400 Mr. 8. V. Wood on the Belgian Equivalents of 
cut through or exist in the Loess itself. If, therefore, the Boulder- 
clay or upper Drift of England has been acted upon by move- 
ments which have similarly affected the Loess of Belgium, it 
follows that both deposits had been thrown down before these 
movements began. It can be shown that these movements 
have not affected the postpliocene gravels that rest on surfaces 
from which the upper Drift has been denuded *, so that they 
must have originated prior to these gravels having been depo- 
sited ; and since, from the great area over which the denudation 
has extended, we can attribute it to nothing but the action of 
the sea, we must assume either that it resulted during an emer- 
gence of the bed of the upper-Drift sea, or that a second general 
submergence and elevation took place. Although the evidence 
collected by geologists appears to me to indicate that parts of the 
south of England and of the north of France have been sub- 
merged (and that violently), and still further denuded, subse-. 
quently to the general disturbance and denudation produced by 
these circular phenomena, and subsequently to the area having 
been converted into land, yet there is no trace of any second 
general subsidence and elevation. It therefore seems to me 
that we have no alternative than to infer that these circular move- 
ments originated under the upper-Drift sea; and in that case, as 
the Loess is disturbed by those movements, it must have been 
deposited prior to the elevation of the bed of that sea. 
In describing the lower Drift of the Eastern Counties, I dwelt 
upon the mode in which the position occupied by it relatively to 
the lower tertiaries indicated that the bay depositing it advanced 
inland by erosion as much as or more than by depression— differ- 
ing entirely in this respect from the overlying Boulder-clay. 
The latter in the east of England, where not denuded, spreads 
evenly over the Eocene tertiaries which the lower Drift had not 
reached, and over the cretaceous and oolitic deposits where they 
come out from under the Kocene by original relationship of 
deposit. In this respect the Boulder-clay fully resembles the 
Loess, although in the eastern counties of England there 
. were at the time of its deposit no eminences that, rising above 
the sea, escaped its envelope, as did the higher ridges of the | 
Ardennes. 
On the other hand, we have, in a section given by Sir Chas. 
Lyell in his paper on Belgium before referred to, a parallel, in the — 
case of the Campinian sands, to the erosive action exerted by the 
sea of the lower Drift. The section is that at Dieghem, seven 
miles north-east of Brussels. Sir Charles describes sands at that 
* The postpliocene gravels of the Thames valley have, however, been 
powerfully disturbed by the movements subsequent to those of the circular — 
character. 
