nature, chlorine and sodium are not found in a free
or separate state; they hunted each other up long ago, and united to
produce the enormous quantities of rock salt that the earth holds. One
can give his imagination free range in trying to picture what takes
place when two or more elements unite chemically, but probably there is
no physical image that can afford even a hint of it. A snake trying to
swallow himself, or two fishes swallowing each other, or two bullets
meeting in the air and each going through the centre of the other, or
the fourth dimension, or almost any other impossible thing, from the
point of view of tangible bodies, will serve as well as anything. The
atoms seem to get inside of one another, to jump down one another's
throats, and to suffer a complete transformation. Yet we know that they
do not; oxygen is still oxygen, and carbon still carbon, amid all the
strange partnerships entered into, and all the disguises assumed. We can
easily evoke hydrogen and oxygen from water, but just how their
molecules unite, how they interpenetrate and are lost in one another, it
is impossible for us to conceive.

We cannot visualize a chemical combination because we have no experience
upon which to found it. It is so fundamentally unlike a mechanical
mixture that even our imagination can give us no clew to it. It is
thinkable that the particles of two or more substances however fine,
mechanically mixed, could be seen and recognized if sufficiently
magnified; but in a chemical combination, say like iron sulphide, no
amount of magnification could reveal the two elements of iron and
sulphur. They no longer exist. A third substance unlike either has taken
their place.

We extract aluminum from clay, but no conceivable power of vision could
reveal to us that metal in the clay. It is there only potentially. In a
chemical combination the different substances interpenetrate and are
lost in one another: they are not mechanically separable nor
individually distinguishable. The iron in the red corpuscles of the
blood is not the metal we know, but one of its many chemical disguises.
Indeed it seems as if what we call the ultimate particles of matter did
not belong to the visible order and hence were incapable of
magnification.

That mysterious force, chemical affinity, is the true and original
magic. That two substances should cleave to each other and absorb each
other and produce a third totally unlike either is one of th