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CHAPTER XVI
HOW MAN PROVED OUR EXISTENCE

THE SCRIBE'S NOTE ON CHAPTER SIXTEEN

Several men of note declared that "little particles" revolved around the atoms of matter, and that it was the motion of these particles which produced the well-known æther waves of light.

This idea was suggested by the result of certain mathematical calculations.

It was some time before real experimental proof was obtained.

The electron tells its own tale of this great discovery.

When the electron speaks of a spectrum line being shifted up or down the scale, it means towards the violet or the red end respectively.

We may picture the spectrum as analogous to the keyboard of a piano.

In the second part of this chapter, the electron explains how it has enabled man to discover that certain stars are approaching the earth, while others are receding from it.

We electrons had waited long ages for man to acknowledge our services, but we did not despise the acknowledgment which a few men accorded us upon the basis of their mathematical calculations. It was natural, however, that we should want something more definite than this.

You can imagine our joy when real experimental proof of our existence was established. Perhaps you think that we should have been satisfied with this. But even this did not bring acknowledgment from many outside scientific circles, and not even from all within those circles. As our services to man are universal, we feel that all men should become acquainted with our doings. Indeed that was the chief argument used by my fellow-electrons, who urged me to write this autobiography. The story of our actual discovery by man is an interesting one.

It all came about in a very simple manner, but in quite a different way from what most electrons expected. Man reasoned within himself that if we electrons really did revolve around atoms and thus produce waves in the æther, as had been suggested, he ought to be able to affect our movements by disturbing the æther in which we were revolving. Of course man cannot disturb the æther directly; he must employ some of us to do this for him. He caused us to produce a very powerful magnetic field, which, as you know, is a disturbance of the æther. Man did not bother thinking about us in this connection; he simply sent an electric current around an electro-magnet, but I have explained to you the very active part we play in electric and magnetic actions.

From my story in the preceding chapter, you are aware that man had observed the meaning of the bright lines in the spectrum of any incandescent body. When he examined the æther waves we send out from sodium atoms, he found two very distinct lines in the yellow. Because of the brightness of these lines, man selected a sodium flame to experiment with in the present case.

You will picture a great host of my fellow-electrons revolving around the atoms in a sodium flame. The flame was placed between the poles of a very powerful electro-magnet, and a beam of æther waves (light) produced by us was directed into the spectroscope. The experimenter focussed all his attention upon one of the bright yellow lines. He noted very carefully the exact position in which we placed it. He then produced the magnetic field around the flame, in which my fellow-electrons were revolving at a steady pace, and, behold, the line which he was watching split up into two lines, one taking up a position a little higher up the spectrum scale, and the other going a little lower down towards the red end. What could this mean?

Man had no difficulty in knowing the cause of this alteration; indeed, it was exactly what he had hoped would take place. Of the two new lines, one represented waves a little shorter, while the other line indicated waves a little longer or farther apart, than the original waves forming the single line. This could only come about by some of the electrons having had their rate of revolution increased, while that of others had been reduced. These alterations were due to the æther disturbance (the magnetic field). Those electrons whose orbits happened to lie in one position had their rate of revolution increased, while those whose orbits lay in another position had their speed reduced. Man was convinced at last that we "particles" were real existing things.

Whenever man withdrew the æther disturbance, the electrons fell back into their natural rate of revolution, and the original single line appeared in the spectrum.

I took no part in the original experiment which gave absolute proof of our existence, but since then I have been present in a laboratory when the same experiment has been repeated.

This is not the only case in which we alter the positions of definite lines in the spectrum. Indeed, we have given man some interesting information about the motions of distant stars – information which he could not have obtained in any other way. We have sent wireless messages from distant stars, indicating that they were approaching the earth, while electrons aboard other stars have signalled that they are receding from the earth. All this may seem mysterious to you, and yet our actions in the matter are very simple. Indeed, we do nothing but what I have told you of in the preceding chapters. We send out definite wave-lengths in the manner described already. But if we are on board a star which is travelling towards the earth, our waves will naturally follow a little closer at each other's heels. On the other hand, if the star is receding from the earth, the waves must be a little farther apart than they would be if the star were at rest.

