194 
THE OEOLOaiST. 
leaving behind it those significant terraces which may be seen on the slopes 
of the hills abutting on the Talleys of the Calder, the Hodder, the Kibble, 
and the Irwell, from about Ramsbottom to its various sources. The con- 
tents of these drift deposits also indicate several widely different conditions 
of things. There must have been many quiescent periods, and also many 
gradual depressions of the surface, during the formation of the various 
coal-seams, and the deposition of the rocks and shales by which they are 
overlaid. After the latest deposits there must have been a gradual up- 
heaval, with occasional fractures, from the bed of a deep ocean, and, as the 
bottom came nearer the surface, the more powerful would be the currents, 
and hence the variable, but extensive denuding action of water which is 
everywhere apparent. 
There is, however, good evidence that within the historic period the 
coast of Lancashire, at least, has again undergone considerable depression. 
In the times of the Somans there was probably no estuary of the Mersey. 
Ptolemy does not include this now-important opening in his topography of 
the coast. The dredging operations at Liverpool continually afford proofs 
of recent land-surface ; and even hazel branches, containing nuts, were 
dug up from a considerable depth during the formation of the Sandon 
Doct. Along the shore from near Formby towards Preston, there are the 
remains of an extensive ancient forest. Many ti'unks of trees were ex- 
posed during the formation of the East Lancashire Railway, and are still 
to be seen in the pools on each side of the road. The roots of these are 
mostly below high-water mark, and in some places the trunks extend into 
the sea ; but all of these must originally have flourished at a much higher 
elevation. About Southport they are so numerous, that they have been 
used to form ornamental fences for some of the gardens. 
At Blackpool, and on towards Fleetwood, the sea is washing down the 
cliffs at the rate of about one yard in breadth per annum ; and tradition 
states, on very probable grounds, that nearly half a mile, in breadth, of this 
part of the Lancashire coast has disappeared within the last hundred and 
fifty years. There are therefore strong reasons for supposing that Lanca- 
shire is at present undergoing a gradual depression. In Scotland, on the 
contrary, according to Mr. Geikie, the reverse operation is in progress, and 
it may form an interesting subject for some speculative mathematical geo- 
loi^ist to inquire whether this apparent flexibility of the earth's crust is 
due to internal local action, irregularly applied, or whether it is the natural 
result of those mechanical laws which govern the earth when considered 
as a comparatively solid film resting upon a fluid interior. 
In the discussion Mr. Hull said these discoveries of marine shells in the 
drift were yery interesting ; but there were also in the neighbourhood the 
more recent gravels of the valleys. These are of later date, and, accord- 
ing to the jud:.rment of some, are most undoubtedly of the same age as the 
Amiens and Thames valley gravels, and many others which are yielding 
works of human art in diSerent parts of Britain and the Continent ; and 
he thought it very important that the attention of local geologists should 
be turned to the subject, because there is no reason, as far as we can see, 
why our river-terraces here should not yield flint-implements, and the re- 
mains of some of the extinct mammalia which appear to have been con- 
temporary with man. With regard to the 2>^ew Red Sandstone boulders 
which Mr. Wilkinson says are 800 feet above the sea, of course it would 
be improper to sa3^tliey are not of this formation, but the identification is 
very questionable. He did not think the Xew Red Sandstone in the north 
of England attained to such a height. To suppose that boulders are car- 
ried from a lower level to a higher is a very unlikely thing indeed, except 
