and on the Drift of the Eastern Counties. 199 
structure of the county, be expected; good sections, however, 
showing the passage may be found in the pit behind Sizewell 
Gap already alluded to, in a pit a mile west of Leiston, on the 
Saxmundham road, and in a pit at Hoo, a mile on the Charsfield 
side of the bridge over the Deben. Over Suffolk, the upper 
part of the lower Drift is marked by beds of coarse gravel, the 
stones being large and angular, and sparsely scattered in the 
sand: they are unlike the gravels that occasionally, even in this 
area, occur near the base of the deposit, the latter bemg more 
rounded and thicker-bedded, while the former have the character 
of being ice-borne, and much resemble the small boulders occur- 
ring in the Drift clay. The characteristic pebble of the lower- 
Drift beds is a pink quartzite, which I have identified more 
nearly with a quartzite from Freyburg than with any other. It 
is probable that the lower-Drift bay, of which only the lower and 
western border touched England, extended across the north of 
Europe to a great distance in the direction of Germany, and that 
the gravels accumulated in it were largely supplied with detritus 
carried from that country along the southern shore of the bay. 
The depression that introduced the upper Drift seems to 
have been both sudden and uniform; and if the view be well 
founded which I have taken as to the formation of the valley- 
system* of Hastern England—that all the inequalities of surface 
now exising there are of an origin later than the Drift—we may 
conceive that a sudden, though moderate, depression would at 
that time have submerged the very extensive area occupied by 
the Jurassic, Cretaceous, and Tertiary strata: the materials of 
these, and particularly the two former, it is well known, have 
largely contributed to the upper Drift, the supply of which 
appears to have been chiefly furnished from the British strata. 
The thickness of this upper Drift over Suffolk and Essex does not, 
where least denuded, exceed the maximum thickness of the lower 
Drift ; and its deposition seems to have ceased before the spread- 
ing of the great erratics of the northern counties commenced. 
At any rate, the great erratics are generally absent over the 
southern part of the eastern counties; and as no denudation 
could well have removed them, but must have allowed them to 
sink upon the uncovered beds, we may assume that the causes 
giving rise to the erratic distribution of northern England did 
not exist over these more southern counties. Probably before 
the high lands of the northern part of England were submerged, 
the great plain then formed by the strata newer than the Trias 
had sunk to a depth beneath the sea too great to arrest icebergs 
on their transit, if these were the means of spreading the erratics ; 
on the other hand, the greater distance of these counties from 
* Phil. Mag. ser. 4. vol. xxvii. p. 180. 
