260 
A few solitary shells iu sand and stones are not enough. It 
is wonderful how the wind can carry, especially with the broken 
water of a storm-driven wave, shells and stones far on to the 
land. We must be careful not to be taken in by blown sand, 
even when there are here and there small layers of shells in it. 
I have myself seen a Nassa travelling up the slope of a sand- 
dune under the action of the wind alone. When such 
shells drop over into the trough beyond, and get buried up, 
they might well be taken by some to indicate that the whole 
shore has been so far raised. 
We should examine carefully whether the deposit is un- 
doubtedly marine, the shells, stones, sand, &c., showing clear 
evidence of having been sorted by water ; and, secondly, 
whether it is quite clear that, under no conditions of long 
shelving shore, they can have been carried thither with the 
relative height of sea and land in other respects unchanged. 
Yet there are raised beaches, and, as they are conspicuous 
features in a coast section, there are plenty of descriptions of 
them. Sedgwick and Murchison described a raised beach in 
Barnstaple or Bideford Bay (Trans. Geol. Soc., series 2, vol. v., 
p. 279). De la Beche, in the Geological Observer, describes 
and gives sketches of some raised beaches (p. 452 et scq.), 
and gives some useful cautions at p. 261. In the Report on 
the Geology of Devon and Cornwall he mentions more. 
Godwin Austen, Pengelly, Carne, have, too, described various 
others, and a useful summary is given by Mr. Ussher in 
the Geol. Mag., 1879. 
So for the submerged forests, there are sources of error often 
overlooked. If a low estuary or seaboard marsh gets silted up, 
as, for instance, the Wash, the mouth of the Somme, or the 
marsh behind the shingle bank at Westward Ho, and then 
along the seaward side sand-dunes are blown, as at the mouth 
of the Somme, or shingle drifts along the coast, and forms a 
bank, as at Westward Ho, then the high tides are checked, 
and peat accumulates, and trees grow in the shelter behind the 
bank. But in a changing, sea -washed coast, these banks of 
sand and shingle are sometimes swept away, and the sea rushes 
with every tide across the forest land ; soon the trees perish at 
their roots, break off, and perhaps are floated away or buried 
up in mud and sand. The water, too, running with every ebb 
into and through the porous soil, carries off some of the under- 
lying silt, and so, sometimes, the whole is lowered gently 
towards the sea. 
Again, we must be careful that we have not got only the 
waterlogged wood and drifted vegetation sunk in the estuary 
