118 THE SOIL. 



still the produce could not in any case be greater than 

 in proportion to the amount of nutritive substances in 

 the soil. But, in fact, they were far greater, and the 

 roots actually absorbed more nutritive substances than 

 the water could possibly have conveyed to thorn, even 

 under the most favourable circumstances. 



These experiments have, for the first time, afforded 

 direct proof that plants possess the power of absorbing 

 their necessary nutritive elements from a soil in which 

 they are present in physical combination, i.e. in a state 

 wherein they have lost their solubility in water ; and 

 the comportment of arable and cultivated soil in general 

 shows that the nutritive substances contained in them 

 must be present in the same form as in the artificial 

 turf soil of these experiments, with this difference, how- 

 ever, that the earthy particles in the arable soil are 

 not merely the vehicles of these substances, but their 

 source. In a soil consisting of turf-powder, a second 

 crop will not succeed so well as the first, unless the 

 nutritive substances which have been removed are 

 again supplied ; nor will the soil regain its fertility, 

 however long it be left fallow. 



The benefit derived from mechanical tillage of the 

 ground depends upon the law, that the nutritive sub- 

 stances existing in a fruitful soil are not made to change 

 their place by the water circulating in it ; that the cul- 

 tivated plants receive their food principally from the 

 earthy particles with which the roots are in direct con- 

 tact, out of a solution forming around the roots them- 

 selves ; and that all nutritive substances lying beyond 

 the immediate reach of the roots, though in themselves 

 quite effective as food, are not directly available for the 

 use of the plants. 



There are no isolated laws in nature, but they are 

 all together links in one chain of laws, which are in 

 turn subordinate to a higher and a highest law. 



"With the natural law, that organic life is developed 

 only in the outermost crust of the earth which is ex- 

 posed to the sun, is most intimately connected the 

 power of the fragments of that crust which form the 



