Chalk and Flint of the South-east of England, 77 



kindness of Dr. Bailiey of West Point, New York, from various 

 parts of Asia and America. 



I will now venture to digress for a brief space to inquire whe- 

 ther the original organic incoherent condition of the chalk, as 

 shown by the above investigations, may not offer a satisfactory 

 explanation of the formation of the grooves and furi'ows on the 

 surface of chalk rocks, and of the vertical funnels or sand-pipes 

 with which in certain districts the cretaceous strata are traversed ; 

 and of the origin of the beds of loose, but not water-worn, flint 

 nodules, which are so constantly met with lying on the surface of 

 the rock, and immediately beneath the turf of the downs, and 

 with scarcely any intermixture of transported materials ; phseno- 

 mena, that have very recently been brought under the notice of 

 this Society. From what has been advanced, it is manifest that 

 the chalk when first deposited at the bottom of the ocean must 

 have been in the state of a fine white detritus or mud, resembling 

 in appearance and in chemical and organic composition, the chalk 

 now in progress of formation along the coasts of the Bermuda 

 Islands ; some layers of which are as rich in animalculites as any 

 of the American tertiary formations. The veins and beds of flint, 

 probably originated from the periodical introduction of thermal 

 waters highly charged with silica, into the calcareous sediment : 

 and the subsequent conversion of the incoherent detritus into 

 compact white chalk, must have resulted in part from pressure, 

 and from the infiltration of crystallized carbonate of lime ; a pro- 

 cess which at the present moment is in constant action on the 

 shores of the Bermudas, and whose effects are seen in the spe- 

 cimens on the table, in which the sediment thrown down by the 

 sea is shown in various states, from that of a white pulverulent 

 earth, to the compact limestone with which the forts and bridges 

 of those islands are constructed. 



It may, therefore, with great probability be assumed, that at 

 the period when the cretaceous strata of the south-east of En- 

 gland were exposed to those elevatory movements which ulti- 

 mately raised them, together with the Wealden deposits on which 

 they repose, above the level of the sea, the lowermost beds of 

 chalk were already consolidated ; but the uppermost and latest 

 deposits were in the state of the soft Bermuda earth. Upon the 

 emergence of the chalk above the sea, those last formed and con- 

 sequently least coherent beds, would be the first exposed to the 

 destructive effects of the waves ; and if the elevation were gra- 

 dual, successive strata would be subjected to the same agency, 

 until the chalk-hills were lifted up above the operation of these 

 denuding causes. The drainage of the elevated portions of the 

 soft calcareous rock would then commence, and give rise to nu- 

 merous streams and rills, by which the surface would be worn 



