80 Reviews — Delesse's Liihologie du Fond des Mers. 



deposits, which on the coasts were chiefly composed of sands or of 

 conglomerates ; they produced effects of erosion and of transport 

 which worked over a vast extent of ground and with exceptional 

 energy, so that there resulted from them a veritable cataclysm." 



The word just written ''cataclysm," and the frequent recuiTence 

 in the last few paragraphs of the adverb •' suddenly," in reference 

 to such phenomena as the upheaval of mountain-chains, will doubt- 

 less jar upon the ears of most British geologists ; but it must be 

 remembered that cataclysmal geology still, with certain modifications 

 of course, holds its own across the Channel. It is, however, a 

 welcome recognition of the great effects of subaerial denudation by 

 M. Delesse, that he lays it down as an axiom (p. 139, vol. i.) that 

 the bottom of the sea is always, and necessarily, less furrowed and 

 sculptured than the surface of the land. 



Leaving for the present the other subjects treated of at length by 

 M. Delesse, I think I cannot do better than give briefly the results 

 of his investigations of the sea-bottom off our own coasts. The 

 maps accompanying his work will show the details which space will 

 not permit me to refer to here. 



"With regard to the orography of the " Ocean Britannique," as M. 

 Delesse calls our seas (excepting the Channel and the North Sea), he 

 shows how Britain and Ireland stand on a sort of terrace, the boundary 

 of which on the Atlantic side coincides sufficiently exactly with the 

 600 feet contour line (below sea-level, of course), in such a manner that 

 were the British Islands elevated 600 feet, they would be joined to 

 France and to Denmark, but the Faroe Islands, Iceland, and Rockall 

 would still be islands. As is natural in the neighbourhood of a 

 mountainous centre, the surface of this terrace is very irregular 

 around Scotland ; especially there are to be noted two valleys ex- 

 tending under the sea to the West of Scotland, separating it on the 

 one hand from the Hebrides, and on the other from Ireland. 



The littoral deposits of the south of England are naturally very 

 similar to those of the north of France, and are equally referable to 

 the geological formations along the coast-line. Among the sub- 

 marine deposits sand stands pre-eminent. Next in point of frequency 

 comes gravel, which is found in oddly-shaped masses at various 

 points, especially to the west of the British Isles, south of Cork in 

 the Bristol Channel, between Land's End and the Sorlingues Islands, 

 and also in the Channel. In the eastern part of the Channel gravel 

 occupies a large surface, and seems to unite the Greensand of Upper 

 Normandy to that of England. In the Bristol Channel and to the 

 .south of Ireland M. Delesse suggests that the origin of the gravel is 

 probably a submarine outcrop of Old Eed Sandstone ; south of 

 Exmouth and of Star Point it may be referred to the prolongation 

 under the sea of the arenaceous Triassic beds. 



The distribution of mud is next investigated. The patches of 

 mud-bottom in the Channel are due doubtless to the Paleozoic 

 schists, the Triassic clays, the Liassic marls, and the Eocene clays. 

 They can be traced from DoA^er to the Lizard. 



Off the west coast of Ireland a few patches only are to be found, 



