64 
same Inferior Oolite formation, and where, as I have stated, 
the waters lost are only partially, if at all, returned to the 
stream below the locality where the loss arises ?” 
For the simple reason that the impervious beds of the Fuller’s 
Earth overlie them, to block and prevent their reappearance 
at the ground surface, except through the intermediation of 
faults or bore holes artificially made through such impervious 
beds. Above the Fuller’s Earth lies the Great Oolite, less 
permeable than the Inferior, with its store of waters, similarly 
imprisoned by the clays of the Forest Marble above. 
The existence of such an equalizing natural reservoir as I have 
mentioned is illustrated in the fact of the uprising disposition 
of the waters, as manifested at Cirencester and Boxwell. It is 
demonstrated at Chalford by the diminished variation in the 
discharge of the springs during dry weather and during periods 
of heavy rainfall, being between 1 and 10% only, instead of 
between 1 and 30, the variation found in the flow of the Thames, 
taking the whole area of its basin. Thus, to summerise, 12 cu. 
ft. per mile per minute means only 2,5, inches of rain during 
the whole year, (running off per square mile) such being the 
low rate of flow during the days of dry weather. 30 times 
this, or say 81 inches, is the rate during the hours or days of 
spasmodic flood flow. Between these extremes are the periods 
of ordinary summer and full winter flow; and so the year’s 
rainfall is accounted for through the Thames valley. 
The natural reservoir in the valley above the Chalford 
springs, by its action of equalization, increases the dry weather 
flow there from 2,5, inches to a rate of 7} inches per annum, 
(running off per square mile.) It diminishes the spasmodic 
flood somewhat, viz.: from 81 inches to a rate of 75 inches per 
annum, as well as its duration, and between the periods it 
establishes more general uniformity of flow. 
The gaugings, as will be seen by the Charts, were taken in a 
general way weekly, i.e., every Saturday afternoon, at Chalford, 
after the mills shut down, and daily, in the early morning, 
before they began work, at Brimscombe Port. A careful 
comparison of them with the rainfall will illustrate the con- 
ditions and office of the stream. 
