Liebig's Organic Chemistry applied to Agriculture. 555 



conviction that the carbonic acid emitted at night by plants enters 

 them originally in that state, and that the oxygen absorbed does 

 not serve for the combustion of the carbon, he at last, (p. 30,) pro- 

 duces 'a decisive proof which, in his opinion, clearly shows that 

 the plants give a greater quantity of oxygen to the air than they 

 withdraw from it. He rests this proof on the known fact of 

 air-bubbles beneath ice, which are said to be filled with pure 

 oxygen; and this oxygen is stated to be derived only from plants. 

 Dr. Liebig asserts that it is pure oxygen, and we must give him cre- 

 dit ; and he adds also, that this oxygen is always increasing in 

 quantity, and never diminishing. But, I ask, must this be considered 

 as a proof of that great art of making experiments, only to be learnt 

 in chemical laboratories ? If it is so to be considered, I am glad that 

 I have learnt it in other places. How is it possible that Dr. Liebig 

 can expect to solve, in ditches and ponds, such delicate problems, in 

 such a way as to render them in the least degree useful to science } 

 He does not seem to know that ice absorbs gases ; that certainly 

 water is never separated from the air hermetically, as it were, 

 by ice ; that in water a continual absorption and exchange takes 

 place between the gases ; that carbonic acid is more easily absorbed 

 by water than oxygen ; that frost separates from the water the gases 

 which it has absorbed ; that such a separation especially takes place 

 at points and edges, and, consequently, at leaves and small branches ; 

 that — but this is enough to prove, that he who considers the solution 

 of the above-mentioned problem so very easy a task, must have but a 

 superficial knowledge of the matter , and that this remnant of know- 

 ledge is arrogantly employed for the purpose of showing up, as ig- 

 norant fellows, all those botanists who have entertained different 

 opinions, although founded on innumerable facts. Though I cer- 

 tainly am not partial to Mr. Meyen, and decidedly differ from 

 him in the solution of the problem in question, yet I assert boldly 

 that, in conceiving his theory, he has evinced a degree of sagacity 

 and of knowledge of chemistry much superior to that of Dr. Liebig 

 in his chapter on the Assimilation of Carbonic Acid. Not to 

 mention his frequent contradictions, his historical, physical, and phy- 

 siological perversions, he shows in this chapter a want of knowledge 

 in even his own chemistry, by producing his untenable theory of 



