204 Professor E. Forbes on 



enumerated in ascending order, the Plastic clay, the Bognor 

 series (equivalents of the true London clay), the Bracklesham 

 series, and the Barton series, upon which lie the Headon Hill 

 sands, and those fresh-water strata that, spreading out, form 

 the gently undulating country, extending from near the base 

 of the chalk ridge to the sea. 



Owing to the section at Headon Hill, near Alum Bay, being 

 so clear and conspicuous, and their position being in the loftiest 

 tertiary hill that exhibits its internal structure in the island, 

 the fresh-water and fluvio-marinebeds which compose that ele- 

 vation have long attracted attention, and have been described 

 by many observers, the first of whom was the late Professor 

 Webster. The apparent slight inclination of these beds, as 

 seen in the Headon section, except at the point where they are 

 suddenly curved in conformity with the verticality of the chalk 

 and the beds immediately above it, appear to have led geolo- 

 gists to the notion that the fluvio-marine portion of the Isle 

 of Wight was composed entirely of continuations of the beds 

 forming Headon Hill. Two observers only suspected a dis- 

 crepancy, viz., Mr Prestwich, who in a short communication 

 to the British Association at Southampton, expressed his be- 

 lief that Hempstead Hill, near Yarmouth, would prove to be 

 composed of strata higher than those of Headon ; and the 

 Marchioness of Hastings, who, having given much time to the 

 search for the remains of fossil vertebratain the tertiaries of the 

 Isle of Wight and Hordwell, declared her conviction thatthese 

 remainsbelonged to distinct species, accordingas they were col- 

 lected at Hordwell, Hempstead, and Hyde, and that these three 

 localities could not, as was usually understood, belong to the 

 same set of strata. The recently published monograph of the 

 pulmoniferous molluscs of the English eocene tertiaries, by 

 Mr Frederic Edwards, afforded also indications of the shells 

 therein so well described and figured having been collected in 

 strata of more than one age. 



A few days' labour at the west end of the island convinced 

 Professor Forbes that the surmises alluded to were likely to 

 prove true, and that the structure of the north end of the 

 island had been in the main misunderstood. After four months' 

 constant work at both extremities, and along the intermediate 



