Royal Instituiion. 137 



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 geologists 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 discrepancy, viz. Mr. Prestwich, who, in a short communication to 

 the British Association at Southampton, expressed his belief 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 

 vertebrata in the tertiaries of the Isle of Wight and Hordwell, 

 declared her conviction that these remains belonged to distinct 

 species, according as they were collected 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 pub- 

 lished monograph of the pulmoniferous moUusks of the English 

 Eocene Tertiaries, by Mr. Frederic Edwards, afforded also indications 

 of the shells therein so well described and figured having been col- 

 lected in strata of more than one age. 



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

 fessor 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 country, he succeeded in 

 making out the true succession of beds, with most novel and gratifying 

 results. During this work he was greatly aided by his colleague, Mr. 

 Bristow, and by Mr. Gibbs, an indefatigable and able collector 

 attached to the Geological Survey. 



The freshwater strata of Whitecliff Bay proved to be wholly mis- 

 interpreted. Instead of their being constituted out of the Headon 

 Hill strata only, more than a hundred feet thickness of them are 

 additional beds characterized by peculiar fossils, and resting upon a 

 marine stratum that overlies the Bembridge limestone, the equiva- 

 lent of which at Headon is a soft concretionary calcareous marl, 

 scarcely visible except in holes among the grass immediately under 

 the gravel on the summit of the hill. 



Ttie beds of the true Headon series, in fact, are all included in the 

 subvertical portion of the Whitecliff sections and are there present 

 in their full thickness. They are succeeded by peculiar strata of 

 intermediate character, for which the name of St. Helen's beds is 

 proposed, and which become so important near Hyde that they con- 

 stitute a valuable building stone. The Bembridge limestone that 

 lies above is the same with the Biustead limestone near Ryde, out 

 of which were procured the remains of quadrupeds of the genera 

 Anoplotherium, Palieotherium, &c., identical with those found in the 

 gypsiferous beds of Montmartre. The Sconce limestone near Yar- 

 mouth is also the same, and none of these limestones are identical 

 with any of those conspicuous among the fluvio-marine strata at 



Ann.S^Mag.N.Hist. ^Qv,2. Vol.xii. 10 



