396 Salisbury . — The Soils of Blakeney Point : A Study of Soil 
boat House during the period since this area has been under close observa- 
tion, and are therefore known to vary between 3-8 years in age. 
Examination of the carbonate content of these shows, like the drift 
line, a fairly high percentage, ranging from 0-28 per cent, to o*6i per cent, 
by weight and averaging 0*425 per cent. To appreciate the significance 
of these figures it must be borne in mind that dune soils are much heavier, 
bulk for bulk, than ordinary soils. If, for instance, we wished to compare these 
data with those of woodland soil on clayey loam we should have to add 
about 60 per cent, to the figures for the embryo dunes. 
In one cubic decimetre of an embryo dune the average carbonate 
content is very nearly 6*i grm. 
So long as any dune exhibits accretion each new layer of sand, 
consisting of particles brought in from the exposed sand of the sea-shore 
or the estuary, will contain its quota of shell fragments. So that, assuming 
growth to be fairly continuous, the embryo dune will exhibit, within broad 
limits, a certain homogeneity of carbonate content, in striking contrast to 
the diminishing content found in natural soils of ancient origin in which 
leaching has in course of time established a vertical gradient. (Cf. Salisbury, 
‘Stratification and Hydrogen-ion Concentration of the Soil in relation to 
Leaching’, Journal of Ecology, loc. cit., 1922.) 
Since sand grains and shell fragments have very different specific 
gravities (sand grains 1*42, sheik fragments c. 2*7~2*9) the proportion of 
calcium in the layers deposited during any given wind storm will clearly 
vary with the velocity of the wind. On the whole very high winds will 
tend to deposit sand having a higher calcium content than winds of low 
velocity. On the other hand, however, it must be recognized that the 
larger fragments of shells present a larger surface for an equivalent volume 
than the more or less isodiametric sand grains, and may therefore be more 
readily wind borne despite their higher specific gravity. 
Table III. Carbonate Content of Wind-borne Sand deposited at 
c. 24 ft. above Mean Sea-level. 
Sample. 
Carbonate. 
0/ 
Sample. 
Carbonate. 
0/ 
1 
Vo 
0.31 
7 
Vo 
o *35 
2 
°*35 
8 
0-40 
3 
°*44 
9 
o -37 
4 
0.32 
10 
0.38 
5 
0.50 
1 1 
0.36 
6 
°-45 
12 
0-40 
Total average, c.385 %. 
Analyses of sand which has accumulated in the loft of the Lifeboat 
House, about 24 ft. above mean sea-level, give a fair indication of the 
character of sand carried by the higher velocities of wind. It will be seen 
