313 



2. On the Nutrition of Vegetables, by Dr H. R. Madden, 

 Penicuik. Part First. Communicated by Dr Christison. 



The object of the author in this part of his investigation, is to 

 shew that the portion of the food of plants which they receive from 

 the soil, and which he endeavours to prove is chemically combined 

 with it, — although to appearance generically the same in all soils, — 

 is not composed, as some imagine, of one single proximate principle, 

 the same in all circumstances, but consists of several principles va- 

 rying in their respective proportions in different soils. And he far- 

 ther attempts to establish the general proposition,, that the varying 

 proportion of these principles may be one great cause of the relative 

 fitness of different kinds of soil for the cultivation or nourishment of 

 different kinds of vegetables. 



In the course of explaining these views, which were supported 

 chiefly by speculative considerations, but which the author hopes to 

 confirm by experimental researches in which he isnow engaged, he had 

 occasion to refer to the doctrine recently advanced by Liebig, that the 

 relative fitness of different soils to different plants seems to depend, 

 not on the organic matter contained in them, but in a great measure 

 on their relative composition as to saline ingredients corresponding or 

 not corresponding with the composition and amount of saline ingre- 

 dients in plants. The author controverts this proposition, and en- 

 deavours to prove by reference to the composition of those soils in 

 which wheat reciprocally thrives or languishes, that Liebig' s doc- 

 trine is untenable. It is well known that a sandy soil, which, after 

 one process of manuring, will raise in succession an excellent crop of 

 turnips, barley, hay, and oats, nevertheless does not answer at all 

 well for wheat ; — which, on the contrary, produces most abundantly 

 on a clayey soil. Liebig holds the cause of this difference to be, 

 that in sandy soils there is not enough of the saline ingredients, 

 more especially of potash-salts, which are essential to the constitu- 

 tion of wheat. The author proves, however, by calculations founded 

 partly on experiments by Liebig himself, and partly on experimental 

 researches of his own, that sandy soil, after being properly treated 

 with farm-yard manure, not only contains a much larger amount of 

 saline matters, including potash-salts, than is required for the consti- 

 tution of a superior crop of wheat-straw and grain, but likewise, that 

 it actually supplies three times the quantity of salts, and among these, 

 three times the quantity of potash, required for a fine wheat crop, to 

 the turnips, barley, hay, and oats successively raised on it, and near- 



