sugar.
The water is rendered a conductor of electricity. Long ago
Faraday explained this as due to the presence of free atoms of
the dissolved salt in the solution, carrying electric charges. We
now speak of the salt as "ionised." That is it is partly split up
into ions or free electrified atoms of chlorine, sodium,
magnesium, etc., according to the particular salt in solution.
This fact leads us to think that these electrified

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atoms moving about in the solution may be the cause of the
clumping or flocculation. Such electrified atoms are absent from
the sugar solution: sugar does not become "ionised" when it is
dissolved.

The suspicion that the free electrified atoms play a part in the
phenomenon is strengthened when we recall the remarkable
difference in the action of sodium chloride and magnesium
chloride. In each of the solutions of these substances there are
free chlorine atoms each of which carries a single charge of
negative electricity. As these atoms are alike in both solutions
the different behaviour of the solutions cannot be due to the
chlorine. But the metallic atom is very different in the two
cases. The ionised sodium atom is known to be _monad_ or carries
but _one_ positive charge; whereas the magnesium atom is _diad_ and
carries _two_ positive charges. If, then, we assume that the
metallic, positively electrified atom is in each case
responsible, we have something to go on. It may be now stated
that it has been found by experiment and supported by theory that
the clumping power of an ion rises very rapidly with its valency;
that is with the number of unit charges associated with it. Thus
diads such as magnesium, calcium, barium, etc., are very much
more efficient than monads such as sodium, potassium, etc., and
again, triads such as aluminium are, similarly, very much more
powerful than diad atoms. Here, in short, we have arrived at the
active cause of the phenomenon. Its inner mechanism

58

is, however, harder to fathom. A plausible explanation can be
offered, but a study of it would take us too far. Sufficient has
been said to show the very subtile nature of the forces at work.

We have here an effect due to the sea salts derived by denudation
from the land which has been slowly augmenting during geological
time. It is certain that the ocean was practically fresh water in
remote ages. During those times the silt from the great rivers
would have been carried very far from the land. A M