551 
stagnant on the surface, from the clayey or 
Impervious nature of the soil or superior stra- 
tum, The first of these causes bogs, swamps, 
tend morasses, and is the most difficult to be 
■remedied. 
I It may be laid down as a maxim, that 
[springs are formed in the bowels of the earth, 
jby water percolating through the strata 
[where they are of a porous texture, and 
lit continues to descend till it meets with 
[a stratum of clay that intercepts it in its 
[course ; where, being collected in large quan- 
tities, it is forced to seek a passage through 
the porous strata of sand, gravel, or rock, 
that may be above the clay, following the 
i course of these strata till they approach the 
1 surface of the earth, or are interrupted by 
any obstacle which occasions the water to rise, 
[thus forming springs, bogs, and the other 
phenomena of this nature; which being va- 
riously diversified in different circumstances, 
produce that variety of appearances in this 
respect that we often meet with. 
This being the case, we may naturally con- 
clude, that an abundant spring need never be 
| expected in any country that is covered to a 
I great depth with sand without any stratum 
: of clay to force it upwards, as is the case in 
| the sandy deserts of Arabia, and the immea- 
[surable plains of Lybia: neither are veto 
! expect abundant springs in any soil that con- 
I sists of an uniform bed of clay from the sur- 
| face to a great depth ; for it must always be 
| iii some porous stratum that the water flows 
| in abundance ; and it can be made to flow 
horizontally in that, only when it is support- 
ed by a stratum of clay, or other substance 
that is equally impermeable by water. Hence 
j the rationale of that rule so universally esta- 
1 Wished in digging for wells, that it you begin 
with sand or gravel, &c. you need seldom 
! hope to find water till you come to clay ; and 
j if you begin with clay, you can hope for none 
i in abundance till you reach to sand, gravel, 
or rock. 
It is necessary that the farmer should at- 
I tend to this process of nature with care, as 
his success in draining bogs and every spe- 
cies of damp and spouting ground, will in a 
| great measure depend upon his thorough 
I knowledge of this, his acuteness in perceiv- 
ing in every case the variations that may be 
I occasioned by particular circumstances, and 
| his skill in varying the plan of his operations 
i according to these. As the variety ot cases 
that may occur in this respect is very great, 
it would be a tedious task to enumerate the 
l whole, and describe the particular method of 
; treating each ; we shall therefore content our 
i! selves with enumerating a few particular cases 
to show in what manner the principles above- 
i established may be applied to practice. 
Let fig. 57, Plate Miscel. represent a per- 
i pendicular section of a part of the earth, in 
( which AB is the surface of the ground, be- 
neath which are several strata of porous sub- 
i stances that allow the water to sink through 
them till it reaches the line CD, that is sup- 
[ posed to represent the upper surface of a 
I solid bed of clay ; above which lies a stratum 
; «f rock, sand, or gravel. In this case it is 
: plain that when the water reaches the bed of 
clay, and can sink no farther, it must be 
there accumulated into a body ; and seeking 
for itself a passage, it flows along the surface 
•f the clay, among the sand or gravel, from 
DRAINING. 
D towards C ; till at last it issues forth* at 
the opening A, a spring of pure water. 
If the quantity of water that is accumulated 
between D and C is not very considerable, 
and the stratum of clay approaches near the 
surface ; in that case the whole of it will issue 
by the opening at A, and the ground will re- 
main dry both above and below it. But if 
the quantity of water is so great as to raise it 
to a considerable height in the bed of sand 
or gravel, and if that stratum of sand is not 
discontinued before it reaches the surface of 
the ground, the water, in this case, would not 
only issue at A, but would likewise ooze out 
in small streams through every part of the 
ground between A and a, forming a barren 
patch of wet sandy or gravelly ground upon 
the side of a declivity, which every attentive 
observer must have frequently met with. 
To drain a piece of ground in this situation 
is perhaps the most unprofitable task that a 
farmer can engage in, not only because it is 
difficult to execute, but also because the 
soil that is gained is but of very little va- 
lue. It is lucky, however, that patches of 
this kind are seldom of great breadth, al- 
though they sometimes run along the side of 
a declivity in a horizontal direction for a 
: great length. The only effectual method of 
draining this kind of ground, is to open a 
ditch as high up as the highest of the springs 
at a, which should be of such a depth as not 
only to penetrate through the whole bed of 
sand or gravel, but also to sink so far into the 
bed of clay below, as to make a canal in it 
sufficiently large to contain and carry off the 
water. Such a ditch is represented by tire 
dotted lines aez : but as the expence of mak- 
ing a ditch of such a depth as this would sup- 
pose, and of keeping it afterwards in repair, 
is very great, it is but in very few cases that 
this mode of draining would be advisable ; 
and never, unless where the declivity hap- 
pens to be so small as that a great surface is 
lost for little depth, as would have been the 
case here if the surface had extended in the 
direction of the dotted line ad. 
