502 LOWER OOLITIC ROCKS OF ENGLAND : 
the lost water may reappear in lower portions of the valley, or it 
may be lost to the drainage area. 
In Wiltshire and Gloucestershire, in the Avon above Malmes- 
bury, waters pass underground into absorbent beds of Great 
Oolite, and are imprisoned between the Fuller's Earth and Forest 
Marble clays ; while again the Churn above Cirencester, loses 
about 2,000 gallons a minute.* These waters if pent up will 
naturally overflow, or they may uprise again in the lower courses 
of the river through fissures where the strata are faulted. 
At West Cranmore in Somerset a pond is supplied by a spring 
that issues from the Inferior Oolite in a field south-east of the 
school : the spring is never known to fail, but in dry seasons the 
pond disappears and the water sinks underground. 
Referring to the Midland Counties, Prof. Judd remarks that 
occasionally the whole volume of a stream thus disappears, and 
for a portion of its course, sometimes several miles in length, it 
becomes subterranean. Among the interesting examples of the 
disappearance of rivers, which thus leave their beds for a con- 
siderable distance quite dry, may be mentioned the River Witham, 
near Thistleton ; the River Glen, between Little Bythatn and 
Careby ; and the brook which flows by the village of Benefield.f 
At Benefield, three miles west of Oundle, there are stated to 
be nine circular holes called the " Swallows," through which the 
land-floods flow and disappear. 
Mr A. C. G. Cameron informs me that, in Bedfordshire, the 
Rieeley brook flows down from the clay-lands about Knotting, until 
at Riseley it meets with the Oolite limestones cropping out beneath 
the Oxford Clay. The water then sinks into the Cornbrash, until 
arrested by the clays below, which throw T it out again. In dry 
seasons the bed of the stream is often dry for a considerable 
distance. 
Natural swallet or swallow-holes occur in some places, as along 
the scarp of Inferior Oolite and Midford Sand, that extends from 
Chelynch to Ingsdons Hill, north of Doulting. My attention 
was drawn in 1891, by Sir R. H. Paget, to one that had been 
recently developed on the south of Bodden, where a hole about 
20 feet deep bad suddenly been formed in the Liassic strata 
beneath the Oolitic scarp. 
Prof. Judd observes that "the lines of junction of rocks like 
the Upper Estuarine Clays and the Lincolnshire Oolite are often 
marked by a series of these natural drains ; in many cases a slight 
depression of the surface-level indicating their position. In some 
cases the volume of water carried off by means of a swallow-hole 
is very great, and the roar produced by it in descending is heard 
at some distance. In the case of the smaller swallow-holes, they 
may often be detected by placing the ear near the surface of the 
ground. These awallow-holes are well known to fox-hunters, for 
the long sinuous fissures worn by the constant passage of water 
* J. H. Taunton, Proc. Cotteswold Club, vol. vi. pp. 304, &c. 
t Geol. Rutland, p. 268. 
