All About X-Rays

Willard E. Case’s Most Interesting Lecture on “Luminescence.”

EVERYTHING ILLUSTRATED.

The Speaker Had Provided Himself With Everything in the Line of Apparatus That Would Tend to Make Clearer the Statements He Made so Clearly and He Held the Closest Attention of His Audience. Text of the Lecture.

The first of a promised series of lectures to be delivered before the Cayuga County Medical Society was given in Assembly hall at the High school last night by Willard E. Case. The subject was one of timely interest — “Luminescence, Including the X or Roentgen Rays.”

The audience, composed of the members of the society and their guests, was a large and cultured one. The subject, dealing as it did with the marvelous results of the most recent scientific research, was in itself of fascinating interest, and in the hands of so competent an authority as the lecturer of the evening was clothed with increased interest. The acoustic properties of the hall are so lamentably poor that it was difficult for some of the audience to hear one sentence from beginning to end without the utmost difficulty; had the attention been less close it would have been impossible. But the attention was absorbed from the first word to the last, and in a measure this great difficulty was overcome by the effort of the audience.

Mr. Case had the advantage of an unlimited supply of apparatus for his illustrations. The most expensive apparatus was at his command, and, under such conditions, his experiments were more elaborate and more complete than one less fortunate than himself could hope to present. He had evidently spared nothing in time, labor and money to illustrate his lecture. The arrangement of the experiments must have been a matter of much thought and great expense.

There was absolutely nothing lacking, and, it is assured, until Mr. Case again consents there will not be another lecture in Auburn with such a prodigality of illustration. The result of the elaborate preparations was highly gratifying to the audience. They have seen that which they never had seen and probably never will see again.

The lecture is appended word for word as delivered. Those who were unfortunately unable to hear it will find the perusal of it pleasant enough, but the lack of the illustrations is the loss of half its interest.

Mr. Case was introduced by Dr. F. H. Parker and Dr. Belton conducted the experiments for the most part. Mr. Case spoke from his manuscript. The lecture was as follows:

Mr. Chairman, Ladies and Gentlemen:

I am to speak to-night on luminescence, interesting to us all because by it we can see not only to read as of old, but to read without opening the book. Some twenty years ago the world was agog over the discovery of the telephone and electric light; to-day the pendulum has swung the other way. Twenty years is a long time for one oscillation, but it has brought us a discovery which is epoch making; and before the century ends and the pendulum’s cycle is completed light without heat will have made its introduction, and electricity from coal may come under consideration demand.

In the first instance high oscillation of matter is necessary to produce luminescence and electricity is necessary to produce high oscillation. We all know how amber was first rubbed and found to attract light bodies; this property was called by the Greeks after their name of amber, Electron, or as we call it, electricity. It might have been called by any other name. We only know some of its laws; we do not know what it is any more than we know what gravity is. As we all know many other ways of producing electricity have been since discovered. Volta found two dissimilar metals immersed in an acid solution produced it. Faraday found a closed coil of wire whirled in a magnetic field generated it; and on this latter principle our electric light machines are constructed.

In this lecture I shall choose that form of luminescence as my subject which is produced by electricity of very high pressure; not that form of electricity which is used to make the ordinary electric light of to-day, but that which has been lately discovered and which carries us further into that field of research on the border land of science that has given us such wonderful results within the last year.

As electricity is a phenomenon familiar to us all, it is not necessary for me to dwell on its more familiar effects, as that for instance of heating a conductor as it does when it passes through the filament of an incandescent lamp; on its effects of attraction and repulsion of currents for each other, as in the case of electric motors; nor of its effects on a magnetic needle, as in our instruments for measuring electricity.

We know those effects can take place at a distance; but many of us have not stopped to think how these effects are brought about, nor how they could act across space. If space is empty could force act across it? An unthinkable proposition. Now to have a conceivable notion of those new phenomena of which I am to speak, and that were until recently unknown, it would be advisable to refresh our minds with the old controversy over light.

