28 MANURING THE SOIL. [chap. ii. 
thus not supplied with more food at a time 
than they can properly take up and digest, 
and a healthy circulation of the fluids is 
kept up through the whole plant. But, 
what, it may be asked, is to be done with a 
garden, the soil of which has become black 
and slimy like half-rotten peat ? The quick¬ 
est remedy is covering it with lime, as that 
combines readily with the humic acid, and 
reduces it to a state of comparative dry¬ 
ness : or, if the sub-soil be good, the ground 
may be trenched, and the surface-soil buried 
two spits deep; in either case it will be ne¬ 
cessary thoroughly to drain the garden to 
prevent a recurrence of the evil. 
All the different kinds of soil found on 
level ground, consist of two parts, which are 
called the surface-soil and the sub-soil; and 
as the sub-soil always consists of one of 
the three primitive earths, so do these earths 
always enter, more or less, into the com¬ 
position of every kind of surface-soil. The 
primitive earths are —silex, (which includes 
sand and gravel,) clay, and lime, which in¬ 
cludes also chalk; and most sub-soils consist 
of a solid bed or rock of one or other of these 
