SWALLOW HOLES. 503 
through the jointed limestone rocks constitute retreats for foxes 
from which it is almost impossible to effect their dislodgment." 
The drainage of the land is facilitated in places, and more 
especially in Northamptonshire and Lincolnshire by artificial 
swallow-holes or " dumb-wells " excavations dug through 
clayey beds, such as the Upper Estuarine Series, into the Lincoln- 
shire Limestone. Moreover, as Prof. Judd remarks, " when a 
tract of Boulder Clay overlapping limestone is drained, it is only 
necessary to carry the pipes to the outcrop of a thick bed of 
limestone and to allow them to terminate in an excavation in the 
latter."* 
The distribution of the towns and villages is influenced in a 
marked way by the geological formations that appear at the 
surface, as on these depended the sources of water-supply which 
directly influenced the original settlements. 
Hence we find most of the centres of population placed on 
permeable strata, on the slopes of escarpments or at the foot of 
hills, where shallqw wells or natural springs afforded a ready 
supply of drinking water ; while the larger portions of the wide 
vales are thinly populated, excepting where the clays are covered 
by gravel. Some of the earlier settlements were fixed according 
to the old fords, where the outcrop of strata caused shallows, and 
afforded ready means of crossing streams, as at Midford and 
Freshford, Telisford, Iford, and Bradford-on-Avon.f 
Inferior Oolite Series. 
The Inferior Oolite and Midford Sand are essentially water-bearing 
strata, the water being supported by the Upper Lias clay, which throws 
out many springs along the escarpment and from isolated hills. 
In South Dorsetshire the Inferior Oolite is thin, but the underlying 
Midford (or Bridport) Sands arc capable of yielding plentiful supplies of 
water. I have no records, however, of well-borings in this area. 
At Casfcleton, Sherborne, a well-boring that was carried into the Inferior 
Oolite (see p. 80), found water at a depth of 30 feet, and from 150 to 270 
gallons per minute was the yield ; this inflow was however probably con- 
nected with the river. H. W. Bristow noted that springs were again met 
with at depths of 123 to 143 feet, and the water then overflowed at the 
surface, the yield amounting to 170 gallons per minute. 
At Yeovil, water is obtained from a boring, carried into the Midford (or 
Yeovil) Sands, on the hill to the south-east of the town. 
A strong spring, known as the Seven Sisters, is thrown out of the 
Sands, near Gorton Denham, north of Sherborne ; another important 
spring issues from similar beds, north of Creech Hill, Milton Clevedon. 
"Wells sunk 30 or 40 feet in the Inferior Oolite between West Cranmore, 
Chelynch, and Doulting are apt to be low in dry weather, for the area 
is to some extent drained by springs ; and at "West Cranmore the Inferior 
Oolite probably rests directly on the Carboniferous Limestone (see p. 90). 
There are many springs on Brent Knoll, which have been utilized for the 
local water-supply. Some of the springs issue from the Midford Sand, 
others from the Middle Lias. J 
* Geol. Rutland, p. 267. 
f Rev. J. Townsend, Character of Moses, pp. 189, 190. 
J See " Notes of my Life," by Archdeacon G. A. Denison, Ed. 2. 1878 ; pp. 
405-7. 
