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.
Assuming, 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 assisting the deliberations of
the farmer on this point, some additional suggestions will be made under
appropriate heads.
ARRANGEMENT MUST HAVE REFERENCE TO SYSTEM.
The absolute necessity of some regularity of plan in our work, must be
manifest. Without system, we can never, in the outset, estimate the
cost of our operation; we can never proportion our tiles to the quantity
of water that will pass through them; we can never find the drains
afterwards, or form a correct opinion of the cause of any failure that
may await us.
We prefer, in general, where practicable, parallel lines for our minor
drains, at right angles with the mains, because this is the simplest and
most systematic arrangement; but the natural ravines or water-courses in
fields, seldom run parallel with each other, or at right angles with the
slope of the hills, so that regular work like this, can rarely be
accomplished.
If the earth were constructed of regular slopes, or plains of uniform
character, we could easily apply to it all our rules; but, broken as it
is into hills and valleys, filled with stones here, with a bank of clay
there, and a sand-pit close by, we are obliged to sacrifice to general
convenience, often, some special abstract rule.
We prefer to run drains up and down the slope; but if the field be
filled with undulations, or hills with various slopes, we may often find
it expedient, for the sake of system, to vary this course.
If the question were only as to one single drain, we could adjust it so
as to conform to our perfect ideal; but as each drain is, as it were, an
artery in a complicated system, which must run through and affect every
part of it, all must be located with reference to every other, and to
the general effect.
Keeping in mind, then, the importance of some regular system that shall
include the whole field of operation, the work should be laid out, with
as near a conformity to established principles as circumstances will
permit.
ARRANGEMENT MUST HAVE REFERENCE TO THE FALL.
In considering what fall is necessary, and what is desirable, we have
seen, that although a very slight inclination may carry off water, yet
a proportionably larger drain is necessary as the fall decreases,
because the water runs slower.
"It is surprising," says Stephens, "what a small descent is
required for the flow of water in a well-constructed duct. People
frequently complain that they cannot find sufficient fall to carry
off the water from the drains. There are few situations where a
sufficient fall cannot be found if due pains are exercised. It has
been found in practice, that a water-course thirty feet wide and
six feet deep, giving a transverse sectional area of one hundred
and eighty square feet, will discharge three hundred cubic yards of
water per minute, and will flow at the rate of one mile per hour,
with a fall of no more than _six inches per mile_."
Messrs. Shedd and Edson, of Boston, have superintended some drainage
works in Milton, Mass., where, after obtaining permission to drain
through the land of an adjacent owner, not interested in the operation,
they could obtain but three inches fall in one hundred feet, or a half
inch to the rod, for three quarters of a mile, and this only by blasting
the ledges at the outlet. This fall, however, proves sufficient for
perfect drainage, and by their skill, a very unhealthful swamp has been
rendered fit for gardens and building-lots. In another instance, in
Dorchester, Mass., Mr. Shedd informs us that in one thousand feet, they
could obtain only a fall of two inches for their main, and this, by nice
adjustment, he expects to make sufficient. In another instance, he has
found a fall of two and a half inches in one hundred feet, in an open
paved drain to be effectual.
It is certainly advisable always to divide the fall as even as possible
throughout the drains, yet this will be found a difficult rule to
follow. Very often we have a space of nearly level ground to pass
through to our outfall; and, usually, the mains, in order that the minor
drains may be carried into them from both sides, must follow up the
natural valleys in the field, thus controlling, in a great measure, our
choice as to the fall. We are, in fact, often compelled to use the
natural fall nearly as we find it.
It is thought advisable to have the mains from three to six inches lower
than the drains discharging into them, so that there may be no
obstruction in the minor drains by the backing up of water, and the
consequent deposition of sand or other obstructing substances. Wherever
one stream flows into another, there must be more or less interruption
of the course of each. If the water from the minors enters the main with
a quick fall, the danger of obstruction in the minor, at least, is much
lessened. A frequent cause of partial failure of drains, is their not
having been laid with a regular inclination. If, instead of a gradual
and uniform fall, there should be a slight rising in the bed of a drain,
the descending water will be interrupted there till it accumulate so
high as to be above the level of the rising. At this point, therefore,
the water must have a tendency to press out of the drains, and will
deposit whatever particles of sand or other earthy matter it may bring
down.
Drains must, therefore, be so arranged, that in cutting them, their beds
may be as nearly as possible, straight, or, at least, have a constant,
if not a regular and equal fall.
ARRANGEMENT MUST HAVE REFERENCE TO THE OUTLET.
All agree that it is best to have but few general outlets. "In the whole
process of draining," says an engineer of experience, "there is nothing
so desirable as permanent and substantial work at the point of
discharge." The outlet is the place, of all others, where obstruction is
most likely to occur. Everywhere else the work is protected by the earth
above it, but here it is exposed to the action of frost, to cattle, to
mischievous boys, to reptiles, as well as to the obstructing deposits
which are discharged from the drains themselves. In regular work, under
the direction of engineers, iron pipes, with swing gratings set in
masonry, are used, to protect permanently this important part of the
system of drainage.
