the Upper and Lower Drift of the Eastern Counties. 395 



in part at least, with the epoch of the formation of the loess. 

 I conceive that the more intense cold had passed away or re- 

 ceded northwards before the principal mass of the Loess was 

 thrown down " *. 



In his late work on the 'Antiquity of Man 't> Sir Charles 

 reverts very fully to the subject of the Loess ; but he does not 

 express any further opinion as to the relationship borne by it to 

 the Boulder-clay, and seems disposed to correlate it with the 

 limon des plateaux of the Somme Valley. 



This superposition of the Loess to the Campinian sands enve- 



* In the table annexed to the paper, Sir Charles places the Loess on the 

 same horizon as the " Brick-earth and Drift " of England, and classes it as 

 postpliocene or pleistocene. The Brick-earth, however, I regard as of later 

 date than the Boulder-clay, being a formation deposited in the valleys which 

 were formed by the forces that upheaved the bed of the Boulder-sea, when 

 extensive denudations took place, by which not only the Boulder-clay, but 

 the lower Tertiaries skirting the Thames Valley were denuded, the Brick- 

 earth and associated gravels having afterwards been deposited on the de- 

 nuded surfaces. The term Drift has been used to designate beds of so many 

 distinct ages, that it is impossible to say, on a correlation of deposits, what 

 precise meaning is to be attached to it. It has been used to designate not 

 merely the boreal deposits accumulated before the valleys existing in the 

 newer secondary and the tertiary strata were formed, but also those accu- 

 mulated since the formation of the principal part of those valleys. The 

 terms pleistocene (or postpliocene) and quarternary are equally the subjects 

 of confusion, as both have been used in reference, not only to deposits 

 newer than the valleys, but also to deposits, such as the Loess and Campi- 

 nian sands, that are older than the valleys, and between which latter beds 

 and the upper Tertiaries I believe no physical break whatever to exist. I 

 have attempted to show (Phil. Mag. s.4. vol. xxvii.p. 180) that the whole of 

 the valleys that in England exist in strata newer than the Trias originated 

 in series of circular movements that elevated the bed of the Boulder-clay 

 sea, and as to such of them as are south of the Thames, or immediately 

 adjoin that river on the north, by the additional action of rectilinear 

 movements that supervened on the circular; and I hope in a future 

 communication to show the origin of the valleys in similar strata of 

 North France and Belgium to be due to the same and other contempo- 

 raneous circular movements. In this respect I regard the great physical 

 break, caused by these circular movements at the close of the glacial epoch, 

 as a dividing horizon, above or below which the newer deposits oi this 

 area (although differing but little between themselves, as far as concerns 

 their organic contents,) group themselves ; for though in point of time the 

 division between either group is insignificant, yet in point of change of sur- 

 face arising from subterranean convulsion, all that took place over this area 

 since the commencement of the Jurassic period is, I believe, as nothing 

 in comparison with the complete break-up of the surface ensuing at the 

 close of the glacial epoch. In referring, therefore, to a deposit as " drift," 

 except when quoting from others, I may be understood as referring to deposits 

 older than the valleys formed by the circular movements ; and it would, I 

 conceive, tend to obviate confusion if the terms pleistocene, or post- 

 phocene, and quarternary were in like manner confined to deposits newer 

 than the valleys thus formed. 



t London, 1863. 



26* 



