PROCEEDINGS OF GEOLOGICAL SOCIETIES. 
233 
the result of several years' observations, by Mr. Stacy, tlie manager of 
the mills at Wolvereote, would be received with interest, and would, 
if carried out in other places, lead to valuable results. There were no 
mills for thirty miles above "Wolvereote, and the navis^ation, though 
" flashes " were still sent down, had virtually ceased. jNIr. Stacy had found 
that, in the summer months, the river had a mean velocity of 58 feet per 
minute, when the total yield was 8120 cubic feet per minute, exclusive 
of the quantity brought down by " flashes," which it was difficult to 
estimate. During the winter months, in fine weather, without frost or 
rain, the river had a mean velocity of 919 feet per minute, and taking 
the sectional arja as 181"5 square feet, this gave a volume of 17,224 cubic 
feet per minute. In moderate rainy weather, without floods, when the 
level of the river just reached the high- water navigation mark, the total 
quantity of water passing through tlie mill was 28,189 cubic feet per 
minute. At the end of December, 1862, under similar conditions, the 
total yield was 35,498 cubic feet per minute, of which 7738 cubic feet 
might be taken as the water passing from the main stream to AVytham. 
These data suggested the necessity of adopting a standard at various sta- 
tions, so that the results might be compared with the rainfall when the 
gaugings were taken. At the same time, obsf^rvations were made on the 
river below the influx of the Chervvell and the Ock, \Nhen the yield was 
found to be 50,995 cubic feet per minute, being an excess of 15,197 
cubic feet as compared with AVolvercote, and of which excess it was esti- 
mated that 7G89 cubic feet were brought in by the Cherwcll, and the re- 
mainder by the Ock and the smaller perennial streams. The verification 
of these quantities was prevented by a fall of rain of nearly half an inch, 
in a few hours, which, at the expiration of thirty six hours, doubled the 
volume of the Thame stream, and added about thirty per cent, to the 
vohune of the main river. At "Wolvereote, on the 5th of Januar}^, 18G3, 
after about one inch of rain, the increase was from 27,98(i to 48.418 cubic 
feet per minute. The rainfall from the 1st to the 7tli January, 18G3, inclu- 
sive, produced a flood in the Thames under circumstances peculiarly 
favourable for observation. The rain recorded during this period averaged 
T61 inch over the whole watershed; Dalton's gauge, at Hemel Hemp- 
stead, showing a fall of 1*52 inch, and a percolation of 1"10 inch. The 
gaugings of the main river at Wolvereote then amounted to 82,500 cubic 
feet per minute, and at Clifton Hampden, below Abingdon, to 181,832 
cubic feet per minute. Of this latter quantity 44,755 cubic feet were deli- 
vered by the Cherwell (or an increase of 37,006 cubic feet as due to the 
flood), 24,864 cubic feet by the Ock, and 29,713 cubic feet by the many . 
smaller streams, watercourses, and land-drainage outfalls, issuing into 
the river between "Wolvereote and Clifton Hampden, a distance of about 
twenty miles by the river, with an average fall of two feet per mile, from 
a computed watershed of eighty square miles. It should be stated that 
the rainfall on this occasion, on the southern part of the district, was in 
excess of the average more than half an inch. 
The statt' of the navigation between Lechlade and Oxford was then de- 
scribed. It was remarked that from running on one stratum, the Oxford 
clay, and from other causes, it. had ceased to be ; although the physical . 
condition of the river bed, and its easy gradients, ofi'ered facilities for na- 
vigation; for the whole fall in this distance, 31 miles, was only 51 feet 3 
inches, or about 1 foot 7^ inches on an average per mile. 
The highest recorded floods on the Thames, since January 8, 1734, were 
then alluded to, and details were given of that which occurred March 
29-31, 1862. The action of land-drainage on flood-water was next con- 
TOL. VI. 2 H 