The Greeks thought that rays of light came to the eye in straight lines; the earliest philosophers thought that something went from the eye to the object seen; this idea later was believed up to the eleventh century, when Arabian astronomers maintained that it proceeded from the object to the eye. Sir Isaac Newton maintained the emission theory: viz., that something came straight from the sun to the eye. In 1664 Hooke suggested the theory that “light is propagated by a quick, short and vibratory motion in a homogeneous medium in such a way that every pulse or vibration of the luminous body will generate a sphere, which will continually increase and grow larger as the wave or rings on the surface of water swell into larger and larger circles about the point. In the hands of Huyghens this was disproved in part; still it was in the main correct, and with what Young and Fresnel have given us, we believe wave motion comes from the luminous body to the eye. To have waves we must have something to oscillate as water does in a wave; it moves up and down and not forward.

Now what I wish to show by this idea of wave motion is that there must be something of which waves can be made, and outside the atmosphere of the earth we think something fills space, because light comes to us from the sun; this medium which acts as the transmitter of motion and energy we call luminiferous ether; it is assumed to occupy all space. This may seem very dry and old to you all, but in science we cannot assert that which we cannot prove, so we must have an hypothesis as to the medium through which these forces act.

Faraday taught us that electric attraction or repulsion depended on the intervening medium; Maxwell following Faraday demonstrated mathematically that electro-magnetic waves traverse space with the velocity of light; Hertz that it could be refracted and brought to a focus. It would have been unscientific to have looked for another medium to transmit these waves, closely resembling light as they do, so the law of Newton was followed. Of two explanations the more simple is to be assumed.

In the following experiments which I will show, you must imagine a something which pervades all space, something of so fine a structure that a piece of wood or glass is but a coarse net work to it, something which permeates all things as water does a sponge. If by electricity we set this something in rapid vibration, we get luminescence and other effects which are new to this generation. Now electricity sets this something, called ether, in motion; and by it the electro-magnetic waves are carried with a velocity of light; and if they were short enough we could see them. Hertz showed that these waves are quite analogous to light and propagated in air with the velocity of light. By a beautiful device he produced rapidly oscillating currents of high frequency, or of such a great number per second that wave lengths from 1000 miles to a few feet were produced. This means nothing to us unless we know that if they vibrate three hundred thousand times a second the waves will each be 6-10 of a mile long. We want waves about 1-70,000 of an inch to make light; or four hundred millions per second.

As I have said, Hertz in this simple way produced them six feet long, or about one hundred and fifty billion per second. It was known to him that the lightning flash was oscillatory—that is, it vibrates back and forth like a spring when set in motion—and that the discharge from the leyden jar is the same, as Henry proved to us; so Hertz ran a wire carrying an electric current on one side of a room with a leyden jar in circuit. Every time the jar discharged itself across an open space provided in the circuit, it shook up the current at a tremendous rate, producing very short waves. He then constructed a similar circuit of wire but not conveying electricity, and moved it away from the first until they were exactly a wave length apart, when it responded. Similar wave lengths were then set up in it by resonance as it is called. He thus found by the distance he moved it away, the wave length; and, with Maxwell’s discovery of the velocity of electro-magnetic waves, the interpretation he put on the matter was that as light and electricity move at the same rate through space, it is probable the undulations which convey them were in the same medium, and, as induced electricity penetrates everything, it followed that the ether through which its undulations are propagated must pervade all space and all things. The ether vibrates athwart the path of the wave’s advance as the waves of a flag across its length. The most we can say, our knowledge of the ether being very elementary, is that we believe in one ether for heat, light, electricity and magnetism.

The ideal light consists of very short wave lengths. Our electric light of today consists of comparatively long wave lengths. With every reduction of the wave length, we approach the production of electric light with great economy. We now produce it with great loss: 3-10 of 1 per cent. coal efficiency in the ordinary electric lamp. If an organist wishes to strike the highest note on his instrument he would not press on the key-board and play every note, yet that is what we are doing in the manufacture of light. We have to produce all the heat rays from the dark, through the red to the white, in the electric or gas lamp of to-day; and we have to keep on producing them all the time we are making light. Of the production of the ideal light, nature has given us a hint in the glow worm and the firefly. Their light though able to be seen at a distance, produces no heat that can be detected.

