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’+, 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 toit. 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 of 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, Imay be understood as referring to deposits 
older than the valleys formed by the circular movements ; and it would, I 
conceive, tend to obyiate confusion if the terms pleistocene, or post- 
pliocene, and quarternary were in like manuer confined to deposits newer 
than the valleys thus formed. 
+ London, 1863. 
26* 
