312 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



that the 130-foot and 100-foot terraces are not really separate, but 

 Mr. Monckton found four well-marked terraces in the valley of the 

 Wey at Farnham, evidently corresponding to those of the Thames. 



5. Elevation of about 90 feet. A very long period of time elapsed after 



the Thames reached its new base line, for the lateral erosion was 

 enormous. The extensive gravels of the middle terrace were de- 

 posited, with brick earths to the east. These brick earths must 

 have been laid down in still or slow-moving water, and the authors 

 suggest that the Thames was at this period ponded back owing to 

 differential elevation to the north, reaching a maximum over the 

 great flat plain of the North Sea. The contemporaneo\is fauna in- 

 cludes EJcphas primigcnius, E. antiquus, Rhinoceros vicffarhinus, 

 R. Icptorhinus, R. antiquitatis, Ovibos inoschatus and Spcrmophihis 

 cri/tli rogenoides. Mousterian. 



6. Elevation of about 20 feet. A fourth terrace of gravel ("third ter- 



race") deposited. Resting on this terrace at Uxbridge are Magda- 

 lenian implements. 



7. Great elevation (at least 90 feet) and formation of buried channel. 



8. Gradual sinking to present level. 



For many reasons the 130-foot and lower terraces must be more 

 recent than the maximum glaciation (chalky bowlder clay). Prob- 

 ably, as suggested by Mr. Salter and "by Messrs. Sherlock and Noble 

 (79), prior to this the Thames occupied a more northerly course, but 

 was forced into its present position by the ice. 



That the climate was still cold when the 100-foot terrace began to 

 be formed is shown by the animal remains, which include reindeer 

 and Mierotus, but it was ameliorating rapidly, and finally permitted 

 the presence of Hippopotamus. The occurrence of Corbicula flumi- 

 nalis in the gravels of the highest terraces allies them with the 

 marine gravels of March and Holderness, already described. Ac- 

 cording to H. Menzel this mollusk is characteristic of the first inter- 

 glacial of the whole of northern Europe (i. e., after the first glacia- 

 tion of north Germany). The presence of Paludina dUuvicma is also 

 characteristic of the first interglacial of northern Europe. 



The fauna of the middle terrace, deposited after considerable eleva- 

 tion is very peculiar, containing a mixture of warm and cold forms — 

 the presence of Ovibos inoschatus and Spermophilue indicate a much 

 colder climate than Hippopotamus could exist in, and there are also 

 a number of deposits on this horizon which indicate very severe 

 climatic conditions. At Grays and Crayfqrd the brick earths cover 

 paleolithic floors with Mousterian implements. A similar floor at 

 Stoke Newington is overlain by the " warp and trail " of W. G. Smith, 

 generally considered as evidence of a severe climate. 



On the same level as the third terrace, but in the Lea Valley, and 

 also both overlain and underlain by brick earth, are the arctic glacial 

 beds of Ponders End, described by S. W. Warren and others in 

 1912 (80). 