By means of currents of very high frequency and pressure Tesla has been able, with the aid of Hertz air gap, to pass, by induction, through the glass of an ordinary incandescent lamp enough energy to light it without the use of wires. He suspends two sheets of metal one above the other some distance apart, each connected with one terminal of the coil. If an exhausted tube is moved around between these sheets or placed at rest, it remains luminous, no wires being connected with it. To what extent this illumination may be useful, experiment alone will determine. Alternating currents have always been considered dangerous, but Tesla has shown with this apparatus that the higher in frequency the oscillations, the less dangerous they become. In this way we may be able to light our houses, the ceiling and floors being covered with thin metal which is hidden and connected with the generator. The lamps would always be lighted when the current was on, and could be moved about from place to place, no wires being attached to them. What the physiological effect on the occupants of the house would be I dare not hazard a guess. Still, when we stop to think, it becomes apparent even at this moment we are bathed in these waves, which are generated in every electric station within miles. Every electric wire is sending them off. The shortest wave these machines produce is 600 miles long. They are chasing each other through space at an enormous rate, crossing and recrossing each other at every point; so the effect of this higher potential might not be injurious. You will see that these short waves produce luminescence in vacuum; and it may be possible by the proper arrangement of currents and rarefied gases to obtain an economical light without heat. When these waves become short enough they affect the eye. The eye only responds to waves from 1-70,000 to 1-37,000 of an inch in length, while one of the waves generated by an alternating electric machine is 600 miles long. To affect the eye the waves must oscillate at the enormous rate of four hundred millions per second, an inconceivable number. And so I may state that the problem which the world to-day is trying to solve is to find: First, an efficient way of making electricity; and, secondly, a way to utilize it in the production of these short waves; or light without heat.

Under the conditions in which we live only a small proportion of the energy of coal can be utilized in the steam engine. The second law of thermodynamics stares us in the face. The meaning of which is: if we heat a body, we put heat or motion into it which we cannot get back unless we cool it down to absolute zero, or 460 degrees below Fahrenheit, when it can exercise no expansive power. It is impossible to do this, so we use only a small fraction of the heat we make. The energy efficiency of the modern steam engine and dynamo is not over 10 per cent., and it is not to their defects of construction that most of the loss is due, but to the interference of the law of which I have just spoken. To avoid this law, and to get an economical efficiency from coal, it must be converted directly into electricity without heat, as zinc is oxidized in the galvanic battery without heat, producing electricity direct. It is an inexorable law of nature that, under the conditions in which we live, a great waste must necessarily accompany the transformation of heat into any other form of energy. No cunningly devised furnace, feed water heater, cut off, triple expansion apparatus, pyro generator or gas engine will save this heat. Instead of getting ten incandescent lamps to the horse power we ought to get 200.

Are we to go on burning a coal mine every time we want a little light? And the corollary to that question is the one which you have doubt to asked yourselves this evening, viz: What is to be done when all the coal is used up? for the line of my argument has led you to think of matter in motion, always in motion, and of some energy as heat from coal generating that motion. As a partial answer to that question, or rather as a suggestion looking to its eventual solution, Dr. Belton will show you a little radiant matter engine or heat engine. It has been running day and night since I got it 18 years ago. Crookes devised it to show the motion of matter in a vacuum. It runs by heat, and heat is everywhere within the confines of our atmosphere. Matter in motion, the belt attached to the wheels of nature, drives this little machine. You, as well as I, can therefore imagine how in some such way nature’s force may yet be utilized to produce power as well as light. The problem has not yet been solved, but a way will be found enabling us to convert this energy of coal into electricity direct. But it is not likely that it will be done soon, as evolution governs here as elsewhere, and such a tremendous discovery will probably be the result of the work of many minds. Much is being done on this subject, and some results accomplished; still not of an economical character.

