Farm drainage Part 16

Mains must be laid from the outfall, through the lowest parts; and into the mains the smaller drains must be conducted, upon such a system as that there may be the proper fall or inclination throughout, and that the whole field shall be embraced.

Again, a perfect _plan_ of the completed work, accurately drawn on paper, should always be preserved for future reference. Now it is manifest, that it is impossible to lay out a given field, with proper mains and small drains, dividing the fall as equally as practicable between the different parts of an undulating field, preserving a system throughout, by which, with the aid of a plan, any drain may at any time be traced, without making distances conform somewhat to the system of the whole.

It is easily demonstrable, too, that drains at right angles with the mains, and so parallel with each other, are the shortest possible drains in land that needs uniform drainage. They take each a more uniform share of the water, and serve a greater breadth of soil than when laid at acute angles. While, therefore, it may be supposed that in particular parts of the field, distances somewhat greater or less might be advisable, considered independently, yet in practice, it will be found best, usually, to pay becoming deference to order, "Heaven's first law,"

and sacrifice something of the individual good, to the leading idea of the general welfare.

In the letter of Mr. Denton, in another chapter, some remarks will be found upon the subject of which we are treating. The same gentleman has, in a published paper, ill.u.s.trated the impossibility of strict adherence to any arbitrary rule in the distances or arrangement of drains, as follows:

"The wetness of land, which for distinction's sake, I have called 'the water of pressure,' like the water of springs, to which it is nearly allied, can be effectually and cheaply removed only by drains devised for, and devoted to the object. Appropriate deep drains at B B B, for instance, as indicated in the dark vertical lines, are found to do the service of many parallel drains, which as frequently miss, as they hit, those furrows, or 'lips,' in the horizontal out-crop of water-bearing strata which continue to exude wetness after the higher portions are dry.

[Ill.u.s.tration: Fig. 35.--The vertical dotted lines show the position of parallel drains.]

"A consideration, too, of the varying inclinations of surface, of which instances will frequently occur in the same field, necessitates a departure from uniformity, not in direction only, but in intervals between drains. Take, for instance, the ordinary case of a field, in which a comparatively flat s.p.a.ce will intervene between quickly rising ground and the outfall ditch. It is clear that the soak of the hill will pervade the soil of the lower ground, let the system of drainage adopted be what it may; and, therefore, supposing the soil of the hill and flat to be precisely alike, the existence of bottom water in a greater quant.i.ty in the lower lands than in the higher, will call for a greater number of drains. It is found, too, that an independent discharge or relief of the water coming from the hill, at B, should always be provided, in order to avoid any impediment by the slower flow of the flatter drains.

[Ill.u.s.tration: Fig. 36.]

"Experience shows that, with few exceptions, hollows, or 'slacks,'

observable on the surface, as at B B, have a corresponding undulation of subsoil and that any system which does not provide a direct release for water, which would otherwise collect in and draw towards these spots, is imperfect and unsatisfactory. It is found to be much more safe to depend on relief drains, than on the cutting of drains sufficiently deep through the banks, at A A, to gain a fall at a regular inclination.

"Still, in spite of experience, we often observe a disregard of these facts, even in works which are otherwise well executed to a depth of four feet, but fettered by methodical rules, and I feel compelled to remark, that it has often occurred to me, when I have observed with what diligent examination the rules of depth and distance have been tested, that if more attention had been paid to the _source_ of injury, and to the mode of securing an effective and permanent _discharge_ of the injurious water, much greater service would be done."

In conclusion, as to distances, we should advise great caution on the part of beginners in laying out their drains. Draining is too expensive a work to be carelessly or unskillfully done. A mistake in locating drains too far apart, brings a failure to accomplish the end in view. A mistake in placing them too near, involves a great loss of labor and money. Consult, then, those whose experience has given them knowledge, and pay to a professional engineer, or some other skillful person, a small amount for aid, which will probably save ten times as much in the end. We have placed our own drains in porous, though very wet soil, at fifty feet distances, which, in most soils, might be considered extremely wide. We are fully satisfied that they would have drained the land as well at sixty feet, except in a few low places, where they could not be sunk four feet for want of fall.

In most New England lands that require drainage, we believe that from 40 to 50 feet distances, with four feet depth, will prove sufficient. Upon stiff clays, we have no experience of our own of any value, although we have a field of the stiffest clay, drained last season at 40 feet distances and four feet depth. In England, this would, probably, prove insufficient, and, perhaps, it will prove so here. One thing is certain, that, at present, there is little land in this country that will pay for drainage by hand labor, at the English distances in clay, of 16 or 20 feet. If our powerful Summer's sun will not somehow compensate in part for distance, we must, upon our clays, await the coming of draining plows and steam.