You will understand that the electrons are revolving at the same speeds in both cases, but the forward movement of the star crowds the waves together, while a receding star stretches them out a little farther apart. The result at the receiving end is that the crowded waves are just as though they had come from electrons revolving at a greater speed than is actually the case. Hence the line appears farther along the spectrum, up the scale of frequencies, than would have been the case had the star not been moving forward in the line of sight. Thus if the hydrogen lines, of which I have spoken elsewhere, should appear higher up the spectrum than usual, then man knows that the star from which these waves are coming is approaching the earth.

It will be evident that when known lines in the spectrum are shifted down the scale (towards the red end of the spectrum), then the rate of the waves has been decreased, and man knows that the star carrying these stimulating electrons is receding from him.

You will observe that we electrons perform no new duty in connection with this matter; it is entirely the motion of the body carrying us that alters the positions of the lines. But I must hasten on to tell you of some personal experiences.

CHAPTER XVII
MY X-RAY EXPERIENCES

THE SCRIBE'S NOTE ON CHAPTER SEVENTEEN

The present generation were all very much interested in the discovery of X-rays.

With the aid of a battery and an induction coil, man causes an energetic electrical discharge to pass through a vacuum tube.

When the flying electrons strike upon a little metal target placed in their path, they produce the well-known Roentgen rays.

We have all become familiar with the great penetrating powers of these rays.

The electron may be left to tell its own story.

It was no surprise to us that we could produce what man calls X-rays, but we were very much surprised at the use to which man put these splashes which we made in the æther. A limited number of us had been producing X-rays on our own account for many ages, but I shall tell you of that in a later chapter, when you will hear how we made the world talk.

I must tell you of my own experiences in connection with these X-rays, which I hear some men describe also as Roentgen rays. I found myself once more within a large vacuum tube, and as soon as I felt a crowd of my fellows pushing me forward, I was quite prepared to be shot across the tube, as on previous occasions. Personally, I was not prepared for what was to come. Just as we reached the centre of the tube we collided with a metal plate or target. It was no joke to be pulled up so suddenly when travelling at a terrific speed. I noticed at the time that our very sudden stoppage had a peculiar effect upon the æther. Of course we never bothered about a name for this disturbance; it is man who requires to have names for everything. He was quite right to call this æther disturbance "X-rays," for even now he does not know the real nature of these. I have heard him describe them as thin pulses in the æther, but there is something more.

I may as well confess that although we observed this æther disturbance arising from our sudden stoppage, we paid little attention to it, until it became apparent that man was continuing to produce these rays for some special purpose. He had discovered that we could shoot these rays right through many solid substances which were not transparent to light. But I have not told you how man came to know that we could produce these penetrating rays.

On one occasion we were sending out these rays, which, by the way, do not cause any sensation in man's visionary apparatus. The room was in darkness. Some of the invisible rays fell upon a collection of small chemical crystals which were fixed on the surface of a screen. Our fellow-electrons, who were attached to the atoms of the crystals, were bestirred into action. They could not reflect the X-rays, but they set up regular trains of waves in the æther, some of which came within the range that affects man's vision. Man knew that this chemical screen could not produce light on its own account, and it became apparent that the vacuum tube must be sending some æther waves towards the chemical screen.

As the electrons on the screen produced an æther disturbance different from that which fell upon it, man called this a fluorescent screen.

At first we took merely a passing interest in the experiments which man made with these X-rays of ours, for it seemed to us as though man thought them only good enough for amusing his friends. Indeed, we paid little heed to what he was doing, until we observed that the rays were being used by surgeons. We were interested at once, for here we could serve man.

My first experience in this connection was quite interesting. A young girl had got a needle into her hand while she was playing about, and the surgeons were at a loss to know where the needle had lodged. We lost no time in producing X-rays which could penetrate the flesh of the hand, and reach the fluorescent screen on the other side. The bones of the hand blocked the way of our rays, but not so completely as the needle did. Hence we produced upon the screen a faint shadow of the flesh of the hand, a much deeper image of the bones, and a black shadow of the needle. This enabled the surgeon to see where the needle was hiding.

