322 PROP. T. G. BONNET AND KEY. E. HILL ON THE [Aug. 1 899, 



to be due to the action of an ice-sheet which had crept from 

 Scandinavia across the present bed of the Baltic. Two explanations 

 maybe offered of its precise method of working: — One, that the 

 pressure of the immense body of ice tore off huge masses from the 

 Chalk, which for a time had opposed its progress, and carried them 

 onwards (though not necessarily for any great distance) in such 

 wise that they became mixed up with the materials of its terminal 

 or subglacial moraine ; the other, that the Chalk is in situ, but that 

 the Drift has been either forced into glens and depressions in it, or 

 banked up against pre-existing cliffs. Of these alternatives we 

 regard the latter as the less improbable, because, as already stated, 

 the Chalk, in both Moen and Riigen, for hundreds of yards is as 

 clearly in situ as it is between Freshwater Gate and the Neerlles in 

 the Isle of Wight. But we must remember that in these islands 

 the present coast-line cannot be identical with that which existed 

 in the Ice Age. The Drift is constantly slipping down, much as it 

 does at Cromer and in Holderness, and before long is swept away 

 by the waves.^ As the Chalk-cliffs rise steeply, commonly have 

 no talus at their base, and do not project as headlands, we infer 

 that this rock recedes almost as fast as the Drift. Hence the 

 contour-line corresponding to the present Ordnance datum must 

 have been, in Glacial times, not less than some few hundred yards 

 away on the seaward side. If so, the tripartite arrangement of the 

 i^rift, often so orderly, becomes more than ever difficult to explain 

 on the hypothesis that the material was transported or thrust up 

 from the lowland now covered by the Baltic. -. Again, as boulders 

 are scattered over the plateau, often at heights of at least 300 feet 

 above sea-level, the ice must either have overridden the sand ^ 

 (Oberdiluvium) and dropped them on it, or have deposited them 

 in that or the upper Boulder Clay, which has been subsequently 

 washed away, and must have done this, in either case, without dis- 

 turbing the generally even bedding in one or other of the sands. Only 

 twice, atr most, as already mentioned, did we see anything in Riigen 

 resembling the Contorted Drift of Cromer, and certainly nothing in 

 the cliffs of Moen. The steep angles at which these bedded Drifts 

 lie are sometimes very puzzling, but the absence of anything like 

 contortions was no less singular. In short, though both forms of 

 the ice-thrust hypothesis were kept constantly in view, we could 

 find nothing in either island which was favourable to it, and very 

 much which was hostile. 



A third hypothesis accounts for the association of Drift and Chalk 

 by folding or faulting,^ or by both. Obviously such disturbances 



^ The proofs of slipping were very conspicuous in both islands at the time of 

 our visit. 



^ According to the Geological Map of Kiigen the sand of the forest (p. 312), 

 with probably the whitish Boulder Clay near the Waldhalle, belongs to the 

 ' Upper Diluvium,' and the tripartite Drift to the ' Lower Diluvium ' : the former 

 of which seems to be more widespread than, and generally unconformable 

 with, the other. 



^ Faidting was the explanation advocated by Puggaard and adopted by 

 Lyell. 



