REASON OF INCREASE IN CROPS. 195 



roots ; the jy^^'rmanence of high returns, and that alone, 

 affords a safe criterion of the total store or qunntitij of 

 nutritive substances in the ground. 



Tlie liigh returns yielded by one field above another 

 result from this, that the particles of the mineral con- 

 stituents lie nearer together m the one field than in the 

 other : they depend upon the closeness of the nutritive 

 substances. The following table may make this point 

 clearer : — 



Cunnersdorf, Miiuscgast, Kotitz, Obcrbobritzscli, Oberschona. 



Fiff. I. 1851. WiNTEE-RVE. 



Fig. II. 1852. Potatoes. 



Fig. III. 1853. Oats. 



