178 
with indications of partial subsidences, he admits that the effects may 
have been produced by landslips; and that it is possible to account 
for contorted strata resting upon others, which are horizontal, by 
supposing that the latter were not operated upon by agents which set 
the superincumbent masses in motion. ‘To account, however, for 
some of the more complex phenomena of the coiled or contorted 
drift, he proposes an explanation founded on the effect of drifted 
ice upon loose materials. In the account given by Messrs. Dease 
and Simpson, of their discoveries in the arctic regions*, it is 
stated, that in latitude about 71° N. and longitude 156° W. they 
found a long low spit of land, named Point Barrow, composed of 
gravel and coarse sand, and in some parts more than a quarter of a 
mile broad, which the pressure of the ice had forced up into nume- 
rous mounds, resembling at a distance huge boulder rocks. Mr. 
Lyell also states, that so many facts have come to his knowledge of 
the manner in which masses of ice, even of moderate size, in the 
Baltic, and still more in the Gulf of St. Lawrence, push before 
them large heaps of boulders, that he can scarcely doubt of its 
power to produce, under favourable circumstances, phenomena si- 
milar to those exhibited in the mud cliffs of Norfolk. 
The intercalation of huge masses of solid chalk, and of chalk 
rubble, in the body of the drift, Mr. Lyell also states is not easy, 
under all circumstances, of being explained. With respect to the 
masses of solid chalk, he thinks they may, in part, be accounted for 
by the action of the sea on the ancient line of chalk cliffs, before or 
during the deposition of the drift, and by which pinnacles or needles 
of chalk would be undermined, thrown down and subsequently en- 
veloped in the till or stratified clay and sand: he also explains the 
occurrence of accumulations of chalk rubble unmixed with any of 
the adjacent materials, by considering the rubble as the talus of 
former chalk cliffs, buried up at a later period by drift. 
In describing the boulders associated with the drift, Mr. Lyell re- 
fers to Mr. R. C. Taylor’s memoir for an account of their nature 
and great diversity of character. On the shore near Cromer, Mr. 
Taylor mentions some derived from the cliffs, four tons in weight : 
one called Black Meg standing six to eight feet high; and another 
composed of granite being nearly six feet in diameter. Mr. Rose is 
quoted as an authority for the occurrence of boulders several tons 
weight, in the till, in the interior of Norfolk. It is impossible, Mr. 
Lyell states, for those who have seen the boulder formation of the 
countries surrounding the Baltic, to doubt that the so-called dilu- 
vium of the east of England had a similar origin. Of the sources 
from which the blocks were derived, he conceives that some of them 
may be ascribed to rivers flowing from the westward, and transport- 
ing masses of ice charged with detritus derived from secondary 
Strata, in the same manner as the St. Lawrence annually sends 
down into the gulf shoals of drifting ice, laden with fragments of 
rock and other earthy materials ; but he is inclined to think that a 
* Journ. of Royal Geograph. Soc., vol. vil. p. 221. 
