DIRECTION, DISTANCE, AND DEPTH OF DRAINS.
DIRECTION OF DRAINS.--Whence comes the Water?--Inclination of
Strata.--Drains across the Slope let Water out as well as Receive
it.--Defence against Water from Higher Land.--Open
Ditches.--Headers.--Silt-basins.
DISTANCE OF DRAINS.--Depends on Soil, Depth, Climate, Prices,
System.--Conclusions as to Distance.
DEPTH OF DRAINS.--Greatly Increases Cost.--Shallow Drains first
tried in England.--10,000 Miles of Shallow Drains laid in Scotland
by way of Education.--Drains must be below Subsoil plow, and
Frost.--Effect of Frost on Tiles and Aqueducts.
DIRECTION OF DRAINS.
Whether drains should run up and down the slope of the hill, or directly
across it, or in a diagonal line as a compromise between the first two,
are questions which beginners in the art and mystery of drainage usually
discuss with great zeal. It seems so plain to one man, at the first
glance, that, in order to catch the water that is running down under the
soil upon the subsoil, from the top of the hill to the bottom, you must
cut a ditch across the current, that he sees no occasion to examine the
question farther. Another, whose idea is, to catch the water in his
drain before it rises to the surface, as it is passing up from below or
running along on the subsoil, and keep it from rising higher than the
bottom of his ditch, thinks it quite as obvious that the drains should
run up and down the slope, that the water, once entering, may remain in
the drain, going directly down hill to the outlet. A third hits on the
Keythorpe system, and regarding the water as flowing down the slope,
under the soil, in certain natural channels in the subsoil, fancies they
may best be cut off by drains, in the nature of mains, running
diagonally across the slope.
These different ideas of men, if examined, will be found to result
mainly from their different notions of the underground circulation of
water. In considering the Theory of Moisture, an attempt was made to
suggest the different causes of the wetness of land.
To drain land effectually, we must have a correct idea of the sources of
the water that makes the particular field too wet; whether it falls from
the clouds directly upon it; or whether it falls on land situated above
it and sloping towards it, so that the water runs down, as upon a roof,
from other fields or slopes to our own; or whether it gushes up in
springs which find vent in particular spots, and so is diffused through
the soil.
If we have only to take care of the water that falls on our own field,
from the clouds, that is quite a different matter from draining the
whole adjoining region, and requires a different mode of operation. If
your field is in the middle, or at the foot, of an undrained slope, from
which the water runs on the surface over your land, or soaks through it
toward some stream or swamp below, provision must be made not only for
drainage of your own field, but also for partial drainage of your
neighbor's above, or at least for defence against his surplus of water.
The first, and leading idea to be kept in mind, as governing this
question of the direction of drains, is the simple fact that _water runs
down hill_; or, to express the fact more scientifically, water
constantly seeks a lower level by the force of gravitation, and the
whole object of drains is to open lower and still lower passages, into
which the water may fall lower and lower until it is discharged from our
field at a safe depth.
Water goes down, then, by its own weight, unless there is something
through which it cannot readily pass, to bring it out at the surface. It
will go into the drains, only because they are lower than the land
drained. It will never go _upward_ to find a drain, and it will go
toward a drain the more readily, in proportion as the descent is more
steep toward it.
To decide properly what direction a drain should have, it is necessary,
then, to have a definite and a correct idea as to what office the drain
is to perform, what water is to fall into it, what land it is to drain.
Suppose the general plan to be, to lay drains forty feet apart, and four
feet deep over the field, and the question now to be determined, as to
the _direction_, whether across, or up and down the slope, there being
fall enough to render either course practicable. The first point of
inquiry is, what is expected of each drain? How much and what land
should it drain? The general answer must be, forty feet breadth, either
up and down the slope, or across it; according to the direction. But we
must be more definite in our inquiry than even this. From _what_ forty
feet of land will the water fall into the drain? Obviously, from some
land in which the water is higher than the bottom of the drain.
If, then, the drain run directly _across_ the slope, most of the water
that can fall into it, must come from the forty feet breadth of land
between the drain in question, and the drain next above it. If the water
were falling on an impervious surface, it would all run according to the
slope of the surface, in which case, by the way, no drains but those
across, could catch any of it except what fell upon the drains. But the
whole theory of drainage is otherwise, and is based on the idea that we
change the course of the underground flow, by drawing out the water at
given points by our drains; or, in other words, that "the water seeks
the lowest level in all directions."
