J. Hendrick and W. G. Ogg 469 



Conclusions. 



The general conclusious to be drawn from the chemical composition 

 of the mechanical separates is that Craibstone soil, which may be 

 taken as representative of a large class of glacial drift soils of the north 

 of Scotland, is composed largely of particles wluch have not undergone 

 profound chemical weathering, but consists of the original granitic 

 minerals mechanically ground with only comparatively superficial 

 chemical alteration. 



The coarser particles w Inch form so large a part of this soil contain 

 great stores of lime in particular, and also of other bases such as potash, 

 soda, and magnesia. 



There is a wide difference between such a soil as that of Craibstone 

 and soils of the south-east of England, for instance, which are composed 

 of materials which have been subjected to age-long chemical weathering. 

 When, as at Rothamsted, such soils are of glacial origin, they probably 

 represent glacial detritus derived mainly from materials profoundly 

 weathered long before the glacial period. 



It is necessary, therefore, to examine carefully the whole circum- 

 stances and to exercise much caution before we apply to soils of 

 Craibstone type conclusions arrived at either as to physical and chemical 

 properties or manurial requirements by the study of the soils of the 

 south-east of England. 



We wish to express our indebtedness to Mr James Btrachan, M.A., 

 B.Sc, now in the Soudan, formerly of this Department, who made the 

 chemical analvses of the mechanical fractions of Craibstone soil. 



{Received November loth, 1915.) 



