230 THE FARMER OF TO-MORROW 



ing minerals that make up our soils are prac- 

 tically the same the world over, so the experi- 

 ment holds good for broad conditions. Take 

 these ordinary rocks and grind them in a 

 mortar until they are as fine as the soil par- 

 ticles themselves. How fine this should be can 

 be determined by the number of particles re- 

 quired to form a linear inch. In our clay soils, 

 the particles number 5,000 and over; in silt, 

 500 to 5,000; very fine sand, 250 to 500; fine 

 sand, 100 to 250. 



Thus a cubic inch of clay would contain 

 125,000,000,000 particles. This type of soil 

 is an ordinary one. By a calculation it is sim- 

 ple enough to determine how much greater 

 surface it would present to the soluble action 

 of water than if the clay were a solid cube of 

 one inch dimensions. Apply the parallel of 

 the solubility of glass here. 



Such a test actually was made by Frank K. 

 Cameron and James M. Bell (The Mineral 

 Constituents of the Soil Solution, Bulletin 30, 

 Bureau of Soils ) , and prolonged over a course 

 of months. It was conducted by means of an 

 ingenious electrical contrivance which insured 

 a continuous flow of water over the rock 

 particles. 



