494 
TOPOGRAPHY OF BLAKENEY POINT. 
their lee sides the surface of the shingle, being protected, strip- 
like “ islands ” of partially stabilised shingle occur where many 
plants gain a footing and flourish. The positions of the 
Characteristic fans — the form in which the shingle advances 
over the marshes (Fig. 6 and centre of Fig. 12,) — are 
closely related to the occurrence of gaps in the ranks of the 
Suseda bushes. The presence of other plants, especially those 
like Silene maritima and Arenaria peploides, which form 
extensive mats with deep-seated plexus of rhizomes, will also 
operate as stabilising factors, though much less effectively than 
Suaeda, which is matchless in this connection. In view of this 
importance of vegetation, any special circumstance which 
promotes its establishment must be reckoned as a factor 
co-operating in stabilisation. Important among these is the 
proper supply of tidal drift to the bank (Fig. 12,), for this 
not only contributes in a conspicuous way to the formation of 
a soil, but also is in itself a condition favourable to the germi- 
nation of seeds, as well as being the means of introducing 
many seeds to the bank. 
The high degree of mobility often shewn by sections of 
shingle beaches fronting on reclaimed marshes is. probably 
largely due to the starving of the' beach of its proper drift 
(which mainly comes from the lee side) consequent on 
embanking — well illustrated by the Blakeney spit, where it 
borders the reclaimed marshes opposite Salthouse. 
The presence of dunes on the beach is another factor 
operating as a very efficient mechanical barrier to the advance 
of the sea. 
Mobility Effects along the Main Beach. 
In view of the conspicuous way in which evidence of land- 
ward drift of shingle forces itself on the attention of the 
observer, it will be convenient here to epitomise the whole 
matter. It will be understood that throughout the length of 
the main bank shingle is liable to be shot over the crest by the 
onshore gales, especially when they accompany very high 
