TDE 



QUARTERLY JOURNAL 



OP 



THE GEOLOGICAL SOCIETY OF LONDON. 



PROCEEDINGS 



OF 



THE GEOLOGICAL SOCIETY. 



April 22, 1868. 



The Rev. John Carne, Penzance; J. Whitaker Hulke, Esq., F.R.S., 

 F.C.S., 10 Old Burlington Street, W. ; and Lewis Thomas Lewis, 

 Esq., Gadlys, Aberdare, were elected Fellows. 



The following communications were read : — 



1. On the Disposition of Iron in variegated Strata. 

 By George Maw, Esq., F.L.S., F.G.S., &c. 



(Plates XI.-XV.) 



Contents. 



1. Literature. 



2. The states of combination of iron in the principal stratified rocks. 



3. The primary condition of iron in red beds. 



4. The bleaching of red beds due to abstraction of the colouring oxide, 

 6. Discoloration and bleaching connected with joints. 



6. The variegation of the Keuper marls. 



7. The influence of organic matter in inducing variegation. 



8. Variegation due to the decomposition of bisulphide of iron, 



9. Variegated Cambrian slates. 



10. The discoloration of red beds by lime and magnesia. 



11. The condition of the iron in the depleted areas of red and purple beds. 



12. The ferruginous banding of yellow sandstones. 



13. The variegated iron-ore deposits of the Northamptonshire OoHtes. 



14. Disposition of manganese in variegated strata. 

 16. General conclusions. 



Of those secondary changes which have modified the original 

 chemical and physical constitution of rocks none seem to have more 



VOL. XXIV. PART I. 2 c 



