208 ON THE EROSION OF THE SHORES OF THE SEVERN ESTUARY. 
At one point the Trias comes down to the shore line, and here a 
small bay has been eroded. 
6 . — From the mouth of the Wye to the mouth of the Usk. 
By far the major portion of this stretch of coast is formed of 
alluvium very slightly raised above high water mark. It has, how- 
ever, for more than a century been protected from the water by a 
continuous embankment which stretches from Caldicot pill to the 
mouth of the Usk. Between the mouth of the Wye and Caldicot 
pill two masses of Keuper are exposed on the shore, and at each 
locality the erosion has been considerable. The more northerly of 
these masses of Keuper occurs at Red Cliff, about a mile to the 
north of New Passage. The larger and more southerly extends from 
New Passage to the Roman camp at Sudbrook. The northern part 
of the exposure is partially protected from erosion by the landing 
stage and by the breakwater in connection with the Sudbrook ship 
building works, but where not so protected the erosion is considerable. 
The strata forming the southern part of the exposure are more 
massive tlian those forming the northern, and are finely exposed near 
the western vallum of the Roman camp. More than half the camp 
has been denuded away, and further evidence of the activity of 
marine erosion is afforded by the undercutting of the harder bands 
in the Keuper, the production of a system of large pot-holes, and 
the widening of the major joints till some are converted into deep 
little ravines which run twelve or fifteen yards inland. It is equally 
clear, however, that little or no change is now in progress, and it 
hardly seems possible that such marked results could be produced 
under present conditions of erosion. 
The only other spot to the east of the mouth of the Usk, where 
the monotony of the alluvium is broken is at Gold Cliff, which is 
formed by a patch of Keuper capped by Rhaetic and Lower Lias. 
In former times the erosion here has clearly been very great, and a 
Keuper plain-of-marine-erosion stretches from 100 to 150 yards sea- 
ward from the base of the cliff. The cliff has, however, for many 
years (a local farmer said since 1815) been cased in masonry. 
