244 МВ. К. S. ADAMSON : АХ ECOLOGICAL STUDY 
The following complete analysis is again from Foreman * :— 
Over Gault. Over Greensand. 
Moisture... 23:66 3:24 
Organic matter ......... 9.69 773 
Insol. siliceous matter... 63°87 T362 
Lime (СаО) ............ 5:95 ШЕ 
Magnesia (MgO) ...... 0:285 0728 
Phosphoric Acid (P5O;) — (14 0112 
Potash (К5О)............ 0048 0185 
The first of these, that over Gault, corresponds to the calcareous clay in 
the wood, while the second shows some resemblance to the loam. Те 
similarity of the loam to this soil both in mechanical and chemi ‘al analyses is 
further reason for associating it with Greensand. The two types of soil in 
the wood gave considerable differences as regards the percentage of carbonate 
of lime. This was estimated by the amount of CO, evolved in treatment with 
hydrochloric acid. Various methods were used, but that of Amos + was 
found most satisfactory. As the amount of organic material was com- 
paratively so small it was not considered necessary to undertake any special 
methods to counteract the effect of CO, given off from that source $. The 
loam soils gave little or no effervescence on the application of acid, while the 
clays showed considerable differences in this respect. Some of them gave 
a vigorous effervescence, while others showed a just visible amount or none. 
The percentage of lime, calculated on the dry weight of the soil dried at 
1009 C., in the marl ranged from 7 to 1:5 per cent. : more than half the 
samples gave 3 to 4 per cent.; while the loam soils ranged from 155 to 
practically none at all, giving an average of 0'8 per cent. 
Foreman * gives 1 per cent. as the average lime-content of the Cambridge- 
shire Boulder Clays for agricultural soils. However, one of his examples, 
from a clay above Gault, gave 5°71 per cent. for the first seven inches. The 
higher average percentage for the clay in the wood would seem to be due to 
the lessening in the amount of leaching out that takes place there as 
compared with an agricultural soil. 
The water in the calcareous clay soil is neutral to test-paper, that of the 
loam is also neutral or with a slight tendency to acidity locally. 
The humus-content of these soils has-also been studied as being a factor 
with a distinct influence on the vegetation. The amount of humus present 
was obtained by heating to a red heat for a prolonged period a dried 
sample of soil which was as free as possible from portions of roots and 
other extraneous matters that would vitiate the results. The samples 
were taken from the layers of soil about the roots of the principal 
species of the ground flora. The heating was continued till a constant 
* Foreman, 1907, рр. 167-169. T Amos, 1905, t Marr, 1909, 
