the Upper and Lower Drift of the Eastern Counties. 401 
place as lying upon the deeply eroded face of the Eocene tertia- 
ries; but, being unfossiliferous, he does not identify them. A 
reference, however, on M. Dumont’s map to the place where 
this section occurs leaves no doubt that the covering sands 
shown in the section are those mapped by M. Dumont as the 
sables campiniens. A short distance south of this place the 
sands pass beneath the Loess that, according to M. Dumont, 
caps the heights on either side of the valley at Brussels. 
The precise margin of the lower-Drift bay, which, as I have 
shown, can be detected accurately at one part of Essex, appears 
to be obscured in Belgium beneath the Loess. By analogy and 
by assuming a uniformity of depression over either area to have 
taken place on the introduction of the upper Drift, we may infer 
that the margin of this bay in Belgium passed along the northern 
flank of the Ardennes, from which it derived the quartzites that 
constitute so considerable a proportion of its included pebbles, 
the Loess spreading over this margin and concealing it, as is the 
case with the western margin, that, in Essex, passes under and is 
hidden by the Boulder-clay. 
In another section, given by Sir Charles Lyell, he shows the 
Loess at Tournay to rest upon the lower beds of the Kocene series, 
which there crop out, at their original margin of deposit, without 
(so far as the section represents) any intervening bed of sand or 
rolled stones. It. would thus appear that the margin of the 
lower- Drift bay passed to the north of Tournay. In another 
section at Dileghem, two miles N.N.W. of Brussels, Sir Charles 
shows the Loess resting upon a bed of sand, which, although un- 
fossiliferous, he refers, from similarity of appearance, to the same 
sands as those described by him at Cassel as belonging to the 
Diest group. The Diest sands, however, are not indicated by 
M. Dumont anywhere west or south of a point about ten miles 
north-east of Brussels—a still greater distance from Cassel. 
Dileghem, where this section occurs, is represented by M. Du- 
mont as at the margin of the Loess and the Campinian sands, 
where the latter pass under the former. It would seem, there- 
fore, that the unfossiliferous sands of Dileghem, upon which the 
Loess rests, belong to the Campinian series, the more especially 
so as we have seen that at Dieghem, a few miles only N.K. of the 
former place, the Campinian sands shown to occur there by M. 
Dumont agree with Sir Charles’s section of that place. If, there- 
fore, the Loess at Dileghem is underlain by the Campinian sands, 
the margin of the lower-Drift bay would pass somewhere be- 
tween that place and Tournay ; but if otherwise, it would pass 
between Dieghem and Dileghem. I, however, for the reasons 
stated, strongly incline to the former alternative, and I have 
adopted it in the hypothetical extension of the boundary given 
