346 
THE CRETACEOUS ROCKS OF BRITAIN. 
There is no note of its existence either at Richmond or at 
Streatham, and we know there is nothing like it along the outcrop 
in Surrey, but a similar bed appears at the outcrop in Kent, near 
Maidstone. At Chartham, near Canterbury, a boring proved only 
“ eight inches of dark sand ” at the base of the Chalk Marl* with 
Gault below. At Dover, again, in the shaft of *the Dover Coal 
Exploration, there is but 3 feet of marly greensand with phosphate 
nodules resting directly on the Gault, as compared with 16 feet 
at Folkestone. 
Thus, so far as the available evidence goes, it appears that the 
area of erosion occupied by the Cambridge Greensand can be 
traced southwards as far as London and probably thence into 
Kent. The facts suggest the existence of a strong current setting 
off the land east of Dover and flowing in a west-north-west 
direction to the latitude of London, where it was deflected north¬ 
ward in the direction of Ware, Hitchin, and Cambridge. It is, of 
course, just possible that the flow of the current was in a reverse 
direction, but the complete absence of any signs of current action 
at this particular epoch in Norfolk, Lincolnshire, or Yorkshire 
makes it very unlikely that such a current came from the north 
or north-east. It might possibly have set from the north-west 
through the Cheshire Straits across Stafford, Leicester, Northamp¬ 
ton, and Huntingdon, but we have reason to believe j that the 
set of the current which brought the material of the Gault, was 
probably from the south-east, and it is most likely that the current 
which caused erosion of the Gault came from the same quarter. 
There is, moreover, another line of evidence which tells against 
the idea of a current from the north-west; this is as follows :— 
The Cambridge Greensand has yielded many blocks and frag¬ 
ments of igneous and Palaeozoic rocks, including pieces of granite, 
hyperite, basalt, felstone, gneiss, schist, conglomerate, red sand¬ 
stone, slate, quartzite, and hornstone, with a few pieces of dark 
grey limestone. Some of them certainly resemble Scotch and Nor¬ 
wegian rocks, but the whole assemblage could not be matched 
in the north of England or in Scotland, nor, so far as is known, in 
Norway. Mr. Whitaker, however, has suggested that they may 
have come from the buried land which lay to the east of England. 
It is true one cannot be quite sure that the rock fragments were 
brought by the current which eroded the Gault and formed the 
Cambridge nodule bed, for the stones may have been derived from 
the Gault as well as the phosphate nodules. Stones have actually 
been found in the Gault both at Cambridge and Folkestone, but 
those we have seen were of small size and always waterworn, whereas 
the erratics of the Cambridge Greensand are large angular and 
subangular blocks, some of them more than a foot in length and 
equal in mass to a cubic foot of rock. Some large blocks, 
* See account given by Mr. Whitaker, Quart. Journ. Geol. Soc., Vol. xlii, 
p. 35. 
t See Cretaceous Rocks of Britain, Vol. i. p. 412. 
