THE SOIL OF THE FAKM. 401 



dipped. Sand very quickly causes water to rise, but not higher than 

 about twenty to twenty-three inches. Loamy soils will lift water by ca- 

 pillary attraction thirty-five or thirty-six inches ; and lastly, clay broken 

 into fragments as large as split-peas, only raises water 5.7, 9.5, and 12 

 inches high. 



Capillarity is constantly exerted by soils, and the fact that it is con- 

 tinued from the deeper layers towards the surface during frost, accounts 

 for the pla.shy condition of paths and roads when the thaw sets in. This 

 subject will once more occupy us when we consider land drainage. 



INI ui.N'CE OF POROSITY UPON FERTILITY. The influence of porosity 

 upon the fertility of soils has already been alluded to. It has been long 

 known that soil possesses strong deodorising power, and it can easii\ 

 shown to decolourise solutions and to transmit a colourless and odourL-s 

 filtrate. Liquid manure, when filtered through a certain depth of earth, 

 becomes thoroughly purified. It is this property of soil which makes it 

 available for the purification of sewage, and in this case it is assisted by 

 the oxidising influence of the air. After running over and through a suf- 

 ficient area and section of land, sewage will be found to be perfectly 

 colourless, and to have lost its offensive odour. 



Further, it has been demonstrated by Professor Way and others, that 

 watery solutions of ammonia, potash, salts and soluble phosphates, when 

 filtered through ordinary soils, are robbed of almost the whole of these 

 tances. They are held back by the soil in a state of physical or phy- 

 sico-chemical combination ; and although capable of being once more par- 

 tially detached by the copious use of pure water, they are to a great 

 maneiitly retained by the soil. 



Thus the three most important fertilizers are found to be specially at- 

 tra< nd held )>v tin- soil, a fact which bears upon the best mean-* 



of applying >ud, icea to the land. 



peculiar power seems to In- duo to a somewhat obscure adh 



fore.-. It has in-. -n compared to the decolourising action of animal char- 



and also to the curious manifestation of adhesion or >ur- 

 in dyeing. In this process particles of colouiin^ mat- 

 OVed from solution ,,r su>pen>ion, and become tirmly fixed to 

 union but not easily explainable- phenomenon. | n , 



I to remove Colouring mat t.-r. smell, and even 

 'lutioti from nd to lix them in its pores or iut 



,v certain that, as the forces ah- 



; a soluble form from the jut raetahle and insoluble mass of 

 esc particle^ will b.- t OD06 by t he .surface-attract j ( ,u 