DEPTH OF DRAINS.

Cheap and temporary expedients in agriculture are the characteristics of us Americans, who have abundance of land, a whole continent to cultivate, and comparatively few hands and small capital with which to do the work. We erect temporary houses and barns and fences, hoping to find time and means at a future day, to reconstruct them in a more thorough manner. We half cultivate our new lands, because land is cheaper than labor; and it pays best for the present, rather to rob our mother earth, than to give her labor for bread.

The easy and cheap process in draining, is that into which we naturally fall. It is far easier and cheaper to dig shallow than deep drains, and, therefore, we shall not dig deep unless we see good reason to do so. If, however, we carefully study the subject, it will be manifest that superficial drainage is, in general, the result of superficial knowledge of the subject.

Thorough-drainage does not belong to pioneer farming, nor to a cheap and temporary system. It involves capital and labor, and demands skill and system. It cannot be patched up, like a brush fence, to answer the purpose, from year to year, but every tile must be placed where it will best perform its office for a generation. In England, the rule and the habit in all things, is thoroughness and permanency; yet the first and greatest mistake there in drainage was shallowness, and it has required years of experiments, and millions of money, to correct that mistake.

If we commit the same folly, as we are very likely to do, we cannot claim even the originality of the blunder, and shall be guilty of the folly of pursuing the crooked paths of their exploration, instead of the straight highway which they have now established. To be sure, the controversy as to the depth of drains has by no means ceased in England, but the question is reduced to this, whether the least depth shall be three feet or four; one party contending that for certain kinds of clay, a three-foot drain is as effectual as a four-foot drain, and that the least effectual depth should be used, because it is the cheapest; while the general opinion of the best scientific and practical men in the kingdom, has settled down upon four feet as the minimum depth, where the fall and other circ.u.mstances render it practicable. At the same time, all admit that, in many cases, a greater depth than four feet is required by true economy. It may seem, at first, that a controversy, as to one additional foot in a system of drainage, depends upon a very small point; but a little reflection will show it to be worthy of careful consideration. Without going here into a nice calculation, it may be stated generally as an established fact, that the excavation of a ditch four feet deep, costs twice as much as that of a ditch three feet deep. Although this may not seem credible to one who has not considered the point, yet it will become more probable on examination, and very clear, when the actual digging is attempted. Ditches for tiles are always opened widest at top, with a gradual narrowing to near the bottom, where they should barely admit the tile. Now, the addition of a foot to the depth, is not, as it would perhaps at first appear, merely the addition of the lowest and narrowest foot, but rather of the topmost and widest foot. In other words, a four-foot ditch is precisely a three-foot ditch in size and form, with an additional foot on the top of it, and not a three-foot ditch deepened an additional foot.

The lowest foot of a four-foot ditch is raised one foot higher, to get it upon the surface, than if the ditch were but three feet deep. In clays, and most other soils, the earth grows harder as we go deeper, and this consideration, in practice, will be found important. Again: the small amount of earth from a three-foot ditch, may lie conveniently on one bank near its edge, while the additional ma.s.s from a deeper one must be thrown further; and then is to be added the labor of replacing the additional quant.i.ty in filling up.

On the whole, the point may be conceded, that the labor of opening and finishing a four-foot drain is double that of a three-foot drain.

Without stopping here to estimate carefully the cost of excavation and the cost of tiles, it may be remarked, that, upon almost any estimate, the cost of labor, even in a three-foot drain in this country, yet far exceeds the cost of tiles: but, if we call them equal, then, if the additional foot of depth costs as much as the first three feet, we have the cost of a four-foot tile-drain fifty per cent. more than that of a three-foot drain. In other words, 200 rods of four-foot drain will cost just as much as 300 rods of three-foot drain. This is, probably, as nearly accurate as any general estimate that can be made at present. The principles upon which the calculations depend, having been thus suggested, it will not be difficult to vary them so as to apply them to the varying prices of labor and tiles, and to the use of the plow or other implements propelled by animals or steam, when applied to drainage in our country.

The earliest experiments in thorough-drainage, in England, were at very small depths, two feet being, for a time, considered very deep, and large tracts were underlaid with tiles at a depth of eighteen, and even twelve inches. It is said, that 10,000 miles of drains, two feet deep and less, were laid in Scotland before it was found that this depth was not sufficient. Of course, the land thus treated was relieved of much water, and experimenters were often much gratified with their success; but it may be safely said now, that there is no advocate known to the public, in England, for a system of drainage of less than three feet depth, and no one advocates a system of drainage of less than four feet deep, except upon some peculiar clays.