It may often be convenient to run parallel drains down a slope, bringing
each out into an open ditch, or at the bottom of some bank, thus making
a separate outlet for each. This practice, however, is strongly
deprecated. These numerous outlets cannot be well protected without
great cost; they will be forgotten, or, at least, neglected, and the
work will fail.
Regarding this point, of few and well-secured outlets, as of great
importance, the arrangement of all the drains must have reference to it.
When drains are brought down a slope, as just suggested, let them,
instead of discharging separately, be crossed, near the foot of the
slope, by a sub-main running a little diagonally so as to secure
sufficient fall, and so carried into a main, or discharged at a single
outlet.
It may be objected, that by thus uniting the whole system, and
discharging the water at one point, there may be difficulty in
ascertaining by inspection, whether any of the drains are obstructed, or
whether all are performing their appropriate work. There is prudence and
good sense in this suggestion, and the objection may be obviated by
placing _wells_, or "peep-holes," at proper intervals, in which the flow
of the water at various points may be observed. On the subject of wells
and peep-holes, the reader will find in another chapter a more
particular description of their construction and usefulness.
The position of the outlet must, evidently, be at a point sufficiently
low to receive all the water of the field; or, in other words, it must
be the lowest point of the work. It will be fortunate, too, if the
outlet can be at the same time high enough to be at all times above the
back-water of the stream, or pond, or marsh, into which it empties; and
high enough, too, to be protected by solid earth about it. In any case,
great care should be taken to make the outlet secure and permanent. The
process of thorough-drainage is expensive, and will only repay cost,
upon the idea that it is permanent--that once well done, it is done
forever. The tiles may be expected to operate well, for a lifetime; and
the outlet, the only exposed portion of the work, should be constructed
to endure as long as the rest.
It is true that this portion of the work may be reached and repaired
more conveniently than the tiles themselves; but it must be remembered
that the decay of the outlet obstructs the flow of the water, produces a
general stagnation throughout the drains, and so may cause their
permanent obstruction at various points, hard to be ascertained, and
difficult to be reached. Considering our liability to neglect such
things as perish by a gradual decay, as well as the many accidental
injuries to which the outlet is exposed, there is no security but in a
solid and permanent structure at the first.
To illustrate the importance attached to this point in England, as well
as to indicate the best mode of securing the outlet, the drawings below
have been taken from a pamphlet by Mr. Denton. Fig. 37 represents the
mode of constructing the common small outlets of field drainage.
[Illustration: Fig. 37.--SMALL OUTLET.]
The distinguished engineer, of whose labors we have so freely availed
ourselves, remarks as follows upon the subject:
"Too many outlets are objectionable, on account of the labor of
their maintenance: too few are objectionable, because they can only
exist where there are mains of excessive length. A limit of twenty
acres to an outlet, resulting in an average of, perhaps, fourteen
acres, will appear, by the practices of the best drainers, to be
about the proper thing. If a shilling an acre is reserved for
fixing the outlets, which should be _iron pipes, with swing
gratings_, in masonry, very substantial work may be done."
Figures 38 and 39 represent the elevation and section of larger outlets,
used in more extensive works.
[Illustration: Fig. 38.--LARGE OUTLET.]
[Illustration: Fig. 39.--LARGE OUTLET.]
It is almost essential to the efficiency of drains, that there be fall
enough beyond the outlet to allow of the quick flow of the water
discharged. At the outlet, must be deposited whatever earth is brought
down by the drains; and, in many cases, the outlet must be at a swamp or
pond. If no decided fall can be obtained at the outlet, there must be
care to provide and keep an open ditch or passage, so that the
drainage-water may not be dammed back in the drains. It is advised,
even, to follow down the bank of a stream or river, so as to obtain
sufficient fall, rather than to have the outlet flooded, or _back-water_
in the drains. Still, there may be cases where it will be impossible to
have an outlet that shall be always above the level of the river or pond
which may receive the drainage water. If the outlet must be so situated
as to be at times overflowed, great care should be taken to excavate a
place at the outlet, into which any deposits brought down by the drain,
may fall. If the outlet be level with the ground beyond it, the smallest
quantity of earth will operate as a dam to keep back the water.
Therefore, at the outlet, in such cases, a small well of brick or
stonework should be constructed, into which the water should pour.
There, even if the water stand above the outlet, will be deposited the
earth brought along in the drain. This well must at times, when the
water is low, be cleared of its contents, and kept ready for its work.
The effect of back-water in drains cannot ordinarily be injurious,
except as it raises the water higher in the land, and occasions deposits
of earthy matter, and so obstructs the drains. We have in mind now, the
common case of water temporarily raised, by Winter flowage or by Summer
freshets.
