M.— AGRICULTURE 241 



In the old Russian Empire, and the modern union of Soviets, there are 

 soils which have been produced in a great variety of climates in Russian 

 Europe and Asia. The Russian soil workers set themselves to collect 

 these and to examine them critically, and came to the conclusion that soils 

 produced from a geological formation in a cool climate were very different 

 from those produced from the same geological formation in a hot climate, 

 and that those produced in a moist climate were very different from those 

 produced from the same parent materials in an arid climate. They 

 showed indeed that very different soils may be formed from the same rock 

 in different climates and that, on the other hand, similar soils may be 

 produced from different rocks in similar climates. That, for example, 

 our granitic soils, produced in the cool humid climate of Scotland, would 

 have been very different if produced in a hot humid climate in tropical 

 Africa, and that if produced in a hot arid climate in Asia they would have 

 been different both from those produced in cool humid Scotland and in a 

 hot humid African climate. In fact they showed that soils cannot be 

 classified and characterised on a geological basis. Possibly some of them, 

 and still more some of their enthusiastic converts in other lands, go too far 

 in excluding geological origin altogether as a factor in soil formation. 



The next great feature of the Russian system is the classification of soils 

 according to what is found in the soil profile. The profile, as is now well 

 known to all of us, though that was not so twenty years ago, is a section of 

 the soil from the surface down to the parent material. If such a section is 

 examined it is almost invariably found to consist of a number of different 

 layers, called horizons, which are generally easily distinguishable from one 

 another. When a great many such profiles are examined from different 

 parts of the world it is found that they fall into a number of definite types 

 characteristic of the different types of soil. The profile is an expression 

 of the results of the different soil-forming factors and therefore characterises 

 the different types of soils as produced by the action of these factors. This 

 is expressed by saying that the profile is the resultant of the pedogenic 

 • processes. The modern soil surveyor studies morphology of soil profiles 

 and classifies his soils accordingly. 



This is in outline very simple, in practice it is often very difficult and is 

 apt to give rise to differences of opinion, especially when those accustomed 

 to the profiles of one part of the world are introduced to a new region with 

 conditions different from those to which they are accustomed. It will be 

 seen, too, that this scheme of a profile made up of horizons is a develop- 

 ment of the old division of the soil into soil and subsoil. But there is an 

 important difference, the terms soil and subsoil were applied to cultivated 

 soils mainly, and the soil was, generally speaking, the layer which had been 

 mixed and influenced by the implements and processes of cultivation, 

 while the subsoil was the layer which was not touched by instruments of 

 cultivation. Such a division is of no use to the modern student of soil 

 morphology and genetics. The processes of cultivation have turned 

 over and mixed the surface layers and have also modified those below the 

 region reached by the plough. The modern soil investigator, therefore, 

 insists that the profile must be studied in undisturbed soil which has 

 existed in its natural condition for a long period of time. To him the 