The general principle seems well established, that depth will compensate for width; or, in other words, that the deeper the drain, the farther it will draw. This principle, generally correct, is questioned when applied to peculiar clays only. As to them, all that is claimed is, that it is more economical to make the drains but three feet, because they must, even if deep, be near together--n.o.body doubting, that if four feet deep or more, and near enough, they will drain the land.

In speaking of _clay_ soil, it should always be borne in mind, that clay is merely a relative term in agriculture. "A clay in Scotland," says Mr.

Pusey, "would be a loam in the South of England." Professor Mapes, of our own country, in the _Working Farmer_, says, "We are convinced, that, with thorough subsoil plowing, no clay soil exists in this country which might not be underdrained to a depth of four feet with advantage."

There can be no doubt, that, with four-foot drains at proper distances, all soils, except some peculiar clays, may be drained, even without reference to the changes produced in the mechanical structure of soil by the operation. There is no doubt, however, that all soils are, by the admission of air, which must always take the place of the water drawn out, and by the percolation of water through them, rendered gradually more porous. Added to this, the subsoil plow, which will be the follower of drainage, will break up the soil to considerable depth, and thus make it more permeable to moisture. But there is still another and more effective aid which Nature affords to the land-drainer, upon what might be otherwise impracticable clays.

This topic deserves a careful and distinct consideration, which it will receive under the t.i.tle of "Drainage of Stiff Clays."

In discussing the subject of the depth of drains, we are not unmindful of the fact that, in this country, the leaders in the drainage movement, especially Messrs. Delafield, Yeomans, and Johnston, of New York, have achieved their truly striking results, by the use of tiles laid at from two and a half to three feet depth. On the "Premium Farm" of R. J. Swan, of Rose Hill, near Geneva, it is stated that there are sixty-one miles of under-drains, laid from two and a half to three feet deep. That these lands thus drained have been changed in their character, from cold, wet, and unproductive wastes, in many cases, to fertile and productive fields of corn and wheat, sufficiently appears. Indeed, we all know of fields drained only with stone drains two feet deep, that have been reclaimed from wild gra.s.ses and rushes into excellent mowing fields. In England and in Scotland, as we have seen, thousands of miles of shallow drains were laid, and were for years quite satisfactory. These facts speak loudly in favor of drainage in general. The fact that shoal drains produce results so striking, is a stumbling-block in the progress of a more thorough system. It may seem like presumption to say to those to whom we are so much indebted for their public spirit, as well as private enterprise, that they have not drained deep enough for the greatest advantage in the end. It would seem that they should know their own farms and their own results better than others. We propose to state, with all fairness, the results of their experiments, and to detract nothing from the credit which is due to the pioneers in a great work.

We cannot, however, against the overwhelming weight of authority, and against the reasons for deeper drainage, which, to us, seem so satisfactory, conclude, that even three feet is, in general, deep enough for under-drains. Three-foot drains will produce striking results on almost any wet lands, but four-foot drains will be more secure and durable, will give wider feeding-grounds to the roots, better filter the percolating water, warm and dry the land earlier in Spring, furnish a larger reservoir for heavy rains, and, indeed, more effectually perform every office of drains.

In reviewing our somewhat minute discussion of this essential point--the proper depth of drains--certain propositions may be laid down with considerable a.s.surance.

TILES MUST BE LAID BELOW THE REACH OF THE SUBSOIL PLOW.

Let no man imagine that he shall never use the subsoil plow; for so surely as he has become already so much alive to improvement, as to thorough-drain, so surely will he next complete the work thus begun, by subsoiling his land.

The subsoil plow follows in the furrow of another plow, and if the forward plow turn a furrow one foot deep, the subsoil may be run two feet more, making three feet in all. Ordinarily, the subsoil plow is run only to the depth of 18 or 20 inches; but if the intention were to run it no deeper than that, it would be liable to dip much deeper occasionally, as it came suddenly upon the soft places above the drains.

The tiles should lie far enough below the deepest path of the subsoil plow, not to be at all disturbed by its pressure in pa.s.sing over the drains. It is by no means improbable that fields that have already been drained in this country, may be, in the lifetime of their present occupants, plowed and subsoiled by means of steam-power, and stirred to as great a depth as shall be found at all desirable. But, in the present mode of using the subsoil plow on land free from stones, a depth less than three and a half or four feet would hardly be safe for the depth of tile-drains.

TILES MUST BE LAID BELOW FROST.

This is a point upon which we must decide for our selves. There is no country where drainage is practiced, where the thermometer sinks, as in almost every Winter it does in New England, to 20 below zero (Fahrenheit).

All writers seem to a.s.sume that tile-drains must be injured by frost.

