63 
by the Cambrian and Silurian rocks. The Devonian and Carbon- 
iferous beds were first raised up on the summit of the crest and 
then overturned, the Coal Measures being thus overlaid by the 
Mountain Limestone, Devonian and even by the Silurian itself. 
To explain the movement here described, the attention of the 
members is directed to a theoretical Section of the Coalfield of 
Belgium and the N. of France,* which includes most uf the 
distinctive features alluded to, and may be regarded as typical. 
Beneath a covering of Chalk lie the Coal Measures, which on the 
N. side of the basin, both here and elsewhere, occupy their 
natural position with a general dip towards the S., but on the 
8. side have been folded back upon themselves, throwing the 
strata into a series of contortions which these sections only 
partially represent, the Coal Measures being overlaid by the 
older rocks as already described. 
The chief faults associated with this disturbance are three in 
number, viz. :— 
1.—The great fault or “Grand faille” separating the lower 
Devonian of the Dinant basin from the more recent and over- 
turned strata of the Namur basin. 
2.—The “limiting or boundary fault (faille limite)” between 
what Dr. Hovelacque calls the “scraps of pressure”ft and the 
productive coal beds. 
And 3.—The “ fault of return or reversed fault (faille de retour)” 
between the overturned strata on the S. side of the coal basin, 
and the coal beds which lie in their true position on the N. side, 
probably corresponding with the overlap fault of Radstock, 
although differing from it in some respects. 
The “Great fault” is evidently the result of the thrust from the 
S. already referred to, for the movement does not seem to have: 
* See Section No. I. 
t+ The Devonian and Carboniferous rocks tilted up and pushed 
towards the N. (Editor.) 
