“eC 
59 
“able, but I do not at all mean to say by that that they are equal 
“both to all or part of our Lower Coal (or more exactly our 
“Middle Coal) and your Upper Coal ; in my opinion they are 
“intermediate between the two, and are situated immediately 
‘above our highest beds of the North of France and below 
“ our lowest beds of St. Etienne, Gard, &c.” 
Of the Millstone Grit few particulars appear to be given in the 
various treatises on the French and Belgian Coalfield, but in the 
sections given by Professor Prestwich in his Coal Commission 
report, he has noted its presence ; and in a paper contributed by 
M. Henry Laporte to the North of England Engineers in 1878, 
he speaks of certain Grits in the Hardinghem Coalfield as being 
very like Millstone Grit, with which there is little doubt they are 
identical. 
The Mountain Limestone appears to be invariably present on 
the Continent, and M. Laporte has described it in descending 
‘order as follows :— 
Carboniferous Lime- E J 
Limestone with Productus Undatus 
Limestone with Productus Giganteus 
stone 366 yards { 
Limestone with Productus Cora 
On this it may be noted, that, this formation is thinner on the 
Continent than in England, where, in the gorge of the Avon its 
thickness has been estimated at 2,338 feet, and on the Mendips 
its thickness is apparently even greater. 
It may be remarked that for a time it was believed that the 
Boulonnais Coalfield, which is overlaid by one bed of Limestone 
and rests upon another, must belong to the Carboniferous Lime- 
stone, in which case it would have been the equivalent of the Ber- 
wickshire and Scotch Coal Measures ; hut subsequent investigation 
thas established the fact that this part of the coalfield of France 
is identical with the general basin of Valenciennes and elsewhere, 
the Limestone by which it has been overlaid in the Boulonnais 
‘area being due to a great physical disturbance of which the writer 
‘will presently have to speak. 
