COAL MEASURES IN THE SOUTH-EAST OF ENGLAND. 
241 
There are, however, in all this area certain indications of the 
proximity of old land and of pre-cretaceous denudation, in the 
presence of Quartz and Lydian-stone pebbles, accompanied by 
extraneous secondary fossils in the Lower Greensands of Surrey, 
and in the like old-rock pebbles, with the addition of slate- 
pebbles, in that formation in north Wiltshire; while the banks 
of shingle, bryozoa, and sponges of the same age at Faringdon, 
point to still and sheltered waters, probably of no great depth, 
and to adjacent dry land. Again, on the north of London, we 
have in the Lower Greensand of Buckinghamshire and Bedford- 
shire shingle-beds consisting almost entirely of fossils derived 
from Jurassic strata, with a remarkable collection of larger 
quartz, quartzite, and other rock pebbles, probably from the 
old palaeozoic axis, which at first stood out in the midst of the 
Lower Secondary seas, and was only finally submerged in the 
seas of the Gault and Chalk periods. It was no doubt owing 
to the gradual shallowing of the old seas as they approached 
the then palaeozoic land that the thinning out of the Lower 
Secondary rocks from the north-west to the south-east, which, 
we before noticed, is owing. 
In this country the newer strata, overlying the palaeozoic 
rocks on parts of the presumed old palaeozoic range, have been 
sunk into without result — in the Wealden at Hastings to a 
depth of 486 feet, in the upper beds of the same at Earlswood, 
near Reigate, to about 900 feet, through chalk at Chichester, 
to 945 feet, and at Southampton, through Tertiary strata and 
chalk, to a depth of 1,317 feet. Unfortunately all these works, 
fall short of the mark which we as geologists wish to attain. 
In a scientific point of view, no experiments could have 
greater interest, and in an industrial point of view no experi- 
ments could be more important, than such as would serve to 
determine the position of this great underground range of 
older rocks connecting the Ardennes and the Mendips.r'AiVe 
have ascertained that it lies at no great depth beneath the over- 
lying newer strata, and if the strike of the line of disturbance 
were in a straight line, we should have no difficulty in determin- 
ing its course ; but from what we know of its range in the 
proved part of the 800 miles, it is certain that while it has a 
general east and west bearing, it is subject to considerable 
local deflections. Thus, while Mr. Grodwin- Austen is disposed to 
place the supposed coal trough in the Valley of the Thames or 
under the North Downs, I am disposed to place it further north, 
in Essex and Hertfordshire ; and while my friend considers it 
continuous, I consider it to be most likely broken up into basins. 
Again, if the axis of the Ardennes consisted of an anticlinal line, 
the problem would be simplified, but it consists of a series of 
such parallel lines, and therefore whether or not the one which 
YOL. XI. — NO. XLIV. R 
