1803.} On Draining and Watering. O43

The water thus condensed on the summits of hills descends between the strata of the incumbent soil, sometimes for many miles together; but generally from the nearest eminences into the adjoining vallies,

Thus there isa stratum of marlon the surface of thélands about* Derby, which extends many miles in most directions. This stratum of marl-is of various thickness from i0 te 150 feet, and beneath it lies a stratum of sand, which is also of various thickness from a few inches to six or eight feet, and of vari- ous degrees of duration; and beneath this lies another stratum of mar! to an unknown depth. On the top.of Radborne com- mon, about five miles north-west from Derby, the sandy stra- tum is quite loose, and rises above the stratum of marl, which is deficient at the summit of the bill. Three or four strong springs of water burst out on the sides of this hill, which thus originate from the moisture of the atmosphere éandensed on the cold summit, and passing through the sandy stratum be- tween the two strata of marl.

In the road to Duffield, about two miles north of Derby, the sand-stratum is cemented into stone, as well as in some situe- tions near Radborne-common above mentioned. This stratum of sand-stone is some feet in thickness, and lies four or five yards deep, beneath the upper stratum of marl, dividing it trom the lower one. At Normanton, about two valle 3 south from Derby, the sand-stratum consists of a loose sand, s white and pure, that it is imagined it might be used in the ma- nufacture of flint-glass, and lies about twelve feet deep, be- neath the upper stratum of marl, dividing it from the under ene. In the town of Dax»y on boring with design to sink a

well, after having passed about thirteen yards through marl, some sand was brought up by the auger, and water follow ed..

The dews therefore, which are pe rpetually condensing on the summits of these alls. descend beneath the upper and_un- der strata of marl, through the thin stratum of sand, which divides them, and form St. Alkmund’s well, and many ether springs in the vicinity of Derby; and probably all those which supply the wells within the town.

But there is a situation, where the manner of the produc- tion of springs Is most agreeably visible; it is about a-mile from the city of Lichfield, near the cold bath erected by John Floyer, in a beautiful piece of ground, which was formerly Dr. Darwin’s botanic garden.

In this place a g rotto about six yards wide and ten long has been excavated on the side of a hill consisting of siliceow

sand-stone with this peculiar circumstance; that the upper stratum of the sand-rock, which is there slat five feet thick, is divided from the lower stratum of it by a sheet of clay not more than three or four inces in thickness; on the upper suz-