It should be remembered that even when the outlet is under water, if
there is any current in the stream into which the drain empties, there
must be some current in the drain also; and even if the drain discharge
into a still pond, there must be a current greater or less, as water
from a level higher than the surface of the pond, presses into the
drains. Generally, then, under the most unfavorable circumstances, we
may expect to have some flow of water through the pipes, and rarely an
utter stagnation. If, then, the tiles be carefully laid, so as to admit
only well-filtered water, there can be but little deposit in the drain;
and a temporary stagnation, even, will not injure them, and a trifling
flow will keep them clean. Much will depend, as to the obstruction of
drains, in this, and indeed in all cases, upon the internal smoothness,
and upon the nice adjustment of the pipes. In case of the drainage of
marshes, and other lands subject to sudden flood, a flap, or gate, is
used to exclude the water of flowage, until counterbalanced by the
drainage-water in the pipes.
[Illustration: Fig. 40.--OUTLET PIPE WITH FLAP TO EXCLUDE FLOOD-WATER.]
We are quite sure that it is not in us a work of supererogation to urge
upon our farmers the importance of careful attention to this matter of
outlets. This is one of that class of things which will never be
attended to, if left to be daily watched. We Americans have so much work
to do, that we have no time to be careful and watchful. If a child fall
into the fire, we take time to snatch him out. If a sheep or ox get
mired in a ditch, we leave our other business, and fly to the rescue.
Even if the cows break into the corn, all hands of us, men and boys and
dogs, leave hoeing or haying, and drive them out. And, by the way, the
frequency with which most of us have had occasion to leave important
labors to drive back unruly cattle, rendered lawless by neglect of our
fences, well illustrates a national characteristic. We are earnest,
industrious, and intent on _doing_. We can look forward to accomplish
any labor, however difficult, but lack the conservatism which preserves
the fruit of our labors--the "old fogyism" which puts on its spectacles
with most careful adjustment, after wiping the glasses for a clear
sight, and at stated periods, revises its affairs to see if some screw
has not worked loose. A steward on a large estate, or a corporation
agent, paid for inspecting and superintending, may be relied upon to
examine his drainage works, and maintain them in repair; but no farmer
in this country, who labors with his own hands, has time even for this
most essential duty. His policy is, to do his work now, while he is
intent upon it, and not trust to future watchfulness.
We speak from personal experience in this matter of outfalls. Our first
drains ran down into a swamp, and the fall was so slight, that the mains
were laid as low as possible, so that at every freshet they are
overflowed. We have many times, each season, been compelled to go down,
with spade and hoe, and clear away the mud which has been trodden up by
cattle around the outlet. Although a small river flows through the
pasture, the cows find amusement, or better water, about these drains,
and keep us in constant apprehension of a total obstruction of our
works. We propose to relieve ourself of this care, by connecting the
drains together, and building one or more reliable outlets.
GRATINGS OR SCREENS AT THE OUTLET.
There are many species of "vermin," both "creeping things" and "slimy
things, that crawl with legs," which seem to imagine that drains are
constructed for their especial accommodations. In dry times, it is a
favorite amusement of moles and mice and snakes, to explore the devious
passages thus fitted up for them, and entering at the capacious open
front door, they never suspect that the spacious corridors lead to no
apartments, that their accommodations, as they progress, grow "fine by
degrees and beautifully less," and that these are houses with no back
doors, or even convenient places for turning about for a retreat. Unlike
the road to Hades, the descent to which is easy, here the ascent is
inviting; though, alike in both cases, "_revocare gradum, hoc opus hic
labor est_." They persevere upward and onward till they come, in more
senses than one, to "an untimely end." Perhaps stuck fast in a small
pipe tile, they die a nightmare death; or, perhaps overtaken by a
shower, of the effect of which, in their ignorance of the scientific
principles of drainage, they had no conception, they are drowned before
they have time for deliverance from the straight in which they find
themselves, and so are left, as the poet strikingly expresses it, "to
lie in cold _obstruction_ and to rot."
In cold weather, water from the drains is warmer than the open ditch,
and the poor frogs, reluctant to submit to the law of Nature which
requires them to seek refuge in mud and oblivious sleep, in Winter,
gather round the outfalls, as they do about springs, to bask in the
warmth of the running water. If the flow is small, they leap up into
the pipe, and follow its course upward. In Summer, the drains furnish
for them a cool and shady retreat from the mid-day sun, and they may be
seen in single file by scores, at the approach of an intruding footstep,
scrambling up the pipe. Dying in this way, affects these creatures, as
"sighing and grief" did Falstaff, "blows them up like a bladder;" and,
like Sampson, they do more mischief in their death, than in all their
life together. They swell up, and stop the water entirely, or partially
dam it, so that the effect of the work is impaired.
