14 
The stagnant water which had filled the pores of 
the soil, (allowing, and aiding in some cases, deposits 
of peroxide of iron, and in others, deposits of carbo- 
nate of iron or of lime, any of which will cement the 
earthy or stony particles together, forming hard pan,) 
is removed, and its place is at once supplied by fresh 
air from the surface, which air is in its turn driven 
down into the drains by the falling of rain; and this 
process is constantly repeated. The subsoil is thus 
made more porous and friable while being mixed 
with the surface soil, and the deposits which cemented 
the particles of soil can no longer be made. 
Experience has shown that these renewed acces- 
sions of fresh air are very valuable in promoting the 
healthy growth and the quality of all cultivated crops. 
It will be noticed that for more readily admitting 
fresh air, draining is necessary, even in the most por- 
ous subsoil. Every new working of the ground 
increases the efficiency of the drains, and extends that 
action which gradually but surely improves the depth 
and character of the soil. | 
The water of rains running over the surface 
injuriously washes away the soil. This evil is averted 
by drains, which allow the surplus water to pass read- 
ily through the soil; while in filtering through, it im- 
parts to the soil those substances useful to vegeta- 
tion which rain water always contains, in more or less 
abundance. When the water is thus readily carried 
away, the soil becomes drier, sweeter, and more fri- 
able; the hard lumps of clay lands crumble away 
