280 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1917. 



England and Ireland, namely, that a raised beach of a definite age, 

 after extending fairly continuously at a nearly uniform height for 

 perhaps a hundred miles, disappears abruptly even on a coast suit- 

 able for its preservation. The weaker parts of the crust where most 

 of the bending occurs are likely to prove most unstable, so that on 

 them the sea rarely stays long in one position, and raised beaches are 

 not developed. 



I do not propose to enter into a discussion of the value of plants 

 and animals as climatic gauges or for correlation. Suffice it that as 

 their present distribution is undoubtedly governed principally by 

 climate, either present or not long past, so must their former dis- 

 tribution. The use I have made of them for correlation is seen in 

 the individual cases; only the facies is employed save where a species 

 is definitely characteristic of a certain horizon, such as Corhicula 

 fuminalis and Paludina diluviana in the older interglacial. The 

 "Chellean fauna," characterized by the coexistence of Elephas anti- 

 qmis and E. prhmf/enius, with H ippopofanius major and other large 

 Quaternary mamm-als, is a very useful facies for correlation. 



A means of correlation which proved somewhat disappointing 

 was the sequence of archeological stages. The Acheulian horizon 

 especially seems to be vague, for it overlaps or grades into the 

 Chellean on the one hand and the Mousterian on the other, and it 

 appears to occur both before and after the second glaciation of Eng- 

 land and north Germany. In general, the relations of the stages 

 appear to be as follows : 



Cold period: Pre-Chellean. 



Warm period: Chellean 



Chelleo-Aclieulian. 

 Cold period : Acheulian-Mousterian. 

 Warm period : IMousterian. 



jAmngnacian. 

 Cold period: iSolutrean. 



[Magdalenian. 



This is based on the sequence of faunas associated with the imple- 

 ments as described by many authors. 



1. THE NORTH GERMAN PLAIN IN THE GLACIAL PERIOD. 



The whole of the evidence as to the succession of stages in the 

 north German plain was summarized in 1913 by C. Gagel (6), who 

 finds undoubted proof of a plurality of glaciations. His chief lines 

 of evidence are: 



1. The occurrence in many places of beds of ground moraine, sep- 

 arated by extensive fluvio-glacial deposits and connected with others 

 which are grouped into terraces of very different heights above the 

 present streams. Between ih^ formation of these different terraces 

 very deep and energetic erosion is demonstrable. 



