Geologists' Association. 329 



to the " Devil's Dyke," at the summit of the escarpment overlooking the Weald ; and 

 here illustrating his remarks by maps, showing the changes in the physical geography 

 of this part of the globe, which have occurred during various geological epochs, 

 Prof. Rupert Jones explained the theories which had been advanced to account for 

 the denudation of the Weald. He first referred to the hypothesis of the upheaval 

 of the elliptical area of the Weald causing axial and transverse fissures in the Chalk. 

 This upheaval gave rise to several rivers running north, and corresponding ones run- 

 ning south, which now drain the Wealden area. The advocates of the sub-aerial 

 denudation hypothesis maintain that the action of rain and rivers suflSced to com- 

 plete the work of denudation ; but it is contended, on the other hand, that it must 

 have been consummated by submarine action. This latter opinion was strongly 

 advocated by Mr. Mackie, who had very ingeniously shovm the manner in which the 

 sea would act, and form a long bay corresponding to the present Wealden area before 

 the formation of the Straits of Dover. The Professor concluded his address by 

 some general observations on the changes which had occurred in the physiography 

 of this part of the globe. Mr. Woodward concurred in the opinion that Mr. Mackie 's 

 theory had scarcely received that careful consideration which it seemed to him it 

 deserved, and adduced various phenomena that would be difiicult to account for on 

 the hypothesis of sub-aerial denudation alone. Returning to Brighton by way of the 

 western valley and past Furze Hill, the area of the Tertiary Deposits, the party 

 traversed the whole length of the coast section, and alighted at Kemp Town, to 

 observe the " Elephant Bed," which was especially well seen, in consequence of a 

 recent fall of a portion of the cliff. This remarkable bed, and the underlying 

 "raised beach '' resting on the undisturbed Chalk, were very attentively examined. 

 After luncheon, the new Museum (not yet opened to the public) was visited. The 

 visitors were received by Mr. T. Davidson, F.R.S., Chairman of the Museum Com- 

 mittee, and Mr. G. Scott, the Curator ; and the Davidson collection of foreign fossils 

 and volcanic products, the Willett collection of Cretaceous fossils, and the contents 

 of the Museum generally, were subsequently inspected. Mr. Woodward lucidly 

 explained the general arrangement of the Museum, which he regarded with especial 

 interest, as well as the great share which Mr. Davidson had taken in bringing 

 together a collection which would be worthy of the important town of Brighton. 

 Prof. Rupert Jones then discoursed on the Elephant Bed, attributing this great 

 aggregation of Chalk debris against undisturbed Chalk to a " banking up " which 

 would be produced by a reflex action of the tides, consequent upon the obstruction of 

 the isthmus which then extended across what are now the Straits of Dover. After 

 thanks had been duly tendered and responded to by Mr. Davidson, the members, 

 proceeded to the Aquarium, to visit which they had been very courteously invited. 

 Thus, the remainder of the time at the disposal of the party was instructively and 

 agreeably spent, and the return to London by the evening train concluded the day's 

 proceedings. 



Ordinary Evening Meeting. — June 6th, 1873. — Robert Etheridge, Esq., F.R.S., 

 F.G.S., Vice-President, in the Chair. — " On Ammonite Zones in the Upper Chalk of 

 Margate, Kent," by F. A. Bedwell, Esq., M.A. The author described, and showed 

 by sections, the exact positions in the cliS's to the east and west of Margate, of 

 fifteen large Ammonites, twelve of which lie between the Flagstaff and the Clifton 

 Ville Hotel, a space of about half a mile, and some of them exceed three feet in 

 diameter. All these twelve are in a bed closely approximating to an exact parallel 

 with a faint line of nodular flints, which undulates over this part of the clifi", and are 

 at a constant distance of eight feet below that line. From these facts were deduced 

 the following ijiferences : — (1) The presence of an Ammonite Zone, and of (2) a 

 true sea floor. (3) The parallelism of this, with the horizontal flints, and (4) that all 

 the horizontal bands of flint must be assumed to have been aggregated before the 

 Chalk moved. Particulars were also given of three other beds of Ammonites, one 

 to the west of Margate, another forty feet below that first mentioned, and a fourth at 

 Pegwell Bay, at the top of the clifl'near the landing stage; and it was conjectured 

 that the first and second are identical, and also the third and fourth. Specimens 

 from the first and second beds were respectively identified by Mr. Etheridge as A. 

 leptophyllus and A. Lewesiensis. Similar beds elsewhere were referred to, but details 

 could only be given of one, which is to be seen at low water, near the Black Rock at 

 Brighton. A remarkable bed of continuous solid flint, between three and four inches 

 thick, extends round and under the Isle of Thanet. Between the Foreland and 

 Pegwell Bay it is in the upper part of the clifl', while it sinks below the shore at 

 Pegwell Bay and Kingsgate, rises again to the west at the back of Margate Harbour, 

 but disappears immediately, appears again to the south as pointed out by Mr. 

 Whitaker, in his " Geology of the London Basin," at Cap Point, near Walmer, and 

 again at Shepherds Well station, ten miles inland, where it is surmounted by the soft, 

 almost flintless, Chalk of Margate, and it is known throughout the island by the weU 



