Liebiga Organic Chemistry applied to Agriculture. 561 



of themselves, without any necessity for another view of the matter 

 in their place. But enough of this : it is not worth while examining 

 such ill-considered matters in all their points. Let us pass on 

 to the following chapters, of which I shall have the less to say, 

 seeing that the previous observations apply to them also in many 

 cases. 



Dr. Liebig, in speaking of " the origin and operation of humus," 

 briefly explains the received theory of its formation from woody 

 fibre, but in a very superficial way (as compared with Mulder, 

 in Bull. d. Sc. Phys. et Nat. en Neerlande, 1840, p. 1. etc.). He 

 then gives us a short view of the development of a plant, as he sup- 

 poses that it takes place. In doing this, he introduces a new law, 

 which, as being full of very deep wisdom, he has caused to be print- 

 ed in italics, namely, "The size of a plant is in proportion to 

 the surface of its organs, namely, the leaves, which are destined 

 to conduct food into it." How bad then must be the condition 

 of the enormous Cactus, which has no leaves at all, or the gigantic 

 Cecropias and Palm-trees, with the small number of their leaves ! 

 Suddenly, however. Dr. Liebig forgets his whole theory, and says, 

 the small Turnip of Teltow, attains the weight of several pounds 

 when planted in a soil where it is forced to take as much nourish- 

 ment as it can. What has, in this case, become of Dr. Liebig's car- 

 bonic acid and ammonia, which exist everywhere in sufficient quan- 

 tity, and neither of which originates in the soil ? The Turnip of Tel- 

 tow grows near Berlin, in a light sandy soil, and in the islands of 

 the river Elbe, in a marshy ground, which contains much clay and 

 a great portion of humus. But in both these places it is a small 

 root, notwithstanding the great difference of soil and cultivation. 

 I think Dr. Liebig, in speaking of this little Turnip, should have 

 been aware that there are some principles and relations, which 

 he cannot comprehend with all his genius and knowledge. I pass 

 by his explanation of vegetable life, since he there speaks of a matter 

 of which he has not the slightest knowledge. But I must advert to 

 a proposition occurring at p. 49 : *' The nutrition of both animals 

 and vegetables is inconceivable without a secretion of excrementiti- 

 ous matter." Here again is more confusion. There are many very 

 different things which are conceivable. The secretion of excremen- 



