece had, previous to its drainage, necessarily been cultivated in narrow stretches, with an open water furrow between them; but it was now laid quite plain, by which one-eighth of the continuation of acreage has been saved. Not, however, being confident as to the soil having already become so porous as to dispense entirely with surface drains, Mr. Hammond had drawn two long water furrows diagonally across the field. On examining these, it appeared that very little water had flowed along any part of them during these 12 hours of rain,—no water had escaped at their outfall; the entire body of rain had permeated the mass of the bed, and passed off through the inch pipes; no water perceptible on the surface, which used to carry it throughout. The subsoil is a brick clay, but it appears to crack very rapidly by shrinkage consequent to drainage."

*Obstructions.*—The danger that drains will become obstructed, if not properly laid out and properly made, is very great, and the cost of removing the obstructions, (often requiring whole lines to be taken up, washed, and relaid with the extra care that is required in working in old and soft lines,) is often greater than the original cost of the improvement. Consequently, the possibility of tile drains becoming stopped up should be fully considered at the outset, and every precaution should be taken to prevent so disastrous a result.

The principal causes of obstruction are silt, vermin, and roots.

Silt is earth which is washed into the tile with the water of the soil, and which, though it may be carried along in suspension in the water, when the fall is good, will be deposited in the eddies and slack-water, which occur whenever there is a break in the fall, or a defect in the laying of the tile.

Whenever it is possible to avoid it, no drain should have a decreasing rate of fall as it approaches its outlet.

If the first hundred feet from the upper end of the drain has a fall of three inches, the next hundred feet should not have less than three inches, lest the diminished velocity cause silt, which required the speed which that fall gives for its removal, to be deposited and to choke the tile. This defect of grade is shown in Fig. 17. If the second hundred feet has an inclination of more than three inches, (Fig. 18,) the removal of silt will be even better secured than if the fall continued at the original rate. Some silt will enter newly made drains, in spite of our utmost care, but the amount should be very slight, and if it is evenly deposited throughout the whole length of the drain, (as it sometimes is when the rate of fall is very low,) it will do no especial harm; but it becomes dangerous when it is accumulated within a short distance, by a decreasing fall, or by a single badly laid tile, or imperfect joint, which, by arresting the flow, may cause as much mischief as a defective grade.

Owing to the general conformation of the ground, it is sometimes absolutely necessary to adopt such a grade as is shown in Fig. 19,—even to the extent of bringing the drain down a rapid slope, and continuing it with the least possible fall through level ground. When such changes must be made, they should be effected by angles, and not by curves. In increasing the fall, curves in the grade are always advisable, in decreasing it they are always objectionable, except when the decreased fall is still considerable,—say, at least 2 feet in 100 feet. The reason for making an absolute angle at the point of depression is, that it enables us to catch the silt at that point in a silt basin, from which it may be removed as occasion requires.



Fig. 19 - THREE PROFILES OF DRAINS, WITH DIFFERENT INCLINATIONS.

A Silt Basin is a chamber, below the grade of the drain, into which the water flows, becomes comparatively quiet, and deposits its silt, instead of carrying it into the tile beyond. It may be large or small, in proportion to the amount of drain above, which it has to accommodate. For a few hundred feet of the smallest tile, it may be only a 6-inch tile placed on end and sunk so as to receive and discharge the water at its top. For a large main, it may be a brick reservoir with a capacity of 2 or 3 cubic feet. The position of a silt basin is shown in Fig. 19.

The quantity of silt which enters the drain depends very much on the soil. Compact clays yield very little, and wet, running sands, (quicksands,) a great deal. In a soil of the latter sort, or one having a layer of running sand at the level of the drain, the ditch should be excavated a little below the grade of the drain, and then filled to that level with a retentive clay, and rammed hard. In all cases when the tile is well laid, (especially if collars are used,) and a stiff earth is well packed around the tile, silt will not enter the drain to an injurious extent, after a few months' operation shall have removed the loose particles about the joints, and especially after a few very heavy rains, which, if the tiles are small, will sometimes wash them perfectly clean, although they may have been half filled with dirt.

Vermin,—field mice, moles, etc.,—sometimes make their nests in the tile and thus choke them, or, dying in them, stop them up with their carcases. Their entrance should be prevented by placing a coarse wire cloth or grating in front of the outlets, which afford the only openings for their entrance.

