accumulation of the Cambridgeshire Pleistocene Deposits 69 



Implements are scarce, but in both pits I have found some 

 suggestion of upper palaeolithic forms, and in each pit a water- 

 worn pot-boiler has been discovered. 



In the Barnwell Station pit the common mammal is the rein- 

 deer, associated with the mammoth, tichorhine rhinoceros and 

 horse. In the Geological Magazine for 1916 (p. 339), Miss E. W, 

 Gardner and I recorded the occurrence of an arctic flora in this 

 deposit, with abundance of leaves of Betula nana. A long pre- 

 liminary list of the other plants which indicate arctic conditions 

 was made by the late Mr Clement Reid, F.R.S., but has not yet 

 been published. A few worked flints of undeterminable date 

 have been found, but the fauna indicates the late palaeolithic 

 period, and the late date of these deposits seems to be shewn by 

 the fact that whereas all the others are apparently connected 

 with the old drainage line extending from Cambridge to Somers- 

 ham, these are almost certainly parallel 'to the present course of 

 the Cam : they appear indeed to be the upper portion of the 

 deposits filling an old buried channel of the Cam, evidence for the 

 occurrence of which is borne out by certain observations made by 

 Prof Hughes in the paper to which reference has been given. 



C. Climatic Changes. 



There is much difference of opinion as regards the occurrence 

 of alternating glacial and interglacial periods in Pleistocene times, 

 and it would seem that some light is thrown upon this question 

 by the Cambridgeshire deposits and those of adjoining counties. 



I take the prevalent view that the implement-bearing deposits 

 from the beginning of Chellean times post-date the period of the 

 Chalky Boulder Clay, though others hold a different view, but as 

 the local evidence bearing upon this question has already been 

 recorded I need not enlarge upon this point. 



If the succession as outlined above be correct the following 

 climatic changes seem to have occurred after the cold period 

 marked by the accumulation of the Boulder Clay : 



(a) A warm period during the formation of the Corbicula- 

 bearing strata. Arguments in favour of this are well known. 



(6) A cold period during the accumulation of the Observatory 

 gravels(?) and the newer loams. No evidence of this has been 

 advanced in this area, and a few remarks are necessary. 



The fauna of the Observatory gravels tells us nothing, and 

 the loams have hitherto furnished no organic remains, but a 

 widespread development of loam marks the Mousterian period, 

 and N.W. Europe is believed to have been subjected to a cold 

 climate during part of the period. 



