498 A. Bljtt on the prohahle Cause of 



This part of the series is in part older than the Calcaire 

 grossier, and there are at least one, probably two gaps in it. 

 The following series, on the contrary, is continuous : — 



Lower Headon, freshwater and brackish, 7 to 8 alternations 



(arc 13 and the first part of 14). 

 Middle Headon, marine, 1 alternation, at 14. 

 Upper Headon, freshwater and brackish, 5 alternations, 



between arcs 14 and 15. 

 Osborne, freshwater, 3 alternations, between arcs 15 



and 1'. 

 Bembridge limestone, freshwater, 3 alternations, between 



arcs 1' and 2'. 

 Bembridge oyster-bed, marine, at least 1 alternation, 



at 2'. 

 Bembridge marl, freshwater, 6 alternations, arcs 2' and 3'. 

 Hempstead marl, freshwater and brackish, 2 alternations, 



4' or 5' ? 

 Hempstead Corbula-beds, marine, imperfect above by de- 

 nudation, 1 alternation. 



The profiles of the different stages are taken at different parts 

 of the island which have lain at different levels. Bearing 

 this in mind, the series may be fitted into the curve, and at 

 any rate correspond with them pretty closely. 



The number of alternations in this last continuous part of this 

 series of deposits is about the same as in the contemporaneous 

 deposits of the Paris-basin, although the beds are more than 

 three times as thick (48 metres in the Paris-basin, 156 metres 

 in the Isle of Wight). 



With the marine deposits of Hempstead the marine form- 

 ations of England are interrupted, and it is only in the 

 Pliocene that we have indications of a new marine submergence. 

 The basalts and volcanic eruptions of Ireland and the Hebrides 

 are probably, at any rate in part, Miocene. Basaltic dykes 

 extend in places across the whole of England ; but the chief 

 outbreaks were on the western side, and hence they can be 

 traced through the Faroes to Iceland. 



We will now see whether we can fill up the curve from 

 7', where the continuous profile from the Paris-basin closes, 

 up to recent times. The uppermost bed of the Paris-basin 

 lies upon the boundary between Oligocene and Miocene. As 

 we have already seen, the Miocene period in France had five 

 oscillations. In Transylvania (according to Koch, in the 

 Foldtani Kozlony) there are five Miocene stages, namely : — 

 Koroder beds, Kettosmezo beds, Hidalmas beds, Mezoseger 

 beds, and Feleker beds. All these stages are marine. Even 



