Drainage increases the coldness of the subsoil in Winter. Whether this is a gain or loss to the agriculturist, is not for us to determine. The object of our labor is, to lay the whole subject fairly before the reader, and not to extol drainage as the grand panacea of bad husbandry.

Although water will not conduct heat downwards, yet it doubtless prevents the deep freezing of the ground. It has already been seen, that the temperature of the earth, a few feet below the surface, is above the freezing point, at all times. The fact that the ground does not freeze, usually, even in New England, where every Winter brings weather below Zero, more than four or five feet deep, in the most exposed situations, shows conclusively the comparatively even temperature of the subsoil. The water which flows underground is of this subsoil temperature, and, in Winter, warms the ground through which it flows. In land thoroughly drained, this warm water cannot rise above the drains, and so cannot defend the soil from frost.

Drained land will, undoubtedly, freeze deeper than undrained land, and this is a fact to be impressed upon all who lay tiles in a cold climate. It is a strong argument for deep drainage. "Drain deep, or drain not," is a convenient paraphrase of a familiar quotation. How often do we hear it said, "My meadow never freezes more than a foot deep; there will never be any trouble from frost in that place, if the tiles are no more than two feet deep." Be assured, brother farmer, that the frost will follow the water-table downward, and, unless the warm water move in sufficient quantity through your pipes to protect them in Winter, your work may be ruined by frost. So long as much water is flowing in pipes, especially if it be from deep springs, they will be safe from frost, even at a slight depth.

Dr. Madden says, that it has been proved that one great source of health and vigor in vegetation, is the great difference which exists between the temperature of Summer and Winter, which, he says, in dry soils, often amounts to between 30° and 40°; while, in very wet soils, it seldom exceeds 10°. This idea may have value in a mild climate; but, probably, in New England, we get cold enough for our good, without artificial aids. In another view, drainage is known to be essential, even in Winter.

Fruit trees are almost as surely destroyed by standing with their feet in cold water all Winter, as any of us "unfeathered bipeds" would be; while the solid freezing of the earth around their roots does not harm them. Perhaps the same is true of most other vegetation.

The deep freezing of the ground is often mentioned as a mode of pulverization—as a sort of natural subsoiling thrown in by a kind Providence, by way of compensation for some of the evils of a cold climate. Most of those, however, who have wielded the pick-axe in laying four-foot drains, in clay or hard-pan, will have doubts whether Jack Frost, though he can pull up our fence-posts, and throw out our Winter grain, has much softened the earth two feet below its surface.

That the frost comes out of drained land earlier than undrained, in Spring, we are satisfied, both by personal observation, and by the statements of the few individuals who have practiced thorough-drainage in our cold climate.

B. F. Nourse, Esq., whose valuable statement will be found in a later chapter, says, that, in 1858, the frost came out a week, at least, earlier from his drained land, in Maine, than from contiguous undrained land; and that, usually, the drained land is in condition to be worked as soon as the frost is out, quite two weeks earlier than any other land in the vicinity. Our observations on our own land, fully corroborate the opinion of Mr. Nourse.

The reasons why the frost should come out of drained land soonest, are, that land that is dry does not freeze so solid as land that is wet, and so spaces are left for the permeation of warm air. Again, ice, like water, is almost a nonconductor of heat, and earth saturated with water and frozen, is like unto it, so that neither the warmth of the subsoil or surface-soil can be readily imparted to it. Dry earth, on the other hand, although frozen, is still a good conductor, and readily dissolves at the first warm breath of Spring above, or the pulsations of the great heart of Nature beneath.

CHAPTER XVI.
POWER OF SOILS TO ABSORB AND RETAIN MOISTURE.

The first and most natural objection made, by those not practically familiar with drainage operations, to the whole system is, that the drains will draw out so much of the water from the soil, as to leave it too dry for the crops.

If a cask be filled with round stones, or with musket balls, or with large shot, and with water to the surface, and then an opening be made at the bottom of the cask, all the water, except a thin film adhering to the surface of the vessel and its contents, will immediately run out.

If now, the same cask be filled with the dried soil of any cultivated field, and this soil be saturated with water, a part only of the water can be drawn out at the bottom. The soil in the cask will remain moist, retaining more or less of the water, according to the character of the soil.

