o4 
In comparing the overlying formations met with in Somerset- 
shire with those which prevail in the coalfields of the North of 
France and Belgium, a remarkable contrast presents itself, there 
being there almost an entire absence of everything between the 
Coal. Measures and the Greensand, which itself is absent in places, 
the Chalk resting directly and unconformably upon the upturned 
edges of the Coal Measures. 
The thickness of strata which has thus disappeared, as esti- 
mated by Professor Prestwich from the points of outcrops nearest 
London, is as follows :— 
Weald. Clay and. Hastings Sand ae ie 2,000 
Purbeck and Portland Beds ... sh oe 70 
Kimmeridge Clay... Bac aes .. 450 
' Coral Rag and Oxford Clay... aoe no tOO 
Oolites ie an a bis ofr OO) 
Lias ae §.- bi ne sve 4 GOD 
New. Red Sandstone .., set 4 ... 800 
Total em ome 2.5) DELO 
An examination of the overlying formations shows that 
throughout the entire range of the French and Belgian Coal- 
field, the Coal Measures are either overlaid by the Chalk alone, 
or by the Chalk and Greensand, but in certain areas these are 
hidden by a covering of Tertiary Strata, the complete section in 
the latter case being as follows :— 
Shaft Sections and Borings near Mons. 
Quaregnon Shaft. 
Brick Earth and Gravel... Ss = 16 6 
Tertiary Sands... ide te nian Lee 
White Chalk ... oh Us 2. (B8BaD. 
Chalk Marl ~~... re, a sp ete 
gir RRs = ass ea a 4 0 
Coal Measures at 494 4 
? a 
