of the mines. They are both known in commerce under the
name of "bay-salt," to distinguish them from the "rock-salt" of the
mines. Great natural beds of the bay-salt are found in the Cape de
Verde islands; also in Turk's island and Saint Martin's in the West
Indies, and on Kangaroo Island, near the coast of Australia.

"`There is still a third plan of making salt out of the sea. That is,
by boiling the water, as we are doing; but this makes the worst of all
salt; besides, it is far more expensive to manufacture salt in this way
than to buy it from other countries. Indeed, this last plan would never
be adopted, were it not that some foolish governments force their people
to pay a heavy duty for importing salt into their country, thus making
it still cheaper for them, costly as it is, to manufacture the article
at home.'

"`What makes the sea salt, papa?'

"`That is one of the phenomena about which naturalists have a difference
of opinion. Some of them say there are vast beds of salt at the bottom
which keep the water always impregnated. I think this notion is very
childish; and they who hold it offer only childish arguments to support
it. Others assert that the salt water of the ocean is a primitive
fluid--that it was always as it now is--which you will perceive is
giving no reason at all, more than saying, "it is salt, because it was
salt always." This is an equally irrational theory. Others, again,
believe that the saltness of the ocean is caused by the flowing into it
of salt rivers. These, I think, hold the true opinion; but
unfortunately they have failed, as far as I know, to answer the
objections which have been raised against it. Your papa has reflected a
good deal upon this subject, and believes that he can explain away all
the difficulties that oppose this last theory. Probably he may take an
early opportunity of doing so; but it will require more time than he can
spare at present.'

"`Is the sea equally salt at all places?' inquired the philosopher
Frank, after a short pause, during which he had been busily reflecting
on what had been said.

"`No; it is more so at the Equator than in the colder regions around the
Poles. It is less salt in gulfs and inland seas than in the open ocean.
This I believe I can also explain, because it would support the theory
regarding the rivers of which we have just spoken. The difference of
saltness in different parts of the sea is, however, very trifling.'

"