Vol. 55.] CHALK AJ?D DRIFT IX MO EN" AXD EIJaEJ^-. 321 



sloping lines of fliat.^ After about 10 yards, masked by slip, the 

 Boulder Clay is exposed for some little distance in craglets by the 

 beach. 



These groups of sections may, we hope, suffice as types of those 

 examiueil during our stay at Sassnitz. We have only to add that 

 the lower Boulder Clay, though sometimes it differed but slightly 

 from the upper, did so sufficiently to show that a repetition in con- 

 sequence of folding was not possible. Pebbles are fairly common 

 in both clays, but less so than in the average Boulder Clay of 

 Eastern England. They are generally more or less well rounded, 

 and consist mainly of crystalline rock, with some grits or quartzites, 

 hard dark argillites, and limestones. Flints are not frequent, and 

 chalk is rare. Both clays, but more particularly the lower one, bear a 

 general resemblance to the Cromer Till, especially to its representative 

 near Lowestoft, and to the lowest Boulder Clay near Bridlington, 

 allowing for the frequent absence of chalk-pebbles. The lower 

 clay is of a rather deeper grey than the upper, and in drying it 

 becomes more definitely jointed, breaking into rude prisms ; larger 

 boulders are somewhat commoner in it, and they frequently form a 

 layer almost at the base. Still, they are also present in the upper 

 clay, and no doubt in the Oberdiluvium as well, for they are often 

 dotted over the surface of the ground in the forest. 



lY. CoTs'CLIJSIONS. 



What is the explanation of this singular collocation of ChaJk 

 and Glacial Drift ? It must be the same in the case of both Moen 

 and Riigen, for the sections in the two islands, though not identical, 

 differ only in detail. We must remark at the outset that to liken 

 them to the sections in the cliffs near Cromer is, in our opinion, mis- 

 leading and erroneous.^ In the former the Glacial Drift is a local 

 incident in the Chalk ; in the latter the Chalk is similarly related 

 to the Drift. In Norfolk, so far as we can teJl, the Chalk «is never 

 in situ ^ ; in the two Baltic islands it is almost invariably so. 



Some of the sections in these islands would be most simply ex- 

 plained by claiming the Glacial Drift as an episode of the age of 

 Beleynnitella mucronata. But this hypothesis, we imagine, would 

 find few defenders and does not need serious discussion. 



The next hypothesis, which at the present time numbers many 

 supporters, asserts the strange intercalation of the Drift and Chalk 



1 This relation covild not be mistaken, for some of the clay had fallen out- 

 wr.rds and formed a recess in the cliff, with the Clialk for a wall, about the 

 height of a man, on the right (or more northerly) side. 



^ Phenomena resembling those of the Lower Till of the Cromer district, so 

 far as we can ascertain from the literature^of the subject, may occur on the 

 North German mainland. Perhaps also thfey may be found at Arkona, the 

 noi'thernmost extremity of Riigen, but this we had not time to Tisit. 



^ We refer, of course, to the Chalk-masses in the Drift. The former rock is 

 in situ below it, as can be often seen, bat only rises a very little distance above 

 the shore. 



Q. J. G. S. jS^o. 219. Y 