Roots.—The roots of many water-loving trees,—especially willows,—will often force their entrance into the joints of the tile and fill the whole bore with masses of fibre which entirely prevent the flow of water. Collars make it more difficult for them to enter, but even these are not a sure preventive. Gisborne says:

"My own experience as to roots, in connection with deep pipe draining, is as follows: I have never known roots to obstruct a pipe through which there was not a perennial stream. The flow of water in summer and early autumn appears to furnish the attraction. I have never discovered that the roots of any esculent vegetable have obstructed a pipe. The trees which, by my own personal observation, I have found to be most dangerous, have been red willow, black Italian poplar, alder, ash, and broad-leaved elm. I have many alders in close contiguity with important drains, and, though I have never convicted one, I cannot doubt that they are dangerous. Oak, and black and white thorns, I have not detected, nor do I suspect them. The guilty trees have in every instance been young and free growing; I have never convicted an adult. These remarks apply solely to my own observation, and may of course be much extended by that of other agriculturists. I know an instance in which a perennial spring of very pure and (I believe) soft water is conveyed in socket pipes to a paper mill. Every junction of two pipes is carefully fortified with cement. The only object of cover being protection from superficial injury and from frost, the pipes are laid not far below the sod. Year by year these pipes are stopped by roots. Trees are very capricious in this matter. I was told by the late Sir R. Peel that he sacrificed two young elm trees in the park at Drayton Manor to a drain which had been repeatedly stopped by roots. The stoppage was nevertheless repeated, and was then traced to an elm tree far more distant than those which had been sacrificed. Early in the autumn of 1850 I completed the drainage of the upper part of a boggy valley, lying, with ramifications, at the foot of marly banks. The main drains converge to a common outlet, to which are brought one 3-inch pipe and three of 4 inches each. They lie side by side, and water flows perennially through each of them. Near to this outlet did grow a red willow. In February, 1852, I found the water breaking out to the surface of the ground about 10 yards above the outlet, and was at no loss for the cause, as the roots of the red willow showed themselves at the orifice of the 3-inch and of two of the 4-inch pipes. On examination I found that a root had entered a joint between two 3-inch pipes, and had traveled 5 yards to the mouth of the drain, and 9 yards up the stream, forming a continuous length of 14 yards. The root which first entered had attained about the size of a lady's little finger; and its ramifications consisted of very fine and almost silky fibres, and would have cut up into half a dozen comfortable boas. The drain was completely stopped. The pipes were not in any degree displaced. Roots from the same willow had passed over the 3-inch pipes, and had entered and entirely stopped the first 4-inch drain, and had partially stopped the second. At a distance of about 50 yards a black Italian poplar, which stood on a bank over a 4-inch drain, had completely stopped it with a bunch of roots. The whole of this had been the work of less than 18 months, including the depth of two winters. A 3-inch branch of the same system runs through a little group of black poplars. This drain conveys a full stream in plashes of wet, and some water generally through the winter months, but has not a perennial flow. I have perceived no indication that roots have interfered with this drain. I draw no general conclusions from these few facts, but they may assist those who have more extensive experience in drawing some, which may be of use to drainers."

Having considered some of the principles on which our work should be based, let us now return to the map of the field, and apply those principles in planning the work to be done to make it dry.

*The Outlet* should evidently be placed at the present point of exit of the brook which runs from the springs, collects the water of the open ditches, and spreads over the flat in the southwest corner of the tract, converting it into a swamp. Suppose that, by going some distance into the next field, we can secure an outlet of 3 feet and 9 inches (3.75) below the level of the swamp, and that we decide to allow 3 inches drop between the bottom of the tile at that point, and the reduced level of the brook to secure the drain against the accumulation of sand, which might result from back water in time of heavy rain. This fixes the depth of drain at the outlet at 3-1/2 (3.50) feet.

