96 FIRST PRINCIPLES OF AGRICULTURE. 



important source of potash is the Stassfurt mines of 

 Germany. These mines consist of deposits of crude 

 salts, which have doubtless been formed by the evapo- 

 ration of the water in an inland sea. They have been 

 worked since 1862 ; and, while enormous quantities have 

 been removed, the extent of the deposits is so great 

 as to appear inexhaustible. 



These salts, as mined, contain relatively small per- 

 centages of actual potash, and considerable quantities 

 of other salts, some of which are injurious to plants, 

 though a number of the crude salts are used directly 

 upon the land. 



The crude products of the mines, shipped and sold in 

 this country, consist chiefly of kainit and sylvinit, and the 

 manufactured products are muriate of potash, sulphate of 

 potash, and sulphate of potash and magnesia. 



These salts are all completely soluble in water, and 

 equally available as sources of food to plants. The 

 forms have reference mainly to the effect, good or bad, 

 upon the growth of plants, of the constituents with 

 which the potash is combined, or the other salts 

 with which the potash is associated. Chlorides are be- 

 lieved to be less desirable than the sulphates for cer- 

 tain crops. 



Forms of Potash. — The commercial potash salts 

 used are of two distinct chemical forms, — one in which 

 the potash is combined with chlorine to form chloride 

 of potassium, or, as it is more generally called, "muriate 

 of potash ; " the other in which the potash is combined 

 with sulphuric acid to form " sulphate of potash." 



Kainit. — This is the only crude product that is 



