phere it must have been derived. Did not the fields of Virginia
receive their nitrogen from the same source as wild plants?

Is the supply of nitrogen in the excrements of animals quite a
matter of indifference, or do we receive back from our fields a
quantity of the elements of blood corresponding to this supply?

The researches of Boussingault have solved this problem in the most
satisfactory manner. If, in his grand experiments, the manure which
he gave to his fields was in the same state, i.e. dried at 110 deg
in a vacuum, as it was when analysed, these fields received, in 16
years, 1,300 pounds of nitrogen. But we know that by drying all the
nitrogen escapes which is contained in solid animal excrements, as
volatile carbonate of ammonia. In this calculation the nitrogen of
the urine, which by decomposition is converted into carbonate of
ammonia, has not been included. If we suppose it amounted to half as
much as that in the dried excrements, this would make the quantity
of nitrogen supplied to the fields 1,950 pounds.

In 16 years, however, as we have seen, only 1,517 pounds of
nitrogen, was contained in their produce of grain, straw, roots, et
cetera--that is, far less than was supplied in the manure; and in
the same period the same extent of surface of good meadow-land (one
hectare = a Hessian morgen), which received no nitrogen in manure,
2,062 pounds of nitrogen.

It is well known that in Egypt, from the deficiency of wood, the
excrement of animals is dried, and forms the principal fuel, and
that the nitrogen from the soot of this excrement was, for many
centuries, imported into Europe in the form of sal ammoniac, until a
method of manufacturing this substance was discovered at the end of
the last century by Gravenhorst of Brunswick. The fields in the
delta of the Nile are supplied with no other animal manures than the
ashes of the burnt excrements, and yet they have been proverbially
fertile from a period earlier than the first dawn of history, and
that fertility continues to the present day as admirable as it was
in the earliest times. These fields receive, every year, from the
inundation of the Nile, a new soil, in its mud deposited over their
surface, rich in those mineral elements which have been withdrawn by
the crops of the previous harvest. The mud of the Nile contains as
little nitrogen as the mud derived from the Alps of Switzerland,
which fertilises our fields after the inundations of the Rhine.