II

The molecules and atoms and electrons into which science resolves matter

are hypothetical bodies which no human eye has ever seen, or ever can

see, but they build up the solid frame of the universe. The air and the

rocks are not so far apart in their constituents as they might seem to

our senses. The invisible and indivisible molecules of oxygen which we

breathe, and which keep our life-currents going, form about half the

crust of the earth. The soft breeze that fans and refreshes us, and the

rocks that crush us, are at least half-brothers. And herein we get a

glimpse of the magic of chemical combinations. That mysterious property

in matter which we call chemical affinity, a property beside which human

affinities and passions are tame and inconstant affairs, is the

architect of the universe. Certain elements attract certain other

elements with a fierce and unalterable attraction, and when they unite,

the resultant compound is a body totally unlike either of the

constituents. Both substances have disappeared, and a new one has taken

their place. This is the magic of chemical change. A physical change, as

of water into ice, or into steam, is a simple matter; it is merely a

matter of more or less heat; but the change of oxygen and hydrogen into

water, or of chlorine gas and the mineral sodium into common salt, is a

chemical change. In 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 the profound

mysteries of science. Of the nature of the change that takes place, I

say, we can form no image. Chemical force is selective; it is not

promiscuous and indiscriminate like gravity, but specific and

individual. Nearly all the elements have their preferences and they will

choose no other. Oxygen comes the nearest to being a free lover among

the elements, but its power of choice is limited.

Science conceives of all matter as grained or discrete, like a bag of

shot, or a pile of sand. Matter does not occupy space continuously, not

even in the hardest substances, such as the diamond; there is space,

molecular space, between the particles. A rifle bullet whizzing past is

no more a continuous body than is a flock of birds wheeling and swooping

in the air. Air spaces separate the birds, and molecular spaces separate

the molecules of the bullet. Of course it is unthinkable that

indivisible particles of matter can occupy space and have dimensions.

But science goes upon this hypothesis, and the hypothesis proves itself.

After we have reached the point of the utmost divisibility of matter in

the atom, we are called upon to go still further and divide the

indivisible. The electrons, of which the atom is composed, are one

hundred thousand times smaller, and two thousand times lighter than the

smallest particle hitherto recognized, namely, the hydrogen atom. A

French physicist conceives of the electrons as rushing about in the

interior of the atom like swarms of gnats whirling about in the dome of

a cathedral. The smallest particle of dust that we can recognize in the

air is millions of times larger than the atom, and millions of millions

of times larger than the electron. Yet science avers that the

manifestations of energy which we call light, radiant heat, magnetism,

and electricity, all come from the activities of the electrons. Sir J.

J. Thomson conceives of a free electron as dashing about from one atom

to another at a speed so great as to change its location forty million

times a second. In the electron we have matter dematerialized; the

electron is not a material particle. Hence the step to the electric

constitution of matter is an easy one. In the last analysis we have pure

disembodied energy. "With many of the feelings of an air-man," says

Soddy, "who has left behind for the first time the solid ground beneath

him," we make this plunge into the demonstrable verities of the newest

physics; matter in the old sense--gross matter--fades away. To the three

states in which we have always known it, the solid, the liquid, and the

gaseous, we must add a fourth, the ethereal--the state of matter which

Sir Oliver Lodge thinks borders on, or is identical with, what we call

the spiritual, and which affords the key to all the occult phenomena of

life and mind.

As we have said, no human eye has ever seen, or will see, an atom; only

the mind's eye, or the imagination, sees atoms and molecules, yet the

atomic theory of matter rests upon the sure foundation of experimental

science. Both the chemist and the physicist are as convinced of the

existence of these atoms as they are of the objects we see and touch.

The theory "is a necessity to explain the experimental facts of chemical

composition." "Through metaphysics first," says Soddy, "then through

alchemy and chemistry, through physical and astronomical spectroscopy,

lastly through radio-activity, science has slowly groped its way to the

atom." The physicists make definite statements about these hypothetical

bodies all based upon definite chemical phenomena. Thus Clerk Maxwell

assumes that they are spherical, that the spheres are hard and elastic

like billiard-balls, that they collide and glance off from one another

in the same way, that is, that they collide at their surfaces and not at

their centres.

Only two of our senses make us acquainted with matter in a state which

may be said to approach the atomic--smell and taste. Odors are material

emanations, and represent a division of matter into inconceivably small

particles. What are the perfumes we smell but emanations, flying atoms

or electrons, radiating in all directions, and continuing for a shorter

or longer time without any appreciable diminution in bulk or weight of

the substances that give them off? How many millions or trillions of

times does the rose divide its heart in the perfume it sheds so freely

upon the air? The odor of the musk of certain animals lingers under

certain conditions for years. The imagination is baffled in trying to

conceive of the number and minuteness of the particles which the fox

leaves of itself in the snow where its foot was imprinted--so palpable

that the scent of a hound can seize upon them hours after the fox has

passed! The all but infinite divisibility of matter is proved by every

odor that the breeze brings us from field and wood, and by the delicate

flavors that the tongue detects in the food we eat and drink. But these

emanations and solutions that affect our senses probably do not

represent a chemical division of matter; when we smell an apple or a

flower, we probably get a real fragment of the apple, or of the flower,

and not one or more of its chemical constituents represented by atoms or

electrons. A chemical analysis of odors, if it were possible, would

probably show the elements in the same state of combination as the

substances from which the odors emanated.

The physicists herd these ultimate particles of matter about; they have

a regular circus with them; they make them go through films and screens;

they guide them through openings; they count them as their tiny flash is

seen on a sensitized plate; they weigh them; they reckon their velocity.

The alpha-rays from radio-active substances are swarms of tiny meteors

flying at the incredible speed of twelve thousand miles a second, while

the meteors of the midnight sky fly at the speed of only forty miles a

second. Those alpha particles are helium atoms. They are much larger

than beta particles, and have less penetrative power. Sir J. J. Thomson

has devised a method by which he has been able to photograph the atoms.

The photographic plate upon which their flight is recorded suggests a

shower of shooting stars. Oxygen is found to be made up of atoms of

several different forms.