34 HULL SCIENTIFIC AND FIELD NATURALISTS’ CLUB. 
within the feather-edge of the Holderness clays, is not more than 
to to 15 feet.* A short way within this edge no change of level 
takes place, the water-line being held always in the same position 
by the pressure of the superincumbent clay. 
The discharge along the south-east edge of this basin, though 
varying in degree, never ceases: while after frequent and heavy 
rainfalls it changes greatly. At such times the outflow finds its 
way underground with considerable force into the sea and the 
Humber. Besides this subterranean outflow there is an overflow 
on the mid basin drainage, which also finds its way to the 
Humber and then into the ocean. It consists of a line of springs 
running over and rising through breaks in the thin edge of the 
clay which covers the inner margin of the out-cropping chalk. 
The increase or decrease in the discharge from this line of over- 
flow is entirely due to the elevation or depression of the water-line 
in the chalk beneath, consequent on an excess or diminution in 
the rainfall. Considerable as are these surface and subterranean 
discharges into river and sea, they are, in my opinion, equalled by 
the vast body of water issuing in an opposite direction. Along the 
base of the outer margin of the chalk towards the north and west 
numerous permanent and intermittent springs issue of every size, 
from a tiny driblet to a stream sufficiently powerful to turn a mill. 
From the village of Warter northwards to Settrington the 
springs are most abundant, notwithstanding that these points of 
greatest discharge are along the most elevated portion of the edge 
of the basin, at the height of 400 to 500 feet above sea-level. 
This is partially due to the fact that the clays on which the chalk 
rests are from 50 to roo feet higher than at the escarpment, and 
at distances varying from one mile to two miles from the edge of 
that escarpment, thus forming an anticlinal or ridge, from which a 
large volume of water flows towards the escarpment. Southwards 
from Warter to the Humber, and north-eastwards from Settrington 
to the sea, the springs become weaker and less numerous, and, on 
approaching the sea in one direction and the Humber in the other, 
they gradually flow at lower elevations. This may be due in part 
to an increased facility afforded for the water to drain in these 
directions, and thus relieve the flow at the escarpment. Also the 
springs on that portion of the escarpment situated between 
Settrington and Hunmanby must be weakened by the water inter- 
cepted and drawn off by the great Mid Wold gypsey race. Besides 
the visible discharge along the outer margin of the chalk, water 
* This holds good in Berkshire, the water in the wells on the high levels 
fluctuating to a much greater extent than that in wells at lower levels. Wells 
situated at the foot of the Chalk and close to the Greensand maintain a pretty 
constant head of water at all times.—H.P.S. 
_ 
oe 
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