Why does not the water all run out of the soil, and leave it dry? An answer may be found in the books, which is, in reality, but a re-statement of the fact, by reference to a principle of nature, by no means intelligible to finite minds, called attraction. If two substances are placed in close contact with each other, they cannot be separated without a certain amount of force.

Professor Schübler, of Tubingen, gives the results of experiments upon this point. By dropping water upon dried soils of different kinds, until it began to drop from the bottom, he found that 100 lbs. of soil held by attraction, as follows:

Mr. Shedd, of Boston, gives the result of a recent experiment of his own on this point. He writes thus:

Besides this power of retaining water, when brought into contact with it, the soil has, in common with other porous bodies, the power of drawing up moisture, or of absorbing it, independent of gravitation, or of the weight of the water which aids to carry it down into the soil. This power is called capillary attraction, from the hair-like tubes used in early experiments. If very minute tubes, open at both ends, are placed upright, partly immersed in a vessel of water, the water rises in the tubes perceptibly higher than its general surface in the vessel. A sponge, from which water has been pressed out, held over a basin of water, so that its lower part touches the surface, draws up the water till it is saturated. A common flower-pot, with a perforated bottom, and filled with dry earth, placed in a saucer of water, best illustrates this point. The water rises at once to a common level in the pot and outside. This represents the water-table in the soil of our fields. But, from this level, water will continue to rise in the earth in the pot, till it is moistened to the surface, and this, too, is by capillary attraction.

The tendency of water to ascend, however, is not the same in all soils. In coarse gravelly soils, the principle may not operate perfectly, because the interstices are too large, the weight of the water overcoming the power of attraction, as in the cask of stones or shot. In very fine clay, on the other hand, although it be absorptive and retentive of water, yet the particles are so fine, and the spaces between them so small, that this attraction, though sure, would be slow in operation. A loamy, light, well pulverized soil, again, would perhaps furnish the best medium for the diffusion of water in this way.

It is impossible to set limits to so uncertain a power as this of capillary attraction. We see that in minute glass tubes, it has power to raise water a small fraction of an inch only. We see that, in the sponge or flower-pot, it has power to raise water many inches; and we know that, in the soil, moisture is thus attracted upwards several feet. By observing a saturated sponge in a saucer, we shall see that, although moist at the top, it holds more and more water to the bottom. So, in the saturated earth in a flower-pot, the earth, merely moist at the surface, is wet mud just above the water-table. So, in drained land, the capillary force which retained the water in the soil to the height of a few inches, is no longer able to sustain it, when the height is increased to feet, and a portion descends into the drain, leaving the surface comparatively dry.

Thus, it would seem, that draining may modify the force of capillary attraction, while it cannot affect that of adhesive attraction. It may drain off surplus water, but, unaided, can never render any arable land too dry. If, however, the surplus water be speedily taken off by drainage, and the capillary attraction be greatly impaired, so that little water is drawn upwards by its force, will not the soil soon become parched by the heat of the sun, or, in other words, by evaporation?

Without stopping in this place, to speak of evaporation, we may answer, that, in our burning Summer heat, the earth would be burnt up too dry for any vegetation, were it not for a beneficent arrangement of Providence, which counteracts the effect of the sun's rays, and of which we will now make mention.

Power to imbibe moisture from the air.—We have spoken, in another place, of the absorption, by drained land, of fertilizing substances from the atmosphere. Dry soil has, too, a wonderful power of deriving moisture from the same source.

Different soils possess this power in unequal degrees. During a night of 12 hours, and when the air is moist, according to Schübler, 1000 lbs. of perfectly dry

Sir Humphrey Davy found, that the power of attraction for water, generally proved an index to the agricultural value of soils. It is, however, but one means of judging of their value. Peaty soils and strong clays are very absorbent of water, although not always the best for cultivation.

Sir H. Davy gives the following results of his experiments. When made perfectly dry, 1000 lbs. of a

Here again, we find in the soil, an inexplicable but beneficent power, by which it supplies itself with moisture when it most needs it.

Warm air is capable of holding more vapor than cooler air, and the very heat of Summer supplies it with moisture by evaporation from land and water. As the air is cooled, at nightfall, it must somewhere deposit the water, which the hand of the Unseen presses out of it by condensation.

