108 ACTION OF SALTS, 



general principle is wanted, which will enable the farmer to 

 say what the action of a salt will be ; and whether he may 

 apply one, or less than one per cent, of it, without risking 

 his crop. 



145. Such a general principle can be deduced from the 

 known chemical action of the elements of soil, aided by the 

 living plants, upon each other. It is this tenth principle of 

 agricultural chemistry, the base of all salts acts ever the 



SAME IN agriculture. PECULIARITY OF ACTION DEPENDS ON 

 THE ACID OF THE SALT. 



146. Forget, reader, all other principles which have been 

 presented to you. Banish from your mind, if you will, all 

 that has been said, on the origin and nature of soil. Put it 

 down, all, all to the account of book farming. Let it be 

 branded all as theory, and that too as the worst of theories, 

 theory fruitless, a goodly blossom bearing no fruit, a Dead 

 Sea apple ; but do not condemn the principle now enunciated. 

 Let that stand alone, by itself, for itself In all its length 

 and breadth, it is the great practical principle of agricultural 

 chemistry. It opens veins rich in results, more precious 

 than mines of gold. 



147. The action of salts in agriculture, is to be regarded 

 in a twofold light. First, a large proportion of salts is found 

 in plants, composed of alkalies and alkaline bases of earths, 

 united to a mineral acid, such as sulphuric, muriatic, phos- 

 phoric. These salts are taken up by the roots of plants 

 when dissolved in water, and thus form a constituent of veg- 

 etables. Secondly, a large quantity of alkali and alkaline 

 earths is united in plants, with a vegetable acid. In this 

 case the salts of the soil have been decomposed by the 

 living plant. What is the consequence ? The base, if 

 alkali, lime, alumina, magnesia, iron, acts upon geine, ren- 

 dering that soluble, and it is then taken up as such, or it 