To prevent injuries from this source, there should be, at every outlet,
a grating or screen of cast iron, or of copper wire, to prevent the
intrusion of vermin. The screen should be movable, so that any
accumulation in the pipe may be removed. An arrangement of this kind is
shown in Fig. 40, as used in England. We know of nothing of the kind
used in this country. For ourself, we have made of coarse wire-netting,
a screen, which is attached to the pipe by hinges of wire. Holes may be
bored with a bit through even a hard tile, or a No. 9 wire may be
twisted firmly round the end of it, and the screen thus secured.
This has thus far, been our own poor and unsatisfactory mode of
protecting our drains. It is only better than none, but it is not
permanent, and we hope to see some successful invention that may supply
this want. So far as we have observed, no such precaution is used in
this country; and in England, farmers and others who take charge of
their own drainage works, often run their pipes into the mud in an open
ditch, and trust the water to force its own passage.
OF WELLS AND RELIEF PIPES.
In draining large tracts of land of uniform surface, it is often
convenient to have single mains, or even minors, of great length.
Obstructions are liable to occur from various causes: and, moreover,
there is great satisfaction in being certain that all is going right,
and in watching the operation of our subterranean works. It is a common
practice, and to be commended, to so construct our drains, that they may
be inspected at suspicious points, and that so we may know their real
condition.
For this purpose, wells, or traps, are introduced at suitable points,
into which the drains discharge, and from which the water proceeds again
along its course.
These are made of iron, or of stone or brick work, of any size that may
be thought convenient, secured by covers that may be removed at
pleasure.
Where there is danger of obstruction below the wells, relief pipes may
be introduced, or the wells may overflow, and so discharge temporarily,
the drainage water. These wells, sometimes called silt basins, or traps,
are frequently used in road drainage, or in sewers where large deposits
are made by the drainage water. The sediment is carried along and
deposited in the traps, while the water flows past.
These traps are large enough for a man to enter, and are occasionally
cleared of their contents.
When good stone, or common brick, are at hand, occasional wells may be
easily constructed. Plank or timber might be used; and we have even seen
an oil cask made to serve the purpose temporarily. In most parts of New
England, solid iron castings would not be expensive.
The water of thorough-drainage is usually as pure as spring-water, and
such wells may often be conveniently used as places for procuring water
for both man and beast, a consideration well worth a place in
arrangements so permanent as those for drainage.
The following figures represent very perfect arrangements of this kind,
in actual use.
[Illustration: Figs. 41 & 42.--WELL WITH SILT BASIN, OR TRAP, AND
COVER.]
The flap attached to a chain at A, is designed to close the incoming
drain, so as to keep back the water, and thus flush the drain, as it is
termed, by filling it with water, and then suddenly releasing it. It is
found that by this process, obstructions by sand, and by per-oxide of
iron, may be brought down from the drains, when the flow is usually
feeble.
SMALL WELLS, OR PEEP-HOLES.
By the significant, though not very elegant name of peep-holes, are
meant openings at junctions, or other convenient points, for watching
the pulsations of our subterranean arteries.
In addition to the large structures of wells and traps, such as have
been represented, we need small and cheap arrangements, by which we may
satisfy ourselves and our questioning friends and neighbors, that every
part of our buried treasure, is steadily earning its usury. It is really
gratifying to be able to allow those who "don't see how water can get
into the tiles," and who inquire so distrustfully whether you "don't
think that land on the hill would be just as dry without the drains," to
satisfy themselves, by actually seeing, that there is a liberal flow
through all the pipes, even in the now dry soil. And then, again,
"The best laid schemes o' mice an' men
Gang aft agley."
and drains will get obstructed, by one or other of the various means
suggested in another place. It is then convenient to be able to
ascertain with certainty, and at once, the locality of the difficulty,
and this may be done by means of peep-holes.
These may be formed of cast iron, or of well-burnt clay, or what is
called stone-ware, of 4, 6, or 10 inches internal diameter, and long
enough to reach from the bottom of the drain to the surface, or a little
above it.
The drain or drains, coming into this little well, should enter a few
inches above the pipe which carries off the water, so that the incoming
stream may be plainly seen. A strong cover should be fitted to the top,
and secured so as not to cause injury to cattle at work or feeding on
the land. The arrangement will be at once seen by a sketch given on the
following page.
[Illustration: Figs. 43 & 44.--SMALL WELL, OR PEEP-HOLE, AND COVER.]
In our own fields, we have adopted several expedients to attain this
object of convenient inspection. In one case, where we have a sub-main,
which receives the small drains of an acre of orchard, laid at nearly
five feet depth, we sunk two 40-gallon oil casks, one upon the other, at
the junction of this sub-main with another, and fitted upon the top a
strong wooden cover. The objections to this contrivance are, that it is
temporary; that it occupies too much room; and that it is more expensive
than a well of cast iron or stone-ware of proper size.
