Ultimate atoms of matter are asserted to be impenetrable. That is, if
a mass of them really touched each other, that mass would not be
condensible by any force. But atoms of matter do not touch. It is
thinkable, but not demonstrable, that condensation might go on till
there were no discernible substance left, only force.
Matter exists in three states: solid, liquid, and gas. It is thought
that all matter may be passed through the three stages--iron being
capable of being volatilized, and gases condensed to liquids and
solids--the chief difference of these states being greater or less
distance between the constituent atoms and molecules. In gas the
particles are distant from each other, like gnats flying in the air; in
liquids, distant as men passing in a busy street; in solids, as men in
a congregation, so sparse that each can easily move about. The
congregation can easily disperse to the rarity of those walking in the
street, and the men in the street condense to the density of the
congregation. So, matter can change in going from solids to liquids
and gases, or _vice versa_. The behavior of atoms in the process is
surpassingly interesting.
Gold changes its density, and therefore its thickness, between the two
dies of the mint that make it money. How do the particles behave as
they snuggle up closer to each other?
Take a piece of iron wire and bend it. The atoms on the inner side
become nearer together, those on the outside farther apart. Twist it.
The outer particles revolve on each other; those of the middle do not
move. They assume and maintain their new relations.
Hang a weight on a wire. It does not stretch like a rubber thread, but
it stretches. Eight wires were tested as to their tensile strength.
They gave an average of forty-five pounds, and an elongation averaging
nineteen per cent of the total length. Then a wire of the same kind
was given time to adjust itself to its new and trying circumstances.
Forty pounds were hung on one day, three pounds more the next day, and
so on, increasing the weights by diminishing quantities, till in sixty
days it carried fifty-seven pounds. So it seems that exercise
strengthened the wire nearly twenty-seven per cent.
While those atoms are hustling about, lengthening the wire and getting
a better grip on one another, they grow warm with the exercise. Hold a
thick rubber band against your lip--suddenly stretch it. The lip
easily perceives the greater heat. After a few moments let it
contract. The greater coldness is equally perceptible.
A wire suspending thirty-nine pounds being twisted ninety-five full
turns lengthened itself one sixteen-hundredth of its length. Being
further twisted by twenty-five turns it shortened itself one fourth of
its previous elongation. During the twisting some sections took far
more torsion than others. A steel wire supporting thirty-nine pounds
was twisted one hundred and twenty times and then allowed to untwist at
will. It let out only thirty-eight turns and retained eighty-two in
the new permanent relation of particles. A wire has been known to
accommodate itself to nearly fourteen hundred twists, and still the
atoms did not let go of each other. They slid about on each other as
freely as the atoms of water, but they still held on. It is easier to
conceive of these atoms sliding about, making the wire thinner and
longer, when we consider that it is the opinion of our best physicists
that molecules made of atoms are never still. Masses of matter may be
still, but not the constituent elements. They are always in intensest
activity, like a mass of bees--those inside coming out, outside ones
going in--but the mass remains the same.
The atoms of water behave extraordinarily. I know of a boiler and
pipes for heating a house. When the fire was applied and the
temperature was changed from that of the street to two hundred degrees,
it was easy to see that there was a whole barrel more of it than when
it was let into the boiler. It had been swollen by the heat, but it
was nothing but water.
Mobile, flexible, and yielding as water seems to be, it has an
obstinacy quite remarkable. It was for a long time supposed to be
absolutely incompressible. It is nearly so. A pressure that would
reduce air to one hundredth of its bulk would not discernibly affect
water. Put a ton weight on a cubic inch of water; it does not flinch
nor perceptibly shrink, yet the atoms of water do not fill the space
they occupy. They object to being crowded. They make no objection to
having other matter come in and possess the space unoccupied by them.
Air so much enjoys its free, agile state, leaping over hills and
plains, kissing a thousand flowers, that it greatly objects to being
condensed to a liquid. First we must take away all the heat. Two
hundred and ten degrees of heat changes water to steam filling 1,728
times as much space. No amount of pressure will condense steam to
water unless the heat is removed. So take heat away from air till it
is more than two hundred degrees below zero, and then a pressure of
about two hundred atmospheres (14.7 pounds each) changes common air to
fluid. It fights desperately against condensation, growing hot with
the effort, and it maintains its resilience for years at any point of
pressure short of the final surrender that gives up to become liquid.
Perhaps sometime we shall have the pure air of the mountains or the sea
condensed to fluid and sold by the quart to the dwellers in the city,
to be expanded into air once more.
The marvel is not greater that gas is able to sustain itself under the
awful pressure with its particles in extreme dispersion, than that what
we call solids should have their molecules in a mazy dance and yet keep
their strength.
Since this world, in power, fineness, finish, beauty, and adaptations,
not only surpasses our accomplishment, but also is past our finding out
to its perfection, it must have been made by One stronger, finer, and
wiser than we are.