COAL MEASURES IN THE SOUTH-EAST OF ENGLAND. 235 
of 2 miles, increasing to 7 or 8 miles near Charleroi, and con- 
tinued in France with a width of from 6 to 7 miles, where it has 
been followed under the chalk to within 30 miles of Calais, 
and there thins out. 
Connected with these coal-fields a great line of disturbance, 
affecting the palaeozoic rocks, has been traced from Westphalia 
through Belgium to northern France, and it is on the northern 
flanks of the older rocks of the Ardennes range of hills, which 
have been formed by this disturbance, that the coal-fields of 
Belgium lie. The same line of disturbance is again exhibited 
in the Mendips, and is prolonged even as far as the south of 
Ireland. 
In England and South Wales a similar set of phenomena are 
met with at this other end of the axis of elevation. From 
Milford Haven to Tenby, contorted strata of the Mountain 
Limestone and Old Bed Sandstone are flanked on the north by 
the highly-disturbed Pembrokeshire coal-field, whicji is 24 miles 
long by 3 to 6 miles broad. The great coal-field of South 
Wales is 60 miles long by 15 to 18 miles broad ; whilst that of 
Somerset and Gloucestershire (or Bristol and Bath) shows a 
length in the direction of the axis of the Mendips " of about 
12 miles, and in the other direction it measures 26 miles. ^ 
The Coal Measures of South Wales are not covered by 
secondary strata, but a large portion of the Somersetshire coal 
measures are overlaid by some of the lower Secondary rocks, 
which in their turn pass a few miles to the eastward under the 
Chalk. At Clandown, near Bath, the Coal Measures are worked 
beneath 360 feet of Lias and New Bed Sandstone, and they have 
been followed under these superincumbent strata for a distance 
of 5 to 6 miles from their outcrop, where they are at a depth 
of about 500 ft. beneath the surface. But between this point 
and the well at Kentish Town, no trial for coal or water has 
been carried to the base of the secondary rocks, or has reached 
more than about 600 ft. beneath the sea level, and the whole 
area extending to the channel is occupied by upper Secondary 
or by Tertiary strata. 
There can, however, be little doubt of the continuity of the 
range of the palaeozoic rocks under these newer formations 
from Belgium to Somerset ; but whether or not the Coal Mea- 
sures were ever continuous between the two districts ; and 
whether, if they were, they have been removed by denudation, 
leaving only the lower palaeozoic rocks, requires further dis- 
cussion. 
So far as the identity of any particular bed of coal or of rock 
may serve to establish a correlation between the coal* measures 
of Bristol and South Wales and those^)f France and Belgium, 
it is not possible, nor should we expect it ; for the variation in 
