6 
STIRRING THE SOIL. [chap. i. 
operate only partially, and are yet almost as 
necessary to be attended to. When manure 
is applied, the ground is generally well dug, 
in order to mix the manure intimately with 
the soil; and when the soil appears worn 
out, or poisoned with excrementitious matter, 
from the same kind of plants being too long 
grown in it, it is trenched; that is, the upper 
or surface soil is taken off by spadefuls and 
laid on one side, and the bottom or sub-soil 
is taken out to a certain depth previously 
agreed on, and laid in another heap. The 
surface soil is then thrown into the bottom 
of the trench, and the sub-soil laid on the 
surface, and thus a completely new and fresh 
soil is offered to the plants. These partial 
uses of digging should, however, always be 
applied with great caution, as in some cases 
manure does better laid on the surface, so 
that its juices only may drain into the 
ground, than when it is intimately mixed 
with the soil; and there are cases when, from 
the sub-soil being of an inferior quality, 
trenching must be manifestly injurious. Rea¬ 
son and experience are, in these cases, as 
in most others, the best guides. 
