PLEISTOCENE RIVER-DEPOSITS. 141 



The origin of these gravels has always been a difficult ques- 

 tion, but a suggestion which Mr. Darwin some years ago (1876) 

 did me the honour to communicate gives what appears to be 

 the true explanation of the somewhat puzzling phenomena. 

 Having since had an opportunity of testing the value of the 

 suggestion referred to, I have found it extremely helpful, and 

 believe that my co-workers will agree with me in this opinion. 

 Mr. Darwin, after remarking that his observations were made 

 near Southampton, writes as follows : — " I need say nothing 

 about the character of the drift there (which includes Palaeo- 

 lithic celts), for you have described its essential features in a few 

 words (Great Ice Age, p. 506). It covers the whole country, 

 even plain-like surfaces, almost irrespective of the present out- 

 line of the land. The coarse stratification has sometimes been 

 disturbed; and I find that you allude to 'the larger stones often 

 standing on end,' which is the point that struck me so much. Not 

 only moderately-sized angular stones but small oval pebbles often 

 stand vertically up, in a manner which I have never seen in ordi- 

 nary gravel-beds. This fact reminded me of what occurs in my 

 own neighbourhood in the stiff red clay, full of unworn flints, over 

 the chalk, which is no doubt the residue left undissolved by 

 rain-water. In this clay flints as long and as thin as my arm 

 often stand perpendicularly up, and I have been told by the 

 tank-diggers that it is their ' natural position ' ! I presume that 

 this position may safely be attributed to the differential move- 

 ment of parts of the red clay, as it subsided very slowly from 

 the dissolution of the underlying chalk, so that the flints arrange 

 themselves in the lines of least resistance. The similar but 

 less-strongly marked arrangement of the stones in the drift near 

 Southampton makes me suspect that it also must have slowly 

 subsided, and the notion has crossed my mind that during the 

 commencement and height of the Glacial Period great beds of 

 frozen snow accumulated over Southern England, and that 

 during the summer gravel and stones were washed from the 

 higher land over its surface, and in superficial channels. The 

 larger streams may have cut right through the frozen snow, and 



