ACTION OF SALTS. 109 



forms an alkaline or earthy, or metallic geate, which, enter- 

 ing the plant as such, is there decomposed by the vegetable 

 acid produced in the living plant ; while the acid of the salt 

 thus let loose in the soil, acting on the silicates, forms new 

 salts, which, in their turn, play a similar part to that pro- 

 duced by the original salt. 



148. The eflfect of this action of salts is, that they contin- 

 ually reproduce themselves. The effect may be illustrated 

 by yeast, which added to dough, begets a new portion of 

 the fermenting principle, which again added to new dough, 

 still begets new leaven, and this without end. It is not to 

 be understood, from this illustration, that the action of salts 

 is fermentation. 



149. But let this action be farther illustrated; suppose 

 there is added a salt, composed of muriatic acid and soda, 

 that is common salt, to the soil. By the action of the living 

 plant, this is decomposed. Its soda, or base, then acts on 

 geine. If this has been long in an insoluble and perfectly 

 useless condition, it is now rendered soluble, and hence 

 supplies plants with food. A very marked and decided effect 

 is perceived from applying a small quantity per acre, of a 

 salt, which certainly of itself contains no nutriment for 

 plants. 



150. The effects here produced, may be due to the small 

 quantity of alkali, acting on an indefinite quantity of geine ; 

 but the effect so often observed, of the minute quantity of 

 salts, say one-hundredth of one per cent, of the soil, seems 

 hardly compatible with the explanation. So far as it goes, 

 this is its action ; but very probably the quantity of alkali 

 in the salt sown, is taken up as a geic salt, and immediately 

 carried into the plants. The base then is withdrawn, yet the 

 action continues. It continues through the whole time the 

 fruit is forming. Some other source, therefore, of the per- 



