56 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



ferous series of Berwickshire is not older or inferior to the Mount-ain 

 Limestone, but is its representative in a zone more nearly subordinate 

 to the terrestrial surface of the time ; such are also the calciferous 

 grits of the Mid-Lothian district. The coal-growths alternated with 

 every portion of these depositions, with the exception of those of 

 some extreme depths ; but even with respect to these, we see, as in 

 the Boulonnais, that the continuity of the pure Mountain Limestone 

 series was there once interrupted, by its elevation, first into the sand 

 zones of the time, afterwards into subaerial conditions*, followed by 

 a return of that surface to the region of pure marine calcareous 

 deposits. 



The area of pure Mountain Limestone has really a somewhat 

 greater extension southwards than as above indicated : this is a con- 

 sideration of some importance, inasmuch as every portion of this area 

 of sea-bed appears ultimately to have been brought up into those 

 conditions by which it became covered by coal-growths. The line 

 through Belgium must be made to include the district of the Con- 

 dros, and that known as *' entre Sambre et Meuse." The Carboni- 

 ferous series which thence passes beneath the Cretaceous beds of the 

 N.E. of France is very extensive, and it is obvious that the calcareous 

 mass of Berlaimont, conformably with the structure of the region to 

 the east of it, requires considerable extension and expansion, perhaps 

 equal to that presented in the Meuse section about Dinant ; if so, it 

 is not impossible but that some coal-beds may exist in the direction 

 of Loquinol. 



Tournay is the most N.W. point at which the Mountain Lime- 

 stone is exposed in the Belgian district ; but, as will be seen by the 

 Map, it has a considerable spread beneath ; it was found immediately 

 below the chalk at and north of Lille, and it ranges thence to some 

 point between Cassel and St. Omerf . 



The massive character of the Carboniferous series in the Boulon- 

 nais, as it passes under the Oolitic deposits, west and south, indicates 

 continuity in those directions : in like manner we may feel sure that 

 the Mendip limestones are continued south and east from Frome ; 

 so that the Mountain Limestone area may be safely carried beneath 

 our own S.E. counties across the eastern end of the Channel, and so 

 into Picardy ; but as such, it nowhere reappears from beneath the 

 secondary formations round the great depression of the Paris basin. 



This mere sketch may perhaps suffice | ; and without troubling 

 ourselves with the progressive changes in the distribution of the 

 areas of land and water during the Middle and later Palaeozoic periods, 

 or without overlaying the suggestions of the present communication 

 by the mass of detail by which we may ascertain what the geogra- 



* Quart. Journ. Geol. Soc. vol. ix. p. 243. 



t See the Memoir of M. d'Archiac, Etudes sur la Formation Cretacee, &c., 

 pp. 118 et seg., in Memoires de la Soc. Geol. de France, 2 ser. vol. ii. 



J The object of the present paper is to point out lines along which coal may 

 possibly be met with. The more speculative points will form the subject of an 

 " Inquiry into the Physical Geography of the Palajozoic period," which will 

 shortly be laid before the Geological Society. 



