398 Salisbury . — The Soils of Blakeney Point : A Study of Soil 
Here then the source of additional calcium being almost cut off by 
the high main ridge on the seaward side, the leaching action of the 
carbonated rain-water has gone on practically unhindered, and the low con- 
tent as compared with the main ridge is a measure of the time that has 
elapsed since the Laboratory ridge ceased to accrete actively. For equiva- 
lent volumes of soil the average carbonate content here is under 41 per cent, 
of that present in the main ridge, and only about 32 per cent, of the average 
for the embryo dunes. 
The marked leaching action which these data indicate is also reflected 
by the strikingly different carbonate content which may obtain between the 
surface and subsurface (e. g. D 13, D 14), and the fact that the surface inch 
may be entirely devoid of carbonates (cf. samples C 20, C40, C41). 
The Long Hills show the same phenomenon in a more advanced phase. 
The proximal end of these where they abut on the main beach is not cutoff 
from the sea face by the main ridge which stops short of this junction. The 
actual distance from the sandy foreshore is here, moreover, only about 
260 yds. It is in correspondence with this that the sea face at the proxi- 
mal end exhibits a much higher carbonate content than the Long Hills 
generally, viz. 0*75 per cent. With this sole exception the values range 
from 0-5 per cent, downwards, the surface being usually entirely devoid of 
detectable carbonates. 
The average is o-oi per cent, by weight or 0-1344 grm. per cubic deci- 
metre. Comparison of B 8 and B 9, and B 13 and B 14, brings out clearly the 
leaching effect in the vertical direction, and emphasizes the almost complete 
absence of carbonates from the surface layer. 
The Hood, though presenting a still older system than the Long Hills, 
yet shows the same range and average content by weight , as the latter 
(viz. o-oi). This we can attribute to its position, some 160 yds. from the 
foreshore, which facilitates a small amount of accretion. Despite this, the 
greater degree of leaching is brought out when we compare the weight of 
carbonate per unit volume, which here amounts to only 0-1281 grm. per 
cubic decimetre. 
It is clear that for any given plant with its specific capacity for root 
development, the amount of carbonate in a given volume of soil is the 
important consideration. 
The generally xerophytic character of the dune flora is so well known 
as to require no emphasis, but these same transpiration checks which 
enable the dune plants to retain their foliage during the drought conditions 
of summer 1 also involve a smaller intake of the soil solution during the moist 
conditions of spring and autumn. To appreciate fully therefore the significance 
1 During the exceptionally dry summer of 1921 the foliage of several dune and shingle species 
suffered considerably. Notable examples were : Silene maritime i, Frankenia laevis , Erodium 
neglectum , and Convolvulus soldanella . 
