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certain amount of fairly large grains are found. The 

 smaller the particles of which a soil is composed, the 

 greater is its power of raising and retaining water. Beyond 

 a certain point, however, so much resistance is offered to 

 the passage of water between the fine particles that the 

 upward or downward movement of water is very slow. 

 The low water capacity of the Facus soil, in the table 

 given below, is due to the extreme fineness of the soil 

 particles. Generally a clay soil can raise water higher 

 than a sandy soil but the water is raised much more slowly. 

 Small particles give tenacity to the soil and render culti- 

 vation more difficult. As chemical action only takes place 

 on the surface of the soil particles, fine grained soils 

 present a greater surface to the action of the weathering 

 agents. Further, the smaller particles are usually softer, 

 more easily weathered, and are composed of bodies which 

 are capable of yielding more plant food than the larger 

 particles. However, when a soil consists entirely of very 

 fine particles it is so tenacious, badly drained, and badly 

 aerated, that the rate of weathering is reduced to a mini- 

 mum. Conditions for plant growth are therefore most 

 favourable when a soil consists of a mixture of small and 

 large mineral particles. The large particles, or soil skeleton, 

 open up the soil, increase its porosity, and provide the 

 raw material from which the fine particles are derived. 

 In the following table the material washed off in the 

 analysis is called "clay." 



