THE PHILOSOPHY OF FARMING. 581 
collecting in the subsoil, and rising up and 
swamping the surface. In such soils no cultiva- 
tion can succeed without a thorough drainage. 
No exact practical rule can be laid down for 
draining ; yet one axiom may apply to all methods 
employed, or which may be employed, and that 
is, no kind of drainage is perfect which does not 
carry off the superfluous water as quickly as 
possible. After a heavy fall of rain, or continued 
wet weather, main drains should never discharge 
water beyond four or five days at the utmost; 
and the less time they continue to flow, the better 
in all cases. So imperfect, however, is drainage 
in general, that we see main drains pouring out 
water week after week in fine weather, and 
scarcely ever ceasing, unless in continued drought. 
Whatever methods have been employed, acting 
so, they are practically useless. Drains, whatever 
be their kind, ought to be so deep that the water 
which percolates into them should all fall within 
the subsoil without having any chance of coming 
into contact with the soil. For we might as well 
expect to dry a sponge by lifting it out of water 
and letting its base touch the surface, as to dry 
wet ground by allowing the soil to come in contact 
with the water within the drains. If the sub- 
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