23§ M. C. Ray tier , W. N. Jones and J. W. Tayleur. 
indeterminable in amount in A, B, and D on clay-with-flints. It is 
perhaps worth noting in this connexion that the amount of magnesia 
in D Where Calluna does not occur, is considerably lower. 
All the clay-with-flints soils (A, B, and D) give a neutral 
reaction, a feature of some interest in view of the fact that soils 
bearing Calluna are usually acid ( e.g ., Soil G). The two down soils 
C and E are slightly alkaline. 
III. With regard to the existence of an edaphic factor, com¬ 
parative chemical analyses do not throw much light on the problem, 
except in so far as they confirm the view that the heather soil 
is a fertile one, relatively rich in available mineral constituents ; the 
high proportion of magnesia is the only striking feature in the Botley 
soils. This is not peculiar to the soil on which the heather is 
growing, but is a feature common to the three soils A, B, C, and in 
a less degree to D on clay-with-flints outside the Calluna area. 
Comparison with the figures for E shows that while the absolute 
amount of magnesia present in the latter is not much less, the ratio 
of magnesia to calcium carbonate is strikingly different and is in 
excess of that usually found in fertile soils. 
A high percentage of magnesia seems to be a characteristic 
feature of soils on the clay-with-flints. Analyses of these soils 
occurring in Kent and Surrey as given in the recently published 
Board of Agriculture Report (10) show also a high percentage of 
magnesia, although in all the cases given, the proportion of CaC0 3 
is much higher than in the Botley soils. This is due to the fact 
that most of these soils are under cultivation and have been artifi¬ 
cially limed. Three of the natural soils, unlimed, also show a higher 
percentage of CaC0 3 as compared with magnesia than do those on 
Botley Down, viz :— 
MgO -3 -22 -38 
Carbonates as CaC0 3 -02 -07 *06 
The effect of liming is well shown in the case of two adjoining 
fields, one of which has a very low percentage of carbonates (-08 in 
the subsoil), the other has been artificially limed. The former is 
reputed the stiffest soil in the district, and has been laid down to 
grass, the latter yields good crops. The improvement due to liming 
is attributed, no doubt justly, to the improvement in texture induced 
in the soil. The possibility of it being in part due to the altered 
relations between magnesia and calcium carbonate, as suggested by 
the Woburn experiments noted below, does not appear to be elimi¬ 
nated, although it is only fair to add that in the same report a few 