The sun-dried surface of fertile, well drained soil, is in precisely the condition best adapted to receive the refreshing draught, and convey it to the thirsting plants.

We may form some estimate of the vast amount absorbed by an acre of land in a dry season, by considering that the clay loam, in the above statement, absorbed in 12 hours a fortieth part of its own weight.

OF DEW.

Dew is one of the most ordinary forms in which moisture is deposited in and upon the soil, in its natural conditions. The absorbent power of artificially-dried soils, as has been seen, seems to depend much upon their chemical constitution; and that topic has been considered, without special reference to the comparative temperature of the soil and atmosphere. The soil, as we have seen, absorbs moisture from the air, when both are of the same temperature, the amount absorbed depending also upon the physical condition of the soil, and upon the comparative moisture of the soil and atmosphere.

The deposition of dew results from a different law. All bodies throw off, at all times, heat, by radiation, as it is termed. In the day-time, the sun's rays warm the earth, and the air is heated by it, and that nearest the surface is heated most. Evaporation is constantly going on from the earth and water, and loads the air with vapor, and the warmer the air, the more vapor it will hold.

When the sun goes down, the earth still continues to throw off heat by radiation, and soon becomes cooler than the air, unless the same amount of heat be returned, by radiation from other surfaces. Becoming cooler than the air, the soil or plants cool the air which comes in contact with them; and thus cooled to a certain point, the air cannot hold all the vapor which it absorbed while warmer, and part of it is deposited upon the soil, plant, or other cool surface. This is dew; and the temperature at which the air is saturated with vapor, is called the dew-point. If saturated at a given temperature with vapor, the air, when cooled below this point, must part with a portion of the vapor, in some way; in the form of rain or mist, if in the air; in the form of dew, if on the surface of the earth.

If, however, other surfaces, at night, radiate as much heat back to the earth as it throws off, the surface of the earth is not thus cooled, and there is no dew. Clouds radiate heat to the earth, and, therefore, there is less dew in cloudy than in clear nights. If the temperature of the earth sinks below the freezing-point, the aqueous vapor is frozen, and is then called frost.

To radiate back a portion of the heat thus thrown off by the soil and plants, gardeners cover their tender plants and vines with mats or boards, or even with thin cloth, and thus protect them from frost. If the covering touch the plants, they are often frozen, the heat being conducted off, by contact, to the covering, and thence radiated. Dew then is an effect, but not a cause, of cold. It imparts warmth, because it can be deposited only on objects cooler than itself.

It has been supposed by many that the light of the moon promotes putrefaction. Pliny and Plutarch both affirm this to be true. Dew, by supplying moisture in the warm season, aids this process of decay. We have seen that dew is most abundant in clear nights; and although all clear nights are not moonlight nights, yet all moonlight nights are clear nights; and this, perhaps, furnishes sufficient grounds for this belief, as to the influence of the moon.

The quantity of dew deposited is not easily measured. It has, however, been estimated by Dr. Dalton, to amount, in England, to five inches of water in a year, or 500 tons to the acre, equal to about one quarter of our rain-fall during the six summer months!

Deep and well-pulverized soils attract much more moisture, in every form, from the atmosphere, than shallow and compact soils. They, in fact, expose a much larger surface to the air. This is the reason why stirring the ground, even in the Summer drought, refreshes our fields of Indian corn.

CHAPTER XVII
INJURY OF LAND BY DRAINAGE.

Is there no danger of draining land too much? May not land be over-drained? These are questions often and very naturally asked, and which deserve careful consideration. The general answer would be that there is no danger to be apprehended from over-draining; that no water will run out of land that would be of advantage to our cultivated crops by being retained. In other words, soils generally hold, by capillary attraction, all the moisture that is of any advantage to the crops cultivated on them; and the water of drainage would, if retained for want of outlets, be stagnant, and produce more evil than good.

We say this is generally true; but there are said to be exceptional cases, which it is proposed to consider. If we bear in mind the condition of most soils in Summer, we shall see that this apprehension of over-draining is groundless. The fear is, that crops will suffer in time of drought, if thoroughly drained. Now, we know that, in almost all New England, the water-table is many feet below the surface. Our wells indicate pretty accurately where the water-table is, and drains, unless cut as low as the surface of the water in the wells, would not run a drop of water in Summer.

