138 Royal Institution. 



Headon Hill, and with which they have hitherto been confounded. 

 They are far above them, and are distinguished by distinct and pecu- 

 liar fossils. 



Almost all the country north of the chalk ridge, exclusive of the 

 small strip occupied by the marine Eocenes, is composed of marls 

 higher in the series than any of the Headon Hill beds, and hitherto 

 wholly undistinguished, except in the WhitecliflF section, where the 

 age and relative position had been entirely mistaken. These are the 

 Bembridge marls of Professor Forbes. Above them are still higher 

 beds preserved only in two localities, viz. at Hempstead Hill, to the 

 west of Yarmouth, and in the high ground at Parkhurst. For these 

 the name of Hempstead series is proposed. Their characteristic 

 fossils are very distinct, and the highest bed of the series is 

 marine. These beds prove to be identical with the Limburg or 

 Tongrien beds of Belgium and with the Gres de Fontainebleau 

 series in France. We thus get a definite horizon for comparison 

 with the Continent, and are enaliled to show, that inste'ad of our 

 English series of Eocene tertiaries being incomplete in its upper 

 stages as compared with those of France and Belgium, it is really 

 the most complete section in Europe, probably in the world. We 

 are enabled by it to correct the nomenclature used on the Continent, 

 and to prove that the so-called Lower Miocene formations of France 

 and Germany are in true sequence with the Eocene strata, and are 

 linked with them both stratigraphically and by their organic contents. 

 We are also enabled to refer, with great probability, the so-called 

 Miocene tertiaries of the Mediterranean basin, of Spain and Por- 

 tugal, — those of the well-known Maltese type — to their true posi- 

 tion in the series, and to place them on a horizon with the Tongrien 

 division of the Eocenes, As these Maltese beds are unconformable, 

 and evidently long subsequent to the deposition of the great num- 

 mulitic formation, we are enabled to assign an approximate limit 

 to the estimate of the latest age of that important series. From 

 well-marked analogies we get at a probable date even for the Au- 

 stralian tertiaries. Thus the deciphering of the true structure of a 

 small portion of the British Islands can throw fresh light upon the 

 conformation of vast and far- apart regions. 



The peculiar undulatory contour of the surface of the fluvio-marine 

 portion of the Isle of Wight is due to the gentle rolling of these 

 beds in two directions, one parallel with the strata of the chalk ridge, 

 and the other at right angles to it. The valleys and hills running 

 northwards to the sea depend upon the synclinal and anticlinal 

 curves of the latter system of rolls, a fact hitherto unnoticed, and 

 the non-recognition of which has probably been one cause of the 

 erroneous interpretation of the structure of the Isle of Wight, 

 hitherto received. The truncations of these curves along the coast 

 of the Solent exhibit at intervals beautiful and much neglected 

 sections, well worthy of careful study. There is one of these 

 sections near Osborne. Her Majesty's residence stands upon a 

 geological formation hitherto unrecognized in Britain. Near West 

 Cowes there are several fine sections along the shore. The total 



