1889.] THE DISPLACEMENT OF BEACH-LINES. 71 



Finally, we come to the Hamstead (Hempstead) stage. The 

 lower part of that stage is formed by fresh-water and brackish 

 marls showing, besides 1—2 pyritiferous beds of minor impor- 

 tance, two remarkable climatic periods. One dry period is 

 marked by the „ White Band", a more or less indurated ferru- 

 gineous layer rich in fossils, another by a layer of ironstone 

 concretions. The „ White Band" divides between the substages 

 Lower and Middle Hamstead marls, the ironstone band occurs 

 very near to the limit between the Middle and Upper marls. 

 The whole is covered by the marine Corbula beds with one 

 layer of septaria. The Hamstead stage thus represents one 

 oscillation with three climatic alternations; but it is not com- 

 plete, the top being destroyed by denudation. 



The fluvio-marine Oligocene series in the Isle of Wight 

 shows, thus, the following oscillations with the following number 

 of climatic alternations: 



Lower Headon, one oscillation, 7 alternations. 



Middle and Upper Headon, one oscillation with 6 alterna- 

 tions. 



Osborne, 8—10 alternations and probably 2 oscillations. 

 Bembridge, one oscillation with 6 alternations. 

 Hamstead, one imcomplete oscillation with 3 alternations. 



In this series we have three purely marine horizons: the 

 Middle Headon, the Bembridge Oyster bed, and the Hamstead 

 Corbula beds. If we now arrange our series from Wight ac- 

 cording to the curve of eccentricity, we see how admirably 

 *ell they correspond. The Lower Headon corresponds with 

 the arc 2' with 5 periods of precession and, as it shows 7 

 alternations, probably also to the last part of arc 1'. The 

 Mlddle and Upper Headon, with 6 alternations, correspond with 

 the arc 3'; the Osborne, with 8-10 alternations, to the arcs 

 4 ' and 5'; the Bembridge, with 6 alternations, corresponds with the 

 arc 6' and, finally, the incomplete Hamstead, with only 3 alter- 

 nations, with the first half of the arc 7'. The 3 marine beds 

 of the series thus correspond to the three highest eccentricities 