At that side of the swamp which lies nearest to the main depression of the up-land, (See Fig. 21,) is the proper place at which to collect the water from so much of the field as is now drained by the main brook, and at that point it will be well to place a silt basin or well, built up to the surface, which may, at any time, be uncovered for an observation of the working of the drains. The land between this point and the outlet is absolutely level, requiring the necessary fall in the drain which connects the two, to be gained by raising the upper end of it. As the distance is nearly 200 feet, and as it is advisable to give a fall at least five-tenths of a foot per hundred feet to so important an outlet as this, the drain at the silt basin may be fixed at only 2-1/2 feet. The basin being at the foot of a considerable rise in the ground, it will be easy, within a short distance above, to carry the drains which come to it to a depth of 4 feet,—were this not the case, the fall between the basin and the outlet would have to be very much reduced.

*Main Drains.*—The valley through which the brook now runs is about 80 feet wide, with a decided rise in the land at each side. If one main drain were laid in the center of it, all of the laterals coming to the main would first run down a steep hillside, and then across a stretch of more level land, requiring the grade of each lateral to be broken at the foot of the hill, and provided with a silt basin to collect matters which might be deposited when the fall becomes less rapid. Consequently, it is best to provide two mains, or collecting drains, (A and C,) one lying at the foot of each hill, when they will receive the laterals at their greatest fall; but, as these are too far apart to completely drain the valley between them, and are located on land higher than the center of the valley, a drain, (B,) should be run up, midway between them.

The collecting drain, A, will receive the laterals from the hill to the west of it, as far up as the 10-foot contour line, and, above that point,—running up a branch of the valley,—it will receive laterals from both sides. The drain, B, may be continued above the dividing point of the valley, and will act as one of the series of laterals. The drain, C, will receive the laterals and sub-mains from the rising ground to the east of it, and from both sides of the minor valley which extends in that direction.

Most of the valley which runs up from the easterly side of the swamp must be drained independently by the drain E, which might be carried to the silt basin, did not its continuation directly to the outlet offer a shorter course for the removal of its water. This drain will receive laterals from the hill bordering the southeasterly side of the swamp, and, higher up, from both sides of the valley in which it runs.

In laying out these main drains, more attention should be given to placing them where they will best receive the water of the laterals, and on lines which offer a good and tolerably uniform descent, than to their use for the immediate drainage of the land through which they pass. Afterward, in laying out the laterals, the use of these lines as local drains should, of course, be duly considered.

*The Lateral Drains* should next receive attention, and in their location and arrangement the following rules should be observed:

1st. They should run down the steepest descent of the land.

2d. They should be placed at intervals proportionate to their depth;—if 4 feet deep, at 40 feet intervals; if 3 feet deep, at 20 feet intervals.



Fig. 20 - MAP WITH DRAINS AND CONTOUR LINES.

3d. They should, as nearly as possible, run parallel to each other.

On land of perfectly uniform character, (all sloping in the same direction,) all of these requirements may be complied with, but on irregular land it becomes constantly necessary to make a compromise between them. Drains running down the line of steepest descent cannot be parallel,—and, consequently, the intervals between them cannot be always the same; those which are farther apart at one end than at the other cannot be always of a depth exactly proportionate to their intervals.

In the adjustment of the lines, so as to conform as nearly to these requirements as the shape of the ground will allow, there is room for the exercise of much skill, and on such adjustment depend, in a great degree, the success and economy of the work. Remembering that on the map, the line of steepest descent is exactly perpendicular to the contour lines of the land, it will be profitable to study carefully the system of drains first laid out, erasing and making alterations wherever it is found possible to simplify the arrangement.

Strictly speaking, all angles are, to a certain extent, wasteful, because, if two parallel drains will suffice to drain the land between them, no better drainage will be effected by a third drain running across that land. Furthermore, the angles are practically supplied with drains at less intervals than are required,—for instance, at C 7 a on the map the triangles included within the dotted line x, y, will be doubly drained. So, also, if any point of a 4-foot drain will drain the land within 20 feet of it, the land included within the dotted line forming a semi-circle about the point C 14, might drain into the end of the lateral, and it no more needs the action of the main drain than does that which lies between the laterals. Of course, angles and connecting lines are indispensable, except where the laterals can run independently across the entire field, and discharge beyond it. The longer the laterals can be made, and the more angles can be avoided, the more economical will the arrangement be; and, until the arrangement of the lines has been made as nearly perfect as possible, the time of the drainer can be in no way so profitably spent as in amending his plan.