In another part of the same field, we had a spring of excellent water,
where, "from the time whereof the memory of man runneth not to the
contrary," people had fancied they found better water to drink, than
anywhere else. It is near a ravine, through which a main drain is
located, and which is now graded up into convenient plow land.
To preserve this spring for use in the Summer time, we procured a
tin-worker to make a well, of galvanized iron, five feet long and ten
inches diameter, into which are conducted the drain and the spring. A
friendly hand has sketched it for us very accurately; thus:
[Illustration: Figs. 45 & 46.--HOW TO PRESERVE A SPRING IN A DRAINED
FIELD.]
The spring is brought in at _a_ by a few tiles laid into the bank where
the water naturally bursts out. The pipe _b_ brings in the drain, which
always flows largely, and the pipe _c_ carries away the water. The small
dipper, marked _d_, hangs inside the well, and is used by every man,
woman, and boy, who passes that way. The spring enters six inches above
the drain, for convenience in catching its water to drink.
By careful observation the present Winter of 1858-9, the impression that
there is some peculiar quality in this water is confirmed, for it is
ascertained that it is six degrees warmer in cold weather than any other
water upon the farm. The spring preserves a temperature of about 47 deg.,
while the drain running through the same well, and the other drains in
the field, and the well at the house, vary from 39 deg. to 42 deg..
We confess to the weakness of taking great satisfaction in sipping this
water, cool in Summer and warm in Winter, and in watching the mingled
streams of spring and drainage water, and listening as we pass by, to
their tinkling sound, which, like the faithful watchman of the night,
proclaims that "all is well."
POSITION AND SIZE OF THE MAINS.
Having fixed on the proper position of the outlet, for the whole, or any
portion of our work, the next consideration is the location of the
drains that shall discharge at that point. It is convenient to speak of
the different drains as _mains_, _sub-mains_, and _minors_. By _mains_,
are understood the principal drains, of whatever material, the office of
which is, to receive and carry away water collected by other drains from
the soil. By _minors_, are intended the small drains which receive the
surplus water directly from the soil. By _sub-mains_, are meant such
intermediate drains as are frequently in large fields, interposed across
the line of the minors, to receive their discharge, and conduct their
water to the mains.
They are principally used, where there is a greater length of small
drains in one direction than it is thought expedient to use; or where,
from the unequal surface, it is necessary to lay out subordinate systems
of drains, to reach particular localities.
Whether after the outlet is located, the mains or minors should next be
laid out, is not perhaps very important. The natural course would seem
to be, to lay out the mains according to the surface formation of the
land, through the principal hollows of the field, although we have high
authority for commencing with the minors, and allowing their
appropriate direction to determine the location of the mains.
This is, however, rather a question of precedence and etiquette, than of
practical importance. The only safe mode of executing so important a
work as drainage, is by careful surveys by persons of sufficient skill,
to lay out the whole field of operations, before the ground is broken;
to take all the levels; to compare all the different slopes; consider
all the circumstances, and arrange the work as a systematic whole.
Generally, there will be no conflict of circumstances, as to where the
mains shall be located. They must be lower than the minors, because they
receive their water. They must ordinarily run across the direction of
the minors, either at right angles or diagonally, because otherwise they
cannot receive their discharge. If, then, in general, the minors, as we
assume, run down the slope, the mains must run at the foot of the slope
and across it.
It will be found in practice, that all the circumstances alluded to,
will combine to locate the mains across the foot of regular slopes; and
whether in straight or curved lines, along through the natural valleys
of the field.
In locating the mains, regard must always be had to the quantity of
water and to the fall. Where a field is of regular slope, and the
descent very slight, it will be necessary, in order to gain for the main
the requisite fall, to run it diagonally across the bottom of the slope,
thus taking into it a portion of the fall of the slope. If the fall
requires to be still more increased, often the main may be deepened
towards the outlet, so as to gain fall sufficient, even on level ground.
If the fall is very slight, the size of the main may be made to
compensate in part for want of fall, for it will not be forgotten, that
the capacity of a pipe to convey water depends much on the velocity of
the current, and the velocity increases in proportion to the fall. If
the fall and consequent velocity be small, the water will require a
larger drain to carry it freely along. The size of the mains should be
sufficient to convey, with such fall as is attainable, the greatest
quantity of water that may ever be expected to reach them. Beyond this,
an increase of size is rather a disadvantage than otherwise, because a
small flow of water runs with more velocity when compressed in a narrow
channel, than when broadly spread, and so has more power to force its
way, and carry before it obstructing substances.
We have seen, in considering the size of tiles, that in laying the minor
drains, their capacity to carry all the water that may reach them is not
the only limit of their size. A one-inch tile might in many cases be
sufficient to conduct the water; but the best drainers, after much
controversy on the point, now all agree that this is a size too small
for prudent use, because so small an opening is liable to be obstructed
by a very slight deposit from the water, or by a slight displacement,
and because the joints furnish small space for the admission of water.