Upon the best view the writer has been able to take of the two systems
as to the direction of drains, there is but a very small advantage in
theory in favor of either over the other, in soil which is homogeneous.
But it must be borne in mind that homogeneous soil is rather the
exception in nature than the rule.
Without undertaking to advance or defend any peculiar geological views
of the structure of the earth, or of the depositions or formations that
compose its surface, it may be said, that very often the first four feet
of subsoil is composed of strata, or layers of earth of varying
porosity.
Beneath sand will be found a stratum of clay, or of compact or cemented
gravel, and frequently these strata are numerous and thin. Indeed, if
there be not some stratum below the soil, which impedes the passage of
water, it would pass downward, and the land would need no artificial
drainage. Quite often it will be found that the dip or inclination of
the various strata below the soil is different from that of the surface.
The surface may have a considerable slope, while the lower strata lie
nearly level, as if they had been cut through by artificial grading.
The following figure from the Cyclopedia of Agriculture, with the
explanation, fully illustrates this idea.
"In many subsoils there are thin partings, or layers, of porous
materials, interspersed between the strata, which, although not of
sufficient capacity to give rise to actual springs, yet exude
sufficient water to indicate their presence. These partings
occasionally crop out, and give rise to those damp spots, which are
to be seen diversifying the surface of fields, when the drying
breezes of Spring have begun to act upon them. In the following
cut, the light lines represent such partings.
"Now, it will be evident, in draining such land, that if the drains
be disposed in a direction transverse or oblique to the slope, it
will often happen that the drains, no matter how skillfully
planned, will not reach these partings at all, as at A. In this
case, the water will continue to flow on in its accustomed channel,
and discharge its waters at B.
[Illustration: Fig. 34--DRAINS ACROSS THE SLOPE.]
"But again, even though it does reach these partings, as at C, a
considerable portion of water will escape from the drain itself,
and flow to the _lower level_ of its old point of discharge at D.
Whereas, a drain cut in the line of the slope, as from D to E,
intersects all these partings, and furnishes an outlet to them at a
lower level than their old ones."
These reasons are, it is true, applicable only to land of peculiar
structure; but there are reasons for selecting the line of greatest fall
for the direction of drains which are applicable to all lands alike.
"The line of the greatest fall is the only line in which a drain is
relatively lower than the land on either side of it." Whether we regard
the surplus water as having recently fallen upon the field, and as being
stopped near the surface by an impervious stratum, or as brought down on
these strata from above, we have it to be disposed of as it rests upon
this stratum, and is borne out by it to the surface.
If there is a decided dip, or inclination, of this stratum outward down
the slope, it is manifest that the water cannot pass backward to a cross
drain higher up the slope. The course of the water must be downward upon
the stratum on which it lies, and so all between two cross drains must
pass to the lower one. The upper drain could take very little, if any,
and the greater the inclination of this stratum, the less could flow
backward.
But in such case a drain down the slope gives to the water borne up by
these strata, an outlet of the depth of the drain. If the drain be four
feet deep, it cuts the water-bearing strata each at that depth, and
takes off the water.
In these cases, the different layers of clay or other impervious
"partings," are like the steps of a huge stairway, with the soil filling
them up to a regular grade. The ditch cuts through these steps, letting
the water that rests on them fall off at the ends, instead of running
over the edges. Drains across the slope have been significantly termed
"mere catch-waters."
If we wish to use water to irrigate lands, we carefully conduct it along
the surface across the slope, allowing it to flow over and to soak
through the soil. If we desire to carry the same water off the field as
speedily as possible, we should carry our surface ditch directly down
the slope.
Now, looking at the operation of drains across the slope, and supposing
that each drain is draining the breadth next above it, we will suppose
the drain to be running full of water. What is there to prevent the
water from passing out of that drain in its progress, at every point of
the tiles, and so saturating the breadth below it? Drainpipes afford the
same facility for water to soak out at the lower side, as to enter on
the upper, and there is the same law of gravitation to operate in each
case. Mr. Denton gives instances in which he has observed, where drains
were carried across the slope, in Warwickshire, lines of moisture at a
regular distance below the drains. He could ascertain, he says, the
depth of the drain itself, by taking the difference of height between
the line of the drain at the surface, and that of the line of moisture
beneath it. He says again:
"I recently had an opportunity, in Scotland, of gauging the quantity
of water traveling along an important drain carried obliquely across
the fall, when I ascertained with certainty, that, although the land
through which it passed was comparatively full of water, the drain
actually lost more than it gained in a passage of several chains
through it."
