184 ON FALLOWING. 



in this manner a continued change of water and 

 fresh supphes of the vital principle are produced. 

 It is evidently this principle which establishes 

 the greatest value of the operation of hoeing. 

 And although not recognised by Jethro Tull, 

 was what gave effect to his favourite process of 

 horse-hoeing. It is this also which produced 

 the increased fertility so much and so justly ex- 

 tolled by Mr. Curwen, in his mode of culture, 

 that of repeatedly stirring the surface between 

 the growing vegetables ; and not, as he supposed, 

 the absorption of the volatile gas tlius extricated, 

 by the leaves of plants. Had Mr. Curwen*s con- 

 ception been just, the plants at a considerable 

 distance from the loosened soil, must have been 

 benefited by the floating of the vapour, or gas, 

 by the wind, but which I take for granted was 

 not the case. The fact is, clay, as soon as sa- 

 turated with water, retains it in a state of stag- 

 nation, to the exclusion of fresh supplies : and 

 thus, plants growing in it, are exposed to poison- 

 ing and starvation. And when the surface is 

 operated upon by a drying sun, it contracts and 

 opens, in large clefts or fissures, through which 

 the vapour escapes; whilst the roots are closely 

 grasped in a dry mass, and thus by the other ex- 

 treme, the vegetable is placed in a state of starv- 

 ation. By repeatedly hoeing and stirring the 



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