But supposing that the stratum of clay, 
after approaching towards the surface at A, 
continued to keep at a little depth below 
ground ; and that the soil which lay above it 
was of a sandy or spongy nature, so as to al- 
low the water to penetrate it easily ; even 
supposing the quantity of water that flowed 
front D to C was but very inconsiderable, 
instead of rising out at the spring A, it would 
flow forward along the surface of the clay 
among the porous earth that forms the soil, 
so as to keep it constantly drenched with 
water, and of consequence render it of very- 
little value. 
Wetness arising from this cause is usually 
of much greater extent than the former ; and 
as it admits of an easy cure, it ought not to 
be delayed ; as a ditch of a very moderate 
depth opened at A, and carried through a 
part of the stratum of clay (as represented 
by the dotted lines A kf), would intercept 
and carry off the whole of the water, and 
render tire field as dry as could be desired. 
It is, therefore, of very great consequence to 
the farmer accurately to distinguish between 
these two cases, so nearly allied to each 
other in appearance; and as this can be 
easiest done by boring, every one who has 
much ground of this kind ought to provide 
himself with a set of boring-irons, which he 
will likewise find use for on other occasions. 
We might here enumerate a great variety 
of cases which might be reduced to the same 
head with the foregoing ; but as any attentive 
reader may, alter what has been said, be able 
easily to distinguish these, we shall only in 
general observe, that every soil ol a soft and 
porous texture that lies upon a bed of hard 
clay, whatever its situation in other respects 
may be, will in some measure be subjected 
to this disease. And if it is upon a declivity 
of any considerable length, the undermost 
parts of the field will be much damaged by 
it, unless ditches are thrown up across the 
declivity at proper distances from one ano- 
ther, to" intercept the water in its descent. 
It may likewise be not improper here to 
observe, that in eases of this nature, unless 
where the soil is of a very great depth, the 
malady will always be increased by raising 
the ridges to a considerable height ; as will 
appear evident by examining fig. 58. in which 
the line AB represents the surface of a field 
of this nature, and CD the surface of the 
bed of clay. Now if this field was raised- 
into high ridges', as at FFF, so that the fur- 
rows F F F descended below the surface of the 
clay, it is plain that all the water that should 
sink through the middle of. the ridge, would 
run along the surface of the clay till it came 
to tire sides of the ridge LLLLLL, which 
would thus be kept- continually soaked with 
water. Whereas, if the ground had been 
kept level, as in the part of the field from G- 
to H, with open furrows H, at moderate dis- 
tances from each other, the water would im- 
mediately sink to the clay, and Ire carried off 
by the furrows, so as to damage the soil far 
less than when the ridges are high. If the 
soil is so thin as that the plough can always- 
touch the clay, the ridges ought to be made 
narrow and quite flat,, as from G to H: but 
if there is a little greater depth of soil, then 
it ought to be raised into ridges of a mode- 
rate height, as from Id to B, so as to allow 
the bottom of the furrow to reach the clay: 
but neither is this necessary where the soil is 
of any considerable depth. 
Some industrious farmers having ground: 
in tills situation, have been at the very great 
expence of making a covered drain in each 
furrow. But, had they rightly understood. 
the nature of the disease, they never would: 
have thought of applying such a remedy, as 
must appear evident at first sight to those 
who examine tire figure. The success was 
what might be expected from such a foolish, 
undertaking. 
These observations, it is hoped, will be- 
sufficient as to the manner of treating wet,, 
sandy, or porous soils. We now proceed to* 
take notice of such as are of a stiff clayey na- 
ture, which are often very different in appear- 
ance, and require a different treatment, from< 
these. 
Suppose that the stratum, of sand or gravel 
DC, fig. 59. should be discontinued, as at E< 
and that the stratum above it should be of a 
coherent clayey nature: in this case, the 
water that flowed towards E, being there 
pent in on every side, and being accumulated* 
there in great quantities, it must at length 
force a passage for itself in some way ; and 
pressing strongly upon the upper surface, if 
any one part is weaker than the rest, it there- 
would burst forth and forpi a spring .(as sup- 
