19 
gaugings of the Thames at Lechlade, and found the minimum 
flow to be 20 millions of gallons per diem, which would be 
equivalent to but seven cubic feet per minute on a drainage 
area of 323 square miles. The river Churn was taken as a 
typical stream flowing from the Cotteswolds in the direction 
of the general dip, or nearly so; and a section of the valley 
course was exhibited, the section being extended to Swindon, 
for the purpose of connecting the stratigraphic lines with those 
ascertained by the sinking recently made there, at a depth 
of 747 feet, by the Great Western Railway Company. A loss 
of water amounting to 2,403,000 gallons per diem was stated 
to occur between Colesborne and North Cerney in traversing 
the loose rocks of the Inferior Oolite, which it did not appear 
was again restored to it. The rivers Ray and Cole, and other 
streams flowing principally over impermeable clays from the 
Marlborough Hills south of Swindon, were described, as also 
the well-sinking at Swindon, which passed through 
Made Ground... ihe ce Ace aaa ... 8 feet 
Kimmeridge Clay ... ape oe sc . 64 » 
Coral Rag... ae ae i ree .- 40 7 
Oxford Clay with 'Kelloway Rock... Ice we OTB 
Cornbrash ... Ake a0 sits ei . 18 4 
Forest Marble aa bes saz ee Bromo nie, 
Total eee eee ese we 736 1 
When, after firing a shot, a salt spring broke in, discharging at 
the rate of about 2000 gallons an hour. The spring was very 
similar in composition to sea water. The river Frome was next 
referred to—its drainage area with tributaries above Stone- 
house, stated to be 79 square miles. According to the Thames 
standard of 12 cubic feet per minute for each square mile, this 
would give but 276 cubic feet per minute for each square mile 
for the dry weather flow of the stream at Chalford; but it is 
found to be nearly three times as much. Where does the 
water come from? This was considered, and the aggregate 
flow of the springs at Chalford was attributed mainly to the 
equalizing effect of the natural subterranean reservoir existing 
c2 
