279 
THE POSITION OF THE SILUKIAN, DEVONIAN, AND 
CARBONIFEROUS ROCKS IN THE LONDON AREA. 
By Robert Etheridge, F.R.S., etc. 
[PLATE VII.] 
S long ago as 1856 a distinguished author and physicist 
communicated to the Geological Society a remarkable 
paper upon 66 The possible extension of the Coal-Measures be- 
neath the south-eastern part of England.” * Speculative as 
those views and generalizations then seemed to be, they but 
foreshadowed, and almost foretold, what of late has been to a 
great extent realized. 
Competent geologists were then appealed to, to admit the 
broad generalizations put forth as to the extension from the 
Continent (Belgium and France) of the older rocks (Coal- 
Measures) beneath the superincumbent strata of London Clay, 
Chalk, Gault, Lower Greensand, and Wealden, in the south-east 
of England generally. 
This problem was then, as now, of national importance, and 
gave rise to much speculation as to the continuity of certain for- 
mations or rock masses occurring beneath the German Ocean, 
from the Belgian and German areas, and also under the English 
Channel from the north-east of France. Although Mr. Austen’s 
paper bore the title of the 66 Possible extension of the Coal- 
Measures beneath the south-eastern part of England,” it had a 
far wider and greater significance than at first sight appears, it 
being certain that with the occurrence of any such extension of 
the Carboniferous rocks from Western Europe we should expect 
still older Palaeozoic rocks to be more or less associated with 
them. This now turns out to be true, so far as the two older 
groups, the Devonian and Silurian, are concerned ; the Devonian 
occurring immediately beneath the Cretaceous group in London, 
and eighteen miles north of it, at Turnford, near Cheshunt ; 
the other, the Wenlock Shale (Upper Silurian), having lately 
been determined at Ware, immediately below the Gault, and 
penetrated about 25 feet. No less than thirty species of fossils 
have been determined from the cores brought up. 
* R. Godwin-Austen, Esq., “ Quart. Journ. Geol. Soc.” vol. xii. pp. 38-46. 
