404 Salisbury. — The Soils of Blakeney Point : A Study of Soil 
The average for all the thirty different loci sampled was 7-17. 
The sand in these early stages is therefore generally alkaline and 
only rarely slightly acid. 
The main ridge shows a similar range, viz. p. H. 6- 9-p. H. 7-3, whilst 
the average for twenty-six localities is slightly more acid than for the 
youngest phase, being 7*029. 
Transferring these values from the logarithmic notation to specific 
alkalinities, the average value for the young dunes is represented by 
a specific value of 1*5, and that of the main ridge by approximately 1. 
Determinations of the ridges D and C made in samples from twenty-five 
loci showed an average value of p. H. 6-4 for the 0-4 in. depth, or a specific 
acidity of approximately 3*98. The values range from p. H. 6* i-p. H. 7*3, 
whilst for the top inch the p. H. may be as low as 5*6. 
Several series were taken at varying depths (cf. C 20-C 35 ; D 12— D 9 ; 
D 13-D 19 ; D 37-D 38). These represent nine locations, and in eight 
show a lower value for the surface inch. The rise in acidity from below 
upwards is somewhat abrupt and corresponds to the region of rapidly 
increasing organic content (cf. D 17, D 18). 
On the Long Hills the range is from p. H. 5*9~p. H. 7*0, with p. H. 6*38 
as the average value for the top four inches (fourteen locations), a slightly 
higher acidity than that of ridge D. Here, too, the surface .layer is the 
most acid. B 19, B 20 offer, it is true, the reverse condition, but these are 
samples from the landward slope of the proximal end where limited accre- 
tion takes place. 
The Hood samples show a p. H. range of from p. H. 5*5-p. H. 6*9, 
with an average of 6*24, corresponding to a specific acidity of about 6*3, or 
rather more than i-| times as acid as the ridges C and D. 
It is then evident that the acidity of dune soils increases with their age. 
The presence of carbonates in appreciable amount in the early phases 
of dune development obviously inhibits at first the realization of an acid 
reaction. But, as we have already shown, the carbonates diminish owing to 
continued leaching action as we pass from the younger to the older dunes, 
so that in the latter the rising acidity develops unhindered. 
If we compare only those dune soils of ridges C, B, and A, in which no 
detectable carbonates are present, we find that the averages still show the 
same increasing acidity, viz. ridge C, p. H. 6*83; B, p. H. 6*28; Hood, 
p. H. 6* 07. Here, then, the rise is clearly not related to carbonate 
content, but is associated with increasing organic content accompanying 
increasing age. 
Comparison of the samples from the Long Hills amongst themselves 
shows that the lowest p. H. value is associated with the highest organic con- 
tent, but the lowest organic content is not associated with the highest p. H. 
value. That the relation is nevertheless a real one seems indicated by those 
