GARDENING AS A SCIENCE. 



253 



converts it into primary raw sap. What 

 this sap may be, it is probable we shall ne- 

 ver be able to determine with precision ; 

 but the suggestion may be ventured, that 

 the elements of water are thus developed, 

 which combine instantly, in the form of the 

 purest water, depositing the carbon in the 

 soil. We do not mean to say that all the 

 carbon of the manure, or vegetable earth, 

 is deposited ; a portion may be, and very 

 probably is, dissolved at the moment of the 

 extrication of both, by an equivalent por- 

 tion of hydrogen ; but what we assert is 

 this — that water does not act as a direct 

 solvent of manure, no such thing as dis- 

 solved liquid manure being taken up, nutri- 

 mentally, by the roots ; and that sap, be it 

 simply aqueous, or a compound of water 

 and some hydro-carbon, is the secondary 

 result of an electrolytic process, nearly al- 

 lied to galvanism. 



If the views expressed be correct, there 

 will be no difficulty in accounting for the 

 darker hue assumed by ground under crop, 

 for the carbon being deposited, remains in 

 it. 



In the Journal of the Royal Agricultural 

 Society, page 250, Dr. Daubeny, in a lec- 

 ture on manures, believes with Liebig, that 

 humus, " during the whole period of its 

 decay, until it has reached that ultimate 

 point at which it ceases to be soluble, and 

 has become a kind of ca-piit mortuum, goes 

 on continually disengaging carbonic acid ; 

 so that the roots of plants fixed in humus 

 of this quality, are surrounded by an at- 

 mosphere of the gas in question, which is 

 therefore held in solution by the water 

 taken up by them as sap." But the 

 proof is here wanting that carbonic acid is 

 so dissolved. Is it not far more likely that, 

 if this aerial acid be produced, it passes at 

 once into the atmosphere, and thence is 

 taken into the vegetable organization by 



the leaves, to be converted into specific 

 fluids and woody fibre ? 



Water certainly does act as a solvent, but 

 not of vegetable mould ; as rain, it conveys 

 into the earth, with every shower, a certain 

 quantity of ammonia, which is a saline sub- 

 stance of extreme utility in vegetation. On 

 this subject, Liebig thus expresses himself: 

 " Any one may satisfy himself of the pre- 

 sence of ammonia in rain, by simply adding 

 a little sulphuric acid to a quantity of rain- 

 water, and evaporating this nearly to dr)'- 

 ness in a clean porcelain basin. The am- 

 monia remains in the residue in combina- 

 tion with the acid, and may be detected by 

 a little powdered lime, which separates the 

 ammonia, and thus renders its peculiar pun- 

 gent smell sensible. The sensation which 

 is perceived upon moistening the hand with 

 rain-water, so different from that produced 

 by distilled water, and to which the term 

 softness is vulgarly applied, is also due to 

 the carbonate of ammonia contained in the 

 former." 



" The ammonia which is removed from 

 the atmosphere by rain and other causes, 

 is as constantly replaced by the putrefaction 

 of animal and vegetable substances." " It 

 is worthy of observation, that the ammonia 

 contained in rain and snow water, possesses 

 an offensive smell of perspiration and ani- 

 mal excrements — a fact which leaves no 

 doubt respecting its origin." To how many 

 gardeners and horticulturists is this fact fa- 

 miliar ? 



We shall have occasion to say more of 

 ammonia, when we consider the products of 

 vegetables ; it will suffice now to remark, 

 that nature has herein provided a corrector 

 of what would, like atmospheric carbonic 

 acid, become a deadly nuisance, and, by 

 bringing down ammonia with the rain, con- 

 verts it into a solvent of vegetable manure, 

 fitted for laboration by the vital principle. 