As to the problem of utilizing electricity to produce light without heat, I can say a beginning only has been made: a large room has been successfully lighted with a beautiful soft light diffused like sunlight, with no one bright spot to attract the eye, and without the non-luminous rays contained in sunlight. I will now give you some idea as to the appearance of the glow. And after that I will complete the story up to date of the other forms of luminescence, some of which can not be seen by the eye, yet they act as light and are light.

We have here three storage batteries which supply the current to this induction coil. The coil is composed of two independent circuits of wire; the primary composed of large wire, and the secondary of many miles of fine wire wound outside the primary. By means of the interrupter every time a current goes through the primary coil attached to the batteries there is set up, by induction through space, in the secondary coil, currents of enormously high pressure, which will spark across space and make waves in the ether of very short length. Remember these two coils of wire do not touch each other. You see the spark is about three inches long. The crackling sound we hear in the telephone just before a thunder storm, is the discharge of electricity many miles from the wire, acting across space by induction, just as this coil acts; and the sparks we see about the telephone are caused in the same way. These sparks are very dangerous to handle. They differ only in degree from frictional electricity.

Now this current is not of sufficiently high frequency to get the effects I wish to show you. So I send the current from the coil into this apparatus invented by Tesla. By means of this leyden jar, and the oscillating spark jumping across the air gap, first used by Hertz and before described, we get enormously high frequency. This highly oscillating spark acts the same as the interrupter on the induction coil, only going infinitely faster than any mechanical contrivance could work, so setting up in its own induction coil, which has to be immersed in oil, tremendously rapid currents.

The sparks which you see coming from my fingers are due to a potential of 200,000 volts, alternating in direction about 1,000,000 per second. I would be enveloped in a sheet of flame if the frequency were four times as fast. As it is, I am bombarded from head to foot by the flying molecules of air; were I not thrown into a profuse perspiration my temperature would rise. Tesla says: “If a man were at the North Pole without clothing and had hold of one of these wires he would never be cold.” As these actions are electro-static and act on the whole body at right angles to it, so large a surface is presented for the current to pass that no danger is to be feared. A small portion of the energy would be fatal if it were concentrated in one part of the body.

These tubes become luminous to a certain point: the fewer molecules of air there are in the tube the more easily are they shaken up by these electrostatic effects. All objects around the machine are so highly charged that by touching them we get sparks; as electricity, like water, tries to keep its level.

These two plates are connected by wires to the Tesla apparatus. One may be imagined to be hidden in the ceiling of a room, the other under the floor; and when I move these two lamps, without wires attached, you will see the faint glow and understand that we have light without heat — a light which cannot be extinguished by water, and yet so ethereal and pure that it can set nothing on fire. (The experiment here performed was very beautiful and was applauded.)

These are not the so-called X-rays, nor can photographs be taken by them. This leads us up to the other forms of ether disturbance and to molecular motion set up by electricity, which produces luminescence, and we arrive in the next in order, the X. or Roentgen rays — a light that penetrates solid bodies and the discovery of which so surprised us a few months ago. It has been said that an amateur photographer may photograph a person or his skeleton in his own house, “through a flight of stairs and a deal door.” I have even heard it suggested that one would have to line his house with lead or glass, which are almost impenetrable to the rays, if one wished to protect himself from the photographic fiend.

The term “a new light” is rather confusing, for it is not a light in the sense in which we are in the habit of thinking. The rays which produce this effect are not very luminous, in fact they may not be luminous at all yet they produce luminosity; the matter is still in dispute. The English school considers them material electrified particles, proceeding in straight lines; the Continental authorities insist that the rays are similar to those of light, transverse undulations in ether. So you see, it is almost the same dispute which proved so vexatious to the ancients.

As I have stated, heat, also, like light, consists of undulatory movements in the ether, but not of so high a frequency; and we know photographs have been taken in a dark room by the heat radiated from a pot of boiling water, but not through opaque bodies. I will utilize the storage battery and the induction coil which I have shown you, and not the Tesla’s apparatus, for my experiments with these X-rays.

