254 



GARDENING AS A SCIENCE. 



This ammonia, and also the potassa in 

 loams, and other saline substances, are ac- 

 tually dissolved by water, and thus duly 

 conveyed by the absorbents of the roots in- 

 to the organism. 



Rain-water collected in cisterns lined 

 with cement, becomes rather hard, because 

 some of its ammonia is abstracted, a defect 

 easily remedied by the addition of a small 

 quantity of this salt to such water. Com- 

 mon hard water from wells contains calca- 

 reous matter dissolved by an excess of car- 

 bonic acid. By exposure to the air, some 

 of this acid escapes, carbonate of lime, 

 (chalk) is deposited, and the water is im- 

 proved ; but for horticultural purposes, no- 

 thing can be compared to the water from 

 rain, which flows through pastures into a 

 pond which has a clay bottom. It is soft, 

 replete with every soluble matter adapted 

 to the nourishment of plants, and far pre- 

 ferable to any that can be obtained from 

 artificial confined depositories. Possessing 

 a natural fluid of so excellent a quality, the 

 gardener will have no occasion to trouble 

 himself with manure-water or any other of- 

 fensive compounds, the results of which, 

 to say the best of them, are ever doubtful, 

 and certainly, in very many instances, posi- 

 tively pernicious or fatal. 



Air. Atmospheric air must at least be con- 

 sidered as important to vegetable life, though 

 not so vitally essential to plants as to ani- 

 mals ; for in fact its direct operation has not 

 yet been clearly made out. To investigate 

 the agency of the atmosphere with any de- 

 gree of satisfaction, its composition must be 

 properly understood. Chemically speaking, 

 one hundred volumes of air consists of 

 twenty-one volumes of oxygen gas, and 

 seventy-nine volumes of nitrogen gas, not 

 in chemical union, but simply mixed. It 

 also contains varying proportions of aqueous 



vapor and carbonic acid. Oxygen gas pos- 

 sesses an extensive range of affinity, and it 

 is obvious, that were it alone to constitute 

 our atmosphere, and left unchecked to exert 

 its powerful efiects, all nature would soon 

 be one scene of universal destruction. It 

 is on this account that nitrogen is present 

 in so large proportion. Possessing no dis- 

 position to unite with oxygen, it is peculiar- 

 ly adapted for this purpose, and exerts no 

 action upon the processes proceeding on the 

 earth. 



The aqueous vapor and carbonic acid gas 

 materially modify the properties of the air. 

 The former falls upon the earth as rain, 

 and brings with it any soluble matter which 

 it meets with in its descent ; the latter per- 

 forms a most important part in the process 

 of vegetable nutrition. 



Carbonic acid, water, and avimonia are 

 the final products of the decay of animal 

 and vegetable matter. In an isolated con- 

 dition, they usually exist in the form of 

 gas. Hence, on their formation, they must 

 escape into the atmosphere. But ammonia 

 has not hitherto been enumerated among 

 the constituents of the air, although, ac- 

 cording to our view, (Liebig) it can never 

 be absent. The reason of this is, that it 

 exists in extremely minute quantity in the 

 amount of air usually subjected to experi- 

 ment ; it has consequently escaped detec- 

 tion. But rain which falls through a large 

 extent of air, carries down in solution all 

 that remains in suspension in it. Now am- 

 monia always exists in rain water, and 

 from this fact we must conclude that it is 

 invariably present in the atmosphere. 



Such are the principal constituents of the 

 air, from which plants derive their nourish- 

 ment, and of which more will be said in 

 our next. 



Wm. W. Valk, m. d. 



Flushing, L. I., Nov. 1847. 



