re A represents the surface-soil; B, the
impervious subsoil of clay; C, the bed of sandy-clay or gravel; and
D, the lower bed of clay, resting upon the rocky strata beneath.

[Illustration: Fig. 10.]

"Springs sometimes communicate with lakes or pools, at higher
levels. In such cases, the quantity of water discharged is
generally so great, as to form at once a brook or stream of some
magnitude. These, therefore, hardly come under the ordinary
cognizance of the land-drainer, and are, therefore, here merely
referred to."

THE WATER OF PRESSURE.

Water that issues from the land, either constantly, periodically, or
even intermittently, may, perhaps, be properly termed a _spring_. But
there is often much water in the soil which did not fall in rain upon
that particular field, and which does not issue from it in any defined
stream, but which is slowly passing through it by percolation from a
higher source, to ooze out into some stream, or to pass off by
evaporation; or, perhaps, farther on, to fall into crevices in the soil,
and eventually form springs. As we find it in our field, it is neither
rain-water, which has there fallen, nor spring-water, in any sense. It
has been appropriately termed the _water of pressure_, to distinguish it
from both rain and spring-water; and the recognition of this term will
certainly be found convenient to all who are engaged in the discussion
of drainage.

The distinction is important in a legal point of view, as relating to
the right of the land-owner to divert the sources of supply to
mill-streams, or to adjacent lower lands. It often happens that an owner
of land on a slope may desire to drain his field, while the adjacent
owner below, may not only refuse to join in the drainage, but may
believe that he derives an advantage from the surface-washing or the
percolation from his higher neighbor. He may believe that, by deep
drainage above, his land will be dried up and rendered worthless; or, he
may desire to collect the water which thus percolates, into his land,
and use it for irrigation, or for a water-ram, or for the supply of his
barn-yard. May the upper owner legally proceed with the drainage of his
own land, if he thus interfere with the interests of the man below?

Again: wherever drains have been opened, we already hear complaints of
their effects upon wells. In our good town of Exeter, there seems to be
a general impression on one