We have here an ordinary glass jar, containing air attached to this air pump. It has two wires leading into it that are called electrodes, and to distinguish them, that by which the current enters Faraday called the anode, that by which it leaves, the cathode. Each electrode exhibits different properties when the current is passing.

For example: small particles of metal may be torn off from the anode, or negative electrode, and projected from its surface; or small particles of air or molecules in the bulb may be violently discharged from the anode. When a current of electricity is passing through the air in a bulb, and when the air is gradually pumped out, you will notice the character of the discharge changes. In different gases the effects differ. After the exhaustion has been carried to a certain point it is more difficult for the current to pass. In hydrogen gas under like conditions, the spark is twice as long as in the air. To make a spark a mile long, virtually a lightening flash, it is calculated that something like one billion ordinary telephone batteries would be required; so you will see that we are dealing with very high pressures.

You will also see the spark less sharply defined and widened out to occupy more space, giving us a beautiful glow. The negative electrode exhibits a bluish or violet color separated from the electrode by a narrow dark space to which I wish to call your special attention. You will see how the character of the current varies in the vacuum as it is made more and more nearly complete.

Some years ago when Professor Crookes began to study these effects of high vacuum, he found that if the glass bulb was exhausted of air to a very high degree, curious effects were produced when the electric current was passed.

Here is a “Crookes tube” exhausted to about 1-10,000 of the pressure of the atmosphere; when the electric charge passes through it the remaining air becomes luminous. The absence of luminosity around the negative electrode in the middle of the tube, is called the negative dark space; there is no fluorescence around the glass in this bulb, nor X-rays produced. This negative dark space is of great interest to us as it is supposed to be the seat of the X-rays.

I will show you some of Crookes’ experiments which tend to prove this. The first one will be a tube, nearly free from air, containing a small windmill supported upon a pivot. The mill is acted upon and set in motion by the negative discharge. This gives us some idea that if space is not too full of matter, the particles have more room to act in and so can obtain a higher velocity and do more work when they meet with any object in their way. Acting like bullets from a repeating rifle they impinge upon the object toward which they are directed, producing motion, heat and light. In this experiment you will see they produce motion; the next experiment will show you that these particles produce heat by bombardment.

In the second experiment the negative discharge is focussed, like the rays of light by a metallic reflector, and produces great heat; heating the platinum disc upon which they are thrown, red hot.

The third experiment will show you that the negative discharge produces fluorescence; which is the property inherent in certain substances of appearing luminous in the dark after having been exposed to sunlight; like some of the calcium salts or luminous paint. In this experiment the tube will contain some rubies at one end, and the negative discharge thrown upon them will show you that the rubies fluoresce.

You will also see the bombardment of the radiant matter produces light when it is thrown on this rhomb of iceland spar which is at the bottom of the tube.

In the fifth, a most beautiful experiment, you will notice that these rays pass through in straight lines. In the path of the negative discharge is a Maltese cross of metal which intercepts the rays. The shadow of the cross is seen on one end of the tube, as only the flying molecules that are not intercepted by the cross strike the glass which fluoresces. So again we see, these rays pass in straight lines only. On dropping the cross and again turning on the current, what before was the shadow of the cross now becomes luminous; from which we infer that the part which is first acted on is tired, and needs a brief rest to restore it. Again I will put the cross into position and you will see the shadow once more; and when I move magnets about the tube you will observe that the shadow changes position, that I am moving the shadow, showing the rays are deflected by magnets.

All these rays, so far as we have seen them, as well as the electric current or discharge can be deflected by a magnet and turned aside from their path; showing you they produce motion, heat, light and are acted on by magnets.

