86 
SECOND BOOK. 
together with stones and humus are what the soils 
we cultivate are made of. 
When we want to describe the kind of soil in our 
field or garden, we speak according to the quantity 
of clay or sand in it. 
5. If more than three-quarters of it is sand, we 
say it is a sandy soil, and if, on the other hand, 
more'than three-quarters of it is clay, we say it is 
a clay soil. Again, should it be nearly half sand and 
nearly half clay, we call it loam. But our garden 
soil has lime and humus in it. How then shall we 
describe it? If about one-fifth of the whole soil is 
lime, we call it marl ; and if there is a greater 
proportion of lime it is a chalky soil. It is a peaty 
soil if a large share in it consists of the decayed 
parts of plants. 
6. And does it matter what kind of soil we have ? 
Yes, indeed it does. For instance, a soil consisting 
entirely of clay or of sand will not do, for it does 
not contain the food that plants need. 
7 . You know why ponds that hold water for any 
length of time are only found in clayey soils. The 
water will not easily drain away from them. But 
it drains away very readily in sandy soils. So it is 
clear that a clayey soil will be wetter than a sandy 
soil, which lets the water run quickly through it; 
and, as some plants thrive with plenty of moisture, 
while others do best in drier situations, the condition 
of the soil is of great importance. 
