in June to 66 degrees at seven inches below the surface, while in the
neighboring water-logged land it would never rise above 47 degrees--an
enormous gain."

In his prize essay on drainage, Dr. Madden confirms the above, and
explains further, as follows: "An excess of water injures the soil by
diminishing its temperature in summer and increasing it in winter--a
transformation of nature most hurtful to perennials, because the vigor
of a plant in spring depends greatly on the lowness of temperature to
which it has been subjected during the winter (within certain limits,
of course), as the difference of temperature between winter and spring
is the exciting cause of the ascent of the sap." In other words, too
much water in the soil may cause no marked difference between the
underground climate of winter and spring.

Dr. Madden shows, moreover, that excess of water keeps out the air
essential not only in promoting chemical changes in the soil itself
and required by the plants, but also the air which is directly needed
by the roots. Sir H. Davy and others have proved that oxygen and
carbonic acid are absorbed by the roots as well as by the foliage, and
these gases can be brought to them by the air only.

Again, drainage alters the currents which occur in wet soil. In
undrained land, evaporation is constantly bringing up to the roots the
sour, exhausted water of the subsoil, which is an injury rather than a
benefit. On the other hand, the rain just fallen passes freely through
a drained soil, carrying directly to the roots fresh air and
stimulating gases.

Wet land also produces conditions which disable the foliage of plants