OF NORFOLK AND SUFFOLK. 
Ill 
of Scandinavian, and others of Cheviot origin, the most 
common, however, being of dolerite, probably from the 
Whin Sill, an igneous bed intrusive in the Carboniferous 
Limestone of the North of England, which may have extended 
also in places over the bed of the North Sea,* Such erratics 
are seldom seen in the cliff section, but may be observed on 
the beach, or by the road side, the accumulation probably 
of centuries of coast erosion. 
Prof. Kendall noticed some years ago in the village of 
Bacton, for example, a large boulder of Laurvigite, a well- 
known Norwegian rock, and there is a small block of Rhomb- 
porphyry from the Christiania fiord in the Castle-Museum, 
which I found last year in one of the Catton brickyards. 
For the purpose of ascertaining the movements of the ice, 
it is not necessary to separate between the Scandinavian 
and the British erratics. These deposits, moieover, are but 
little contorted inland. In this paper I group them all, 
contorted or not, under the term of “ North Sea Drift.” 
The North Sea Drift in its uncontorted form may be 
conveniently studied in a number of brickyards to the north 
of Norwich, at Sprowston, Catton, and Hellesdon. The 
brick-earth of that neighbourhood is not very stony, and the 
erratics are, as a rule, smaller than those found near the 
coast. Small fragments are not uncommon in it of black 
local flint, and of soft chalk, though much of the latter has 
been removed by the infiltration of water charged with 
carbonic acid. One misses, however, in the North Sea Drift, 
the grey tabular flint and hard chalk, with the Neocomian 
and Jurassic detritus so constantly met with in the Chalky 
boulder-clay, the morainic accumulation of the inland ice, 
to be described hereafter. 
Over a great part of the region covered by it the North Sea 
Drift is of no great thickness, and where a good section can be 
obtained, its upper surface is usually seen to have a flat and 
levelled appearance. In this condition it represents, I con- 
sider, the bottom moraine of the ice-sheet, travelling across the 
* Prof. Dwerryhouse has recently identified some of these dolerite 
boulders as of Whin Sill origin. Rep. Brit. Assoc. 11908), p. 244. 