Our farmers dig their wells twenty, and even fifty, feet deep, and expect that, every Summer, the water will sink to nearly that depth; but they have no apprehension that their crops will become dry, because the water is not kept up to within three feet of the surface.

The fact is, that Nature drains thoroughly the greater portion of all our lands; so that artificial drainage, though it may remove surplus water from them more speedily in Spring, cannot make them more dry in Summer. And what thus happens naturally, on most of the land, without injury, cannot be a dangerous result to effect by drainage on lands of similar character. By thorough-drainage, we endeavor to make lands which have an impervious or very retentive subsoil near the surface, sufficiently open to allow the surplus water to pass off, as it does naturally on our most productive upland.

OVER-DRAINING OF PEATY SOILS.

No instance has yet been made public in America, of the injury of peat lands by over-drainage; but there is a general impression among English writers, that peat soils are often injured in this way. The Lincolnshire Fens are cited by them, as illustrations of the fact, that these lands do not require deep drainage.

Mr. Pusey says, "Every one who is practically acquainted with moory land, knows that such land may be easily over-drained, so that the soil becomes dusty or husky, as it is called—that is, like a dry sponge—the white crops flag, and the turnip leaves turn yellow in a long drought."

These Fens contain an immense extent of land. The Great Level of the Fens, it is said, contains 600,000 acres. Much of this was formerly covered by the tides, and all of it, as the name indicates, was of a marshy character. The water being excluded by embankments against the sea and rivers, and pumped out by steam engines, and the land under-drained generally with tiles, so that the height of the water is under the control of the proprietors, grave disputes have arisen as to the proper amount of drainage.

An impression has heretofore prevailed, that these lands would be too dry if the water were pumped out, so as to reduce the water-table more than a foot or two below the surface, but this idea is now controverted.

In July 1857, in company with three of the best farmers in Lincolnshire, the writer visited the Fens, and carefully examined the crops and drainage. We passed a day with one of the proprietors, who gave us some information upon the point in question. He stated, that in general, the occupants of this land entertain the opinion, that the crops would be ruined by draining to the depth of four feet. So strongly was he impressed with the belief that a deeper drainage was desirable, that he had enclosed his own estate with separate embankments, and put up a steam-engine, and pumped out the water to the depth of four feet, while from the land all around him, it is pumped out only a foot and a half below the surface, though in Summer it may sometimes fall somewhat lower.

The crops on this land were astonishing. Our friends estimated that the wheat then growing and nearly ripe, would yield fifty-six bushels to the acre. Although this was considered a very dry season, the crops on the land of our host were fully equal to the best upon the Fens.

The soil upon that part of the Fens is now a fine black loam of twelve or eighteen inches depth, resting upon clay. Upon other portions, the soil is of various depth and character, resting sometimes upon gravel.

Attention is called to these facts here, to show that the common impression that these lands will not bear deep drainage, is controverted among the occupants themselves, and may prove to be one of those errors which becomes traditional, we hardly know how.

Most peat meadows, in New England, when first relieved of stagnant water, are very light and spongy. The soil is filled with acids which require to be neutralized by an application of lime, or what is cheaper and equally effectual, by exposure to the atmosphere. These soils, when the water is suddenly drawn out of them, retain their bulk for a time, and are too porous and unsubstantial for cultivation. A season or two will cure this evil, in many cases. The soil will become more compact, and will often settle down many inches. It is necessary to bear this in mind in adjusting the drains, because a four-foot drain, when laid, may, by the mere subsidence of the land, become a three-foot drain.

A hasty judgment, in any case, that the land is over-drained, should be suspended until the soil has acquired compactness by its own weight, and by the ameliorating effect of culture and the elements.

Mr. Denton, alluding to the opinion of "many intelligent men, that low meadow-land should be treated differently to upland pasture, and upland pasture differently to arable land," says, "My own observations bring me to the conclusion, that it is not possible to lay pasture-land too dry; for I have invariably remarked, during the recent dry Summer and Autumn particularly, that both in lowland meadows, and upland pastures, those lands which have been most thoroughly drained by deep and frequent drains, are those that have preserved the freshest and most profitable herbage."

