58 
A reference to the sections accompanying this paper, Draw- 
ings Nos. 3 and 3a, indicating the flow of the river Frome at 
Brimscombe and Chalford, in connection with the rainfall, shows 
that the rain of Feb., 1880 (viz., 5.28 inches) produced a flow in 
the stream at Brimscombe of nearly 12,000 cubic ft. per minute, 
whilst the previous somewhat heavier summer rain in June, 1879, 
(viz., 5.31 inches) produced but 8,700 cubic feet per minute in 
the stream; and in the same year 3.64 inches in February (suc- 
ceeding 3.43 inches in January) produced 10,800 cubic feet per 
minute in the stream. 
Thus it is abundantly evident that floods are as much or 
rather more dependant on the capacity for infiltration through 
the soil traversed by rain and surface waters and ground evapo- 
ration inversely as on the amount of rainfall directly. 
The conclusions resulting from the long continued experi- 
ments made by the late Mr Cuarues Greaves at Lea, on 
evaporation and percolation, communicated in his valuable. 
paper to the Inst. C.E., Feb. 1876, whilst they show, as do those 
also of Mr Joun Hvans, F.R.S., at Hemel Hempstead, Herts, 
and other observers, increased percolation through ordinary 
soil in the winter as compared with the summer months indicate 
distinctly — 
The magnitude of percolation through sand at all times. 
The smallness of percolation through earth on the whole, ’ 
and consequent magnitude of ground evaporation. 
The excess of evaporation from ground over evaporation 
from a surface of water in winter, and from a surface — 
of water over evaporation from ground in summer. 
To some extent they would appear at variance with the 
conclusions of the French Hydrologists, arising probably from 
difference of physical conditions and of latitude. 
I must now pass to the streams flowing from the Cotteswold 
range over the ground, chiefly permeable, that lies between the 
Upper Lias and the Oxford Clay; and I will take the Churn as 
a typical stream fairly illustrating the others. 
IT annex section through the valley of the Churn, between 
Cheltenham, the Seven Springs at Cubberley, and New Swindon, 
