ACTION OF SALTS. 119 



of salts which may be applied, will be greatest in the 

 carbonates, next in the nitrates, and thirdly in the 

 phosphates. The quantity of any salt which may 

 be used will, after the largest amount, which can be 

 safely employed has been ascertained, depend upon 

 the farmer's ability to produce it. Carbonate of lime, 

 may be used to any extent, according to the farmer's 

 idea of its value. Carbonates of alkali may be used, 

 with benefit. The largest quantity which has been 

 known to be used without injury, has been 53 bush- 

 els of ashes per acre, which are equal to 240 lbs. of 

 potash. The quantity of the carbonates of alkali, 

 which may be used, will be stated more fully here- 

 after. It is not the object of this work, to state 

 quantities to be used, so much as to point out the 

 principles on which salts act. The quantities used, 

 must be determined by experiment, and perhaps 

 when the largest amount, which has been stated, is 

 taken for a new starting point, the ultimate quantity, 

 will be found limited only by the geine in the soil, 

 or applied in conjunction with the salt. 



170. If we now turn to the other division of salts, 

 the poisons, that is those whose acid forms but a 

 small portion of the elements of plants, we find 

 two classes : First, sulphates, as plaster, copperas, 

 Glauber's salts, all of which in small quantities, are 