While, therefore, we have much doubt whether any land, high or low, can be over-drained for general cultivation, it is probable that a less expensive mode of drainage may be sometimes expedient for grass alone.

While we believe that, in general, even peat soils may be safely drained to the same depth with other soil, there seems to be a well-founded opinion that they may frequently be rendered productive by a less thorough system.

The only safety for us, is in careful experiment with our own lands, which vary so much in character and location, that no precise rules can be prescribed for their treatment.

CHAPTER XVIII
OBSTRUCTION OF DRAINS.

But won't these tiles get filled up and stopped? asks almost every inquirer on the subject of tile draining.

Certainly, they will, if not laid with great care, and with all proper precautions against obstructions. It cannot be too often repeated, that tile-drainage requires science, and knowledge, and skill, as well as money; and no man should go into it blindfold, or with faith in his innate perceptions of right. If he does, his education will be expensive.

It is proposed to mention all the various modes by which tiles have been known to be obstructed, and to suggest how the danger of failure, by means of them, may be obviated.

Let not enterprising readers be alarmed at such an array of difficulties, for the more conspicuous they become, the less is the danger from them.

Obstruction by Sand or Silt. Probably, more drains are rendered worthless, by being filled up with earthy matter, which passes with water through the joints of the tiles, than by every other cause.

Fine sand will pass through the smallest aperture, if there is a current of water sufficient to move it, and silt, or the fine deposit of mud or other earth, which is held almost in solution in running water, is even more insinuating in its ways than sand.

Very often, drains are filled up and ruined by these deposits; and, unless the fall be considerable, and the drain be laid with even descent, if earth of any kind find entrance, it must endanger the permanency of the work. To guard against the admission of everything but water, lay drains deep enough to be beyond the danger of water bursting in, in streamlets. Water should enter the drain at the bottom, by rising to the level of the tiles, and not by sinking from the surface directly to them. If the land is sandy, great care must be used. In draining through flowing sand, especially if there be a quick descent, the precaution of sheathing tiles is resorted to. That is done by putting small tiles inside of larger ones, breaking joints inside, and thus laying a double drain. This is only necessary, however, in spots of sand full of spring-water. Next best to this mode, is the use of collars over the joints, but these are not often used, though recommended for sandy land.

At least, in all land not perfectly sound, be careful to secure the joints in some way. An inverted turf, carefully laid over the joint, is oftenest used. Good, clean, fine gravel is, perhaps, best of all. Spent tan bark, when it is to be conveniently procured, is excellent, because it strains out the earth, while it freely admits water; and any particles of tan that find entrance, are floated out upon the water. The same may be said of sawdust.

To secure the exit of earth that may enter at the joints, there should be care that the tiles be smooth inside, that they be laid exactly in line, and that there be a continuous descent. If there be any place where the water rises in the tiles, in that place, every particle of sand, or other matter heavier than water, will be likely to stop, until a barrier is formed, and the drain stopped.

In speaking of the forms of tiles, the superiority of rounded openings over those with flat bottom has been shown. The greater head of water in a round pipe, gives it force to drive before it all obstructions, and so tends to keep the drain clear.

Obstructions at the Outlet. The water from deep drains is usually very clear, and cattle find the outlet a convenient place to drink at, and constantly tread up the soft ground there, and obstruct the flow of water. All earthy matter, and chemical solutions of iron, and the like, tend to accumulate by deposit at the outlet. Frogs and mice, and insects of many kinds, collect about such places, and creep into the drains. The action of frost in cold regions displaces the earth, and even masonry, if not well laid; and back-water, by flowing into the drains, hinders the free passage of water.

All these causes tend to obstruct drains at the outlet. If once stopped there, the whole pipe becomes filled with stagnant water, which deposits all its earthy matter, and soon becomes obstructed at other points, and so becomes useless. The outlet must be rendered secure from all these dangers, at all seasons, by some such means as are suggested in the chapter on the Arrangement of Drains.

Obstruction by roots. On the author's farm in Exeter, a wooden drain, to carry off waste water from a watering place, was laid, with a triangular opening of about four inches. This was found to be obstructed the second year after it was laid; and upon taking it up, it proved to be entirely filled for several feet, with willow roots, which grew like long, fine grass, thickly matted together, so as entirely to close the drain. There was a row of large willows about thirty feet distant, and as the drain was but about two feet deep, they found their way easily to it, and entering between the rough joints of the boards, not very carefully fitted, fattened on the spring water till they outgrew their new house.

