189 



when, apart from chemical composition and other modifying circum- 

 stances, the suitability of soils for cultivating certain kinds of crops has to 

 be considered, a more complete and detailed discrimination becomes in- 

 dispensable. 



Thaer (see Dr. Walmschaffe's " Anleitung zur wissenschaftlichen 

 Bodenuntersuchung ") had distinguished between the following seven 

 classes, namely : stony, sand, loam, clay, marl, lime and humus soils, and 

 as long ago as 1838, Sclriibler* classified soils, according to their mechani- 

 cal condition, as follows : 



Percentage Percentage 



of clay. of sand. , 



Argillaceous soils above 50 below 50 



Loamy soils 30 -- 50 50 -- 70 



Sandy loams 20 -- 30 70 -- 80 



Loamy sands 10 -- 20 80 -- 90 



Sandy soils below 10 above 90 



In the above classes the amount of sand was diminished propor- 

 tionately when lime or humus was present in a soil. 



Ingle f adopts the following classification : 



Percentage 

 of clay. 



Clay 70 95 



Loam 40 70 



Sandy below 10 



To the above he adds marly, calcareous, and humic soils, the appella- 

 tion being dependent upon chemical and physical conditions other than the 

 size of their constituent particles. 



HilgardJ proposes the classification given below: 



Percentage 

 of clay. 



Heavy clay soils 35 and over. 



Clay soils 25 35 



Clay loams 15 25 



Sandy loams 10 15 



Ordinary sandy lands 3 10 



Very sandy soils \ 3 



Professor Whitney, Chief of the Bureau of Soils of the United States 

 Department of Agriculture, puts forward no less than 16 classes of soil, 

 viz. : stony loam, gravel, gravelly loam, dune sand, sand, fine sand, sandy 



* " Grundsatze der Agrikulturcheinie." 

 f " Manual of Agricultural Chemistry.'' 1902, p. 56. 

 ; Foils ; their formation, properties, composition, fcc.,'' 1906, p. 84. 



