374 Mr. Lyell on the Boulder Formation^ 
site of parts of Norfolk and Suffolk, including the eastern 
coast of Norfolk. Into this estuary or bay one or many 
rivers entered, and in the strata then formed were imbed- 
ded the remains of animals and shells of the land, river, 
and sea. Certain parts of this area seem at length to have 
been changed from sea into low marshy land, either be- 
cause the sea was filled up with sediment, or because its 
bottom was upheaved, or by the influence of both these 
causes. Two consequences followed: first, trees grew on 
some spaces gained from the sea; secondl}", in other spots 
freshwater deposits were formed in ponds or lakes, and in 
the channels of sluggish rivers, or grounds occasionally 
overflowed by streams. Next succeeded a period of gra- 
dual subsidence, by which some of the lands supporting 
the forests were submerged, the trees broken down, and 
their roots and stumps buried under new strata. At the 
same time, the freshwater beds, whether resting on crag or 
immediately on chalk, became covered wuth drift, except in 
certain places, such as Mundesley, where for a small space 
the accumulation of drift seems to have been entirely pre- 
vented, perhaps by the continued flow of a small body of 
freshwater. 
1 have met with no fossils so imbedded in the drift as to 
entitle me to form any positive opinion whether it be of fresh- 
water or marine origin. The regularly stratified arrangement 
of a large part of it, and the different materials of the alter- 
nating strata, clearly demonstrate that it was formed gradually, 
and not by any single or sudden flood. The boulders which 
it contains, some of large size, seem to imply, that while a 
great proportion of the mass may have been derived from 
neighbouring regions, part at least has come from a great 
distance. Mr. R. C. Taylor observes, that the shore to the 
west of Cromer exhibits a singular accumulation of travelled 
fi'agments of rocks, whence it would not be difficult to collect 
a tolerably illustrative series. They consist chiefly of rounded 
blocks of granite, basalt, porphyry, trap, micaceous schist, 
sandstones of various kinds, chert, breccia, besides limestone 
and claystone ; also fragments derived from the chalk, plastic 
clay, London clay, green sand, Kelloway’s rock, the oolites, 
lias, and marlstone; in fact almost every formation above the 
coal-measures. These, he says, are of all intermediate mag- 
nitudes up to four tons weight, large bouldered masses ap- 
pearing in the sea at low water, lying mixed with flints upon 
the chalk. One block of granite is stated to be near six feet 
in diameter, and another mass, standing six or eight feet high, 
has for some years been known to the fishermen under the 
