overflows incessantly in the form of Springs, that
carry with them fertility into the adjacent valleys.
(See PI. 67, fig. 1, S.)
The discharges of water from these reservoirs
are much facilitated, and increased in number,
by the occurrence of Faults or Fractures that intersect
the strata.*
There are two systems of Springs which have
their origin in Faults, the one supplied by water
descending from the higher regions of strata adjacent
to a fault, by which it is simply intercepted
in its descent, and diverted to the surface in the
form of perennial springs ; (see PI. 67, fig. 1, H.)
the other maintained by water ascending from
below by. Hydrostatic pressure, (as in Artesian
Wells,) and derived from strata, which at their
contact with the fault, are often at a great depth ;
* Mr. Townsend, in his Chapter on Springs, states, that there
are six distinct systems of springs in the neighbourhood of Bath,
which issue from as many regular strata of subterraneous water,
formed by filtration through either sand or porous rocks, and
placed each upon its subjacent bed of clay. From these, one
system of springs is produced by overflowing in the direction
towards which the strata are inclined, or have their dip; whilst
another system results from the dislocation of the strata, and
breaks out laterally through the fractures by which they are intersected.
It is stated by Mr. Hopkins, (Phil. Mag. Aug. 1834, p. 131),
that all the great springs in the Lime-stone District of Derbyshire
are found in conjunction with great Faults, “ I do not recollect
(says he) a single exception to this rule, for I believe in every instance
where I observed a powerful spring, I had independent
evidence of the existence of a great fault.”
the water is conducted to this depth either by
percolation through pores and crevices, or by
small subterraneous channels in these strata, from
more elevated distant regions, whence it descends,
until its progress is arrested by the Fault. (See
PL 67. Fig. 2, d, and PI. 69. Fig. 2, H. L.)
Besides the advantages that arise to the whole
of the Animal Creation, from these dispositions
in the structure of the Earth, whereby natural
supplies of water are multiplied almost to infinity
over its surface, a further result, of vast and peculiar
importance to Man, consists in the facilities
which are afforded him of procuring artificial
wells, throughout those parts of the world which
are best adapted for human habitation.
The Causes of the rise of water in ordinary
artificial wells, are the same that regulate its
discharge from the natural apertures which give
origin to springs; and as both these effects will
be most intelligibly exemplified, by a consideration
of the causes of the remarkable ascent of
water to the surface, and often above the surface,
in those peculiar perforations which are called
Artesian Wells, our attention may here be profitably
directed to their history.
Artesian Wells.
The name of Artesian Wells is applied to perpetually
flowing artificial fountains, obtained by
boring a small hole, through strata that are des