HARMER : THE PLEISTOCENE DEPOSITS OF EAST AXGLIA. 325 
not to any extent connected by tidal currents. Of 33 British 
shells found near the former, which range into Arctic seas, only 
five were known to J. Gwyn Jeffreys from the English Channel, 
while of 45 southern species occurring in the latter, he records 
only 14 from the shores of the North Sea. 
The map (Fig. 4), copied from one pubhshed by S. V. Wood, 
Jun., in 1880,* will explain the distribution, and, possibly, the 
origin of the Chalky Boulder-claj^ Its entire absence from the 
north-east corner of Norfolk shows that the ice to which it was 
due did not enter East Anglia from that direction. Some 
geologists consider that it came through the gap in the Chalk 
escarpment now forming the Wash, fanning out from the great 
depression of the Fens in all directions, but no evidence in favour 
of this view has been offered at present. j It does not seem 
to me probable that the North Sea ice could have passed through 
the comparatively narrow neck of the Wash gap in sufficient 
volume and thickness to have enabled it to travel 60 miles in 
one direction, towards Leicester, in Sheet 63 (Fig. 4), reaching 
there a height of 730 feet above Ordnance Datum, and in 
another, at an equal distance from the Wash, to climb the Chalk 
escarpment near Royston (Sheet 51), and to heap up its moraine 
upon it to an elevation of more than 500 feet above the level of 
the Fens. 
I hope, in a future paper, to deal more fully with this question, 
as well as with the probable origin of the great glacier which 
spread its moraine over such an enormous area. However, the 
comparatively low-lying area, now forming the Fen basin, may 
have been filled with ice, it was, I have little doubt, from thence 
as a centre that the Chalky Bouldei-clay travelled to the east 
coast in one direction, to the brow of the Thames Valley in 
another, and into Bedfordshire in a third. Reference to the 
map (Fig. 4) will show that it extends further from the Fens in 
some districts than it does in others, and this, I think, can be 
* The Xewer Pliocene Period in England. Quart. Joum. Geol. 
Soe., Vol. xxx\d., PI. XX. 
+ As far as the district to the east of the Lincolnshire Wolds is 
concerned, the evidence shows that the ice moved from north to south, 
and not northwards from the Fens. 
