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salts of lime. The water parcolating downwards will carry with it any- 

 thing it can dissolve. 



It is in this way that rain water (containing carbonic acid gas) is 

 able to dissolve limestone and in time wash it out entirely f ro:n the 

 surface soil. There will be a similar movement of all other salts that 

 are at all soluble in water. 



What then can the cultivator do to check this loss by psrcolatioa. 

 He must remember that it is not in a stiff clay soil that he neai fear 

 losses of this kind but in a loose open sandy soil. 



His object then must be to diminish the porosity of such a soil. 

 This he can do either by compacting the soil with a roller or by bind- 

 ing the soil by the addition of humus or clay. 



It is now left to consider the case of tha water that has nit esoapai 

 beyond the subsoil, and it is this water which is subject to the second 

 mode of loss, i.e. by 



(ii.) Ev'iporation. It must not be im iginei that this process ceases 

 when, after the wetting of a soil by rain the diVY air has caused the 

 surface soil to lose its water by evaporation. 



Evaporation of the water in the surface soil will cause the water in the 

 subsoil 'O assume an upward m )tion. ^Ye have seen t'lat wa er sines 

 by passing from particle to particle, it c in alsj rise in a similar m inner. 

 As it was the action of gravity that caused water to sin'c, wlia^ force is 

 theretocauseit torise asrainst ohe acti )n of o^ravitv ? The force is called 

 surface attraction. 



It must be remembered taat though this force brings Abater up to the 

 surface of the soil, this is not the reason for the expression surface 

 attraction." The word su'fac3 in this case refers only to the sur- 

 face of each soil particle. 



Let the reader illustrate this actio i for himself by taems o£ a si n pie 

 experiment. 



PI ce two flat pieces of glass (say I" by 3") together so that they 

 almost touch, and dip t leir edges to the depth of about J" into a tum- 

 bler full of water coloured wi h red ink. It will be o bserved that the 

 water will rise beticeen the two surfaces to the height of an inch or two. 

 This rise of the water is di^e to surface attraction. The surface of the 

 glass attracting the water with a force sufficient to overcome that of 

 gravity acting in an opposite direction. In the same way the surface 

 of each soil particle is capable of attracting to itself water which will 

 form a film around it, causing the water to pass upwards from particle 

 to particle. Now the finer the particles are and the closer together the 

 more water will pass upwards, because the greater the number of par- 

 ticles the more surface there will be to exert this attractive force The 

 closeness of the particles also assists in this movement, in that there 

 will be a shortei" sp tce for the water to pass, springing as it 

 were from particle to particle. These then are the points which en- 

 able us to control to some extent the water supply. First of all this 

 upward movement must be encouraged, because a supply of water and 

 dissolve ! plant foo l that would other .vise have been beyond the reach 

 of the plant roots, is thereby obtained It must not however be alloved 

 to come right up to the surface, for then the water will be lost to tke 

 plant by evaporation, and also the dissolved m itter will be precipitated 

 out of reach of the roots. How can this be avoided? By bearing in 