A neighbor says, he never wants a tree within ten rods of any land he desires to plow; and it would be unsafe to undertake to set limits to the extent of the roots of trees. "No crevice, however small," says a writer, "is proof against the entrance of the roots of water-loving trees."

The behavior of roots is, however, very capricious in this matter; for, while occasional instances occur of drains being obstructed by them, it is a very common thing for drains to operate perfectly for indefinite periods, where they run through forests and orchards for long distances. They, however, who lay drains near to willows and ashes, and the like cold-water drinkers, must do it at the peril of which they are warned.

Laying the tiles deep and with collars will afford the best security from all danger of this kind.

Thos. Gisborne, Esq., in a note to the edition of his Essay on Drainage published in 1852, says:

Mangold-wurzel, it is said by several writers, will sometimes grow down into tile drains, even to the depth of four feet, and entirely obstruct them; but those are cases of very rare occurrence. In thousands of instances, mangolds have been cultivated on drained land, even where tiles were but 2½ feet deep, without causing any obstruction of the drains. Any reader who is curious in such matters, may find in the appendix to the 10th Vol. of the Journal of the Royal Ag. Soc., a singular instance of obstruction of drains by the roots of the mangold, as well as instances of obstructions by the roots of trees.

Obstruction by Per-oxide of Iron. In the author's barn-cellar is a watering place, supplied by a half-inch lead pipe, from a spring some eight rods distant. This pipe several times in a year, sometimes once a week, in cold weather, is entirely stopped. The stream of water is never much larger than a lead pencil. We usually start it with a sort of syringe, by forcing into the outlet a quantity of water. It then runs very thick, and of the color of iron rust, sometimes several pails full, and will then run clear for weeks or months, perhaps. In the tub which receives the water, there is always a large deposit of this same colored substance; and along the street near by, where the water oozes out of the bank, there is this same appearance of iron. This deposit is, in common language, called per-oxide of iron, though this term is not, by chemists of the present day, deemed sufficiently accurate, and the word sesqui-oxide is preferred in scientific works.

Iron exists in all animal and vegetable matter, and in all soils, to some extent. It exists as protoxide of iron, in which one atom of iron always combines with one atom of oxygen, and it exists as sesqui-oxide of iron, from the Latin sesqui, which means one and a half, in which one and a half atoms of oxygen combine with one atom of iron. The less accurate term, per-oxide, has been adopted here, because it is found in general use by writers on drainage.

The theory is that the iron exists in the soil, and is held in solution in water as a protoxide, and is converted into per-oxide by contact with the air, either in the drains or at their outlets, and is then deposited at the bottom of the water.

In a pipe running full there would be, upon this theory, no exposure to the air, which should form the per-oxide. In the case stated, it is probable that the per-oxide is formed at the exposed surface of a large cask, at the spring, and is carried into the pipe, as it is precipitated. Common drain pipes would be full of air, which might, perhaps, in a feeble current, be sufficient to cause this deposit.

Occasionally, cases have occurred of obstruction from this cause, and whenever the signs of this deposit are visible about the field to be drained, care must be used to guard against it in draining.

To guard against obstruction from per-oxide of iron, tiles should be laid deep, closely jointed or collared, with great care that the fall be continuous, and especially that there be a quick fall at the junctions of minor drains with mains, and a clear outlet.

Mr. Beattie, of Aberdeen, says: Before adopting 4 feet drains, I had much difficulty in dealing with the iron ore which generally appeared at two to three feet from the surface, but by the extra depth the water filters off to the pipes free of ore. Occasionally, iron ore is found at a greater depth, but the floating substance is then in most cases lighter, and does not adhere to the pipes in the same way as that found near the surface. Arrangements should also be made for examining the drains by means of wells, and for flushing them by holding back the water until the drains are filled, and then letting it suddenly off, or, by occasionally admitting a stream of water at the upper end, when practicable, and thus washing out the pipes. Mr. Denton says: "It is found that the use of this contrivance for flushing, will get rid of the per-oxide of iron, about which so much complaint is made."

