PEEPAEATION OF THE SOIL. 115 



u This should be performed by running the surface 

 plough to full depth, and following with a lifting sub- 

 soil plough, the latter propelled by a separate team, 

 with its beam in the bottom of the furrow left by the 

 surface plough, and not skating along the surface, 

 merely scratching or slightly disturbing the bottom of 

 the furrow. This lifting, subsoil plough not only 

 under-cuts the land side so as to enable the next fur- 

 row-slice to break off more deeply and pulverize more 

 completely, but at the same time it lifts the previously 

 turned furrow-slice for a short distance, perfectly dis- 

 integrating its particles; for the resolution of its 

 forces being upward and outward, renders all the 

 soil above it, like that above the mole-track, perfectly 

 divided." 



Nearly all the large crops we have any account of, 

 have been produced, to a large extent, by thorough 

 tillage. Manures are doubtless highly useful,,and have 

 their share in producing results. But it is tillage, 

 beyond any doubt, that gives to fertilizers their great- 

 est value and effect. 



The true philosophy of thoroughly aerating the 

 soil, so that it may not merely admit, but invite, the 

 approach of air and water to the growing roots, is suf- 

 ficiently shown in the fact, that the chemical elements 

 of water and of air constitute ninety per cent, or more 

 of nearly all growing plants. 



In addition to this, it is to be remembered, 

 that the plant-food already in the soil, as well as 

 that applied by the farmer, depends upon the action 



