ACTION OF SALTS OR MINERAL MANURES. 95 



143. On no subject in agriculture, are opinions 

 more divided, than on the manner, how salts or min- 

 eral manures act. Their amount in soil is small. 

 That is soon exhausted. They cannot be artificial- 

 ly supplied, in excess, without inducing very seri- 

 ous injury, and in fact, often produce barrenness ; 

 yet are often decidedly beneficial. It is not less dif- 

 ficult to account for the good, than for the bad effects 

 of salts. Among all the variety of substances act- 

 ing as salts, a distinct theory is generally framed and 

 adopted for each. If any attempt has been made 

 to arrange all the facts relating to this subject, it has 

 ended in this, that they are stimulants. They are 

 to the plants, what condiments are to the food of 

 man. This may do very well as an illustration, and 

 it has been elsewhere said, that " the soil is the 

 plate, the geine the food, the salt the seasoning." 



144. This leads to no practical result, except it 

 be this — that if salts are seasoning, like the season- 

 ing of our food, they must be used sparingly. Some 

 general law is wanting, which shall at once, account 

 for the effects of salts, and while it points out how so 

 very minute a portion as the four-hundredth part of 

 one per cent, produces unquestionably good effects, 

 one per cent, will be injurious. Some general prin- 

 ciple is wanted, which will enable the farmer to say 



