d
their produce, as if by a miracle, when dressed with bone earth
imported from the Continent. But if the export of bones from Germany
is continued to the extent it has hitherto reached, our soil must be
gradually exhausted, and the extent of our loss may be estimated, by
considering that one pound of bones contains as much phosphoric acid
as a hundred-weight of grain.

The imperfect knowledge of Nature and the properties and relations
of matter possessed by the alchemists gave rise, in their time, to
an opinion that metals as well as plants could be produced from a
seed. The regular forms and ramifications seen in crystals, they
imagined to be the leaves and branches of metal plants; and as they
saw the seed of plants grow, producing root, stem and leaves, and
again blossoms, fruit and seeds, apparently without receiving any
supply of appropriate material, they deemed it worthy of zealous
inquiry to discover the seed of gold, and the earth necessary for
its development. If the metal seeds were once obtained, might they
not entertain hopes of their growth?

Such ideas could only be entertained when nothing was known of the
atmosphere, and its participation with the earth, in administering
to the vital processes of plants and animals. Modern chemistry
indeed produces the elements of water, and, combining them, forms
water anew; but it does not create those elements--it derives them
from water; the new-formed artificial water has been water before.

Many of our farmers are like the alchemists of old,--they are
searching for the miraculous seed,--the means, which, without any
further supply of nourishment to a soil scarcely rich enough to be
sprinkled with indigenous plants, shall produce crops of grain a
hundred-fold.

The experience of centuries, nay, of thousands of years, is
insufficient to guard men against these fallacies; our only security
from these and similar absurdities must be derived from a correct
knowledge of scientific principles.

In the first period of natural philosophy, organic life was supposed
to be derived from water only; afterwards, it was admitted that
certain elements derived from the air must be superadded to the
water; but we now know that other elements must be supplied by the
earth, if plants are to thrive and multiply.

The amount of materials contained in the atmosphere, suited to the
nourishment of plants, is limited; but it must be abundantly
sufficient to cover the whole surface