ON THE MOVEMENTS OF THE EAHTh's CRUST olo 



consist of brackish and fresh water marls, in which, besides a pyritif- 

 erous horizon of little importance, and which forms no pala^ontological 

 horizon, we tiud indications of two dry periods. One of these, the so- 

 called ^' White Band,'' a more or less hardened ferruginous bed rich in 

 fossils, forms the boundary between the two substages, the lower and 

 Middle Hamstead Marls; and higher up there is a bed of ironstone 

 concretions, which nearly coincides with the limit between the sub- 

 stages of the Middle and Upper Hamstead Marls. The uppermost part 

 of the Hamstead stage is formed by the marine Corbula bed, in which 

 there is a bed with Septaria. The stage therefore represents one oscil- 

 lation with three climatic alternations; but it is not completely pre- 

 served, the top having been removed by denudation. 



If we now sum up the above statements, we obtain the following 

 numbers of oscillations of shore-lines and climatic alternations : 



Barton, one oscillation, with five climatic alternations. 



Headon Hill Sand, without alternations. 



Break in the series. 



Lower Headon, one oscillation (or a little more), seven alterna- 

 tions. 



Middle and Upper Headon, one oscillation, with six alternations. 



Osborne, with eight to ten alternations, corresponding to two 

 oscillations. 



Bern bridge, one oscillation, with six alternations. 



Hamstead, one (incomplete) oscillation, with three alternations. 



Besides the Eocene Barton there are three well-marked marine Oli- 

 gocene horizons in this series: The Middle Headon, Bembridge 

 Oyster-bed, and Hamstead Corbula beds. The Middle Headon is re- 

 garded by palaeontologists as synchronous with the marine gypsum in 

 the Parish basin. I have fitted the Paris beds, so that tbe marine 

 gypsum coincides with the arc 3', and tiie Fontainebleau Sands with 

 the arc 7'. If we now arrange the equivalent beds in the Isle of Wight 

 in the same arcs, we see that the Isle of Wight profile tits perfectly 

 into the curve of eccentricity, as follows: 



Lower Headon to the arc 2' and perhaps the last part of 1', with 

 seven alterations and seven precessions. 



Middle and Upper Headon, with five alterations, to the arc 3', 

 with five precessions. 



Osborne, with ten alterations, to the arcs 4' and 5', with ten pre- 

 cessions. 



Bembridge, with six oscillations, to the arc 0', with five or six 

 precessions. 



Hamstead, with three alterations, to the first part of arc T, with 

 three precessions. 



It thus appears that the three marine horizons coincide with the three 

 highest eccentricities, the summits of the arcs 3', 0', and 7', while the 



