136 THE CULTURE OF FARM CROPS. 



form a curve, or line which marks the gradual approach 

 of the two. The liquid rises higher as the space 

 between the plates is closer. This is due to capillary ac- 

 tion. The same action is exerted in the spaces between the 

 particles of the soil; the vertical spaces forming tubes through 

 the mass. 



When water is poured into the saucer of a flower pot the 

 soil gradually draws it up until the top is moistened. This 

 takes place in the soil of a field; the water being gradually 

 drawn up from below until the capacity to hold it is fully 

 exercised. Thus there is a constant ebb and flow of water 

 in the soil. The rains descend and sink into the soil 

 finding an outlet in springs at a lower le'vel ; or a rest- 

 ing place in the subsoil ; and it is gradually brought to 

 the surface again by this capillary attraction to supply the 

 crops. The soil is charged with saline and other soluble 

 plant food ; and as the water is everywhere diffused through 

 the soil these fertilizing matters are spread through it, find- 

 ing their way with the waters among the interstices between 

 the smallest particles. As the soil is filled with water in 

 wet weather, and the water sinks, it necessarily carries this 

 saline matter with it, but this is all brought back again as 

 the surface dries and the moisture rises again in obedience 

 to this natural law. Successive portions of water rise to the 

 surface, evaporate into the air, or pass by transpiration 

 through the leaves of plants, leaving fertilizing matter be- 

 hind them. Thus in the growing season a large supply of 

 food for plants is brought up from below, within the reach 

 of their roots, and diffused intimately through the soil, so 

 that the finest fiber of the feeding roots is supplied, and as 

 this ascent of water and evaporation of it, go on all through 

 the dry weather of the summer, the fertilizing matter accum- 

 ulates in the surface soil about the roots of the crops and 

 places within their reach an ample supply of every soluble 

 substance which is existing in the soil. As one may make 

 a fire and see the smoke ascend and become diffused 

 throughout the atmosphere and disappear, but yet perceive 

 its odor even at a long distance from the fire, so the fertiliz- 



