Among the Forces Part 4

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."

No less is it true of atoms. In him all things live and move. Such intense activities could not be without an infinite G.o.d immanent in matter.

THE NEXT WORLD TO CONQUER

Man's next realm of conquest is the celestial ether. It has higher powers, greater intensities, and quicker activities than any realm he has yet attempted.

When the emissory or corpuscular theory of light had to be abandoned a medium for light's interplay between worlds had to be conceived. The existence of an all-pervasive medium called the luminiferous ether was launched as a theory. Its reality has been so far demonstrated that but very few doubters remain.

What facts of its conditions and powers can be known? It differs almost totally from our conceptions of matter. Of the eighteen necessary properties of matter perhaps only one, extension, can be predicated of it. It is unlimited, all-pervasive; even where worlds are non-attractive, does not acc.u.mulate about suns or other bodies; has no structure, chemical relations, nor inertia; is not heatable, and is not cognizable by any of our present senses. Does it not take us one step toward an apprehension of the revealed condition of spirit?

Recall its actual activities. Two hundred and fifty-eight vibrations of air per second produce on the ear the sensation we call _do_, or _C_ of the soprano scale; five hundred and sixteen give the upper _C_, or an octave above. So the sound runs up in air till, above, say, thirty-five thousand vibrations per second, there is plenty of sound inaudible to our ears. But not inaudible to finer ears. To them the morning stars sing together in mighty chorus:

"Forever singing as they s.h.i.+ne, 'The hand that made us is divine.'"

Electricity has as great a variety of vibrations as sound. Since some kinds of electricity do not readily pa.s.s through s.p.a.ce devoid of air, though light and heat do, it seems likely that some of the lower intensities and slower vibrations of electricity are not in ether but in air. Certainly some of the higher intensities are in ether.

Between two hundred and four hundred millions of millions of vibrations of ether per second are the different sorts of heat. Between four hundred and eight hundred vibrations are the different colors of light.

Beyond eight hundred vibrations there is plenty of light, invisible to our eyes, known as chemical rays and probably the Roentgen rays.

Beyond these are there vibrations for thought-transference? Who knoweth?

These familiar facts are called up to show the almost infinite capacities and intensities of the ether. Matter is more forceful, as it is less dense. Rock is solid, and has little force except obstinate resistance. Steam is rarer and more forceful. Gases suddenly born of dynamite touched by fire in the rock under a mountain have the tremendous pressure of eighty thousand pounds to the square inch.

Ether is so rare that its density, compared with water, is represented by a decimal fraction with twenty-seven ciphers before it.

When the worlds navigate this sea, do they plow through it as a s.h.i.+p through the waves, forcing them aside, or as a sieve letting the water through it? Doubtless the sieve is the better symbol. Certainly the vibrations flow through solid gla.s.s and most solid diamond. To be sure, they are a little hampered by the solid substance. The speed of light is reduced from one hundred and eighty thousand miles a second in s.p.a.ce to one hundred and twenty thousand in gla.s.s. If ether can so readily go through such solids, no wonder that a spirit body could appear to the disciples, "the doors being shut."

Marvelous discoveries in the capacities of ether have been made lately.

In 1842 Joseph Henry found that electric waves in the top of his house provoked action in a wire circuit in the cellar, through two floors and ceilings, without wire connections. More than twenty years ago Professor Loomis, of the United States coast survey, telegraphed twenty miles between mountains by electric impulses sent from kites. Last year Mr. Preece, the cable being broken, sent, without wires, one hundred and fifty-six messages between the mainland and the island of Mull, a distance of four and a half miles. Marconi, an Italian, has sent recognizable signals through seven or eight thick walls of the London post-office, and three fourths of a mile through a hill.

Jagadis Chunder Bose, of India, has fired a pistol by an electric vibration seventy-five feet away and through more than four feet of masonry. Since brick does not elastically vibrate to such infinitesimal impulses as electric waves, ether must. It has already been proven that one can telegraph to a flying train from the overhead wires. Ether is a far better medium of transmission than iron. A wire will now carry eight messages each way, at the same time, without interference. What will not the more facile ether do?

Such are some of the first vague suggestions of a realm of power and knowledge not yet explored. They are mere auroral hints of a new dawn.

The full day is yet to s.h.i.+ne.

Like timid children, we have peered into the schoolhouse--afraid of the unknown master. If we will but enter we shall find that the Master is our Father, and that he has fitted up this house, out of his own infinite wisdom, skill, and love, that we may be like him in wisdom and power as well as in love.

OUR ENJOYMENT OF NATURE'S FORCES

We are a fighting race; not because we enjoy fights, but we enjoy the exercise of force. In early times when we knew of no forces to handle but our own, and no object to exercise them on but our fellow-men, there were feuds, tyrannies, wars, and general desolation. In the Thirty Years' War the population of Germany was starved and murdered down from sixteen millions to less than five millions.

But since we have found field, room, and ample verge for the play of our forces in material realms, and have acquired mastery of the superb forces of nature, we have come to an era of peace. We can now use our forces and those of nature with as real a sense of dominion and mastery on material things, resulting in comfort, as formerly on our fellow-men, resulting in ruin. We now devote to the conquest of nature what we once devoted to the conquest of men. There is a fascination in looking on force and its results. Some men never stand in the presence of an engine in full play without a feeling of reverence, as if they stood in the presence of G.o.d--and they do.

The turning to these forces is a characteristic of our age that makes it an age of adventure and discovery. The heart of equatorial Africa has been explored, and soon the poles will hold no undiscovered secrets.

Among the great monuments of power the mountains stand supreme. All the cohesions, chemical affinities, affections of metals, liquids, and gases are in full play, and the measureless power of gravitation. And yet higher forces have chasmed, veined, infiltrated, disintegrated, molded, bent the rocky strata like sheets of paper, and lifted the whole ma.s.s miles in air as if it were a mere bubble of gas.

The study of these powers is one of the fascinations of our time. Let me ask you to enjoy with me several of the greatest manifestations of force on this world of ours.