88 Dr. Wright on the Geology of the 



the existence of fossil shells and Septaria in the brown clay be- 

 neath the coloured strata. 



In 1822 Prof. Sedgwick published* a paper on the geology 

 of the Isle of Wight, in which he confirmed the general correct- 

 ness of Mr. Webster's descriptions. He noticed that the fossils 

 in the brown clay differed from those figured in Brander's ' Fos- 

 silia 1 lantoniensia.' He described the tertiary strata on the north 

 side of the island, which he stated belonged to the lower fresh- 

 water formation, and gave a sketch of the beds from Studland 

 Bay to Hordle on the coast of Hampshire, which he compared 

 with beds in the Isle of Wight. 



In 1838 Mr. Bowerbank published a paper t on the section at 

 Alum and White Cliff Bays, and gave measurements of the dif- 

 ferent beds exposed in these coast sections. He likewise showed 

 that the rich shelly sands of Bracklesham Bay had their equiva- 

 lents in the White Cliff Bay section. 



In 1846 Mr. Prestwich published! his valuable paper on the 

 tertiary formations of the Isle of Wight, in which he drew a com- 

 parison between the beds at White Cliff and Alum Bays, and 

 compared the relative ages of the English beds with those of the 

 French tertiary system. 



None of the works above cited contain an account of the sec- 

 tion which forms the subject of our paper. This appears to be 

 the more remarkable, as the analysis of the different beds com- 

 posing it affords the best key to a knowledge of the true relations 

 of the lacustrine series with the intercalated fossiliferous zones of 

 estuary and marine shells. Indeed I cannot understand how a 

 correct knowledge of these beds can be obtained in any other 

 way. The fact that they have hitherto been studied at Headon 

 Hill alone, is to my mind a sufficient reason why such a variety 

 of opinions prevail regarding them. 



With the view of settling to my own satisfaction the question 

 " whether an upper marine formation actually existed," as the 

 fact appeared doubtful from the way in which it had been alluded 

 to by previous observers, I determined to study the beautiful 

 coast section from Round Tower Point to Alum Bay, and take 

 each bed in succession as it rose from the shore, measure its 

 thickness and note its contents. By this means I hoped to 

 ascertain the genera of shells that were naturally associated 

 together in each of the beds, and thereby to arrive at a true so- 

 lution of the problem. In this investigation I experienced much 

 difficulty, from the extensive founders (or falls) that have taken 

 place in different parts of the section, as well as from the varia- 



* Annuls of Philosophy, vol. iii. 1822, p. 329. 



t Trans, of the Geol. Soc. Lond. vol. vi. Second Series, p. 169. 



X Quart. Journ. of Geol. Soc. vol. ii. p. 2'2ii. 



