1853.] FORBES — ISLE OF WIGHT. 263 



The contour of the surface of the north end of the island depends 

 on the gentle rolling, in two directions, of the tertiary strata, the one 

 series of rolls parallel with the chalk ridge and the other at right 

 angles to it. The former rolls are connected with the movement that 

 elevated vertically the chalk and neighbouring strata. The latter 

 appear also to afPect the chalk, since each north and south valley 

 formed by the synclinal curve of a roll corresponds to the division 

 between two chalk downs, and each down to an anticlinal. All 

 the valleys of the north of the island depend for their form upon 

 synclinals, and all the ridges on anticlinals. All the Eocenes 

 (under which term I include, for reasons hereafter to be stated, all 

 the fluvio-marine beds) are aflFected by these movements. The gra- 

 vels which rest upon them, whether the more ancient or higher level 

 gravels, or the newer, such as those that occupy coombs or that form 

 thick beds (40 feet thick) at Foreland, are unaffected by these move- 

 ments. 



Palseontologically, the Headon beds (exclusive of the marls capping 

 the hill before alluded to) form a distinct group from the Bembridge 

 limestone and its associated marls ; and these in their turn consti- 

 tute a distinct series, so far as fossils are concerned, from the Hemp- 

 stead beds. 



Arguing from both order of superposition and fossil contents, I am 

 induced to maintain that the series of beds hold the following relations 

 to the Paris and Belgian groups : — 



1st, The Headon Hill sands and the freshwater beds lying between 

 them and the Upper marine and Upper freshwater beds in Headon 

 Hill, are, as maintained by Mr. Prestwich, the equivalents of the 

 upper part of the Calcaire grossier. 



2nd. Certain strata, termed by me the St. Helens beds, interme- 

 diate between the Headon series proper and the Bembridge lime- 

 stones, probably in connection with the upper and middle Headons, 

 represent the Gres moyens. 



3rd. The Bembridge limestones and marls are the equivalents of 

 M. d'Archiac's fifth group — the gypseous series, or Calcaire lacustre 

 moyen, with its associated beds, and of the Lower Tongrien of 

 Belgium. 



4th. The Hempstead series represents the fourth group of M. 

 d' Archiac, and possibly part of his third group, the former including 

 the Gres et sables superieurs (Gres de Fontainebleau), and the latter 

 the Calcaire lacustre superieur. It represents also the middle and 

 possibly the upper Limburg beds of Belgium. 



If this arrangement be accepted, the prevalent classification of a 

 considerable portion of theTertiaries of Europe and the Mediterranean 

 basin will be materially affected. Continental geologists are, with 

 a few exceptions, inclined to refer the fourth and fifth groups of 

 M. d'Archiac's arrangement to the Miocene formation. By Sir 

 Charles Lyell, however, they have been regarded as Upper Eocene. 

 It would seem that to this section are referable many of the older 

 tertiaries of France, including important beds of the Bordeaux 

 basin, many of the beds called Molasse, important strata in the 



