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 Mississippi of
those ages would have sent its finer suspensions far abroad on a
contemporary Gulf stream: not improbably right across the
Atlantic. The earlier sediments of argillaceous type were not
collected in the geosynclines and the genesis of the mountains
was delayed proportionately. But it was, probably, not for very
long that such conditions prevailed. For the accumulation of
calcium salts must have been rapid, and although the great
salinity due to sodium salts was of slow growth the salts of the
diad element calcium must have soon introduced the cooperation of
the ion in the work of building the mountain.
59
THE ABUNDANCE OF LIFE [1]
WE had reached the Pass of Tre Croci[2]and from a point a little
below the summit, looked eastward over the glorious Val Buona.
The pines which clothed the floor and lower slopes of the valley,
extended their multitudes into the furthest distance, among the
many recesses of the mountains, and into the confluent Val di
Misurina. In the sunshine the Alpine butterflies flitted from
stone to stone. The ground at our feet and everywhere throughout
the forests teamed with the countless millions of the small black
ants.
It was a magnificent display of vitality; of the aggressiveness
of vitality, assailing the barren heights of the limestone,
wringing a subsistence from dead things. And the question
suggested itself with new force: why the abundance of life and
its unending activity?
In trying to answer this question, the present sketch
originated.
I propose to refer for an answer to dynamic considerations. It is
apparent that natural selection can only be concerned in a
secondary way. Natural selection defines