So far as authority goes, there seems, with the exception of some
advocates of the Keythorpe system, of which an account has been given,
to be very little difference of opinion. Mr. Denton says:
"With respect to the direction of drains, I believe very little
difference of opinion exists. All the most successful drainers
concur in the line of the steepest descent, as essential to
effective and economical drainage. Certain exceptions are
recognized in the West of England, but I believe it will be found,
as practice extends in that quarter, that the exceptions have been
allowed in error."
In another place, he says:
"The very general concurrence in the adoption of the line of
greatest descent, as the proper course for the minor drains in
soils free from rock, would almost lead me to declare this as an
incontrovertible principle."
Allusion has been made to cases where we may have to defend ourselves
from the flow of water from higher undrained lands of our neighbor. To
arrest the flow of mere surface water, an open ditch, or catch-water, is
the most effectual, as well as the most obvious mode. There are many
instances in New England, where lands upon the lowest slopes of hills
are overflowed by water which fell high up upon the hill, and, after
passing downward till arrested by rock formation, is borne out again to
the surface, in such quantity as to produce, just at the foot of the
hill, almost a swamp. This land is usually rich from the wash of the
hills, but full of cold water.
To effect perfect drainage of a portion of this land, which we will
suppose to be a gentle slope, the first object must be to cut off the
flow of water upon or near the surface. An open ditch across the top
would most certainly effect this object, and it may be doubtful whether
any other drain would be sufficient. This would depend upon the quantity
of water flowing down. If the quantity be very great at times, a part of
it would be likely to flow across the top of an under-drain, from not
having time to percolate downward into it.
In all cases, it is advised, where our work stops upon a slope, to
introduce a cross-drain, connecting the tops of all the minor-drains.
This cross-drain is called a _header_. The object of it is to cut off
the water that may be passing along in the subsoil down the slope, and
which would otherwise be likely to pass downward between the system of
drains to a considerable distance before finding them. If we suppose the
ground saturated with water, and our drains running up the slope and
stopping at 4 feet depth, with no header connecting them, they, in
effect, stop against 4 feet head of water, and in order to drain the
land as far up as they go, must not only take their fair proportion of
water which lies between them, but must draw down this 4 feet head
beyond them. This they cannot do, because the water from a higher
source, with the aid of capillary attraction, and the friction or
resistance met with in percolation, will keep up this head of water far
above the drained level.
In railway cuttings, and the like, we often see a slope of this kind cut
through, without drying the land above the cutting; and if the slope be
disposed in alternate layers of sand or gravel, and clay, the water will
continue to flow out high up on the perpendicular bank. Even in porous
soils of homogeneous character, it will be found that the _head_ of
water, if we may use the expression, is affected but a short distance
by a drain across its flow. Indeed, the whole theory as to the distance
of drains apart, rests upon the idea, that the limit to which drains may
be expected effectually to operate, is at most but two or three rods.
Whether, in a particular case, a header alone will be sufficient to cut
off the flow of water from the higher land, or whether, in addition to
the header, an open catch-water may be required, must depend upon the
quantity of water likely to flow through or upon the land. An
under-drain might be expected to absorb any moderate quantity of what
may be termed drainage-water, but it cannot stop a river or mill-stream;
and if the earth above the tiles be compact, even water flowing through
the soil with rapidity, might pass across it. If there is reason to
apprehend this, an open ditch might be added to the header; or, if this
is not considered sufficiently scientific or in good taste, a tile-drain
of sufficient capacity may be laid, with the ditch above it carefully
packed with small stones to the top of the ground. Such a drain would be
likely to receive sand and other obstructing substances, as well as a
large amount of water, and should, for both reasons, be carried off
independently of the small drains, which would thus be left to discharge
their legitimate service.
Where it is thought best to connect an open, or surface drain, with a
covered drain, it will add much to its security against silt and other
obstructions, to interpose a trap or silt-basin at the junction, and
thus allow the water to pass off comparatively clean. Where, however,
there is a large flow of water into a basin, it will be kept so much in
motion as to carry along with it a large amount of earth, and thus
endanger the drain below, unless it be very large.
DISTANCES APART, OR FREQUENCY OF DRAINS.
The reader, who has studied carefully the rival systems of "deep
drainage" and "thorough drainage," has seen that the distance of drains
apart, is closely connected with that controversy. The greatest variety
of opinion is expressed by different writers as to the proper distances,
ranging all the way from ten feet apart to seventy, or even more.
