18 PEOF. T. G. BONNET AND REV. E. HILL ON THE [Feb. IpOI, 



former, rather higher ground, that of the Stubnitz, stands in the 

 path of the ice-sheet; while the latter (in which direction the 

 ground undulates to the Jasmunder Bodden) is hardly the route 

 which can have been taken by the main mass of ice. 



We may more briefly dismiss another hypothesis, started during 

 the discussion (the reasons which we had given for excluding it 

 having been apparently overlooked), namely, that the present singular 

 association of the Drift with the Chalk is due to subterranean 

 denudation of the latter. The Chalk of Eligen contains bands of 

 flint. The latter, indeed, is rather more nodular in character than 

 in the Upper Chalk of England ; nevertheless we think w^e may 

 fairly allow about 3 inches of solid flint to 6 feet of Chalk. To bring 

 the Drift into its present position often requires the removal by 

 solution of 30 to at least 60 feet of Chalk.^ Thus a band of 

 broken flints should be left (as in England), from some 15 inches 

 to over 2 feet thick. We had been looking out for this band during 

 the whole of our work in 1898; we again searched carefully for it 

 in 1899 ; and we rarely, if ever, found even a solitary fragment 

 ■of flint. Yet we saw such fragments in some of the pipes ! We 

 think, then, that until that difliculty be removed, that hypothesis 

 needs no further discussion; nor does another form of it, the falling- 

 in of the roof of caves, prove more satisfactory. The absence of 

 Chalk-debris below the Drift, the regularity with which the three 

 members of the latter dip towards the steeper wall of the Chalk, 

 and their uniform arrangement, negative the latter modification of 

 the hypothesis. If, then, neither this, nor ice-thrust, nor folding, 

 nor even faulting, satisfactorily explain the peculiar relations of the 

 Drift and the Chalk in Riigen, we can find none better than that 

 which we offered last year, claiming for this at any rate that it 

 accords with all the facts which we have observed. 



In conclusion, we may repeat that we deem ourselves justified, 

 as on the last occasion, in abstaining from further discussion of the 

 agency by which the Drift was deposited. Whether the tripartite 

 Drift were directly laid down by an ice-sheet, or by the intermediate 

 action of water, we should still have to explain how it got into its 

 present abnormal position, and to that point, for good reasons as we 

 think, we have at present restricted ourselves ; for it is entirely 

 distinct from the other. 



Discussion. 



Sir Henry Howorth said that the only claim which he had to 

 enter into the discussion was that he had several times seen the 

 cliffs discussed in the paper from the uncertain vantage of a steamer's 

 deck whence Mr. Hill drew his ' panorama,' and had read the various 

 memoirs which have been published on them by the German geologists. 

 The amount of this literature was much greater, and it went back 

 much farther in time, than was generally supposed ; and the speaker 



^ The cliflPs in which these drifts are intercalated must often be much higher. 

 Prof. Credner, op. cit. p. 429, gives the height of the Waldhalle terrace as 

 230 feet, and the Wissower Klinken as a few feet higher ; so that we deliberately 

 understate our case, and in some instances might even triple the higher figure. 



