The Daily state journal. [volume] (Alexandria, Va.) 1868-1874, 1872-12-20
PRACTICE OF DRAINAGE.
BY NJ. @. JOHNSON.

understandings for the benefit ofour country
readers, who may not have extended works
on the subject or experience Of their own.
It Is from the Itbica Journal.
When about TO commence drainage OPP
GRAFTON the first thing to be done is to find
the proper outlet for the main drain. This
should always be at the lowest part of the
field. The next thing in order. is to fix
the location of the man drain. 1t should
always pass through the principal hol-
low or lowest part Of the field. Its di.
rection should be carefully marked out
with small stakes. Whenthe field slopes in
one direction. or towards one hollow, only
one main drain will be required, but when
the field slopes in many directions, in order
that the parallels may all be lain with the
slope Of the land, it will be necessary to
have large drains to discharge the waters of
each of The minor hollows throughout the
field. 10 save the expense of making sep
srate outlets, they should always, if posi-
bic, be connected with the main Grain, in
which case they are called sub-msins.
When field has q continuous
slope from top TO bottom, the
man drain should be run along the lower
side of the field at right angles to the
slope. If the field is very long, main
drains should be run across the slope every
two hundred yards, and conducted down
the field al its side. Sometimes there
will be knols in the field which will
necessitate the running of sub-msin
entirely around their base. After the main
drain and sub mains have been located and
staked out the next thing in order il to
locate and stake out the parallels. After
they have been staked out and before
the bitches have been opened, the drainage
material should be carted on to the field as
it can then be more easily drawn over.
The drainage material. if tile, should be
spread along the line Of the drains in order
to know the amount needed, allowing some
thing for breakage. In case, however, of
the main and sub-mains the tile should be
placed in piles between the parallels to give
place for their opening. The main drain
should nowbe opened. Work should be COM
menced ut the lower end, as this allows the
water which may gather in the drain, to run
Oh and not hinder the workmen. After
the man drain the sub-mairs should next
be opened. The depth of these will depend
much upon the lay of the land and the ma
ture OF soil. If the field is nearly level it
may be necessary to make an artificial fall,
in which case the depth of the drain, at the
lower end, might have to be six or seven
feet, or even more, while it could not be
more than two or three feet at the upper end.
Again, d to the nature Of the soil, drain
will drain water farther in @ porous soil
than In a tenacious soil, and hence they can
probably be made deeper in such soils.
In deciding on the depth Of the main
drain when the nature OF the soil is not
very marked it may be necessary to run one
or two exploratory drains through the field,
ct the maximum depth that it would be adj
yisable to go in a porous soil, say about
or 81 feet. After this has been open for
short time, by noting the point on the side
at which the greatest flow of water seems to
come in, some idea can be formed Of the
most appropriate depth OF the drain. To test
for the distance between the parallel, several
holes may be dug at different distances
from the drain as ten, twelve, fifteen or
even twenty feet. If the drain seems to
draw water from the hole twenty feet dis
ia 1t, then the drains can be forty feet
apart. II it draws only as far as to the
hole fifteen feet distant, then the drains
should be only thirty feet apart, &c. If
there is any difficulty in Distinguishing
from which hole the drain draws water, on
account of the dryness Of tho soil, several
pal of water might be emptied into the
several holes, and then note whether or
not it makes its appearance at the drain.
The depth of the main drain is usually
from four to five and half feet, though in
some stiff clays it might not be practicable
to drain deeper than three feet. The main
drain should be five or six inches deeper
than the parallels so as TO give them an
open, rapid passage into it, and they should
not enter it at right angles, but should
always be slanted in the direction of the
current to prevent the wearing away Of its
sides.
When an artificial fall is made, the par.
allels at the upper end, on account of their
shallow ness, will have to be nearer togeth-
or than at the lower end of the field. The
best fall for the main drain, that which
renders 1t most effective and durable, seems
TO DO about one foot in one hundred feet.
The fall should never be less than one inch
In $50 feet and never more than feet in 100.
When the fall is greater than that the
drain will have to be stepped. This
may be done either with brick or
stone. The main drain should be dug
with greater slope to its sides than the
parallels, as it has to stand open longer.
After the main and sub-main have been
opened the parallels should be opened and
it's tile lain. In laying the parallels work
should be commenced at the upper end, for
if work was commenced at the lower end OF
the field, as the workman progressed up'
ward the main drain would be filled with
muddy water and be in danger of becoming
choked up with sand and gravel. The
drain may he marked off with plow. In
digging o drain the dirt should be thrown
to the lower side-hence care should al-
ways be taken to place the drainage mate
rial on the upper side.
The narrower the drain is at the bottom
the better. When brought to the required
depth the drain should be bottomed, !. g.
fitted to the tile. There are certain instru-
ments for this especial work. The tile
should now be laid, which may be done
by the workmen on the bank with the aid
OF an instrument for this purpose, or it
may be done by the workmen standing
in the bottom of the drain. If the bot
tom of the drain is very wide the tile
should be wedged. They should be covered
with straw, seaweed, or something to act
rs a filter. Dirt should now be put on to
depth of five or six inches, then it should
be trodden down firmly, when it will act
more perfectly as filter. The rest OF the
L q 4. ont thf,C q