152 SUBTERRANEAN GEOLOGY OF SOUTH-EASTERN ENGLAND.
At Chatham beneath 41 feet of Lower Greensand were 22 feet of
Oxford Clay, in which the boring ended. Thus we have in this case
the disappearance of 1,840 feet of Upper and Middle Oolitic strata
in a distance of 32 miles. And near London, as we have seen, Upper
and Middle Oolitic strata have been hitherto unvariably absent, and
Lower Oolitic beds are only found in two out of the seven borings
which reach Triassic or Palaeozoic rocks.
As strata of Great Oolite age never appear at the surface in south-
eastern England a few words on the nature of the beds of that age
found at Richmond and Meux's will be in place here. At Richmond
they were chiefly limestone with thin partings of sandstone or clay
At the base was a thin "bed of worn shell fragments with particles
of anthracite." At Meux's the Great Oolite beds were at first
supposed to be Lower Greensand, in spite of the presence of a bed
of limestone at the top. But the similarity of the beds below the
Gault at Richmond to those stated to have been found at Meux's
convinced Prof. Judd7 that re-examination of the latter was necessary.
This was a task of some difficulty, most of the specimens obtained
during the progress of the boring having been scattered or lost. It
became obvious also, that there were many discrepancies between
the various accounts given with regard to these beds below the Gault,
which arose, Prof. Judd thinks, "from the circumstance that the
strata in question consisted of hard and compact Oolitic limestones
alternating with marls of a more or less sandy character. Owing to
the method of working by the diamond rock drill, the cores brought
up consisted almost entirely of the former kind of rock, the softer
marls being broken up and to a great extent washed away in the
process of boring. As specimens of the Oolitic limestone were found
at short intervals, it was not unnaturally supposed by those who did
not watch the boring and measure the cores brought up that the
boring was carried on almost wholly in that rock." The late Mr.
Charles Moore of Bath, however, had obtained some specimens 01
the softer beds for examination, and from them had extracted great
numbers of minute fossils, and comparison of these with others
obtained by Prof. Judd himself both at Meux's and at Richmond
showed the identity of the strata immediately beneath the Gault at
both places.
We now come to the Triassic and Palaeozoic rocks found in the
seven borings which are situated either in the Valley of the
7 "Quarterly Journal, Geological Society,'' vols. xl., xli.