20 THE OLIVER PLOW BOOK 



marble will touch six points of the cube and all the rest 

 of the space between the cube and the surface of the 

 marble is air space. The area of the surface of the 

 marble is found by multiplying the diameter squared by 

 3.1416, making 3.1416 square inches of film surface for 

 the water. This is the amount of the film surface dis- 

 played. 



A cube one inch square will hold 1 ,000 marbles one- 

 tenth of an inch in diameter. The square inch of surface 

 of each marble one-tenth of an inch in diameter is one 

 hundredth of what it is on the large marble, or .031416 

 of an inch. This multiplied by 1 ,000, the number of 

 marbles of this diameter required to fill the cube, makes 

 31.416 square inches of film surface, in contrast with the 

 3.1416 displayed in the one marble. Thus, if you take 

 the 1 ,000 marbles in the cube immersing them in water, 

 and withdrawing them as you would the large marble, 

 you would have 31.4+ square inches of surface holding 

 water, against 3.1+ square inches on the large marble. 

 This means that the air spaces have been diminished in 

 size and the water holding content of the soil increased, 

 proving that the finer the soil is broken up, the greater 

 water-holding capacity it has, consequently, the break- 

 ing of the soil into fine particles is necessary to improve 

 it for water holding content. For this reason the 

 ground should be well pulverized when plowing. 



It is further evident, from the marble illustration, that 

 the size of the soil particles has everything to do with 

 the water holding content. As an illustration of the 

 capacities of different soils, for capillary attraction and 

 for holding water, samples of clay, clay loam, loam, 

 sandy loam, and loamy sand were placed in the tubes 

 under the names, small clods being placed on top of the 



