102 ACTION OF SALTS. 



be the effect of salts, applied to soil produced by the 

 decomposition of slate ; even gneiss soil, which oc- 

 curs occasionally in extensive patches, would be 

 benefitted, but much less by such application. But 

 such soil forms an exception, both to the general law, 

 which has. been n stated, of the uniformity of mineral 

 composition, and to the necessity of applying salts 

 ai.d geine in conjunction. These remarks may ex- 

 plain a seemingly possible anomaly to the principle, 

 that the base of all salts acts in one uniform manner' 

 upon geine, and that peculiarities of action depend 

 on the acid of the salt. The effects of the first part 

 of this proposition have been explained ; the effect 

 of the second, is now to be considered. 



156. Perhaps no principle in agriculture, is better 

 established than that an excess of any salt in the 

 usual acceptation of that term, is a cause of barren- 

 ness. Yet it is quite as well established, that the 

 quantity of different salts admits of some latitude; 

 and that some salts do produce better results than 

 Others. Referring to the acid constituents of these 

 salts, it will be found that some acids are organic. 

 They consist of hydrogen, carbon, oxygen, all which 

 under the influence of the living plant, may be dis- 

 sociated, and their elements form geine. Other 

 acids consist of oxygen and nitrogen, essential con- 



