460 PLEISTOCENE DEPOSITS AT TWICKENHAM. [_A-Ug. *894j 



They can be divided into four zones : — 



(1) The lowest and deepest, the ' coarse ballast gravel,' which 



suggests a rapid torrent at the time it was laid down. 



(2) The layer of ' dark sand,' sparsely scattered with gravel, 



which indicates a slackening of the stream. 



(3) The dark-blue loam seam which points to a further slackening 



of the current, the plants and shells all now living in the 

 neighbourhood and indicating a climate like the present. 



The diminishing velocity of the stream in these three zones sug- 

 gests a continuous lowering of the land, and may, therefore, point 

 to the termination of a continental period. 



There is evidence of an old land-surface, on the top of the blue loam 

 seam, over which roamed the bison and the reindeer, and as these 

 animals do not occupy the same areas at the same time, it points to a 

 changing climate of long cold winters, during which the reindeer 

 came south, and short hot summers, when the bison would move 

 northwards. 1 



The bison-bones indicate the very probable presence of river- 

 drift man. 



(4) The overlying coarse reddish-yellow gravels, with (towards the 



bottom) reindeer bones only, and large flints such as could 

 have been carried by ice alone, indicate a much colder 

 climate, probably Arctic (a supposition which is confirmed 

 by the Saiga antelope having been found in this layer 

 in the same district in 1891). 



Discussion (on the preceding two Papers). 



The President congratulated the Authors of the second paper on 

 having succeeded in rescuing so interesting a collection of remains of 

 Thames Valley mammalia. He inquired if Dr. Leeson had obtained 

 the remains of the Saiga antelope from the same horizon as the present 

 ' finds,' and if so he pointed out that these remains — i. e. the Bison 

 •prisms, the Rangifer tarandus, and the Saiga antelope — represented 

 the older fauna of the Thames Valley gravels and brick-earth. 



Sir John Evans expressed his pleasure at Mr. Holmes's further dis- 

 covery of evidence as to the superposition of the old Thames Valley 

 gravels upon the Boulder Clay, as these discoveries supported the view 

 he had always held, that these gravels, whether at a high or at a low 

 level, were ' post-Glacial' in the sense indicated by the Author. 



The finding of the mammalian remains by Dr. Leeson in the low- 

 level gravels at Twickenham was of interest, as proving the existence 

 of the reindeer and bison in the Thames basin at the time of the 

 deposition of these beds. As to some of the remains of other animals, 

 however, he entertained doubts whether, though found in the course 

 of the excavation, they really belonged to the gravels. 



Prof. T. M C K. Hughes was pleased to hear Mr. Holmes bring 

 forward such direct proofs that the mammoth -gravel of the Thames 

 Valley was post-Glacial. He thought that the bones exhibited by 

 1 See Boyd Dawkins, ■ Early Man in Britain,' pp. 189, 191. 



