412 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 23,
refer to different portions of it near mid-tide level, or to the same
portions modified by fresh sections being exposed at different times
by the sea:—South of New Pier the Lower Boulder formation cannot
be easily described. Within a small compass it seems to vary both
in vertical and horizontal succession—in one place a fine, uniform,
tough, and bright yellowish-brown clay more or less laminated, in
another a fine loamy sand—here a rather solid brown clay with a
grey marly or shaly fracture, there a coarse sand charged with stones.
But you cannot travel far without seeing these variations of structure
graduating into, or succeeded by, the main character of the formation,
namely a very hard brown clay generally full of subangular
and rounded stones, varying from the smallest size up to boulders
commonly so called. They consist of porphyry, granite, &c., the
proportion of igneous and metamorphic rocks being greater than in
the upper clay. The loose pebbles on the beach would here appear
to have come chiefly out of this formation; and to it may be traced
nearly all the large boulders which occur at intervals. Some of
these boulders reach the size of 5 feet in diameter. Many of them
continue firmly fixed in the clay, where they have probably remained
since they were first imbedded. The sea washes the clay from
around them, and by the gyratory action of its waves excavates circular
depressions; and in this way it has probably succeeded in uprooting
and displacing some of the boulders* North of Blackpool
Old Pier, a fine clay, loam, and hard stony clay similar to the above
make their appearance under mean- water level. A short distance
to the south of the Gynn, in the bed of the sea, the fine bright yellowish-
brown loam exhibits oblique and curved lamination, the thin
layers cropping out around small synclinal basins. Further north,
near Uncle Tom's Cabin, the finer part of the Lower Boulder formation
assumes the form of a laminated reddish brown sandy loam nearly
as solid as rock. Beyond Uncle Tom's Cabin a similar deposit may
here and there be seen at low water; but there, as on the south
beach, it graduates into the prevailing hard stony clay. Along the
whole shore, nearer to the cliff-line, the hard stony clay may be traced.
It is probably a higher bed than the one containing fine clay and
loam; and a great part of it would appear to have been recently
denuded. Of its former thickness, at least in some places, one may
form an idea from coast-sections north of Uncle Tom's Cabin.
Under the middle sand and gravel, and separated from this formation
by a distinct line of demarcation, the hard stony clay rises in two
places above the base of the cliff, as represented in figs. 3 and 4. In
the most northerly instance the lower part of the cliff, to the height
of at least 20 feet, is composed of it. It likewise forms the solid
floor of the beach for some distance seaward†. This is a favourable
- During the very high tides of January and February 1869, according to
newspaper reports, several large boulders were displaced, and one of them thrown up on the promenade.
† Northwards it disappears under the dipping sand-beds of the middle drift. In the cliffs further south a removal of the talus might reveal sections in addition to those I observed.