The series of laterals which discharge through the mains A, C, D and E, on the accompanying map, have been very carefully considered, and are submitted to the consideration of the reader, in illustration of what has been said above.

At one point, just above the middle of the east side of the field, the laterals are placed at a general distance of 20 feet, because, as will be seen by reference to Fig. 4, a ledge of rock, underground, will prevent their being made more than 3 feet deep.

The line from H to I, (Fig. 20,) at the north side of the field, connecting the heads of the laterals, is to be a stone and tile drain, such as is described on page 60, intended to collect the water which follows the surface of the rock. (See Fig. 4.)

The swamp is to be drained by itself, by means of two series of laterals discharging into the main lines F and G, which discharge at the outlet, by the side of the main drain from the silt-basin. By this arrangement, these laterals, especially at the north side of the swamp, being accurately laid, with very slight inclinations, can be placed more deeply than if they ran in an east and west direction, and discharged into the main, which has a greater inclination, and is only two and a half feet deep at the basin. Being 3-1/2 (3.50) feet deep at the outlet, they may be made fully 3 feet deep at their upper ends, and, being only 20 feet apart, they will drain the land as well as is possible. The drains being now laid out, over the whole field, the next thing to be attended to is

*The Ordering of the Tile.*—The main line from the outlet up to the silt-basin, should be of 3-1/2-inch tiles, of which about 190 feet will be required. The main drain A should be laid with 2-1/4-inch tiles to the point marked m, near its upper end, as the lateral entering there carries the water of a spring, which is supposed to fill a 1-1/4-inch tile. The length of this drain, from the silt-basin to that point is 575 feet. The main drain C will require 2-1/4 inch tiles from the silt-basin to the junction with the lateral, which is marked C 10, above which point there is about 1,700 feet of drain discharging into it, a portion of which, being a stone-and-tile drain at the foot of a rock, may be supposed to receive more water than that which lies under the rest of the land;—distance 450 feet. The main drain E requires 2-1/4-inch tiles from the outlet to the point marked o, a distance of 380 feet. This tile will, in addition to its other work, carry as much water from the spring, on the line of its fourth lateral, as would fill a 1-1/4-inch pipe.(12)

The length of the main drains above the points indicated, and of all the laterals, amounts to about 12,250 feet. These all require 1-1/4-inch tiles.

Allowing about five per cent. for breakage, the order in round numbers, will be as follows:(13)

3-1/2-inch round tiles 200 feet.

2-1/4-inch round tiles 1,500 feet.

1-1/4-inch round tiles 13,000 feet.

3-1/2-inch round tiles 1,600

2-1/4-inch round tiles 13,250

Order, also, 25 6-inch sole-tiles, to be used in making small silt-basins.

It should be arranged to have the tiles all on the ground before the work of ditching commences, so that there may be no delay and consequent danger to the stability of the banks of the ditches, while waiting for them to arrive. As has been before stated, it should be especially agreed with the tile-maker, at the time of making the contract, that every tile should be perfect;—of uniform shape, and neither too much nor too little burned.

*Staking Out.*—Due consideration having been given to such preliminaries as are connected with the mapping of the ground, and the arrangement, on paper, of the drains to be made, the drainer may now return to his field, and, while awaiting the arrival of his tiles, make the necessary preparation for the work to be done. The first step is to fix certain prominent points, which will serve to connect the map with the field, by actual measurements, and this will very easily be done by the aid of the stakes which are still standing at the intersections of the 50-foot lines, which were used in the preliminary levelling.

Commencing at the southwest corner of the field, and measuring toward the east a distance of 34 feet, set a pole to indicate the position of the outlet. Next, mark the center of the silt-basin at the proper point, which will be found by measuring 184 feet up the western boundary, and thence toward the east 96 feet, on a line parallel with the nearest row of 50-foot stakes. Then, in like manner, fix the points C1, C6, C9, C10, and C17, and the angles of the other main lines, marking the stakes, when placed, to correspond with the same points on the map. Then stake the angles and the upper ends of the laterals, and mark these stakes to correspond with the map.

It will greatly facilitate this operation, if the plan of the drains which is used in the field, from which the horizontal lines should be omitted, have the intersecting 50-foot lines drawn upon it, so that the measurements may be made from the nearest points of intersection.(14)