What the effect of frost upon them is supposed to be, does not seem very clear. If filled with water, and frozen, they must, of course, burst by the expansion of the water in freezing; but it would probably rarely happen, that drainage-water, running in cold weather, could come from other than deep sources, and it must then be considerably above the freezing point. Still; we know that aqueduct pipes do freeze at considerable depths, though supplied from deep springs. Neither these nor gas-pipes are, in our New England towns, safe below frost, unless laid four feet below the surface; and instances occur where they freeze at a much greater depth, usually, however, under the beaten paths of streets, or in exposed positions, where the snow is blown away. In such places, the earth sometimes freezes solid to the depth of even six feet.

It will be suggested at once that our fields, and especially our wet lands, do not freeze so deep, and this is true; but it must be borne in mind, that the very reason why our wet lands do not freeze deeper, may be, that they are filled with the very spring-water which makes them cold in Summer, indeed, but is warmer than the air in Winter, and so keeps out the frost. Drained lands will freeze deeper than undrained lands, and the farmer must be vigilant upon this point, or he may have his work ruined in a single Winter.

We are aware, that upon this, as every other point, ascertained facts may seem strangely to conflict. In the town of Lancaster, among the mountains in the coldest part of New Hampshire, many of the houses and barns of the village are supplied with water brought in aqueducts from the hills. We observed that the logs which form the conduit are, in many places, exposed to view on the surface of the ground, sometimes partly covered with earth, but generally very little protected. There has not been a Winter, perhaps in a half century, when the thermometer has not at times been 10 below Zero, and often it is even lower than that. Upon particular inquiry, we ascertained that very little inconvenience is experienced there from the freezing of the pipes. The water is drawn from deep springs in the mountains, and fills the pipes of from one to two-inch bore, pa.s.sing usually not more than one or two hundred rods before it is discharged, and its warmth is sufficient, with the help of its usual snow covering, to protect it from the frost.

We have upon our own premises an aqueduct, which supplies a cattle-yard, which has never been covered more than two feet deep, and has never frozen in the nine years of its use. We should not, therefore, apprehend much danger from the freezing of pipes, even at shallow depths, if they carry all the Winter a considerable stream of spring-water; but in pipes which take merely the surface water that pa.s.ses into them by percolation, we should expect little or no aid from the water in preventing frost. The water filtering downward in Winter must be nearly at the freezing point; and the pipes may be filled with solid ice, by the freezing of a very small quant.i.ty as it enters them.

Neither hard-burnt bricks nor hard-burnt tiles will crumble by mere exposure to the Winter weather above ground, though soft bricks or tiles will scarcely endure a single hard frost. Too much stress cannot be laid upon the importance of using hard-burnt tiles only, as the failure of a single tile may work extensive mischief. Writers seem to a.s.sume, that the freezing of the ground about the drains will displace the tiles, and so destroy their continuity, and this may be so; though we find no evidence, perhaps, that at three or four feet, there is any disturbance of the soil by freezing. We dig into clay, or into our strong subsoils, and find the earth, at three feet deep, as solid and undisturbed as at twice that depth, and no indication that the frost has touched it, though it has felt the grip of his icy fingers every year since the Flood. With these suggestions for warning and for encouragement, the subject must be left to the sound judgment of the farmer or engineer upon each farm, to make the matter so safe, that the owner need not have an anxious thought, as he wakes in a howling Winter night, lest his drains should be freezing.

Finally, in view of the various considerations that have been, suggested, as well as of the almost uniform authority of the ablest writers and practical men, it is safe to conclude, that, in general, in this country, wherever sufficient outfall can be had, _four feet above the top of the tiles should be the minimum depth of drains_.

CHAPTER VIII.

ARRANGEMENT OF DRAINS.

Necessity of System.--What Fall is Necessary.--American Examples.--Outlets.--Wells and Relief-Pipes.--Peep holes.--How to secure Outlets.--Gate to Exclude Back-Water.--Gratings and Screens to keep out Frogs, Snakes, Moles, &c.--Mains, Submains, and Minors, how placed.--Capacity of Pipes.--Mains of Two Tiles.--Junction of Drains.--Effect of Curves and Angles on Currents.--Branch Pipes.--Draining into Wells or Swallow Holes.--Letter from Mr.

Denton.

As every act is, or should be, a part of a great plan of life, so every stake that is set, and every line laid in the field, should have relation not only to general principles, but also to some comprehensive plan of operations.

a.s.suming, then, that the principles advocated in this treatise are adopted as to the details, that the depth preferred is not less than four feet--that the direction preferred is up and down the slope--that the distance apart may range from fifteen to sixty feet, and more in some cases, according to the depth of drains and the nature of the soil--that no tiles smaller than one and a half inch bore will be used, and none less than two inches except for the first one hundred yards, there still remains the application of all these principles to the particular work in hand. With the hope of a.s.sisting the deliberations of the farmer on this point, some additional suggestions will be made under appropriate heads.