as a nitrogenous and phosphatic manure, as the
quantity of potash it generally contains is small. In many soils, more
especially in such a country as Scotland, this deficiency in potash is
not of so much importance, as the value of potash as an artificial
manure is less than is the case with the other two ingredients. In
soils, however, lacking potash, guano ought to be supplemented with some
potash manure. With regard to the nitrogen and phosphoric acid, we may
ask if these two constituents are in the best proportions. This question
does not admit of a direct answer. In the first place, the proportion
in which these two ingredients are present is variable. In the old rich
Peruvian guanos, as we have above shown, the nitrogen was more abundant
than is the case at present. Such guanos, it was found, were best
supplemented with phosphatic manure when applied to the field. In the
"equalised" and "dissolved" guanos, which are now so largely sold,
manufacturers attempt to adjust the percentage of nitrogen and
phosphoric acid to what is considered the best proportion in most cases.
As, however, we have again and again to point out, regard must be had
both to the soil and the crop in determining what is the best proportion
of the manurial ingredients in a manure. For cereals it may be well
supplemented by nitrogenous manures, while for roots it may be well
supplemented by phosphatic manures.

_Mode of Application._

Like all manures, it is desirable to apply it in as fine a condition as
possible, so as to ensure as thorough a mixture with the soil-particles
as practicable. In order, furthermore, to prevent any risk of loss
through volatilisation of the ammonia, as well as to ensure even
distribution, it is best applied mixed with dry earth, ashes, sand, or
some other substance,--not lime, however. The custom of applying along
with the guano common salt, has been proved by numerous experiments to
be highly beneficial to the action of the guano as a manure. The exact
nature of the action of salt as an adjunct to manures is a point which
has elicited much discussion. Its action is probably to be ascribed to a
number of causes. For one thing, it probably acts as an antiseptic in
retarding the fermentative action which has a tendency to go on so
rapidly in such manures as guano. It further increases the power of the
manure to attract moisture from the air--a most important property in
the case of drought. Some experiments by Dr