Many English writers have ranged themselves on one side or the other of
some sharp controversy as to the merits of some peculiar system. Some
distinguished geologist has discovered, or thinks he has, some new law
of creation by which he can trace the underground currents of water; or
some noble noble lord has "patronized" into notice some caprice of an
aspiring engineer, and straight-way the kingdom is convulsed with
contests to set up or cast down these idols. By careful observation, it
is said, we may find "sermons in stones, and good in everything;" and,
standing aloof from all exciting controversies, we may often profit, not
only by the science and wisdom of our brethren, but also by their errors
and excesses. If, by the help of the successes and failures of our
English neighbors, we shall succeed in attaining to their present
standard of perfection in agriculture, we shall certainly make great
advances upon our present position.
As the distances of drains apart, depend manifestly on many
circumstances, which may widely vary in the diversity of soil, climate,
and cost of labor and materials to be found in the United States, it
will be convenient to arrange our remarks on the subject under
appropriate heads.
DISTANCES DEPEND UPON THE NATURE OF THE SOIL.
Water runs readily through sand or gravel. In such soils it easily seeks
and finds its level. If it be drawn out at one point, it tends towards
that point from all directions. In a free, open sand, you may draw out
all the water at one opening, almost as readily as from an open pond.
Yet, even such sands may require draining. A body of sandy soil
frequently lies not only upon clay, but in a basin; so that, if the sand
were removed, a pond would remain. In such a case, a few deep
drains, rightly placed, might be sufficient. This, however, is a case
not often met with, though open, sandy soil upon clay is a common
formation.
Then there is the other extreme of compact clay, through which water
seems scarcely to percolate at all. Yet it has water in it, that may
probably soak out by the same process by which it soaked in. Very few
soils, of even such as are called clay, are impervious to water,
especially in the condition in which they are found in nature. To render
them impervious, it is necessary to wet and stir them up, or, as it is
termed, _puddle_ them. Any soil, so far as it has been weathered--that
is, exposed to air, water and frost--is permeable to water to a greater
or less degree; so that we may feel confident that the upper stratum of
any soil, not constantly under water, will readily allow the water to
pass through.
And in considering the "Drainage of Stiff Clays," we shall see that the
most obstinate clays are usually so affected by the operation of
drainage, that they crack, and so open passages for the water to the
drains.
All gravels, black mud of swamps, and loamy soils of any kind, are
readily drained.
Occasionally, however--even in tracts of easy drainage, as a
whole--deposits are found of some combinations with iron, so firmly
cemented together, as to be almost impenetrable with the pick-axe, and
apparently impervious to water. Exceptional cases of this nature must
be carefully sought for by the drainer.
Whenever a wet spot is observed, seek for the cause, and be satisfied
whether it is wet because a spring bursts up from the bottom; or because
the subsoil is impervious, and will not allow the surface-water to pass
downward. Ascertain carefully the cause of the evil, and then skillfully
doctor the disease, and not the symptoms merely. A careful attention to
the theory of moisture, will go far to enable us properly to determine
the requisite frequency of drains.
DISTANCES DEPEND UPON THE DEPTH OF THE DRAINS.
The relations of the depth and distance of drains will be more fully
considered, in treating of the depth of drains. The idea that depth will
compensate for frequency, in all cases, seems now to be abandoned. It is
conceded that clay-soils, which readily absorb moisture, and yet are
strongly retentive, cannot be drained with sufficient rapidity, or even
thoroughness, by drains at any depth, unless they are also within
certain distances.
In a porous soil, as a general rule, the deeper the drain, the further
it will draw. The tendency of water is to lie level in the soil; but
capillary attraction and mechanical obstructions offer constant
resistance to this tendency. The farther water has to pass in the soil,
the longer time, other things being equal, will be required for the
passage. Therefore, although a single deep drain might, in ten days
lower the water-line as much as two drains of the same depth, or, in
other words, might draw the water all down to its own level, yet, it is
quite evident that the two drains might do the work in less
time--possibly, in five days. We have seen already the necessity of
laying drains deep enough to be below the reach of the subsoil plow and
below frost, so that, in the Northern States, the question of shallow
drainage seems hardly debatable. Yet, if we adopt the conclusion that
four feet is the least allowable depth, where an outfall can be found,
there may be the question still, whether, in very open soils, a still
greater depth may not be expedient, to be compensated by increased
distance.
DISTANCES DEPEND UPON CLIMATE.
