Part 4 (1/2)
The outer particles revolve on each other; those of the middle do not move. They a.s.sume 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 circ.u.mstances.
Forty pounds were hung on one day, three pounds more the next day, and so on, increasing the weights by diminis.h.i.+ng quant.i.ties, 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. Ma.s.ses of matter may be still, but not the const.i.tuent elements. They are always in intensest activity, like a ma.s.s of bees--those inside coming out, outside ones going in--but the ma.s.s 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 s.p.a.ce they occupy. They object to being crowded. They make no objection to having other matter come in and possess the s.p.a.ce 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 s.p.a.ce. 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 surpa.s.ses 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.
MOBILITY OF SEEMING SOLIDS
When a human breath, or the white jet of a steam whistle, or the black cough of a locomotive smokestack is projected into the air it is easy to see that the air is mobile. Its particles easily roll over one another in voluminously infolding wreaths. The same is seen in water.
The crest of a wave falls over a portion of air, imprisoning it for a moment, and the mingled air and water of different densities prevent the light of the sun or sky from going straight down into the black depths and being lost, but by being reflected and turned back it shows like beautiful white lace, constantly created and dissolved with a thousandfold more beauty than any that ever came from human hands. All the three s.h.i.+fting elements of the swift creations are mobile. This seems to be the case because these elements are not solid. The particles have plenty of room to play about each other, to execute mazy dances and minuets with vastly more s.p.a.ce than substance.
Extend the thought a little. Things that seem to us most solid are equally mobile. An iron wire seems solid. It is so; some parts much more so than others. The surface that has been in closest contact with the die as the wire was drawn through, reducing its size by one half, perhaps, is vastly more dense than the inner parts that have not been so condensed. File away one tenth of a wire, taking it all from the surface, and you weaken the tensile strength of the wire one half.
But, dense and solid as this iron is, its particles are as mobile within certain limits as the particles of air. An electric message sent through a mile of wire is not anything transmitted; matter is not transferred, but the particles are set to dancing in wavy motion from end to end. Particles are leaping within ordered limits and according to regular laws as really as the clouds swirl and the air trembles into song through the throat of a singer. When a wire is made sensitive by electricity the breath of a child can make it vibrate from end to end, ensouled with the child's laughter or fancies. Nay, more, and far more wonderful, the wire will be sensitive to the number of vibrations of a certain note of music, and no receiver at the other end will gather up its sensitive tremblings unless it is pitched to the keynote of the vibrations sent. In this way eight sets of vibrations have been sent on one wire both ways at the same time, and no set of signals has in any way interfered with the completeness and audibility of the rest.
Sixteen sets of waltzes were being performed at one and the same time by the particles of one wire without confusion. Because the air is transmitting the notes of an organ from the loft to the opposite end of the church, it is not incapable of bringing the sound of a voice in an opposite direction to the organist from the other end of the church.
The extreme mobility of steel is seen when the red-hot metal is plunged into water. Instantly every particle takes a new position, making it a hundredfold more hard than before it was heated. But these particles of transferred steel are still mobile. A man's razor does not cut smoothly. It is dull, or has a ragged edge that is more inclined to draw tears than cut hairs. He draws the razor over the tender palm of his hand a few times, rearranges the particles of the edge and builds them out into a sharper form. Then the razor returns to the lip with the dainty touch of a kiss instead of a saw. Or the tearful man dips the razor in hot water and the particles run out to make a wider blade and, of course, a thinner, sharper edge. Drop the tire of a wagon wheel into a circular fire. As the heat increases each particle says to its neighbor, ”Please stand a little further off; this more than July heat is uncomfortable.” So the close friends stand a little further apart, lengthening the tire an inch or two. Then, being taken out of the fire and put on the wheel and cooled, the particles snuggle up together again, holding the wheel with a grip of cold iron. Mobile and loose, with plenty of room to play, as the particles have, neither wire nor tire loses its tensile strength. They hold together, whether arms are locked around each other's waist, or hand clasps hand in farther reach. What change has come to iron when it has been made red or white hot? Its particles have simply been mobilized. It differs from cold iron as an army in barracks and forts differs from an army mobilized. Nothing has been added but movement. There is no caloric substance. Heat is a mode of motion. The particles of iron have been made to vibrate among themselves. When the rapidity of movement reaches four hundred and sixty millions of millions of vibrations per second it so affects the eye that we say it is red-hot. When other systems of vibration have been added for yellow, etc., up to seven hundred and thirty millions of millions for the violet, and all continue in full play, the eye perceives what we call white heat. It is a simple ill.u.s.tration of the readiness of seeming solids to vibrate with almost infinite swiftness.
I have been to-day in what is to me a kind of heaven below--the workshop of my much-loved friend, John A. Brashear, in Allegheny, Pa.
He easily makes and measures things to one four-hundred-thousandth of an inch of accuracy. I put my hand for a few seconds on a great piece of gla.s.s three inches thick. The human heat raised a lump detectable by his measurements. We were testing a piece of gla.s.s half an inch thick; and five inches in diameter. I put my two thumbnails at the two sides as it rested on its bed, and could see at once that I had compressed the gla.s.s to a shorter diameter. We twisted it in so many ways that I said, ”That is a piece of gla.s.s putty.” And yet it was the firmest texture possible to secure. Great lenses are so sensitive that one cannot go near them without throwing them discernibly out of shape.
It were easy to show that there is no solid earth nor immovable mountains. I came away saying to my friend, ”I am glad G.o.d lets you into so much of his finest thinking.” He is a mechanic, not a theologian. This foremost man in the world in his fine department was lately but a ”greasy mechanic,” an engineer in a rolling mill.
But for elasticity and mobility nothing approaches the celestial ether.
Its vibrations reach into millions of millions per second, and its wave-lengths for extreme red light are only .0000266 of an inch long, and for extreme violet still less--.0000167 of an inch.
It is easier molding hot iron than cold, mobile things than immobile.
This world has been made elastic, ready to take new forms. New creations are easy, for man, even--much more so for G.o.d. Of angels, Milton says:
”Thousands at his bidding speed, And post o'er land and ocean without rest.”