100 DRY-FARMING 
particles, to form one lineal inch. The clay particles 
are often smaller and of such a nature that they can- 
not be accurately measured. The total number of 
soil particles in even a small quantity of cultivated 
soil is far beyond the ordinary limits of thought, 
ranging from 125,000 particles of coarse sand to 
15,625,000,000,000 particles of the finest silt in one 
cubic inch. In other words, if all the particles in 
one cubic inch of soil consisting of fine silt were 
placed side by side, they would form a continuous 
chain over a thousand miles long. The farmer, 
when he tills the soil, deals with countless numbers 
of individual soil grains, far surpassing the under- 
standing of the human mind. It is the immense 
number of constituent soil particles that gives to 
the soil many of its most valuable properties. 
It must be remembered that no natural soil is 
made up of particles all of which are of the same size; 
all sizes, from the coarsest sand to the finest clay, 
are usually present (Fig. 17). These particles of all 
sizes are not arranged in the soil in a regular, orderly 
way; they are not placed side by side with geo- 
metrical regularity; they are rather jumbled together 
in every possible way. The larger sand grains touch 
and form comparatively large interstitial spaces 
into which the finer silt and clay grains filter. Then, 
- again, the clay particles, which have cementing 
properties, bind, as it were, one particle to another. 
A sand grain may have attached to it hundreds, or 