Climate includes the conditions of temperature and moisture, and so,
necessarily, the seasons. In the chapter which treats of _Rain_, it will
be seen that the quantity of rain which falls in the year is singularly
various in different places. Even, in England, "the annual average
rain-fall of the wettest place in Cumberland is stated to be 141 inches,
while 19-1/2 inches may be taken as the average fall in Essex. In
Cumberland, there are 210 days in the year in which rain falls, and in
Chiswick, near London, but 124."
A reference to the tables in another place, will show us an infinite
variety in the rain-fall at different points of our own country.
If we expect, therefore, to furnish passage for but two feet of water in
the year, our drains need not be so numerous as would be necessary to
accommodate twice that quantity, unless, indeed, the time for its
passage may be different; and this leads us to another point which
should ever be kept in mind in New England--the necessity of quick
drainage. The more violent storms and showers of our country, as
compared with England, have been spoken of when considering _The Size of
Tiles_. The sudden transition from Winter to Summer, from the breaking
up of deep snows with the heavy falls of rain, to our brief and hasty
planting time, requires that our system of drainage should be efficient,
not only to take off large quantities of water, but to take them off in
a very short time. How rapidly water may be expected to pass off by
drainage, is not made clear by writers on the subject.
"One inch in depth," says an English writer, "is a very heavy fall of
rain in a day, and it generally takes two days for the water to drain
fully from deep drained land." One inch of water over an acre is
calculated to be something more than one hundred tons. This seems, in
gross, to be a large amount, but we should expect that an inch, or even
two inches of water, spread evenly over a field, would soon disappear
from the surface; and if not prevented by some impervious obstruction,
it must continue downward.
It is said, on good authority, that, in England, the smallest sized
pipes, if the fall be good, will be sufficiently large, at ordinary
distances, to carry off all the surplus water. In the author's own
fields, where two-inch tiles are laid at four feet depth and fifty feet
apart, in an open soil, they seem amply sufficient to relieve the ground
of all surplus water from rain, in a very few days. Most of them have
never ceased to run every day in the year, but as they are carried up
into an undrained plain, they probably convey much more water than falls
upon the land in which they lie.
So far as our own observation goes, their flow increases almost as soon
as rain begins to fall, and subsides, after it ceases, about as soon as
the water in the little river into which they lead, sinks back into its
ordinary channel, the freshet in the drains and in the stream being
nearly simultaneous. Probably, two-inch pipes, at fifty feet distances,
will carry off, with all desirable rapidity, any quantity of water that
will ever fall, if the soil be such that the water can pass through it
to the distance necessary to find the drains; but it is equally probable
that, in a compact clay soil, fifty feet distance is quite too great for
sufficiently rapid drainage, because the water cannot get to the drains
with sufficient rapidity.
DISTANCES DEPEND UPON THE COMPARATIVE PRICES OF LABOR AND TILES.
The fact, that the last foot of a four-foot drain costs as much labor as
the first three feet, is shown in another chapter, and the deeper we go,
the greater the comparative cost of the labor. With tiles at $10 per
thousand, the cost of opening and filling a four-foot ditch is, in,
round numbers, by the rod, equal to twice the cost of the tiles. In
porous soils, therefore, where depth may be made to compensate for
greater distance, it is always a matter for careful estimate, whether we
shall practice true economy by laying the tiles at great depths, or at
the smallest depth at which they will be safe from frost and the subsoil
plow, and at shorter distances. The rule is manifest that, where labor
is cheap and tiles are dear, it is true economy to dig deep and lay few
tiles; and, where tiles are cheap and labor is dear, it is economy to
make the number of drains, if possible, compensate for less depth.
DISTANCES DEPEND UPON SYSTEM.
While we would not lay down an arbitrary arrangement for any farm,
except upon a particular examination, and while we would by no means
advocate what has been called the gridiron system--of drains everywhere
at equal depths and distances--yet some system is absolutely essential,
in any operation that approaches to thorough drainage.
If it be only desired to cut off some particular springs, or to assist
Nature in some ravine or basin, a deep drain here and there may be
expedient; but when any considerable surface is to be drained, there can
be no good work without a connected plan of operations.
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, illustrated 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.
[Illustration: 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 space 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 quantity 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.
[Illustration: 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 circumstances 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 mass from a deeper one must
be thrown further; and then is to be added the labor of replacing the
additional quantity 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--nobody 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 title 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 grasses 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 assurance.
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 passing 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 deg. below zero
(Fahrenheit).
All writers seem to assume 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 deg. 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, passing 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 passes 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 quantity 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 assume, 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_.