Mains, however, being designed merely to carry off such water as they
may receive from other drains, may in general be limited to the size
sufficient to convey such water, at the greatest flow. It might seem a
natural course, to proportion the capacity of the main to the capacity
of the smaller drains that fall into it; and this would be the true
rule, were the small drains expected to run full.
If our smallest drain, however, be of two-inch, or even one and a half
inch bore, it can hardly be expected to fill at any time, unless of
great length, or in some peculiarly wet place. Considering, then, what
quantity of water will be likely to be conducted into the main,
proportion the main not to the capacity of all the smaller drains
leading into it, but to the probable maximum flow--not to what they
_might_ bring into it, but to what they _will_ bring.
If the mains be of three-inch pipes, other things being equal, their
capacity is nine times that of a one-inch pipe, and two and a quarter
times the capacity of a two-inch pipe.
A three-inch main may, then, with equal fall and directness, be safely
relied on to carry nine streams of water equal each to one inch
diameter, or two and a quarter streams, equal to a two-inch stream. The
three-inch main will, in fact, from the less amount of friction, carry
much more than this proportion.
The allowance to be made for a less fall in the mains, has already been
adverted to, and must not be overlooked. It is believed that the
capacity of a three or four-inch pipe to convey water, is in general
likely to be much under-estimated.
It is a common error, to imagine that some large stone water-course must
be necessary to carry off so large a flow as will be collected by a
system over a ten or twenty-acre field. Any one, however, who has
watched the full flow of even a three-inch pipe, and observed the water
after it has fallen into a nearly level ditch, will be aware, that what
seems in the ditch a large stream, impeded as it is by a rough, uneven
bottom, may pass through a three inch opening of smooth, well-jointed
pipes. When we consider that a four-inch pipe is four times as capacious
as a two-inch pipe, and sixteen times as large as a one-inch pipe, we
may see that we may accommodate any quantity of water that may be likely
anywhere to be collected by drainage, without recourse to other
materials than tiles.
When one three or four-inch pipe is not sufficient to convey the water,
mains may conveniently be formed of two or more tiles of any form. A
main drain is sometimes formed by combining two horse-shoe tiles, with a
tile sole or slate between them, to prevent slipping, as in fig. 47.
[Illustration: Fig. 47. Fig. 48.
Main Drain of two or more Horse-shoe Tiles.]
The combinations represented in the above figures, will furnish
sufficient suggestions to enable any one to select or arrange such forms
as may be deemed best suited to the case in hand. Where the largest
obtainable tile is not large enough, two or more lines of pipes may be
laid abreast.
POSITION OF THE MINOR DRAINS.
Assuming that it is desirable to run the small drains, as far as
practicable, up and down the slope, the following directions, from the
Cyclopedia of Agriculture, are given:
"There is a very simple mode of laying out these (the minor
drains), which will apply to most cases, or, indeed, to all,
although in some its application may be more difficult. The surface
of each field must be regarded as being made up of one or more
planes, as the case may be, for each of which the drains should be
laid out separately. Level lines are to be set out, a little below
the upper edge of each of these planes, and the drains must be then
made to cross these lines at right angles. By this means, the
drains will run in the line of the greatest slope, no matter how
distorted the surface of the field may be."
Much is said, in the English books, about "furrows," and the
"direction of the furrows," in connection with the laying out of drains.
Much of the land in England, especially in moist places, was formerly
laid up by repeated plowings, into ridges varying in breadth from ten to
twenty feet, so as to throw off, readily, the water from the surface.
[Illustration: PART OF FIELD Thoroughly Drained BY B F. NOURSE
ORRINGTON, ME.]
These ridges were sometimes so high, that two boys in opposite furrows,
between the ridges, could not see each other. In draining lands thus
ridged, it is found far more easy to cut the ditches in the furrows,
rather than across or upon the ridges. After thorough-drainage, in most
localities, these ridges and furrows are dispensed with. The fact is,
probably, only important here, as explaining the constant reference by
English writers to this mode of working the land.
Whether we shall drain "down the furrows," or "across the ridges," is
not likely to be inquired of, by Americans.
The accompanying diagram represents a field of about thirty acres, as
drained by the owner, B. F. Nourse, Esq., of Orrington, Me., a
particular description of which will be found in another place.
The curves of the ends of the minors, at their junction with the mains,
will indicate their course--the minors curving always so as to more
nearly coincide, in course, with the current of water in the mains.
THE JUNCTION OF DRAINS.
