554 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 20, 



devoted a paper to the elucidation of the subject of what he has 

 called the " warp " or the " warp of the drift"*. In his paper " On 

 the Soils of Kent " he lamented the slight attention that had up to 

 that time been paid to " the period which intervened between the 

 desiccation of the bed of the glacial sea and the commencement of 

 the historic era of geology." Had Mr. Trimmer lived until the pre- 

 isent day, he would have seen the earlier part of that period receive 

 at least its due share of attention. The closing portion of it, which 

 saw the formation of that warp or subsoil on which the fertility of 

 our fields chiefly depends, has not, so far as I know, received any 

 particular attention since Mr. Trimmer's valuable labours were pre- 

 maturely terminated. 



My attention has for some time past been attracted to this 

 subject, and in my paper on the Brick-pit at Lexdenf I hinted 

 at its importance as containing records of the latest geological 

 changes. 



Mr. Trimmer appears not to have arrived at any satisfactory conclu- 

 sion as to the causes°°which have produced the warp. He says, *'The 

 majority of soils and subsoils in the British Isles are composed only 

 in part of the debris of the rocks on which they rest, and in part of 

 materials transported from various distances by forces of consider- 

 able intensity, differing from ordinary atmospheric action, which 

 were in operation at the close of the glacial period. I have called 

 these results the warp of the drift or the erratic warp"t« But he 

 leaves us in ignorance as to the nature of these forces, further than 

 that, in his " Geology of Norfolk " (Journ. Agric. Soc. vol. vii. p. 465), 

 he says that " it appears to have been a deposit from turbid waters 

 returning to a state of tranquillity." Nevertheless, in his paper " On 

 the Soils of Kent," first referred to, he speaks of the great variability 

 of soil within a few acres. This is a well known fact, and appears 

 incompatible with the explanation of the warp being thrown down 

 from a flood of turbid water, which must have produced very equable 

 soils over moderate areas. 



In stating that the warp differs more or less from the subsoil on 

 which it rests, Mr. Trimmer adds that " on sands it contains a 

 greater mixture of argillaceous matter, producing a sandy loam of 

 different degrees of adhesiveness ; on clay it contains an admixture of 

 sand, producing a clay loam, or, at any rate, clays less adhesive than 

 than those of the subsoils." 



These remarks are undoubtedly just. The warp is influenced in 

 its character by the stratum on which it rests, but at the same time 

 often contains ingredients which cannot have been derived from it. 



Whence, then, have these ingredients come ? 



It is well known that the surface of the subjacent stratum, wher- 

 ever it is of a soft nature, such as clay, sand, gravel, or chalk, is 

 worn into furrows and hollows, sometimes into pits and pipes. The 

 sections I have chiefly had an opportunity of studying for the pur- 

 pose of this paper have been in clay, sand, and gravel, which have, 



* Quart, Journ. Geol. Soc. vol. vii. p. 31 . 



t Ibid. vol. xix. p. 396. J Loc. cit -p. 32. 



