208 GEOLOGY OF THE ISLE OF WIGHT. 



in a comparatively short space of time ; and the 

 disengaged flints, after a very brief exposure to 

 attrition, must have been transported beyond the 

 reach of the waves. 



From the organic composition of the chalk 

 {ante, p. 1 80), it is manifest that when first deposited 

 at the bottom of the ocean, it was a fine white 

 detritus or mud, resembling in its nature and ap- 

 pearance the chalk now in progress of formation, 

 along the coasts of the Bermuda Islands ;* some 

 layers of which are as rich in microscopic shells 

 as any of the cretaceous strata. The veins and 

 beds of flint, as we have previously explained, 

 probably originated from the periodical introduc- 

 tion of thermal waters highly charged with silica, 

 into the calcareous sediment. The subsequent 

 conversion of the incoherent detritus into compact 

 limestone, may have resulted in part from pressure, 

 but principally from the slow infiltration of crys- 

 talline carbonate of lime ; a process which has so 

 rapidly converted the mud of the Bermudas into 

 a rock fit for building, that the imbedded shells 

 in many instances retain their natural colour and 

 polish. 



It may therefore with great probability be as- 

 sumed, that at the period when the cretaceous 

 ■ Wonders of Geology, vol, i. p. (>9. 



