Yol. 62.] THE CLAY-WITH-FLINTS. 133 



The clay and flints left by the dissolution of the Chalk would be present almost 

 everywhere ; whilst the loamy materials that would be formed from the lowest 

 Tertiary beds would most likely be more local.' l 



In 1865 Mr. Thomas Codrington, describing parts of Wiltshire in 

 which this Clay-with-Flints was prevalent, had come to a somewhat 

 different conclusion. He accounted for the presence of the unworn 

 flints and for the peculiar disposition of the deposit in the same 

 way as Mr. Whitaker had done ; but he thought that the original 

 presence of an overlying deposit of clay or loam was essential to its 

 formation. He writes : — 



' Everything seems to indicate a quiet subsidence of the overlying bed into 

 irregularities in the dissolving Chalk. Everything here also favours the sup- 

 position that the origin of the Clay- with-Flints is to be ascribed to the gradual 

 dissolving away of the Chalk-with-Flints under a capping of drift brickearth. 

 .... The Clay-with-Flints must underlie the brickearth, when the latter is 

 present, but the whole of it (that is, the brickearth) may be absorbed into the 

 Clay-with-Flints.' 2 



Lastly, Charles Darwin, writing in 1881, does not refer to 

 Mr. Whitaker' s explanation, but takes it for granted that the whole 

 of the red clay (as well as the flints) was simply the insoluble residue 

 left by dissolution of the Chalk, without the addition of any extra- 

 neous matter. 3 It is clear, however, from the remarks which he 

 makes, that he was puzzled to account for the absence of such a thick 

 residue in many places where it might he expected, and also for its 

 thickness in places where analyses proved that the underlying Chalk 

 contained a very small amount of earthy matter. 



Of these three explanations, I believe that Mr. Codrington's, so 

 far as it differs from Mr. Whitaker's, comes nearest to the truth, for 

 I think that he was right in asserting that the argillaceous part of 

 the Clay-with-Flints has been derived from Tertiary material and 

 not from the Chalk. I dissent from Mr. Whitaker's view, because 

 he contends that the bulk of the clay came from the Chalk, and only 

 admits a local admixture of Tertiary material. Lastly, I consider 

 that Darwin was still further from the truth, because he imagined 

 that the whole deposit had been derived from the Chalk. It is 

 only fair, however, to say that Darwin does not appear to have 

 studied the distribution of the Clay-with-Flints over any large 

 area, and was only incidentally concerned with the manner of its 

 formation. 



What may be termed the ' Chalk-residue theory ' has held the 

 field in this country for many years, but during the last decade 

 geologists have been losing faith in it ; consequently, it seems only 

 right and fitting that the other side of the case should be presented, 

 and discussed more fully than Mr. Codrington had the opportunity 

 of doing. I propose therefore to state the reasons which have 

 induced me to abandon the faith in which I was educated, and I 



1 ' The Geology of London' Mem. Geol. Surv. vol. i (1889) p. 282. 



2 Wiltsh. Arch. & Nat. Hist. Mag. vol. ix (1865) pp. 180-81. 



3 ' The Formation of Vegetable Mould, &c.' 1881, pp. 137-39 & pp. 298-300. 



