1864.] CHEMISTRY OF MANURES. 191 



manures on the soil cm have the slightest effect, so long as th» 

 one ingredient, wholly or partly deficient, remains unsupplied. 



^'or does the mere presence of the cinereal plant-food in tht 

 aoil suffice : it must be availably present. '1 hat is, besides anj 

 portioL, however large, of cinereal element, that may be held in 

 mechanical isolation within the substance of the stones or clods, 

 beyond the reach of the roots ; or that may be locked up in chehi- 

 ical combination, too refractory for the solvent agencies present to 

 subdie; besides any isolated or locked-up portion which may, in 

 truth, be regarded as absent for all immediate purposes of nutri- 

 tion ; there must be a sufficiency of ash-constituents, held lightly, 

 either by the surface-action of the moist and porous earth, or (^ ac- 

 cording to another view) by the chemical attraction of the alumin- 

 ous silicates, in such manner as to be, both physically and chemi- 

 cally, accessible to the roots. No doubt the locked-up materials of 

 one seas, n, may, and do become, in due course of tillage and fal- 

 lowing, the accessible food of the next ; and, indeed, it is to such 

 gradually-decomposing reserves that the prolonged fertility of cer- 

 tain soils, worked l-y tillage and fallowing only, without manure, 

 is due. But for all immediate purposes, a soil is exhausted, when, 

 rich as it may be in the condtions of future I'ertility, it lacks an 

 adequate present supply of the ash-constituents of plants, in free 

 accessible diffusion. 



High Farming: how far justifiable : at what point 

 EXHAUSTIVE. — And here it becomes opportune to resume the 

 question of high farming, which in a previous page was reserved 

 for subsequent elucidation. 



High farming, as already pointed out, is justifiable in so far ai 

 it serves to concentrate, within limits adapted to the assimilative 

 powers and circumstances of annual and biennial plants, the food- 

 supplies diffused by nature over a much wider expanse of time and 

 space, to suit vegetation of perennial growth. But it is of the 

 deepest importance to observe, that the more abundant crops, and 

 apparently increased fertility usually induced by high farming, are 

 in too many cases but the premonitory symtoms of an accelerated 

 process of exhaustion. The semblance of prosperous husbandry 

 thus created is as factitious, as the spendthrift's ruinous magnifi- 

 cence maintained by squandering his capital ; and '' high farming," 

 even when coupled with " high manuring," and the keeping of 

 many cattle for their dung, is often, for the unwary husbandmatt| 

 only a flowery road to destruction. 



