Liebig's Organic Chemistry applied to Agrigulture. 547 



does not leave a residuum of wax; and that nitric acid not only- 

 dissolves starch, but decomposes it. Page 8, he says, "The quali- 

 ties of humus and of humic acid have been transferred in an incon- 

 ceivable way by vegetable physiologists to that constituent of mould 

 to which the same name, has been applied." (By whom ? — I think 

 only by chemists.) We do not know whether to consider it as igno- 

 rance of the history of his own science, or as an intentional falsi- 

 fication of historical facts, when we find that Dr. Liebig does not 

 even suspect that the whole theory of humus, and its application to 

 explaining the manner in which plants are nourished, have been in- 

 vented and fully developed by Saussure, Sprengel, Malaguti, Berze- 

 lius, Mitscherlich, Mulder, and others, who were all chemists; and 

 that but few vegetable physiologists have adopted it from them with- 

 out making any material change. Dr. Liebig does not seem to know 

 that many vegetable physiologists have always asserted humus only 

 to contribute to the nourishment of plants by being converted into 

 carbonic acid. This is the opinion of Senebier, Ingenhouz, Agardh, 

 &c. I myself heard it from my teacher Bartling ; and it was only at 

 a later period that I became acquainted with the theory of humus, as 

 explained in books, and to which I am not inclined to give my 

 assent. But in another part of his book he does seem to know this 

 fact, and speaks there of Senebier, Ingenhouz, &c. We read at page 

 22, " the same current of air which produced by the rotation of 

 the globe, has traversed the space between the equator and the poles, 

 brings to us, on its return to the equator, the oxygen which there 

 (where?) has been produced, and carries to it the carbonic acid 

 of our winters V Must we, in reading this monstrous theory of the 

 winds, ascribe it to an entire ignorance of natural philosophy ? or to 

 an utter confusion of his ideas when the author was writing down 

 this passage ? Page 37 ; — " In those plants of the torrid zone which 

 are filled with milky juices, caoutchouc and wax surround the water 

 with a kind of impenetrable cover, similar to what is observed in oily 

 emulsions, therefore they abound in juice. As in milk the pellicle 

 formed on the surface prevents evaporation, thus in these plants the 

 same effect is produced by the milky juice." Such an assertion 

 would excite a smile on the face of a youth just beginning to study 

 the anatomy of plants, and hardly deserves to be refuted. The 