Sometimes we were called upon to produce rays for detecting bullets in the flesh, or for showing the nature of a fractured bone. We were never surprised to find that our call was to detect a coin in the throat of a child, but in this connection a big surprise awaited some of us. I was not one of the party, but I have the information from some fellow-electrons.

The upper photograph shows the X-ray apparatus in use. The operator is examining the bones of the lady's hand, which she places between the X-ray tube and the fluorescent screen. The rays pass through the flesh, but are obstructed by the bones, the rings, and the bangle, so that a shadowgraph or image is formed upon the screen, which becomes luminous where the rays succeed in reaching it. The actual examination is made in a dark room. Owing to the way X-ray photos are taken (by contact) the image is reversed in a photograph, so that a left looks like a right hand.

A party of electrons were present within an X-ray tube at a large hospital, when they were called upon to produce rays for examining the throat of a little girl. They had become so used to this call that they did not doubt there would be a coin in the child's throat. However, they lost no time in producing the penetrating rays, and you can imagine their surprise when they produced the image of a toy bicycle upon the screen. It seemed ridiculous that such a toy could have entered a child's throat.

When we had shown the surgeons exactly where the toy was, they set to work to remove it. The electrons heard later that the operation was successful in every way. Every one was interested, and we were proud. I do not wish to appear boastful, but I wonder how many operations owe their success to these rays which we produce for man.

It was natural that man should try if these searching rays could affect the chemicals upon a photographic plate, and we soon proved that they could. It made no difference to us whether man kept the plate sealed up in its light-proof envelope, or whether he placed the plate within a wooden box. These protecting covers offered no barrier to our rays. We produced shadowgraphs of any objects placed between our tube and the photographic plate.

Two of my early experiences may be of interest to you. The first of these seemed to me a rather tame affair. Our X-ray tube appeared to be arranged for the amusement of fashionable folk. One grand lady placed her hand behind the fluorescent screen, whereupon we produced an image of the bones of her hand and very dark images of all the many rings upon her fingers. Several of the rings had enormous diamonds, but it was after she had gone away that I overheard two gentlemen speaking about the rings. One asked the other if he had observed the beautiful diamonds, whereupon the other roared with laughter. It seems that we proved them to be imitation diamonds, for our rays could not penetrate them, whereas they have no difficulty in passing through real diamonds. We therefore produced black shadows of the imitation diamonds. Little did the grand lady know how we had exposed her sham jewels.

My second experience was a very curious one. I learned that our tube was being carried to some distance. After a while we were placed beside a peculiar-looking object, which the men referred to as the "mummy." One of the men suggested that they should photograph its feet, but before doing so they darkened the room and set us to work upon the fluorescent screen. The owner of the mummy got rather nervous as to what we might disclose, and as the force urging us into action was somewhat erratic at first, we produced only a very indistinct image. We were greatly amused at the nervous excitement of the owner; he seemed to think our verdict was that there were no bones. However, the man with the apparatus soon got things into better condition, and this enabled us to produce X-rays satisfactorily. The result was that they secured some excellent photographs of the hidden bones of the mummy.

Before telling you how we made the world talk, I should like to give you a clear idea of our relationship to the atoms of matter.

CHAPTER XVIII
OUR RELATIONSHIP TO THE ATOMS

THE SCRIBE'S NOTE ON CHAPTER EIGHTEEN

We have no doubt that an atom of matter is a miniature solar system of revolving electrons.

These electrons, being negative particles of electricity, would repel each other just as any two similarly electrified bodies do.

There must therefore be some equivalent of positive electricity, but whether this exists in the form of a sphere or in separate particles we have no definite knowledge.

One atom differs from another in the number of electrons which go to make up the atom.

The electron explains how the atoms of matter are united to one another, how different compound substances are formed, and how chemical changes take place.

I am sorry that this part of my story must remain incomplete for the present. I am not free to tell you all I know; you must try and get behind the scenes on your own account.

