256 



On the Application of Manures. 



might be expected when we reflect that it must be principally 

 derived from the decomposition proceedings in various parts of the 

 globe of all kinds of animal exuviae, the volatile products of which, 

 until otherwise appropriated, will be retained in the general body 

 of the atmosphere as in a common reservoir. 



" Semper enim quodcunque fluit de rebus, id omne 

 Aeris in magnum fertur mare : qui nisi contra 

 Corpora retribuat rebus, recreetque fluenteis, 

 Omnia jam resoluta forent, et in Aera versa." 



Thus ammonia will be constantly presented to the roots of 

 plants in union with the rain-water that has descended from the 

 heavens, even where the vegetable mould is so entirely destitute of 

 animal matter as to be incapable itself of supplying it. 



There is also another principle which may be called in to ex- 

 plain the manner in which gaseous matters are brought into con- 

 tact with the absorbing surfaces of plants. 



It was originally shown by Saussure that charcoal has the 

 property of absorbing and even condensing within its pores various 

 gaseous matters ; and Faraday observed, not many years ago, the 

 singular facility with which earthy and metallic powders of all 

 descriptions absorb ammonia, when present either in the air or in 

 the bodies with which they are brought into contact. 



Reasoning upon these facts, I was myself led last spring to 

 undertake a few experiments with the view of ascertaining whether 

 vegetable mould had not the same property, and I found accord- 

 ingly that both carbonic acid and ammoniacal gases were con- 

 densed within its pores, as they would be within those of a lump 

 of charcoal. 



Liebig in his late volume has made the same remark, and has 

 extended it to the oxides of iron, to pipe-clay, &c., and hence we 

 have a mode of accounting for the absorption of ammonia by 

 plants, even in countries where the absence or the rare occurrence 

 of rain might otherwise deprive them of a due supply of this ne-. 

 cessary ingredient. 



Nor are we any longer at a loss to trace the ammonia into the 

 substance of the plant, which derives from it its nitrogen. 



That it does actually find its way into the vegetable organiza- 

 tion, we are assured by the researches of Professor Liebig, who 

 ascertained that the saccharine juice which flows from the differ- 

 ent varieties of maple, even when growing in soils that were not 

 manured, contains a large proportion of ammonia. 



The same is the case with the juice extracted from beet-root 

 for the purpose of preparing sugar, and the products of the dis- 

 tillation of herbs, flowers, and roots, with water, contain ammo- 

 niacal salts. 



