502 
THE GEOLGGTST. 
reaching from the Nen to the Withani, with a view to the protection of the 
low lands from the injuries they were subject to from the fresh water flowing from 
higher levels towards the Wash. But besides the former forests of the fen-lands 
mthin the boundary of the Roman sea- bank, large tracts of similar lands, covered 
also with the roots and trunks of trees, are not unfrequfntly revealed at very low 
tides along the Lincolnshire coast without its ancient marine barrier. The 
question that arises most naturally as to how these became submerged, will now 
demand our consideration. 
This fact has always been looked upon as a great mystery by the few scientific 
men who have turned their attention towards it, and various theories have been 
advanced for the purpose of solving the difficulty it presents to us. Some have 
thought that it has been caused by a change in the coastal line, some by the 
agency of earthquakes, and others by the subsidence of the land ; whilst the 
fen- lauds of the interior have generally been considered to have been formed 
through the neglect of the Saxons, in paying no attention to the system of 
artificial drainage introduced by the Romans, which occasioned floods to arise of a 
permanent character, the results of which are still so plainly evident. This last 
theory, however, is utterly untenable, as portions, at least, of the Roman sea-bank 
Lave been raised upon that very peaty stratum filled v. ith roots of trees, which 
we are anxious to account for, and therefore it must have been formed Le/ore the 
Roman occupation of this part of Lincolnshire. Finding that the submersion of 
these forest-lands was not caused by the interference of art with nature, and that 
they extend beyond the sea-bank, and far below the usual level of the sea, the 
next theory that has been brought forward is, that they owe their origin to a 
change in the coastal line through the action of the sea. 
Doubtless great changes have taken place in the form of the Lincolnshire coast, 
and many large estuaries are now completely filled up wbich are known to have 
formerly existed there, whilst from the remains of f .rest-produce beyond its 
present sea coast, it is clear that the land once extended far more to the east 
than it does now, but we can scarcely suppose, as has been suggested, that a 
higher ridge of laud once existed beyond the present tidal line, serving to protect 
a plain lying below the sea level, of which the tree-covered islets, still occasionally 
visible, are a portion. The next theory, however, with regard to the phenomenon 
we are treating of, I believe to be the true one, and that is, that the large por- 
tions of the lowlands of Lincolnshire have sunk belo\y their original level. 
Sub-marine forests are by no means uncommon ; in Yorkshire several instances 
may be brought forward, such as that at Outhorne and other points on the 
Holderness coast. In Hartlepool Bay the remains of a similar forest occasionally 
excites much attention when revealed during the lowest neap tides, amongst which 
are found horns and bones of the ox and red deer, and even the wing-cases of 
land-beetles. The south coast possesses many examples of the same character, 
such as the tract between St. Michael's Mount and Newlyn, the former of which, 
according to Carew, was termed in old days " the rock in the wood," and another in- 
stance was lately revealed by the shifting of the sand in Padstow harbour, whilst a 
similar phenomenon attracted the attention of Giraldus de Parri, or Cambrensis, as 
long ago as 1 188 on the shores of South Wales. Most of the examples of these sub- 
marine forests, if not all, that have come under my notice can only be accounted 
for, in my opinion, by the subsidence of the land. This theory may appear more 
marvellous, and theretore less likely to be true than the preceding ones, but 
■when we find from the study of geology that certain strata, the undoubted deposit 
of water, are now upheaved far above the reach of that element, and that lai-ge 
tracts of land have sunk beneath it, we can only regard such changes as one of 
the usual, but always wonderful operations of nature. Strabo was well acquainted 
■with this motive power in the earth's crust, as well as are our leading modern 
geologists, but as it may be supposed by some that such motive powers are now 
no longer exercised, it will be well to mention an instance of the subsidence and 
elevation of land during the historic period. I will allude, therefore, to that noted 
example afforded by the district about Pozznoli, in the Bay of Baiss, and especially 
made manifest by the pillars of the Temple of Jupiter Serapis at thi.t spot, and 
