482 



Transactions. 



We shall turn now to another example of soil classification by similar 

 methods — " Soils of Cambridgeshire," by F. W. Foreman.* In an intro- 

 ductory note Professor T. H. Middleton says, inter alia, " We were anxious 

 to ascertain whether there exists any close connection between local soils 

 and the underlying rock formation " ; and he comes to the conclusion 

 that " the majority of the mechanical analyses do show a relationship 

 between all the soils on the one formation." 



The soils are treated in the following order : — 



Clay Soils — Sandy Soils 



Boulder clay. Eiver gravel. 



Gault. Lower greensand. 



Kimeridge clay. 

 Ampthill clay. 



In the following table the more important analytical results for the 

 soils of the various clay formations are averaged and summarized for con- 

 venience of comparison : — 



♦Foreman says, "Ampthill clay very closely resembles Kimeridge clay, and the soil derived from it 

 was similar to those from the Kimeridge in every respect." 

 t Fine gravel, coarse sand, and fine sand, 

 j Fine silt and clay. 



The only outstanding features revealed by this table are (1) the markedly 

 high clay content of the Gault, which admittedly distinguishes it from the 

 rest ; (2) the markedly low CaC0 3 content of the Kimeridge and Ampthill 

 clays. 



The boulder clay differs from the Kimeridge clay only in having a higher 

 content of CaC0 3 , though itself in need of lime, we are told. The Gault 

 differs from the Oxford clay only in having a rather greater percentage 

 of the finer fractions. If, however, we take into consideration the analyses 

 given by Rigg of soils from the same geological formation in the adjoining 

 County of Bedfordshire, we find some of these discrepancies completely 

 removed. Thus the average percentage of clay in the pure Gault is 29-3, 

 in good agreement with 29-5 in the Oxford clay soils. We note also that 

 Rigg cites as characteristic of the Oxford clay that " the percentage of 

 calcium carbonate and phosphoric acid is extremely low in all samples 

 taken from this series " — a conclusion in total disagreement with the results 

 of Foreman shown in the table above. 



Both Rigg and Foreman claim that their results show that each 

 geological formation gives rise to soils possessing certain characteristic 



* Journ. Ag. Sci., vol. 2, 1907, p. 160. 



