CORRESPONDENCE. 



53 



ing the lower Neocomian clay strata, " the Middle and Lower division " of 

 Fitton. 



Here, however, there is an abrupt change. The finely stratified deposits 

 which have hitherto prevailed are overlaid by an accumulation of coarse 

 sand and pebbles ; the stratum or strata composed of these materials varying 

 in thickness from a few inches to six or ten feet, and contrasting strongly 

 with the sands beneath. The " pebble-beds " are succeeded by various 

 strata of coarse gritty sand, abounding in concretions of limestone* and 

 chert ; in all of which small pebbles and thin layers of clay are of frequent 

 occurrence. These, in turn, are followed by a series of ferruginous sandy 

 deposits of considerable thickness, which range upwards uninterruptedly 

 to the Gault. 



It is to the occurrence of these " pebble-beds " and of the superincum- 

 bent limestone, in the Greensand of Godalming and elsewhere,f that I 

 would now direct attention, as being possibly connected with the present 

 subject of inquiry. 



There is another subject, however, so closely connected with every ques- 

 tion relating to the Greensand, that I find myself compelled to notice 

 it before proceeding further. 



Mr. R. Godwin- Austen, in a valuable paper " On the possible Extension 

 of the Coal-measures beneath the South-Eastern part of England,"]; argues 

 the existence, during the Oolitic, Wealden, and Neocomian period, of a 

 ridge of old rocks (palaeozoic) extending across our south-eastern counties 

 nearly in the line of the North Downs. This ridge the author traces 

 eastward, in connection with a well-marked Continental axis, called by him 

 the " Axis of Artois," and westward, into the district of Bath and Erome. 

 Eor the capital reasoning upon which that author's supposition is founded, 

 I must refer the reader to the original paper. Yet it cannot fail to strike 

 the observer, that such a ridge, supposing it to have existed as a coast-line 

 during a lengthened period, must have exercised considerable local influ- 

 ence upon the surrounding deposits, whether of the Oolitic or Cretaceous 

 formation ; so that the surrounding deposits ought, in themselves, to con- 

 tain some direct proof of its existence. Such proof, if I mistake not, may 

 really be found in the " pebble-beds " of the Lower Greensand. Of these, 

 Mr. Austen says, "The shingle-beds of the Lower Greensand of Kentand 

 Surrey contain a considerable number of extraneous fossils, such as the 

 bones and teeth of Oolitic saurians, Ammonites Lamberti and Am. crena- 

 ius of the Oxford clay in great abundance, together with Terebratula 

 fimbria and Rhynchonella oolitica; " and instances these as having been 

 derived from the wearing away of members of the Oolitic group, which, 

 he suggests, may have been originally brought up against the southern 

 slope of this old ridge " by a process of successive overlap." 



In confirmation of this opinion I may here mention that, previously to 

 becoming aware of Mr. Austen's researches, I had obtained from the 

 " pebble-beds " of the Lower Greensand of Godalming a series of drifted 

 fossils, ranging in age from the Ox lord clay to the Lias inclusive ; and, 

 from the evidence of these alone, I had come to the conclusion, that at the 

 time of their deposition in the Greensand the rocks from whence they were 

 derived must have existed within a short distance to the northward. § 



* Locally called " Bargate stone." 



t Along the North Downs. A pebble-bed also occurs in the cliff north of Shanklin 

 chine, holding exactly the same position in the Greensand. 

 X Quar. Jour. Gcol. Soc. vol. xii. p. 50. 



§ My reason for looking northward for such land-surface arose partly from the fact of 

 the pebble-beds becoming gradually thicker, and their component parts coarser, in that 

 direction. 



