1868.] MAW VARIEGATED STRATA 391 



rutory of the Museum of Practical Geology, gave the following re- 

 sults : — 



Analysis No. 89. Light ground, Ashdown Sands, near Hastings 

 (fig. 56). 



Iron I Soluble in hydrochloric acid 0130 1 Total 0-225. 



iron... I Insoluble 0095 J 



Present as Sesquioxide of iron 0*145 



,, Protoxide of iron 0'036 



„ Oxides of iron, insoluble, weighed as pro- 

 toxide 0-122 



Analysis No. 90. Yellow portions of Ashdown Sands, near 



Hastings (fig. 56). 



Soluble in hydrochloric acid 0'91 1 1 ^otal iron 0-997. 



Insoluble.... ••• 0-Uob J 



Present as Sesquioxide of iron 1-260 



,, Protoxide of iron 0037 



„ Oxides of iron, insoluble, weighed as 



protoxide O'lll 



The dark area in fig. 56 contained therefore about four times the 

 amount of iron in the light ; and the dark ferruginous band of sepa- 

 ration (of which no determination was made in this example) would 

 contain from 30 to 40 per cent of hydrous sesquioxide of iron. The 

 position of the cracks, c, c, in relation to the darker area is strongly 

 suggestive of infiltration ; and a somewhat similar arrangement of 

 ferruginous colour, in relation to lines of joints, occurs in the Car- 

 boniferous sandstone on the coast south of Whitehaven (fig. 57). 



Fig. 57. — Carhoniferous Sandstone, coast south of Whitehaven, 



Some of the jointed rocks (fig. 58), however, on the same coast, 

 in which the disposition of the light and dark areas is evidently re- 

 lated to the joints, present the very reverse arrangement — the light 

 areas bounding the lines of joining, whilst the general yellow ground 

 occupies the intervening spaces. 



Here, therefore, there appears to be the same kind of inter- 

 changeable arrangements of light to dark, and dark to light, as is 

 found in the other forms of variegation, the exhausted areas being the 

 result, not only of aggregation, but of dispersion, and corresponding 

 with the examples figs. 54 and 55, in which both an isolated depleted 



