342 GEOLOGY OF THE ISLE OF WIGHT. 



rectly attributed by Sir Henry Englefield, to the 

 action of the water that percolates from the surface 

 of the soil through these strata, and issues out on 

 the face of the cliff; the oxidation of the sands 

 and clays is the result of the decomposition of the 

 sulphuret into peroxide of iron. This change is 

 often accompanied by the formation of crystals of 

 sulphate of lime or selenite.* The abundance 

 of nodules of pyrites in these clay cliffs, as well as 

 in those of the Wealden, is so great, that consider- 

 able quantities of this mineral are collected on the 

 shore by the cottagers, for sale to the copperas 

 manufacturers. 



Approaching Atherfield, the undulated outline 

 of the distant horizon on the north, denotes the 

 re-appearance of the central range of chalk downs, 

 which we lost sight of behind Dunnose Point, 

 and is here seen extending in a south-westerly 

 direction towards the southern shore. The station- 

 house on Atherfield Point marks the locality where 

 the junction takes place between the Wealden and 

 the greensand (p. 221). 



The next interesting geological features of 

 this coast, are the cliffs at Brook Point, but 

 the steamers pass at so great a distance from 



* A similar result has taken place in some of the railway clay embank- 

 ments, ami been productive of considerable injury to the woikd. 



