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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 22, 



area occurs on a darker ground, and isolated dark areas on a light 

 depleted ground. 



Fig. 58. — Carboniferous Sandstoiu, coast south of Whitehaven. 



Pig. 59. — Ashdown Sands, 

 Wealden, Hastings. 



The arrangements of yellow banding generally occur quite irre- 

 spectively of the mechanical structui^e of the bed, the stratification 

 being indifferently intersected by it. In other cases, variations of 

 mineral structure seem to have influenced similar rearrangements of 

 the oxide of iron, e.g. the presence of pieces of clay in the Ashdown 

 Sands, Hastings (PL XV. fig. 33), having determined the aggregation 

 of a shell of oxide of iron around them, accompanied by the bleaching of 

 the surrounding sandstone. In another case, lenticular patches of 

 sandstone in the midst of a more clayey bed has determined the 

 aggregation of the ferruginous hne to the point of separation. 



In some parts of the Ashdown sands, at the foot of the Past 

 Cliff, Hastings (fig. 59), a further 

 change has supervened, the connected 

 banding having given place to the se- 

 paration of the oxide of ii'on into 

 small nuclei, the disposition of which 

 faintly indicates the original continu- 

 ous Hues. IS'early all yellow strata 

 coloured with the hydroujs sesquioxide 

 of iron give indications of these se- 

 condary changes. The Calcaire gros- 

 sier (PI. XY. fig. 34) is occasionally 

 faintly banded; and wherever a line 

 occurs darker than the general cream- 

 coloured ground, it is invariably ac- 

 companied by an adjacent line some- 

 what lighter. Although these bands 

 range with the stratification, they 

 can scarcely be due to mere mechanical alternation ; and the darker 

 accumulations seem to have resulted from the impoverishment of 

 the adjacent bleached portions. 



