l food being of the
very highest importance. It is an indispensable food-ingredient for
animal life. With regard to ordinary farm-stock, the amount of salt
which naturally occurs in their food is quite sufficient. In the case,
however, of pastures in countries far removed from the sea, the custom
of specially supplying stock with salt is common. This is done by
placing a piece of rock-salt in the fields.

_Special Sources of Salt._

The salt of commerce is obtained from various sources. Besides the sea,
we have ample sources of salt in the large saline deposits found in many
parts of Europe, especially in Austria, and in England in Cheshire.

_The Action of Salt indirect._

From what has been said above, it is clear that the action of salt as a
manure is indirect and not direct. What the nature of that indirect
action is we shall now proceed to discuss.

In considering the evidence of the manurial value of salt, we are at
once brought face to face with the fact that the experience of its
action in the past has as often been unfavourable as favourable. Salt,
it is well known, is both an antiseptic and a germicide. It is, indeed,
one of the most commonly used of preservatives. When applied in large
quantities to the soil, it has a most deleterious action on vegetation.
This hurtful action of salt has long been known; and it is as often
mentioned in the writings of antiquity on account of its unfavourable as
on account of its favourable action. Thus, for example, among the
ancient Jews it was customary, after the conquest of a hostile town, to
strew salt on the enemy's fields, for the purpose of rendering them
barren and unfertile. And again, among the Romans, for the same purpose,
salt was often spread on a spot where some great crime had been
committed.

While, therefore, its unfavourable action has long been known, the fact
that there are circumstances under which its action is, on the contrary,
favourable for promoting vegetable growth has also been long recognised.
The difficulty for the agricultural student is to reconcile these two
seemingly contradictory experiences. For the English agriculturist the
subject possesses especial interest, since in England it has been in the
past most generally used and its action most discussed since the time of
Lord Bacon, who discusses in his writings the action of solutions of it
on different plants.

The true explanation of salt being so different in its action is to