148 COAL UNDER SOUTH-EASTERN ENGLAND.
for water, with one exception. A very deep trial, known as the Sub-Wealden
Boring, was made : not for the purpose of finding coal, however, but for the more
general one of proving the underground succession of the beds beneath the lowest
part of the great Wealden Series in Sussex. From this trial came most valuable
information. Jurassic beds were found to a very great thickness, and there is every
reason to expect that they continue to a good depth below the 1,900 feet to which
the boring was made, as the Middle Division of the Series was not wholly
pierced.
Geologists who have worked much at the subject were well agreed that the
neighbourhood of Dover was, for various reasons, one of the best for a trial for
underground coal. At Dover has been made the only trial for coal in the South-
East of England (though others are in progress or in prospect), and it has been
successful, for Coal Measures were reached (in 1889) at a depth of 1,113 feet below
Ordnance Datum, beneath Cretaceous and Jurassic beds. The Coal Measures
have since been pierced to a further depth of 762 5 feet, in which thickness nine
seams of coal, with a workable thickness of about 14 feet, have been found.
The second part of our theory as to the underground structure of the South-
East of England has therefore been partly proved, and the existence of one coal-
field has been shown.
It remains now to consider whether things should be left as they are, or
whether it will not be well to make other trial-borings in search of other hidden
coal-fields, and my own opinion is strongly in favour of the latter view. The
extension of the Coal Measures from Dover and the thickness of the formation in
that neighbourhood will of course be worked out, and I believe it is meant to put
down a shaft on the site of the trial-boring, a work of no great difficulty, and of
less depth than many of our colliery-shafts.
Amongst other tracts the Eastern Counties should certainly be thoroughly
examined. Though the only published evidence we have is from the Harwich
boring, yet it should be remembered that this alone, of all the deep trial-borings
for water above alluded to, has reached Carboniferous rocks, giving us therefore
fair reason to speculate on the presence of Coal Measures at no great distance.
Some fresh evidence however has just turned up, and though it does not show
the existence of Coal Measures, it does show that old rocks of some sort come
nearer to the surface in part of Suffolk than anywhere else in the London Basin, as
far as is yet known. I cannot now enter into details, which it is hoped will soon
form the subject of a special paper : enough to say that the depth at which old
rocks have been struck, a few miles from Bury St. Edmund's, is about 520 feet
below Ordnance Datum.
Again, we are not certain what line our underground Coal Measures may take
from Dover, and the opinions of geologists vary somewhat on the matter. On the
one hand most hold that the extension will be found to trend westward, toward
Bristol; but on the other hand some think that it may take a more northerly turn,
toward the Midland coal-field, in which case the Eastern Counties would clearly
benefit. It seems to me that there is no need to limit ourselves to either
view : both extensions may occur.
1 would point out that it is not to be expected that every trial should be
successful. Failures to find coal must be expected ; but even failures will teach
much, and will not only give us much information as to the character of the beds
deep underground (a matter of great practical importance in the search), but may
5 These figures are corrected, since the Report was written, from later information.