The Earthquake in Relation to Geological Structure. 159
Previous to the earthquake the water-level had been
gradually sinking, and the Committee had decided that a
deepening of the wells would be necessary, when the shock
came and caused a rise of 7 to 71/2 feet, this increased level
being maintained for about six months, after which Mr.
Charles Clegg, C.B., the Borough surveyor, informed me
that the level had fallen 4 feet 9 inches. Whether this fall
indicates a permanent relapse to the pre-seismic or some
lower level cannot at present be decided, as the long drought
had caused a general falling off in the water supply through-
out the country.56
All the other wells in the neighbourhood of Colchester
were affected in a similar manner, but, as no systematic
measurements are made, not much is known beyond the
general fact that the shock caused a rise in the level of the
water. At the Castle Brewery well the water is said to have
returned to its former level in November. Mr. Stopes
reports that at the Eagle Brewery the water level in the well
was 22 feet below the surface before April 22nd, but after the
shock it had risen to within 18 feet of the surface, and con-
tinued at that level till the end of August, 1884, since which
no measurements have been taken. Both these wells are
sunk into the Chalk, and sections are given in the Geological
Survey Memoir, 48 S.W.
Messrs. S. Courtauld's well, Bocking.—This well, which is
sunk into the Chalk to a depth of 241 feet, passes through
the following beds57:—
56 [At the time of preparing this section finally for publication (August,
1885) I hear from Mr. J. C. Shenstone, that out of 7 feet rise caused by
the earthquake, nearly 5 feet had been lost last autumn, as reported
above, and that at the present time (Aug. 10th), the water is only 2 feet
above the pre-seismic level. How much of this sinking is due to the
long drought cannot now be determined, but it seems that the water is
gradually falling back to its old level.]
57 Mem. Geol. Survey, vol. iv. ' The Geology of the London Basin,'
Part i., pp. 433-434. By W. Whitaker. 1872.