456 SELECTIONS FROM ADDRESSES. 



spar and mica, two of the most abundant minerals, constituting 

 granite, gneiss, and mica slate rocks, furnishing them by their 

 slow decomposition in the soil. 



Those minerals contain from twelve to sixteen per cent, of 

 potash and soda, combined with silicic acid. They are insolu- 

 ble in water, but by means of carbonic acid, disengaged by de- 

 caying vegetable matter, the silicates are decomposed and car- 

 bonates of the alkalies are formed, which are soluble in water, 

 and go to nourish plants, and serve as solvents of the humus of 

 the soil, so that it can be absorbed by plants. 



The vegetable acids, derived from decaying peat and rotten 

 wood, also have the property of slowly acting upon feldspar 

 and mica, and separate the alkaline matter. A small proportion 

 of the silex is also dissolved by the action of the liberated al- 

 kalies, and goes into the vegetable economy, forming a part of 

 the solid structure of the sap vessels, and shielding the surface 

 of delicate hollow stems with a layer of glass, serving to pre- 

 vent their destruction by mildew and rust, while it prevents the 

 loaded stem from breaking down under its burden of grain. 



Ashes of plants containing these alkalies and soluble sili- 

 cates is one of the best of fertilizers, and may be justly regard- 

 ed as an universal manure, containing all those inorganic ele- 

 ments that are known to be constituents of plants. 



Leached ashes, although deprived of part of its alkaline mat- 

 ter, is valuable as a manure, for it is capable of yielding still 

 more to the searching powers of the rootlets of plants, and 

 contains other materials, insoluble in a great measure in water, 

 which are capable of being slowly taken up by growing vege- 

 tables. Experience has proved that 200 bushels of leached 

 ashes will render fertile for many years the sandy soil of a pine 

 barren, which before was a waste of blowing sand. 



Lime, in the state of carbonate, and in combination with 

 various organic acids of the soil, is also a valuable manure, and 

 operates favorably for a long term of years, enabling soils that 

 were before unproductive, to bear heavy crops of grain. 



Magnesia enters into the composition of all plants, though in 

 smaller proportions than the other mineral ingredients I have 

 named. In the state of phosphate, it is a constituent of both 



