SCIENCE OF GARDENING. 



12^ 



REMARKS ON GARDENING AS A SCIENCE.— No. 4. 

 BY DR. WM. W. VALK, FLUSHING, L. I. 



" It is quite evident," says Liebig, " that the 

 quantities of carbonic acid and oxj'gen in 

 the atmosphere, which remain unchanged 

 by lapse of time, must stand in some fixed 

 relation to one another ; a cause must exist, 

 which prevents the increase of carbonic 

 acid, by removing that which is constantly 

 forming ; and there must be some means 

 of replacing the oxygen which is remov- 

 ed from the air by the processes of com- 

 bustion and putrefaction, as well as by the 

 respiration of animals. Both these causes 

 are united in the process of vegetable life." 



Carbonic acid, or fixed aerial acid, is the 

 inevitable product of combustion and respi- 

 ration ; and the atmosphere is the recipient 

 of the gas so produced. Any one may con- 

 vince himself that it is always present, by 

 exposing a little pure fresh burnt lime, or 

 a glass of strong and clear lime water, to 

 the air, for a few days. Neither of these 

 would hiss, (effervesce,) were a drop or two 

 of any acid applied to it ; but after being 

 so exposed to the air for some time, the 

 lime would be converted to carbonate of 

 lime, and the lime water would lose its pel- 

 lucidity (clearness,) and be covered with an 

 insoluble brittle scale. Both would efl^er- 

 vesce with the extrication of frothy air- 

 bubbles ; and these changes are produced 

 by the attraction exerted by the pure lime 

 upon the carbonic acid of the atmosphere, 

 which causes a union of the two, and the 

 formation of that neutral salt of lime, com- 

 monly known by the term, chalk. If an 

 estimate is wanted of the actual quantity 

 of this acid contained in the air, let us again 

 turn to Liebig. 



" The air contains in maxnno, ti^Ho « of 



carbonic acid, and yVAVo of oxygen gas. 

 A man consumes in one year 166,075 cubic 

 feet of oxygen gas, (or 4-5,000 cubic inches 

 in one day, according to Lavoisier, Seguin, 

 and Davy ;) a thousand million of men must 

 accordingly consume 166 billion cubic feet 

 in one year ; this is equal to yoV o ^^ ^^^ 

 quantity which is contained in the air in 

 the form of carbonic acid. The carbonic 

 acid would thus be doubled in a thousand 

 years, and man alone would exhaust all the 

 oxygen, and convert it into carbonic acid, 

 in three hundred and three times as many 

 years. The consumption by animals and 

 the process of combustion is not introduced 

 into the calculation." 



There is not, perhaps, in the whole econo- 

 my of wonder-displaying nature, a fact more 

 conclusive, more simple, and yet more as- 

 tounding, than the one which the foregoing 

 extract reveals. For if some agency were 

 not unceasingly at work to withdraw that 

 volume of poisonous gas, which every act 

 of combustion and respiration pours into 

 the air, the whole would inevitably be con- 

 verted into a pestilential vapor. Nitrogen 

 is destructive of breathing life, and of it 

 we have seen that no less than four-fifths 

 of the entire atmosphere consists ; the re- 

 maining fifth of oxygen is the sole meliora- 

 tor — and of it every breath we inspire con- 

 sumes a portion. Then, " how does it hap- 

 pen that the proportion of oxygen in the at- 

 mosphere is thus invariably the same? Car- 

 bon and the elements of water form the prin- 

 ciple constituents of vegetables ; the quanti- 

 ty of substances which do not possess this 

 composition being in very small proportion. 

 It is therefore certain, that plants must pos- 



