84 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 13, 



extensions of the masses of crystalline rocks of tlie Cotentin, which 

 occur in the cliffs of its coast at places due east ; the submarine run 

 of these masses is indicated by the rocks across the mtervening sea : 

 it is the umdelding granite ridge, which connects the granite of Al- 

 derney with that of Cape la Hague, that causes the race at that place, 

 and so throughout the whole of that group {vide Map) . On our side 

 of the Channel the mineral character of the ciystalhne rocks is dif- 

 ferent from that of the Cotentin and Brittany ; the granite of Scilly 

 belongs to the west of England group, and due west again is Jones's 

 Bank, a nucleus of soHd rock invested vnXh granite sand and shingle. 

 This conformity of contour-lines to the coast becomes weaker as we 

 proceed seawards, and at the distance of the 50-70-fathom line of 

 soundings has only a general agreement with it ; the deep sea-beds 

 are spread out over this area : beyond these the configuration of the 

 sea-bed begins to put on a new direction, and in its extension west we 

 find that this depends on the form of the mass, which rises between 

 48° and 49° north lat. and 8'30° to 10° west long. 



The places along the opening into the Channel at which we meet 

 with shingle and gravel are very numerous ; some of these are indi- 

 cated on the map, but the scale is too small for the admission of all ; 

 but with respect to them all, we must suppose, as in the case of the 

 Little Sole Bank, that they are the indications of a marginal zone or 

 coast-line. 



It may be objected to this, that these distant sand, gravel and 

 shingle beds may belong to any age, and not in any way be connected 

 with the present seas. In tracing the remains of marine animals sea- 

 wards, we may observe a like gradual comminution with that noticed 

 with respect to mineral materials, long after the foi-ms of shells have 

 ceased to be recognizable. The sea-bed, particularly on the French 

 side of the Channel, is mainly composed of shell-sand, or sand in 

 which few particles of anything but such as show shell-structure 

 occur. Areas of this character are laid down by the French sur- 

 veyors, and occur in the interval between the Land's End of France, or 

 Ushant, and the Little Sole Bank ; yet on the sides of this bank, and 

 more particularly on its western slopes, large, perfect, though decayed 

 shells again occur, and what is more remarkable, Patella vulgata^ 

 Turbo littoreus, &c. Taking the two phsenomena together, the oc- 

 currence of httoral shells and of marginal shingle, we may safely infer 

 that we have at this place the indication of a coast-line of no very 

 distant geological period, buried under a great depth of water, and 

 removed to a great distance from the nearest present coast-line. 



The duration of time, estimated in the ordinary measure, during 

 which the sea must have worked at its present level, must have been 

 very great, from the extent and uniformity which its zones of deposit 

 have attained mth relation to that level ; and it may be argued, that 

 if such be the case, these coarser beds and littoral shells would not 

 now lie exposed on the sea-bed, but would long since have been 

 covered up by the accumulations of fine deep-sea sedimentary matter. 

 The obstruction the Little Sole Bank offers to the flow of the tidal 

 stream into the Channel — the surface-disturbance resulting from it, 



