T. RiGG 387 



gone rather farther afield in order to compare the soils of the immediate 

 vicinity with those used for intensive market-garden culture. This 

 investigation has, however, been primarily concerned with the market- 

 garden soils, and therefore one or two heavy soil formations not suitable 

 for the growth of market-garden crops but included in the investigation 

 have not received perhaps the same detailed examination as those on 

 wliich market-garden crops are extensively grown. 



The investigation may be conveniently divided into three parts. 

 Part I dealing with the methods employed in soil mapping and the 

 relationship of the soil formations to the underlying geological forma- 

 tions. Part II a description of the properties and agriculture of the 

 soil formations and a definition of their properties in terms of chemical 

 and mechanical analyses. Part III the relationship of crops to the 

 soil formations. 



PART I. 



Methods of Soil Maiyping, Soil Defiiiitions and Relationship of 

 the Soil Formations to the Surfice Geology. 



In conducting any soil survey the first question which arises is the 

 means of distinguishing between different soil types. 



The American Bureau of Soils in their extensive surveys have 

 classified soils in "series" according to their structure and colour. 

 Under the "series" name will occur soils which have the "series" 

 characteristic but yet which dift'er widely in texture. Thus the well- 

 known Miami Series is characterized by the light colour of the surface 

 soils and their derivation from glacial material. There are fourteen 

 members of this series and the variation in texture is from gravel 

 and sand to a clay loam. Thus geological origin largely decides series, 

 but the position in the series, whether the conventional terms sand, 

 gravel, clay, etc., should be applied to the soil, is determined by 

 mechanical analysis. 



Hall and Russell in their survey of Kent, Surrey and Sussex used 

 the geological map as a basis on which to work in mapping soil forma- 

 tions. In this region the soils are comparatively uniform over an 

 entire geological outcrop. In some instances, notably the Lower 

 Wealden Beds, a greater variation in texture was found but the soils 

 all had certain features in common, the high percentage of silt being 

 particularly noticeable. Owing to the circumstance that this formation 



26—2 



