412 Salisbury . — -The Soils of Blakeney Point: A Study of Soil 
This, taken in conjunction with the higher carbonate content and lower 
acidity of the latter, is indicative of an edaphic condition not strictly in 
conformity with its position in the series. 
The increasing proportion of fine material on the older banks naturally 
tends to cement together the larger stones more firmly, thus effectively 
contributing to the augmenting stability. In addition, it further reacts on 
the power of water retention, so that plants less tolerant of both drought 
conditions and mobility are able to colonize the shingle. (For a discussion 
of the water relations of shingle beaches, cf. Hill and Hanley, Journal of 
Ecology, vol. ii, pp. 21-35, 1914-) 
Table X. 
Mechanical Analysis of Shingle . 
Percentage of fine particles below 0-5 mm. in diameter. 
Main shingle bank. 
Range observed. 
0/ 
Average. 
0/ 
(a) Bare shingle 
Vo 
2-7-10.6 
Vo 
6.7 
( b ) Under Suaeda bush 
2-8-8-6 
5 
(*r) Fine shingle with grasses 
0.4 
( d ) Fine shingle bare 
0-19 
— 
Lateral banks. 
Bank XVII 
18-19 
18.7 
„ XII (‘Yankee’) 
11-30 
19 
,, VIII (‘ Watchhouse ’) 
28-31 
29 
„ VII 
27-32 
30 
„ IV 
20-35 
26 
„ III 
35 - 6 o 
47 
,, I (oldest) 
33-56 
45 
The two chief pioneers, Arenaria peploides and Silene maritima , are 
both ‘ mat * formers which react freely to burial under shingle and are 
stimulated to more vigorous growth thereby. Both freely develop 
adventitious roots, and Silene maritima not infrequently adventitious buds, 
from the deep-seated and extensive root system. 
Any attempt to dig up either of these species will convince the most 
sceptical of the extent of root and shoot systems and their efficacy as 
shingle binders. 
When NW. gales combine with high tides the main shingle bank 
may at very infrequent and irregular intervals become awash, and in these 
conditions the soil fractions become to some extent elutriated. The finest 
particles are probably carried down to the landward side or on to the 
marshes, the heaviest pebbles may be moved only slightly, whilst the fine 
shingle bestrews the floor of the percolation gully. Therefore such shingle 
patches, as will be seen from Table X (c) and (d), contain an extremely low 
proportion of particles under 0-5 mm., and only about 27 to 31 per cent, 
over 6*5 mm., as compared with 35-61 per cent, elsewhere. This water- 
sifted shingle is the especial home of Poa loliacea , Lepturus filiformis , and 
Sedum acre , whilst the most stable shingle of the main beach supports the 
