ad not been
plowed for several years, and that although nature had done all she
could to clothe the soil with vegetation, the most disheartening feature
in the case was, the poverty of the weeds. A thistle may be a giant or a
dwarf, according to circumstances; here they were all dwarfs. The
plaintain, which I believe is sometimes sown in these districts for
food, has a very deep root; here the plants were abundant, but the
leaves were very small and lay so close to the ground, that, as the
manager informed me, "the sheep were often injured from the amount of
sand which they swallowed with the leaves when feeding."

At Rothamsted, the analyses of the rain water passing through the
ordinary soil of one of my fields, which has been kept free from
vegetation, have shown that the amount of nitric acid liberated in a
soil, and washed out each year, is very large. Taking the ten years
during which these special experiments have been in progress, I should
think that the loss of nitrogen would be equal to, or possibly exceed,
the amount of that substance removed by the average crops grown in the
United States.

The results obtained by the rain gauges, are further completely
confirmed by those in an adjoining field, where wheat and fallow have
been grown alternately for twenty-seven years. The liberation of nitric
acid, during the year of rest, produced for a time a large growth of
wheat, but it was done at a very great waste of the fertility of the
soil, and the produce is now, in proportion, considerably lower than
that grown on the continuously unmanured land.

These results, if they are to be accepted as correct, must bring about a
very considerable change in the generally received views in regard to
fertility. We not only see more clearly the connection between a former
vegetation and the stored up fertility in our soil, but we also see the
importance of vegetation at the present day, as the only means by which
the loss of nitric acid is prevented. The more completely the land is
covered with vegetation, and the more growth there is, the greater will
be the evaporation of water, and the less will be the loss of nitric
acid by drainage.

I was not at all surprised to find, that the surface soil of a wood on
my farm, was poorer in nitrogen than the soil of an old permanent
pasture, to which no manure had been applied for twenty-five years,
though during the whole period, the crop of hay had been removed every
year from th