312 Mr. A. J. Jukes-Browne on the 



are other features about the bluffs which are very puzzling. 

 " One of these is the cavities they contain, filled with stratified 

 alternations of calcareous sands and carbonaceous matter, 

 evidently of ancient date. These cavities led me to suppose 

 the masses might have formed needles or rocks in the glacial 

 sea. But if so, it is difficult to conceive how the large flints, 

 usually covering the chalk surface, could have been preserved 

 upon their upper parts in situ as they are " (loc. cit. p. 551). 



Mr. C. Reid has recently proposed another explanation*. 

 He assumes the existence of a vast ice-sheet filling the North 

 Sea in later glacial times, and supposes that the impact of 

 this against the Norfolk shore was the cause of the contortions 

 both in the Chalk and the Lower Glacial beds. This theory, 

 however, seems open to the same kind of objection as that 

 brought against Mr. Fisher's, viz. that physical considerations 

 render it improbable : it is possible to conceive that the Lower 

 Glacial beds may have been so doubled up ; but it is very 

 doubtful whether the solid scar of chalk could have been 

 squeezed up and contorted in the manner suggested. 



Both these theories involve highly theoretical questions of 

 physics 5 and both assume that the contortions in the chalk 

 were produced in Glacial times. It seems, indeed, more 

 reasonable to suppose that this disturbance had a much more 

 ancient origin, and that the beds of chalk were bent into the 

 curves now visible before the commencement of the Glacial 

 period. If this be assumed, there is then no necessity for 

 calling in the aid of any special agencies, and the older and. 

 simpler view that the masses formed isolated stacks or pinna- 

 cles becomes the natural explanation j moreover the existence 

 of the contortions would then be the very cause which con- 

 duced to the preservation of the bluffs, by enabling them to 

 resist the agencies which broke up the surrounding portions 

 of the chalk. 



There is another fact, mentioned by Lyell, which tends to 

 confirm this view, viz. that glacial beds have been seen under- 

 lying one end of the more northerly mass (see fig. 1) ; and in 

 the ' Philosophical Magazine ' (loc. cit. p. 358) he thus speaks 

 of it : — " I have stated in the ' Principles ' that this mass of 

 chalk at its northern edge actually overlies some beds of blue 

 clay or drift. Now this remarkable superposition was still 

 evident in June 1839, notwithstanding the unusual height of 

 the sea-beach, the clay containing broken chalk-flints being 

 traceable for 7 feet under the chalk. It is known to have 

 extended much further in a seaward direction." Elsewhere 



* Geol. Mag. dec. 2, vol. vii. p. 61. 



