342 Studies or the Falreozoic Soils of North Wales 



Two glaciations have left their marks on the Geology of North Wales, 

 namely the northern glaciation which flowed across the Irish Sea in 

 a direction roughly n.n.e. to s.s.w. and the glaciation radiating from 

 the Arenig and Snowdon mountains. The Northern glacier affected 

 the whole of Anglesey and West Carnarvonshire and the other two 

 counties up to approximately the 600 feet contour line. The drift 

 deposits in Anglesey, although the result of northern glaciation, consist 

 in the main of local material. In the other parts of North Wales affected 

 by the northern glaciation the drift deposits are in the main of external 

 origin. The drift deposits of the local glaciation, which are found in 

 greatest profusion in Carnarvonshire, consist of local materials scraped 

 down from the adjacent mountains^. 



The Welsh drift in Denbighshire and Flintshire is found in the 

 bottoms of upland valleys and is nowhere so extensive as the local 

 drift of Carnarvonshire. 



Referring now to the orographical map, the lines AB and CDEFGH 

 show the boundaries of the Palaeozoic soils of North Wales. West of 

 AB and north of CDEFGH the soils are mainly drift soils formed from 

 material of later origin. It should be added that the Palaeozoic area 

 includes practically the whole of Anglesey and Denbighshire. 



The soils discussed in the present paper are from this Palaeozoic 

 area which will be seen, by reference to the rainfall map, to be also the 

 area of highest rainfall. 



Palaeozoic Soils. 



In presenting an account of the types of soil encountered, the 

 question of classification is naturally important^. The system of 

 classification adopted will naturally depend on the material to be 

 classified and the local conditions. Thus, the Russian soil investi- 

 gators, Sibirtzev, Docuchaiev and others, use a classification based on 

 climatic conditions because climate is the great controlling factor in 

 the regions studied by them. In other regions, where the climate is 

 relatively constant, the petro-geological classification first proposed by 

 Fallou and adopted by Hall and Russell in their work in Kent, Surrey 

 and Sussex, is most suitable. In an area of varying climate, geology 



^ For an account of the Glacial Geology of Western Carnarvonshire, see T. J. Jehu, 

 Trans. Roy. Soc. Edin. vol. xLvn, pt. 1, 2. The general outlines of the Geology of North 

 Wales are given in Ramsay'.s Geological Survey memoir. 



2 See N. M. Tulai'koff, this Journal, vol. ra, pt. 1, p. 80; E. Ramann, Bodenkunde, 

 p. 521 ; and Hall and Russell, this Journal, vol. iv, pt. 2, p. 182. 



