220 AGRICULTURE. 



Fertik Soils. 



The best natural soils are those in which the ma- 

 terials have been derived from different strata, that 

 have been minutely divided by air and water, and are 

 intimately blended together. 



The absorbent power of soils from atmospheric 

 moisture is a proof of their fertility. 



Improvement of Soils. 



If there be an excess of calcareous matter in the 

 soil, it may be improved by the addition of sand and 

 clay. Soils too abundant in sand are benefited by 

 the use of clay, marie, or vegetable matter. Stiff 

 clays and marles have their earthy constituents in an 

 impalpable state of division, and are improved by 

 burning. 



In general the natural operation of water is to 

 bring earthy substances into an extreme state of di- 

 vision. 



Winter Irrigation. 



Water is of a greater specific gravity at 42 than 

 at 32, the freezing point ; hence, in a meadow irri- 

 gated in the winter, the water in contact with the 

 grass is rarely below 40, a degree of temperature 

 not at all prejudicial to the living organs of plants. 



Exhalation. 



From 2000 to 3000 gallons of water are exhaled 

 in a day from an acre of land. 



Limestone. 



When limestone is strongly heated the carbonic 

 acid gas is expelled, and then nothing remains but 

 the pure alkaline earth. 



As a cement, lime, applied in its caustic state, ac- 



