BRITISH POSTGLACIAL & RECENT DEPOSITS. 459 



tion. They are generally more or less well developed where the 

 coast-land is low and shelving, but they appear seldom or never 

 to afford sections so detailed and complete as those of Lanca- 

 shire, Cornwall, and the Fenland, Submarine forests and peat 

 occur most frequently on the east and south coasts, along the 

 shores of sandy bays, where they are exposed at low -water. 

 They testify generally to a considerable loss of land within 

 some recent geological period, and in certain places they even 

 yield evidence of several successive oscillations of the sea-level. 

 Thus, at Tramore Bay, County Waterford, there is a raised 

 estuarine deposit which, according to Mr. Hardman, 1 shows the 

 following succession of beds : — 



1. Bog or peat, passing in parts into alluvium. 



2. Upper gravel-bed, with sea-shells . . . to 8 ins. 



3. Dark peaty sandy layer (shells abundant at base) 1 ft. to 2 ft. 



4. Lower gravel-bed ; shells very abundant . . 3 ins. to 2 ft. 



5. Blue mud-layer, with fragments of wood, extending 



into cracks in (6) . . . .2 ins. to 2 ft 



6. Gravelly brown boulder-clay. 



The boulder-clay, Mr. Hardman thinks, has evidently been 

 denuded by running-water at a time when it formed an old land- 

 surface. Then came a period of submergence, when the beds 5 

 and 4 were deposited. The shell-beds contain the common 

 littoral species, cockle, mussel, periwinkle, etc., and extend to a 

 height of ten feet or thereabout above high-water mark. After 

 the formation of the shell-beds the sea retreated to a lower level, 

 and the accumulation of bed No. 3 ensued. This is a dark, 

 sandy accumulation, abundantly charged with the debris of land- 

 plants, and is probably, as Mr. Hardman says, an old alluvium 

 or freshwater deposit in part ; it passes, however, horizontally 

 into true peat, and there can be no doubt, therefore, that it indi- 

 cates an ancient land -surface. The presence of the overlying 

 bed, No. 2, which contains cockles, proves another submergence, 

 but apparently of limited extent, for this upper shell-bed does 

 not go higher than 2 or 3 feet above high-water. It is overlaid 

 1 Geol. Mag., Dec. ii. vol. i. p. 210. 



