SOME ESSEX WELL-SECTIONS. 57
found that this was closing round the lining-tube, so that it could
not be driven further ; a timbered shaft, 4 feet square, was then made
round the tube to the depth of 386 feet.
The Chalk was so soft, for a great depth, that the tube had to be
carried down to the depth of 844 feet.
Water was met with at the base of the London Clay, at 434 feet
(September, 1887), and still more at 456 feet, when it gave much
trouble and was difficult to keep down, the water rising to 39 feet below
the ground. While boring between 844 and 896 feet water began to
rise rapidly, to 41 feet from the surface (October, 1888), but on
testing the yield the well was pumped dry in 61/2 hours and took
several days to fill again. After further boring the water continued
to rise, and at 916 feet stood 23 feet from the surface (November 7,
1888), but a second pumping-test gave no better result than the first.
After this the water-level fell somewhat, to 41 feet on July 2, 1889,
at 1,048 feet.
At 473 feet sand blew 200 feet up the tube, and at 476 feet it
filled 100 feet of the tube. Since leaving the bottom of the tube it
has come in occasionally.