VALUE OF LAND. 



135 



come parched, and the effect upon the tree be the 

 same as when without efficient drainage. 



But remove the stratum (6), in the last diagram, 

 and the whole earth which was drained is pen- 

 etrated by the atmosphere, decomposition com- 

 mences, heat is obtained, fertility increased, the 

 drains are made efficient, and the pasture-ground of 

 the roots is largely increased. 



The purchaser generally values land by the 

 square foot, but the judicious cultivator estimates 

 it by the cubic foot. If he wishes to increase his 

 income, and is about to add to the superficial area 

 of his arable land, let him consider whether the 

 same amount of money spent in placing another 

 acre of fertile earth immediately under that which 

 he now possesses Avould not yield a more profitable 

 return. 



Jethro Tull considered this subdivision of the 

 soil as the great secret of husbandry, and thought 



