because,
although we are very apt to think our own case an exception to all
general rules, it is not really probable that any new kind of clay will
be discovered hereafter, that is so different from all other clay that
is known, that established principles will not apply to it. So far as
our own observation extends, owners of clay farms always over-estimate
the difficulty of draining their land. There are certain notorious facts
with regard to clay, which mislead the judgment of men on this point.
One of these facts is, that clay is used for stopping water, by the
process called _puddling_. Puddled clay is used for the bottom of ponds,
and of canals, and of reservoirs, and, for such purposes, is regarded as
nearly, or quite impervious.

We see that, on our clay fields, water stands upon the surface,
especially in the ruts of wheels, and on headlands much trodden, late in
the season, and when, in other places, it has disappeared. This is due,
also, to puddling.

Puddling is merely the working of wet clay, or other soil, by beating,
or treading, or stirring, until its particles are so finely divided that
water has an exceedingly slow passage between them, with ordinary
pressure. We see the effect of this operation on common highways, where
water often stands for many days in puddles, because the surface has
been ground so fine, and rendered so compact, by wheels and horses, that
the water cannot find passage. This, however, is not the natural
condition of any clay; nor can any clay be kept in this condition,
except by being constantly wet. If once dried, or subjected to the
action of frost, the soil resumes its natural condition of porosity, as
will be presently explained. They who object to deep drainage, or to the
possibility of draining stiff clays, point to the fact that water may be
seen standing directly over the drains, on thorough-drained fields. We
have seen this on our own fields. In one instance, we had, after laying
tiles through a field, at 50 feet intervals, in the same Autumn, when
the land was wet, teamed across it a large quantity of soil for compost,
with a heavy ox-team. The next Spring, the water stood for many days in
that track which passed across tile-drains, after it had disappeared
elsewhere in the field. A fine crop of Indian corn grew on the field
that year, but the effect of the puddling was visible the whole season.
"One inch of wet and worked clay," says a scientific writer, "will
prevent w