Much difficulty arises in practice, as to connecting, in a secure and
satisfactory manner, the smaller with the larger drains. It has already
been suggested, that the streams should not meet at right angles, but
that a bend should be made in the smaller drain, a few feet before it
enters the main, so as to introduce the water of the small drain in the
direction of the current in the main. In another place, an instance is
given where it was found that a quantity of water was discharged with a
turn, or junction with a gentle curve, in 100 seconds, that required 140
seconds with a turn at right angles; and that while running direct, that
is, without any turn, it was discharged in 90 seconds. This is given as
a mere illustration of the principle, which is obvious enough. Different
experiments would vary with the velocity, quantity of water, and
smoothness of the pipe; but nothing is more certain, than that every
change of direction impedes velocity.
Thus we see that if we had but a single drain, the necessary turns
should be curved, to afford the least obstruction.
Where the drain enters into another current, there is yet a further
obstruction, by the meeting of the two streams. Two equal streams, of
similar velocity and size, thus meeting at right angles, would have a
tendency to move off diagonally, if not confined by the pipe; and,
confined as they are, must both be materially retarded in their flow. In
whatever manner united, there must be much obstruction, if the main is
nearly full, at the point of junction. The common mode of connecting
horse-shoe tile-drains is shown thus:
[Illustration: Fig. 50.--JUNCTION OF DRAINS.]
Having no tiles made for the purpose, we, at first, formed the union by
means of common hard bricks. Curving down the small drain toward the
direction of the main, we left a space between two tiles of the main, of
two or three inches, and brought down the last tile of the small drain
to this opening, placing under the whole a flat stone, slate, or bricks,
or a plank, to keep all firm at the bottom. Then we set bricks on edge
on all sides, and covered the space at the top with one or more, as
necessary, and secured carefully against sand and the like.
We have since procured branch-pipes to be made at the tile-works, such
as are in use in England, and find them much more satisfactory. The
branches may be made to join the mains at any angle, and it might be
advisable to make this part of both drains larger than the rest, to
allow room for the obstructed waters to unite peacefully.
[Illustration: Fig. 51. BRANCH PIPES.]
The mains should be from three to six inches deeper than the minors. The
fall from one to the other may usually be made most conveniently, by a
gradual descent of three or four feet to the point of junction; but with
branch-pipes, the fall may be nearly vertical, if desired, by turning
the branch upward, to meet the small pipe. It will be necessary, in
procuring branches for sole-tiles, to bear in mind that they are "rights
and lefts," and must be selected accordingly, as the branch comes in
upon the one or other side of the main.
The branch should enter the larger pipe not level with the bottom, but
as high as possible, to give an inch fall to the water passing out of
the branch into the main, to prevent possible obstruction at the
junction.
DRAINAGE INTO WELLS, OR SWALLOW HOLES.
In various parts of our country, there are lands lying too flat for
convenient drainage in the ordinary methods, or too remote from any good
outlet, or perhaps enclosed by lands of others who will not consent to
an outfall through their domain, where the drainage water may be
discharged into wells.
In the city of Washington, on Capitol Hill, it is a common practice to
drain cellars into what are termed "dry wells." The surface formation is
a close red clay, of a few feet thickness, and then comes a stratum of
coarse gravel; and the wells for water are sunk often as deep as sixty
feet, indicating that the water-table lies very low. The heavy storms
and showers fill the surface soil beyond saturation, and the water
gushes out, literally, into the cellars and other low places. A dry
well, sunk through the clay, conducts this water into the gravel bed,
and this carries it away. This idea is often applied to land drainage.
It is believed that there are immense tracts of fertile land at the
West, upon limestone, where the surface might readily be relieved of
surplus water, by conducting the mains into wells dug for the purpose.
In some places, there are openings called "sink-holes," caused by the
sinking of masses of earth, as in the neighborhood of the city of St.
Louis, which would afford outlets for all the water that could be poured
into them. In the Report of the Tioga County Agricultural Society for
1857, it is said in the _Country Gentleman_, that instances are given,
where swamps were drained through the clay bottom into the underlying
gravelly soil, by digging wells and filling them with stones.
In Fig. 7, at page 82, is shown a "fault" in the stratification of the
earth; which faults, it is said, so completely carry off water, that
wells cannot be sunk so as to reach it.
Mr. Denton says that in several parts of England, advantage is taken of
the natural drainage existing beneath wet clay soils, by concentrating
the drains to holes, called "swallow-holes." He says this practice is
open to the objection that those holes do not always absorb the water
with sufficient rapidity, and so render the drainage for a time,
inoperative.
These wells are liable, too, to be obstructed in their operation by
their bottoms being puddled with the clay carried into them by the
water, and so becoming impervious. This point would require occasional
attention, and the removal of such deposits.
This principle of drainage was alluded to at the American Institute,
February 14, 1859, by Professor Nash. He states, that there are large
tracts of land having clay soil, with sand or gravel beneath the clay,
which yet need drainage, and suggests that this may be effected by
merely boring frequent holes, and filling them with pebbles, without
ditches. In all such soils, if the mode suggested prove insufficient,
large wells of proper depth, stoned up, or otherwise protected, might
obviously serve as cheap and convenient outlets for a regular system of
pipe or stone drains.
