IRRIGATION. 
than that of forming a fish-pond, of a siiita- pitch. These ridges should be from four 
ble extent and depth, to receive the tail- 
water; whereby the apprehended damage 
may be avoided, and a useful store be cre- 
ated. 
We shall shew what we may term a truly 
ingenious device, whereby water may be 
laid vipon lands that are above the level of 
the stream ; it consists merely of an air-ves- 
sel, A, fig. 3, into which the water descends 
forcibly from the stream, B, and by com- 
pressing the air in the upper part, C, is it- 
self forced to ascend through the conduct- 
ing pipe, D, with such force as to rise to a 
level, E, far above that at which it formerly 
stood. This is the principle of the com- 
mon fire-engine, which, we are all sensible, 
can, when exerted, throw water to a great 
height. By such means, the tail-water may 
also be forced up to such a level as may 
cause it to return into the stream. 
Where the stream runs through the lands 
that are watered, and that its declivity is 
moderate, it will sometimes be found diffi- 
cult to restore the tail-water to its level. 
To effect this with as little expence as pos- 
sible, wooden pipes should be laid from the 
lowest level of the land ^long the bank of 
the stream, but carried horizontally on a 
bank, to such extent as may suffice to con- 
vey the tail-water to the surface of the sur- 
face. This, however, is not applicable to 
all situations ; for where the stream is very 
slow, its declivity would be very trifling. 
Where that happens, the air vessel will be 
found a good plan, provided the height to 
which the water is to be returned, be not 
considerable. In many situations, a water- 
wheel might answer well; observing, that 
in deep, slow waters, that are broad, and 
under the speculator’s own management, it 
will be best to throw a weir across, and 
then to let the whole body of the stream 
rush through a narrow slip, so as to turn a 
wheel placed immediately in the line of the 
water’s run. By this device, the current 
may be made to pass that particular spot 
with sufficient velocity to turn a wheel; 
whereby water might either be ivaised out 
of the river, to supply a main drain, or the 
tail-water might be restored to the stream : 
in either case, one or more pumps would 
be necessary. (See fig. 4.) 
Tlie second mode of laying water ever 
the land, is by means of ridges, whose cen- 
tres are occupied by small horizontal drains, 
out of which the water, furnished by the 
main drain, is allowed to flow to the depth 
of about an inch down each side of the 
to six feet measurement for each face ; the 
drain being about a foot broad, and four 
inches deep ; thus the whole breadth of a 
pitch, declining each way equally, might 
occupy a base of about ten feet at the ut- 
most. The declivities ought not to exceed 
an inch to the foot ; in loose soils, not more 
than half an inch ; else the finer parts will' 
be washed away, and the drains, formed by 
the junctions of the ridges, wilt be filled up, 
whereby the water will be detained, and 
prevented from passing into the next level. 
Fig. 5, shews the profile, or section of a 
range of ridges on the same level, and 
fig. 6, displays an inclined plane, whereon 
ridges are formed in regular succession, the 
catch-drains being a little higher than the 
branch-drains of the next lower level, 
so that the latter may be filled from the 
foriiier : the. water thus gradually descend- 
ing, until thd whole, is gradually absorbed 
by the successive ridges ; or the surplus is 
carried off by a large catch-drain, made to 
direct it into some other succession of 
ridges, as seen in the ground-plan, fig. T. 
The reader will perceive, that the levels 
may lay in any direction, according to the 
cast of the land; and, that where water 
can be had at a due height, all the land be- 
low it may be watered. It matters not if a 
deep valley lay between twm declivities, to 
be watered by the same spring. A pipe, 
of suitable diameter, being made to descend 
one face, and to rise up the other, will con- 
vey the stream with facility to any part ; so 
as to re-assume the level on the opposite 
side. For further insight into that circum- 
stance, see Fluids, Hydraulics, and Hy- 
drostatics. 
It often happens, that small rivers have 
a very winding course among little hills, 
banks, rocky masses, &c., and that they 
suddenly lose many feet of their altitude, 
owing to a fall, or steep declivity; while 
the lower parts of the stream, being more 
expanded, and the water being kept up by 
another impediment, perhaps a few hun- 
dred yards lower, offer a seemingly invinci- 
ble impediment to the conducting it over 
the finely-formed planes, which present 
themselves on either bank. Here the diffi- 
culty is far less than , at first sight is sup- 
posed ; since, by making an outlet from the 
superior level of the stream, through the 
bank which separates it from the planes to 
be, watered, an abundant and certain sup- 
ply may be obtained. ' Thus in fig. 8, the 
upper level, A, and fall, B, are shewn, and 