Some years after these experiments first took place it was discovered that “Crookes tubes,” which I have just shown you, emitted light that was found to pass through thin layers of many substances supposed to be opaque. These were called cathode rays, and are considered now to be the parent of the X-rays. Crookes showed us the effect of cathode rays inside of the tube, but it is only lately their effect outside of the tube has been known. It seems to be a question of degree as to how little air there is left in the tube. When the tube is so much exhausted and the dark negative space which I have shown you expands and fills the tube, the glass alone becomes fluorescent and begins to produce X-rays. Professor Roentgen, experimenting with one of these highly exhausted “Crookes tubes” which was covered with cardboard, accidentally discovered that some sensitive photographic paper that he had left on a bench near by was acted upon; and, as is often the case, this started a new train of thought, the result being that he found rays were produced which acted on sensitive plates through solid bodies, and which were more powerful than cathode rays of which he had full knowledge.

Dr. Sefton will now take a photograph of his own hand, and will have the plate developed that you may see the negative before the close of the lecture. He will use one of the tubes that produce X-rays. (Dr. Sefton arranged the apparatus and proceeded with the experiment while the lecturer continued speaking in description.) You will observe that the luminosity of the tube is entirely due to the fluorescence of the glass, and that the negative space has so increased that it fills the whole tube. The glass only fluoresces. The lamp has two electrodes, one a concave metallic mirror, the cathode, which concentrates the rays and throws them on to the other electrode, the anode, a platinum plate set at an angle of 45 degrees, which reflects the ray in the desired direction. As the vacuum is so perfect it is hard to start the current, and so we have frequently to reduce it a little by heat, driving out the residual molecules of air which have gone into the pores of the glass. The sensitive plate is enclosed in the paper bag with the film side up; it takes something like three minutes to photograph the hand; 15 minutes for the elbow; 30 minutes for the knee. I have photographed the ribs in forty minutes. Of course it all depends on the power of the lamp. Unlike ordinary negatives taken by sunlight, the picture is on the bottom of the film next the glass instead of on top, so the plate must be developed for a long time.

I will now attempt a very difficult experiment — difficult only because the light is so faint it won’t carry it to you all. I fear, decreased in strength as the square of your distance from the object. I have here a wooden box containing a metallic object with the shape of which you are quite familiar, and I want you to look right through the box and see the shape of the object with the aid of the fluorescent screen in front of it, a paper covered with the salts of Tungstate of Calcium which become luminous when the X-rays go through the box and fall on them. The body in the box is very dense, and the rays go through it with difficulty; they go through the box easier, so you see the shadow of the object in the box. (The greatest interest was manifested in this experiment. The box referred to was a cigar box; it was placed in a large box one end of which was the fluorescent screen. The lecturer explained that an “X-ray lamp” was behind the box containing the object the shadow of which would be projected upon the screen. The room was absolutely dark. The experiment was not an entire success as the lecturer had anticipated; but to those sitting in the front the shadow was visible. The lecturer then showed the bones of his hand in the same manner.)

It is stated that the X-rays are not refracted; that is, the rays do not bend in passing from one substance to another, of different density as for example, when we look into a pool of water the ray of light which comes to the eye from the object, say a stone on the bottom, does not come straight to the eye, it is bent at the surface of the water where it enters the air, forming a angle of something like 48 degrees. And perhaps the rays are not polarized, as sunlight is, on being reflected by mirrors which change its character, some of its rays having been quenched. Yet it has been lately reported that the X-rays are differently absorbed by a pair of tourmaline plates when their axes are crossed or paralleled, the rays passing through more easily when the axes are in the later position, better photographs being produced then; which would indicate polarization when the axes are crossed.

We are not yet sure that this distinction of refraction and polarization is evidence of a difference of X-rays from light. It may depend only on the lengths of the waves. Shorter wave lengths require polarizers of much finer structure. The X-rays appear to penetrate bodies according to their density, entirely independent of their other qualities—lead with great difficulty; glass with less; iron, etc., with still less trouble. In photographing the human body the same law applies; the bones being of greater density than the flesh; they go through them with more difficulty; they affect the sensitive photographic plates behind them less, and so we get their shadows. Professor Lodge has in this way seen through a yard of wood. Two lamps are now used in photographing, and focal distance obtained; so we can locate the distance from the eye, say of a needle or bullet in the muscles of any part of the body.

