10 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 

 Suaeda 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 



