126 



SCIENCE OF GARDENING. 



sess the power of decomposing carbonic 

 acid, since they appropriate its carbon for 

 their own use. The formation of their 

 principal component substances must neces- 

 sarily be attended with the separation of the 

 carbon of the carbonic acid from the oxy- 

 gen, which must he returned to the atmos- 

 phere ; whilst the carbon enters into combi- 

 nation with water or its elements. The at- 

 mosphere must thus receive a volume of 

 oxygen for every similar volume of carbonic 

 acid which has been decomposed." 



Thus reasons Liebig ; yet upon this great 

 miracle of nature he advances no novel 

 idea ; he only brings us back to the obser- 

 vations of Sennebier, Dr. Priestly, De 

 Saussure, and others ; but his modes of 

 proof, his deductions from calculation, are 

 his own. That many have doubted the 

 grand facts which he has confirmed, is as 

 true as it is lamentable ; for there is not in 

 all creation one other traceable agency, by 

 Avhich the destructive increase of carbonic 

 acid could be prevented, if we deny it to 

 vegetable vitality! •" The life of plants is 

 closely connected with that of animals, in a 

 most simple manner, and for a wise and 

 sublime purpose. The presence of a rich 

 and luxurious vegetation may be conceived 

 without the concurrence of animal life ; but 

 the existence of animals is undoubtedly de- 

 pendent upon the life and development of 

 plants." 



Plants not only afford the n5.eans of nutri- 

 tion for the growth and continuance of ani- 

 mal organization, but they likewise furnish 

 that which is essential for the support of the 

 important vital process of respiration ; for 

 besides separating all noxious matters from 

 the atmosphere, they are an inexhaustible 

 source of pure oxygen, which supplies the 

 loss the air is constantly sustaining. Ani- 

 mals, on the other hand, expire carbon, 

 which plants inspire ; and thus the compo- 



sition of the medium in which both ex- 

 ist, namely the atmosphere, is maintained 

 constantly unchanged. 



This beautiful reciprocity speaks volumes: 

 it sets aside that weak appeal to the agency 

 of humus, which has of late years been so 

 imperiously urged. The presence of ma- 

 nuring matter in the soil, and the important 

 changes which it operates, have doubtless 

 tended to blind us to the more important 

 agency of the atmosphere ; but Avhy decay- 

 ing vegetable matter, whose decomposition 

 is effect^d by the agency of the air and 

 moisture, should be identified with the ar- 

 tificial himius of the laboratory, is a myste- 

 ry. If such be the results of the applica- 

 tion of chemistry to the theory of agricul- 

 ture, we are free to confess, that we should 

 prefer the ignorant routine of our forefa- 

 thers. They pay a poor compliment to sci- 

 ence, who thus misapply its discoveries. 



As applied to the nutriment of vegeta- 

 tables, Dr. Liebjg has thus far been follow*- 

 ed in his leading principles of chemical 

 philosophy ; his last great proposition being 

 this — that plants derive their nutriment 

 chiefly y?-07w the atmosphere ; during and by 

 which process they purify the air, absorbing 

 that gas which would otherwise so accumu- 

 late as to become destructive to animal 

 life. 



The hypothesis is startling, because it 

 overturns all our ideas previously entertain- 

 ed, respecting the source and channels of 

 the nutrimental sap. It remains then to in- 

 vestigate a little more minutely the agency 

 of manures, and to discover, if it be possi- 

 ble, the effects which they produce upon 

 plants in the different stages of their growth. 

 By the term manure, we wish it to be un- 

 derstood that we mean every substance which 

 is decomposable i?i soils, and capable of be- 

 ing resolved into the elements of water, 

 {oxijgen and hydroge?:,) of carbonic acid, 



