The Soil 
3 
inorganic, matter, makes the soil richer, and higher forms 
of plants are thus able to obtain the necessary nourish- 
ment requisite for their full development and for the 
storing up of varying quantities of materials ultimately 
used as food for the lower and higher order of animals, 
and also for man. We can thus understand how, in the 
course of centuries, the soil would gradually become richer 
and richer, until we get the fertile soils of our farms and 
gardens. 
But not all soils are alike, either in texture or fertility. 
We will briefly consider some of the principal kinds of 
soil, and try to find out something about each of them. 
A. ALLUVIAL SOIL 
This may be taken as the most fertile of all soils. It 
is that soil which is carried down by rivers and deposited 
at their mouths, or where the rivers overflow their banks 
on the lower reaches of their course. It is deposited on 
the flat fields when the water drains away. The over- 
flowing of the River Nile provides an excellent example 
of this; it leaves behind a rich deposit of alluvial soil, 
which is the source of their livelihood to the natives. 
Now we know that this alluvial soil consists of very 
finely divided particles, and contains also a great amount 
of fertilizing matter. As we watch the little streams 
that are formed on the roads during heavy rain we see 
straws, particles of manure, &c., being swept along. The 
tiny streams which also run over the surface of the fields 
carry considerable quantities of fertilizing matter. All 
these make their way into the ditches, and thence into 