Mr. Bergen, at the same meeting, stated that such clayey soil, based on
gravel, was the character of much of the land on Long Island; and we
cannot doubt that on the prairies of the West, where the wells are
frequently of great depth to obtain water for use, wells or
swallow-holes to receive it, may often be found useful. Whenever the
water-line is twenty or thirty feet below the surface, it is certain
that it will require a large amount of water poured in at the surface of
a well to keep it filled for any considerable length of time. The same
principle that forces water into wells, that is, pressure from a higher
source, will allow its passage out when admitted at the top.
We close this chapter with a letter from Mr. Denton. The extract
referred to, has been here omitted, because we have already, in the
chapter preceding this, given Mr. Denton's views, expressed more fully
upon the same subject, with his own illustrations.
It should be stated that the letter was in reply to inquiries upon
particular points, which, although disconnected, are all of interest,
when touched upon by one whose opinions are so valuable.
"LONDON, 52 Parliament Street, Westminster, S. W.
"MY DEAR SIR:--I have received your letter of the 17th August, and
hasten to reply to it.
"I am gratified at the terms in which you speak of my
roughly-written 'Essays on Land Drainage.' If you have not seen my
published letter to Lord Berners, and my recent essay 'On the
Advantages of a Daily Record of Rain-fall,' I should much like you
to look over them, for my object in both has been to check the
uniformity of treatment which too much prevails with those who are
officially called upon to direct draining, and who still treat
mixed soils and irregular surfaces pretty much in the same way as
homogeneous clays and even surfaces, the only difference being,
that the distance between the drains is increased. We have now,
without doubt, arrived at that point in the practice of draining in
this country, which necessitates a revision of all the principles
and rules which have been called into force by the Drainage Acts,
and the institution of the Drainage Commission, whose duty it is to
administer those Acts, and to protect the interests of
Reversioners.
"This protection is, in a great measure, performed by the
intervention of 'Inspectors of Drainage,' whose subordinate duty it
is to see that the improvements provisionally sanctioned are
carried out according to certain implied, if not fixed, rules. This
is done by measuring depth and distance, which tends to a _parallel
system (4 feet deep) in all soils_, which was Smith of Deanston's
notion, only his drains were shallower, _i.e._, from 2 to 3 feet
deep.
"Some rules were undoubtedly necessary when the Commissioners first
commenced dispensing the public money, and I do not express my
objection to the absurd position to which these rules are bringing
us, from any disrespect to them, nor with an idea that any better
course could have been followed by the Government, in the first
instance, than the adoption of the '_Parkes--Smith frequent drain
system_.' This system was correctly applied, and continues to be
correctly applied, to absorbent and retentive soils requiring the
aeration of frequent drains to counteract their retentive nature;
but it is altogether misapplied when adopted in the outcropping
surfaces of the free water-bearing strata, which, though equally
wet, are frequently drained by a comparatively few drains, at less
than half the cost.
"The only circumstance that can excuse the indiscriminate adoption
of a parallel system, is the fact, that all drains do some good,
and the chances of a cure being greater in proportion to the number
of drains, it was not necessary to insist upon that judgment which
ten years' experience should now give.
"My views on this point will perhaps be best understood by the
following extract from an address I recently delivered. [Extract
omitted, see p. 161].
* * * "I use one and a half inch pipes for the upper end of drains
(_though I prefer two-inch_), one half being usually one and a half
and the other half two-inch. This for minor drains; the mains run
up to 9 or 10 inches, and even 18 inches in size, according to
their service.
"There is no doubt sufficient capacity in one-inch pipes for minor
drains; but, inasmuch as agricultural laborers are not mathematical
scholars, and are apt to lay the pipes without precise junctions,
it is best to have the pipes so large as to counteract that degree
of carelessness which cannot be prevented. The ordinary price of
pipes in this country will run thus: + meaning _above_,
and-_below_, the prices named:
1-1/2 inch 15s. +
2 " 20s. -
3 " 30s.
4 " 40s. +
5 " 50s. +
6 " 60s. +
"The price of cutting clays 4 feet deep, will vary from 1d. to
1-1/2d. per yard, according to density and mixture with stone; and
the price of cutting in mixed soils will vary from 1-1/2d. to 6d.,
according to the quantity of pick-work and rock, and with respect,
also, to the price of agricultural labor. (See my tabular table of
cost in Land Drainage and Drainage Systems.)
"I should have thought it would have been quite worth the while of
the American Government to have had a farm of about 500 acres,
drained by English hands, under an experienced engineer, as a
practical sample of English work, for the study of American
agriculturists, with every drain laid down on a plan, with the
sizes of the pipes, and all details of soil, and prices of labor
and material, set forth.
"I am, dear Sir,
"Yours very faithfully,
"The HON. H. F. FRENCH, Exeter. "J. BAILEY DENTON."