Obstruction by Filling at the Joints. One would suppose that tiles might frequently be prevented from receiving water, by the filling up of the crevices between them. If water poured on to tiles in a stream, it would be likely to carry into these openings enough earthy matter to fill them; but the whole theory of thorough-drainage rests upon the idea of slow percolation—of the passage of water in the form of fine dew, as it were—through the motionless particles which compose the soil; and, if drains are properly laid, there can be no motion of particles of earth, either into or towards the tiles. The water should soak through the ground precisely as it does through a wet cloth.

In an article in the Journal of the Society of Arts, published in 1855, Mr. Thomas Arkell states that in 1846 he had drained a few acres with 1¼ inch pipes, about three feet deep, and 21 to 25 feet apart. The drains acted well, and the land was tolerably dry and healthy for the first few years; but afterwards, in wet seasons, it was very wet, and appeared full of water, like undrained land, although at the time all the drains were running, but very slowly. His conclusion was that mud had entered the crevices, and stopped the water out. He says he has known other persons, who had used small pipes, who had suffered in the same way. There are many persons still in England, who are so apprehensive on this point, that they continue to use horse-shoe tiles, or, as they are sometimes called, "tops and bottoms," which admit water more freely along the joints.

The most skillful engineers, however, decidedly prefer round pipes, but recommend that none smaller than one-and-a-half-inch be used, and prefer two-inch to any smaller size. The circumference of a two-inch pipe is not far from nine inches, while that of a one-inch pipe, of common thickness, is about half that, so that the opening is twice as extensive in the two-inch, pipes as in the one-inch pipe.

The ascertained instances of the obstruction of pipes, by excluding the water from the joints, are very few. No doubt that clay, puddled in upon the tiles when laid, might have this effect; but they who have experience in tile-drainage, will bear witness that there is far more difficulty in excluding sand and mud, than there is in admitting water.

It is thought, by some persons, that sufficient water to drain land may be admitted through the pores of the tiles. We have no such faith. The opinion of Mr. Parkes, that about 500 times as much water enters at the crevices between each pair of tiles, as is absorbed through the tiles themselves, we think to be far nearer the truth.

Collars have a great tendency to prevent the closing up of the crevices between tiles; but injuries to drains laid at proper depths, with two-inch pipes, even without collars, must be very rare. Indeed, no single case of a drain obstructed in this way, when laid four feet deep, has yet come within our reading or observation, and it is rather as a possible, than even a probable, cause of failure, that it has been mentioned.

HOW TO DETECT OBSTRUCTIONS IN DRAINS.

When a drain is entirely obstructed, if there is a considerable flow of water, and the ground is much descending, the water will at once press through the joints of the pipes, and show itself at the surface. By thrusting down a bar along the course of the drain, the place of the obstruction will be readily determined; for the water will, at the point of greatest pressure, burst up in the hole made by the bar, like a spring, while below the point of obstruction, there will be no upward pressure of the water, and above it, the pressure will be less the farther we go.

The point being determined, it is the work of but few minutes to dig down upon the drain, remove carefully a few pipes, and take out the frog, or mouse, or the broken tile, if such be the cause of the difficulty. If silt or earth has caused the obstruction, it is probably because of a depression in the line of the drain, or a defect in some junction with other drains, and this may require the taking up of more or less of the pipes.

If there be but little fall in the drains, the obstruction will not be so readily found; but the effect of the water will soon be observed at the surface, both in keeping the soil wet, and in chilling the vegetation upon it. If proper peep-holes have been provided, the place of any obstruction may readily be determined, at a glance into them.

Upon our own land, we have had two or three instances of obstruction by sand, very soon after the tiles were laid, and always at the junction of drains imperfectly secured with bricks, before we had procured proper branch-pipes for the purpose.

A little experience will enable the proprietor at once to detect any failure of his drains, and to apply the proper remedy. Obstructions from silt and sand are much more likely to occur during the first season after the drains are laid, than afterwards, because the earth is loose about the pipes, and more liable to be washed into the joints, than after it has become compact.

On the whole, we believe the danger to tile-drains, of obstruction, is very little, provided good tiles are used, and proper care is exercised in laying them.

CHAPTER XIX
DRAINAGE OF STIFF CLAYS.