1864.] CHEMISTRY OF MANURES. 199 



of its ammonia; and much prominence has been given to the 

 results of such trials, as evidence of the alleged inej0&cacy of 

 cinereal supplies to corn. Among the objections to this line of 

 argument it may be mentioned that the observed difference proba- 

 bly depends, in a considerable degree, on the modification by 

 fire of the ash-constituents themselves. In the uuburnt dung, 

 composed, to a large extent, of decaying straw, the cinereal ele- 

 ments are diffused throughout the organic tissues, in a state of 

 infinitesimal molecular subdivision. By the decay of the dung 

 in the soil, the organic molecules are gradually converted into 

 carbonic acid and water, the proper solvents of cinereal food. 

 Thus considered, a decaying straw containing (say) five per cent. 

 of ash-ingredients, constitutes as perfect a piece of distributive 

 mechanism as can easily be conceived, for spreading throughout 

 the soil the needful cinereal restoratives, along with the liquid and 

 the gas requisite for their solution and final delivery to the roots. 

 But this is not all. The straw acts with equal efl&cacy as a distri- 

 butive vehicle of the urine with which it is soaked, and of the 

 cinereal and volatile plant-food dissolved therein. Before decay, 

 its fibrous tissues constitute a sponge, to absorb and retain, as also 

 widely to expand, the nutrient solution; and when the sponge has 

 brought this solution into contiguity with an extensive surface of 

 soil it silently disappears ; its solid tissues dissolve, — their capil- 

 larity, having done its office, ceases to exist, — the capillarity of the 

 soil comes into play, and its pores delicately take up the ailment 

 which he straw, in the act of its dissolution, as delicately deposited. 

 Hoffmann, in one of his Phantasiestilche^ describes a mysterious 

 hand, which, moving in palpable substance through the air, car- 

 ries a cup of food to one of the personages of his tale, and having 

 set it down before him, vanishes into thin air. Each fragment of 

 straw in dung acts as such a hand to the soil. The substantive, palpa- 

 ble vehicle melts into gas and water when its work is done. Nor is 

 the space left empty by its disappearance without a special use : 

 it forms a channel for the tender rootlet to travel along, — a channel 

 which the decay of the straw at once hollows out, and warms, and 

 lines with aliment; with aliment, as we have seen, finely divided, 

 surface-held, and provided with its appropriate solvent. 



All this delicate adjustment of means to a special end is utterly 

 destroyed by fire, which dissipates the hydro-carbonaceous matter 

 of straw, so that its ash-ingredients, no longer separated by inter- 



