d, which is abundantly supplied with
such manures.

Lastly. And this is the most curious deduction to be derived from
the above facts,--if we plant potatoes, wheat, turnips, peas, and
clover, (plants containing potash, lime, and silex,) upon the same
land, three times manured, we gain in 16 years, for a given quantity
of carbon, the same proportion of nitrogen which we receive from a
meadow which has received no nitrogenised manure.

On a morgen of meadow-land, we obtain in plants, containing silex,
lime, and potash, 984 carbon, 32.2 nitrogen. On a morgen of
cultivated land, in an average of 16 years, in plants containing the
same mineral elements, silex, lime, and potash, 857 carbon, 26.8
nitrogen.

If we add the carbon and nitrogen of the leaves of the beetroot, and
the stalk and leaves of the potatoes, which have not been taken into
account, it still remains evident that the cultivated fields,
notwithstanding the supply of carbonaceous and nitrogenised manures,
produced no more carbon and nitrogen than an equal surface of
meadow-land supplied only with mineral elements.

What then is the rationale of the effect of manure,--of the solid
and fluid excrements of animals?

This question can now be satisfactorily answered: that effect is the
restoration of the elementary constituents of the soil which have
been gradually drawn from it in the shape of grain and cattle. If
the land I am speaking of had not been manured during those 16
years, not more than one-half, or perhaps than one-third part of the
carbon and nitrogen would have been produced. We owe it to the
animal excrements, that it equalled in production the meadow-land,
and this, because they restored the mineral ingredients of the soil
removed by the crops. All that the supply of manure accomplished,
was to prevent the land from becoming poorer in these, than the
meadow which produces 2,500 pounds of hay. We withdraw from the
meadow in this hay as large an amount of mineral substances as we do
in one harvest of grain, and we know that the fertility of the
meadow is just as dependent upon the restoration of these
ingredients to its soil, as the cultivated land is upon manures. Two
meadows of equal surface, containing unequal quantities of inorganic
elements of nourishment,--other conditions being equal,--are very
unequally fertile; that which possesses most, furnishes most hay. If
we do not restore to a meadow the withdrawn elements, its fertility
decrease