One thing I am at liberty to tell you is that my fellow-electrons who are locked up within the atoms are not without hope that they may gain their freedom once more at some future time. I know this first-hand, for I have met some fellow-electrons who have escaped from within an atom, but I shall delay telling you about these fellows till the succeeding chapter. My object in mentioning this fact now is to give you confidence in what I am about to say regarding the nature of the atom.

On one occasion I overheard a conversation between two men who were discussing the construction of matter. One remarked that the atoms were the bricks of the universe, whereupon the other asked how the little bricks were cemented together. I wish that man could have seen a lump of matter as we see it. He would have been surprised to learn that the atoms never really touch each other. They are always surging to and fro, or vibrating, and it is this motion which constitutes the temperature of the body which they compose.

It must be clear, however, that in a solid body one atom attracts another atom across the intervening atomic spaces. This is another duty devolving upon us; what we do, really, is to upset the electric balance between the different atoms, and thus produce electrical attraction.

First of all, perhaps, I should explain that the different kinds of atoms are simply congregations of different numbers of electrons. Of course there is the other part, of which I am forbidden to speak – the part which man vaguely describes as positive electricity. However, you may take it from me that while it is true that the main difference between an atom of gold and an atom of iron, or of oxygen, is in the number of electrons it contains, there is a very important difference in the arrangement of the electrons. You know that they form rings outside one another, all of which revolve at enormous speeds. The number of electrons in the different rings varies according to the kind of atom.

It is quite correct for man to speak of the atoms containing certain definite numbers of electrons, but I should like you to understand clearly that the exact number of electrons is not permanently fixed; one or more electrons can slip off one atom and become attached to a neighbouring atom which happens to be capable of accepting it or them. It is the interchange of these few detachable electrons that causes one atom to attract another. In other words, it is the differently charged atoms which attract each other, just as man crowds a surplus of electrons on to one object and finds it attracted bodily towards another object having a deficiency of electrons.

It is this electrical attraction between the atoms which enables us to build up the particles, or molecules, of matter in such a variety of forms. First of all, we play the most important part within the atoms. We have formed only a limited number of such atoms. I am not free to tell you exactly how many, for man has discovered only about eighty of these different congregations of electrons, each kind of which he calls an element. The way in which we have coupled these different elementary atoms together must appear remarkable to all thinking men; there seems to be no end to the possible variety of combinations.

In one case we unite an atom of chlorine to an atom of sodium and thereby produce a molecule of common salt. In another case we unite an atom of oxygen to two atoms of hydrogen, and the resulting combination is an invisible molecule of ordinary water.

It has always seemed to me very strange how some men have difficulty in regard to these combinations. I have heard a man ask how two different gases, hydrogen and oxygen, when united, should form a liquid, and not a gas. I wish you could see things as we see them. The atoms are neither gaseous, liquid, nor solid; they are little worlds of revolving electrons.

I have spoken of the attraction between atoms, and again between molecules, in form ing a solid body. It will be clear that there is less of this cohesive force in the case of a liquid, whereas it is absent entirely in the case of a gas. In this case the molecules have become so far separated from one another that they cease to attract each other, and if left free they will soon part company, and spread themselves broadcast over the face of the earth.

Whether a substance passes into a solid, a liquid, or a gaseous state, the atoms remain constant, but their vibratory motion is altered very considerably. However, I was about to tell you that we electrons can make some very interesting combinations of atoms. Those I have mentioned so far are of a very simple nature, but we have built up individual molecules containing hundreds of atoms. We link about a hundred atoms together and produce a molecule of what man calls alum, and we require to unite about a thousand atoms together to make one molecule of albumen (the white of an egg).

When man speaks of a chemical change having taken place in a substance, it is simply the electrons who have made a friendly interchange of detachable electrons, thereby causing a different assemblage of the same atoms. During these changes we never alter the nature of the atom. That little world of revolving electrons known as an atom of gold, remains always an atom of gold. But you must not run away with the idea that the atoms will never change. Indeed, man has discovered that the atoms are not eternal, as I shall explain in the following chapter.