Most interesting of all, when the rays are thrown on a non-conductor of electricity it becomes a conductor; and, further, under their influence the salts of the metals, either solid or in solution, behave generally as the metals themselves.

X-rays do not exert any appreciable effects on the combination of hydrogen and chlorine as sunlight does; and, unfortunately, they do not exert any injurious effect on bacteria, so far as is now known. The effects of the rays on the tissues of the human body are interesting. Prolonged or frequent exposure of the skin to their influence sets up an inflammation, a true dermatitis I think you physicians would call it; subsequently the tissues break down and ulcers are formed; if applied to the scalp for a long time the hair dies and falls out.

It is stated that with the aid of the fluorescent screen, one’s heart, lungs and other of the internal organs can be seen, enabling us to observe the performance of their normal, or abnormal, functions. This is true only with very powerful apparatus, giving sparks 8 to 10 inches long.

Already, while on the border land only of the development of this discovery, there is no doubt it has been of great value to the physician in making, or confirming a diagnosis. Already stone in the bladder, abdominal tumors and the condition of diseased lungs have been made out and studied with their aid. Already they have proved of great value to the surgeon in clearing up the doubt of whether he had a fracture or dislocation near or within the ligaments of a joint. Already it enables him to examine with the eye a broken bone and to see its condition. When the bone is set he may actually look at it and see if the bones are in proper position, and this with the bandages applied.

Usually the sensation of prickling of heat is felt when one’s hand is being photographed; and not without reason, as energy is being expended by the rays passing through. As I have said, the rays are useful in locating foreign bodies in the body. They are useful also in detecting gems from their imitations.

There is nothing in the effects known to be due to these rays, inconsistent with their being one of the many varieties of light; in fact Becquerel has lately discovered that certain salts of uranium, after being exposed to sunlight, emit radiations, which, like X-rays, pass through solid bodies and affect photographic plates; these new radiations we think to be light, as they are refracted and polarized. It may be the link between X-rays and ordinary light.

Professor Lynde has kindly consented to manipulate the lantern while I show you on the screen some examples of photographs by X-rays.

(The room was here darkened and the following photographs were shown: New X-ray lamp; — subject being photographed; spectacles in shagreen case; steel eye glasses in leather case; gold, silver and bronze coins in case; various objects in wooden box; various substances; box of instruments; cork screw and cork, needle case and matches; sole; frog, showing broken leg; chicken’s feet; pigeon, 10 days old; child’s hand, 6 years old; boy’s hand; lady’s hand with needle in flesh; man’s hand; man’s hand, showing cuff and cuff links; deformed hand; another deformed hand; mummy’s hand; wrist; man’s broken finger badly set; injured elbow; man’s elbow joint; boy’s ankle; foot, showing outlines of flesh; foot, naked; infant, 3 months old; girl, showing disease of hip bone. The photographs were excellent and many of them were heartily clapped. The lecturer made explanations as they were shown.)

In conclusion, I wish you to remember that luminosity is but a form of light; that down to the time of the discovery of the X-rays all were agreed that light was due to transverse vibrations of ether; and that with the discovery of the X-rays the scientists have become divided into two schools, one holding to the theory of transverse vibrations, the other to a belief that the X-rays are caused by the emission of electrified particles.

The controversy rages about these points, with the probability of success leaning toward the former in view of Becquerel’s experiments with the salts of uranium, and the fact that the X-rays photographs have been taken with the light of a fire-fly.

Before the lecturer left the platform the photograph of Dr. Sefton’s hand which had been taken during the lecture was shown on the screen. The negative was too large to fit into aperture for the slides and it was placed in front of the lens. The image was somewhat indistinct on this account, but the negative was in reality one of the best Mr. Case has yet taken.

At the conclusion of the lecture Mr. Case was most heartily applauded. Dr. John Gerin, in behalf of the medical society and its guests, warmly thanked the lecturer in a happy little speech and the vote of thanks which he proposed was enthusiastically accorded.