UPPER GREENSAND. 65 



underground water naturally moving down the dip-slope of the 

 beds; but, the dip being very gentle, there are springs along 

 nearly the whole Gault outcrop. The most copious occur at 

 Wydcombe, Bierley (utilised for the Niton and VVhitwell Water- 

 works), Niton, Whitwell, south and south-east of Wroxall, and in 

 Greatwood Copse near Shanklin. The natural spring which 

 formerly issued at the last-mentioned locality was utilised for the 

 Shanklin Water-works, the supply of water having been some- 

 what increased by driving a heading into the hill along the 

 junction of the Upper Greensand and Gault. Ventnor is sup- 

 plied by a spring issuing from the same strata, and met with in 

 driving the railway tunnel. Several springs take their rise in the 

 same neighbourhood, and were formerly used to drive a mill in 

 Ventnor Cove. 



Along the central chain of hills the springs are less frequent, 

 owing to the steep inward dip of the strata. But a fine spring 

 issues at Bottlehole Well near Brixton, and another, issuing, 

 however, in the Upper Greensand, gives its name to tlie village 

 of Shorwell. About Chillerton and Gatcombe, where the dip is 

 very gentle, numerous springs rise along the sides, and particularly 

 at the heads of, the valleys. 



At Knighton there are good springs, which, supplemented by a 

 well, are utilised for the supply of Ryde. 



Correlation with the Mainland. 



The zones into which the Gault of Folkestone has been divided 

 by Messrs. De Ranee* and Pricef have not been recognised in 

 the Isle of Wight, and it is the opinion of the latter that the Gault 

 of the Island is of Upper Gault age (Monograph of the Gault, 

 p. 27). This opinion was founded on the occurrence of //weeramMs 

 sulcatus. Ammonites rostratus, Solariitm ornatum, Belcmnites ulti- 

 mus, &c. Of these Ammonites rostratus, and Inoceramus sulcatus 

 are confined to the Upper Gault, but Belemnites ultimus ranges 

 throughout the deposit, while Solariuvi ornatum occurs in the 

 Lower, as well as in the Upper Gault. On the other hand Am- 

 monites dentatus is a variety of Ammonites interruptus which gives 

 its name to the lowest zone of the Gault at Folkestone, from which 

 it would seem that the Lower Gault also is represented in the 

 Isle of Wight. This might be likewise inferred from the absence 

 of any break in or below the Gault of the Island. A couiplete 

 list of the fossils will be found in Table III. of Appendix II. 



Uppf.r Greensand. 



Introduction. 



This rock forms one of the most conspicuous features in the 

 Island, namely the cliff which overhangs the Undercliff from 



* Geol. Mag. for 18^58, p. 163. 



t Quart. Journ. Geol. Soc, vol.xxx. p. 342, 1874, and a Monograph of the Gault, 

 8vo. Loudon. 1880. 



E 66786. jj 



