134 MR. A. J. JUKES-BROWNE ON [May I906, 



trust that my old friend Mr. Whitaker will pardon me for holding a 

 brief against him. 



Some of the facts which militate against the Chalk-residue theory 

 have been already advanced by Mr. Clement Beid and by myself in 

 the Annual Eeports and Memoirs of the Geological Survey. Some of 

 these will be quoted in the sequel, but data for a more detailed 

 consideration of the whole subject are now available, and conse- 

 quently it seems desirable that the whole case should be stated as 

 clearly as possible in one paper. 



II. Composition of the Clay-with-Flints. 

 The material was denned by Mr. Whitaker as 



1 a deposit of stiff brown and reddish clay with large unworn flints, that occurs 

 over the higher parts of the Upper Chalk-tract.' 1 



He also noted that, at its base, there is often a layer of black clay, 

 a few inches thick, which contains black-coated flints. He dis- 

 tinguishes the true ' Clay-with-Flints ' from the loam or brickearth 

 by which it is often overlain, admitting that the latter has been 

 mainly derived from the detrition of the Beading Beds, that it often 

 contains large unworn flints, and that it frequently passes so com- 

 pletely into the Clay-with-Elints that it is difficult to draw a line 

 between them. 2 



I will, however, confine myself to the Clay-with-Flints, as defined 

 by Mr. Whitaker, and pass on to the important point of its composition 

 and contents. 



In its typical development on the west and north-west sides of 

 the London Basin, the material is generally a stiff, unctuous, brown 

 or reddish-brown clay, usually without any visible admixture of 

 sand, but containing unworn flints the outer surfaces of which are 

 generally stained brown. Where sections of such clay are seen below 

 brickearth, the flints do not generally form more than half the bulk 

 of the deposit ; but, where there is a surface-spread of Clay-with- 

 Flints, the upper portion of it contains more flints than clay, and is 

 in fact an angular flint-gravel. This is doubtless a consequence 

 of the washing- away of the fine clay by the rain. 



Mr. Whitaker remarks (op. cit. p. 282) : 



' Besides the unworn flints, there are also sometimes pebbles of flint and of 

 quartz, as well as, more rarely, pieces of old rocks.' 



Again, he mentions the occurrence near Bemenham, in Berkshire, 

 of green-coated flints from the base of the Beading Beds, pebbles of 

 quartz and quartz-rock, and a few small lumps of ironstone. 



Mr. Whitaker, however, does not mention the fact that broken 

 angular flints are very common ingredients. The only passage 

 from which it would appear that he was aware of that fact is that 



1 ' The Geology of London ' Mem. Geol. Surv. vol. i (1889) p. 281. 



2 Ibid. p. 288. 



