260 . SUBTERRANEAN EROSION, 
The circumstance of trunks and roots of large trees being 
fouud below low-water level, has induced a belief that a 
subsidence of the shore at Leasowe, the opposite shore at 
Formby, and of the estuary of the Mersey has taken place from 
deeply-seated subterranean action similar to what is now going 
on in the south of Sweden. 
If the subsidence of those places referred to be due to deeply- 
seated subterranean action, then the rocks at New Brighton 
lying a little way to the south of the space operated on, as also 
Hilbre Islands and Hilbre Point, the latter immediately adjacent 
to the submarine forest, all composed of the new red sandstone, 
would have manifested some degree of sympathy with the area 
under the depressing influence, but no such evidence exists in 
any of those places. They maintain the same elevation they 
had centuries ago, while, on the contrary, the shores adjacent 
are known to have subsided several feet within the last thirty 
years. The cause of this subsidence must therefore be referred 
to some other operating agent or agents than to subterranean 
action. 
The borings recently made under his superintendence, of the 
strata in the alluvium shown in the sections, prove their 
permeability to water, being composed of sand and clay beds 
alternately to a very considerable depth. 
The abrading action of the tidal currents on the edges of the 
strata prepares a ready means of escape for the water and sand 
from underneath the clay during the refluxes of the tides, and 
the hydraulic pressure of the water at a higher level in the 
permeable strata, forces the sand from underneath the clay beds ; 
hence the subsidence of the shore, &c. 
The clay bed near the surface in which the trees grew, 
together with the superimposed peat or vegetable matter, resist 
the abrading power of the water longer than the other materials. 
They therefore remain on the surface and descend conformably, 
with the lower strata undermined, and consequently become 
submerged even under the level of low water. 
Abrasion of the surface of the shore takes place also to a 
considerable extent by the alternate frosts and thaws that occur 
during the winter months. 
The submarine forest on the Formby shore is supposed to be 
due to the same causes that operate at Leasowe. 
A section was shown of Bidston Marsh, which forms a con- 
tinuation of the flat shore at Leasowe, naving also the remains 
of an ancient forest imbedded in peat ina similarmanner. The 
levels taken of the surface upon which trees now grow in the 
S.E. corner of the marsh, and of the surface upon which ‘the 
roots of the ancient trees exist, prove the difference to be only 
18 inches, z.e. the surface upon which the living trees now grow 
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