Proceedings of the Boxjal Society of Edinburgh. 431 

 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, bat which the author hopes to 

 confirm by experimental researches in which he is now 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 Liebia'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- 

 tute 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- 

 ly double the quantity of potash necessary for the wheat to the tur- 

 nips alone. These facts will appear from the following table :_ 

 Salts in an imperial acre of— 



Total Salts. Potash. 



VVllcat J •... 358.3 lb. 60. lb. 



TIic crops of a rota- \ Turnips, . . . 3897... 92~4 . 



tion after a single ( Barley, .... 310.0 ... 40.0 ... 



application of ma- | May, .... 200.0... 20.0 ] 



uure, viz. :— J Oats, .... 207.0... 20.0.'.'. 



Total, 110G.7... 172U... 



