TKANSACTIONS OF Tllli SECTXOiNS. 67 



coal in an adjacent field has reached a depth of GOO feet, and is still in the Keuper 

 marls and clays. 



The tloor;of the brick-pits is of red Keuper marl, restinj^ on which is a thick 

 bed of grey marl, about 16 feet, with insect and fish remains, selenite and pseudo- 

 morphlc salt-crystals, pittings <as of rain-drops, c&c. On its uneven upper surface 

 rests the bone-bed, 2 inches thick, containing rolled Saurian bones, vertebrre, and 

 teeth of Ichtht/osaurwi, ribs of Plesiosatiriis, spines of Neniacanthus monilifer and 

 Ilyhodus minor, teeth, scales, &c. of Ilyhodus, Lavicthys a^ncalis, Ceratodus, &c. 

 Coprolites and large quartzose pebbles are numerous. 



Above this come 5 feet of olack shales, containing a new Starfish, Ophiokpis 

 dnmem, and Aricula contorta, Cardium rhccticmn, Axiims cluaciuus, &c. ; then 

 about 4 feet of light-coloured shales with the same fossils ; and the whole is capped 

 by a bed of rubbly limestone, 3 inches thick, containing casts of Edheria minuta. 

 The beds have a slight dip to the S.E. 



Undulations of the ChalJcin the North of France, and their probable existence 

 under the Straits of Dover. By Professor E. HIbert. 



I showed at the Brighton Meeting that the beds of Ohalk in the north of France 

 are folded so as to form five anticlinal axes having a S.E. and N.W. direction, viz. 



the axis of the Perche, 

 „ „ Seine, 

 „ „ Bray, 

 „ „ Bresle, 

 „ „ Artois. 



On the present occasion I am about to prove that there is another series of folds 

 at right angles to the former, that is to say having a S.W. and N.E. direction. 



The mode of demonstration is very simple and rigorous. I take for example a 

 well-known bed, such as the Chloriiic Marl, and observe its altitude at various 

 points. 



Taking, for example, the region between F(5camp and Paris, which belongs to the 

 S.E. and N.W. anticlinal axis of the Seine, we see the Chloritic Marl at Fecamp at 

 the level of the sea ; the beds rise to the S.E., and the same bed (near Mentheville, 

 10 kilometres off) reaches 270 feet. Then they sink, so that the surface is soon 

 formed of the Micraster cor-testudinariuni beds, which are separated more than 200 

 feet from the Chloritic Marl. They afterwards rise again, and the Chloritic Marl 

 once more attains a height of 2G0 feet at Pavilly. It next descends by 470 feet at 

 least, rises again to 150 feet at Rouen ; and the base of the Ohalk with 31. cor-testu~ 

 dinarium reaches the height of nearly 500 feet. Again a dip takes place between 

 Ilouen and Vernon, this time of 340 feet ; then at Pressagny, near Vernon, the 

 Chloritic Marl appears at 169 feet ; and finally there is a regular dip towards Paris, 

 where the Chloritic Marl is at about 1500 feet below the level of the sea. 



Thus the region between Fecamp and Vernon presents four undulations (Fecamp, 

 Pavilly, Ilouen, and Vernon), the extent of which ranges between 400 and 500 feet. 



By a similar method I find that the region comprised between Treport and 

 Compiegne (the anticlinal axis of the Bresle) presents three bosses, the first having 

 its summit at sea to the N.W. of Tr6port, the second at Aumale, the third at 

 Breteuil. 



The axes of the Bray and of the Boulonnais present similar undulations. Blore- 

 over it is easy to observe that these various bosses are connected among themselves ; 

 thus the centre of the Bray axis is precisely on the line which runs from Rouen to 

 Aumale, and this line, prolonged to the north-east, passes by Picquigny-s.-Somme, 

 where is a rising of the Chalk, crosses at Ari'as the axis of Artois, and fi-om this 

 point is directed towards the ancient rocks which extend from Douai to Tournay. 



Here is then a S.W. and N.E. fold of a well-marked character, and tlie extent of 

 wliich is recognized from Rouen into Artois. 



The Vernon boss is the point whence starts another fold, parallel to the precediu"- 

 one. This fold traverses the Bray near Ville-en-Bray ; it then passes at Breteuil, 

 where a very distinct boss is to be seen. 



