How X-rays were discovered – Victorian medical tech we still use every day

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How X-rays were first discovered
For the discovery of the X-ray in the 1890s, Wilhelm Röntgen was awarded the very first Nobel Prize in Physics in 1901, “in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays subsequently named after him.” (In Germany, X-rays are called Röntgenstrahlen.)

Also worthy of note: Röntgen refused to patent the invention, instead wanting the concept to be built upon, and for it to benefit humanity instead of just one man.

Röntgen’s rays: How X-rays were discovered: As described in 1953

Excerpted from an article in the Daily News (New York, New York) Nov 15, 1953

Dr. Wilhelm Konrad von Roentgen, German physicist, discovered mysterious rays in this laboratory in Wurzberg, called the glowing emanations “X” because he was not certain what they were.

His experiments led to the use of X-rays in medicine and industry in thousand ways.

Early X-ray experiments - 1890s (2)

Roentgen was experimenting with the light emitted by a Crookes tube. He had masked it with black paper, and then doused the lights in his laboratory to see whether he had left any glimmers. He hadn’t, and the room was sealed against light — but there was a glow, not from the Crookes tube itself. But from something else in the room.

This was a plate coated with barium platinocyanide, a compound used by physicists because of its property of fluorescence under certain conditions.

It was Roentgen’s conclusion that the plate glowed because of some emanation which was passing through the masking material enclosing the tube. These were rays of some kind, but not in the visible spectrum. Being uncertain just what they were, Roentgen called them X.

Early X-ray experiments - 1890s (5)

Legend has it that he also found the rays acted on photographic plates when a key left an impression on a plate forgotten in a drawer wear the Crookes tube. Roentgen himself said he first observed this quality of the rays when he saw a shadow cast by a loose wire in the tube.

His finding led to the conclusion that the X-rays would penetrate materials opaque to ordinary light, though to varying degrees. And some materials, such as metals, were impervious, also in varying degrees.

The absent-minded-professor type, Roentgen got so absorbed that it was past suppertime. His wife came to call him to the table. He drew her into the room and asked her to put her hand down on a sensitized plate. Then he turned off the lights, and turned on his Crookes tube. He thus took the first X-ray picture.

The first X-ray - A hand

When the word got around, the reaction of the outer world was slightly comic. Non-scientific people got the notion that there was something indecent about X-rays. They figured you could look right through clothes and nobody was safe from a prying scientist with a prurient mind.

The scientific world, however, caught on at once. A physicist didn’t need anything new in the way of equipment to carry out Roentgen’s experiments. He could use stuff lying around the place. When a whole lot of people started working in the same field, improvements were inevitable.

Hundreds of people have contributed to the progress of X-ray, or Roentgenology, as the science is sometimes called.

It was an immediate and tremendous help to the doctor, both in wounds and in disease. The bonesetter’s task was immeasurably assisted. He could see the break and see the set and didn’t have a chance to make mistakes.

Early X-ray experiments - 1890s (3)

The surgeon was enabled to discover ahead of time whether he was going to encounter unexpected hazards before he laid the patient open. The doctor who once had to probe around for a bullet could locate it at once. (One of the first actual uses of X-ray in the U. S. was to spot a bullet in a leg; the slug had moved four inches from the hole where it entered.)

The dentist is able to spot decay and abscess in the teeth. The use of the X-ray in TB is well-known to everyone. The gastroenterologist can follow the workings of the alimentary canal by watching the shadows thrown by the barium “meal” as it works its way downward, thus indicating conditions like ulcers, tumorous growths or diverticulosis.

The genito-urinary man, by using certain dyes, can see what’s happening in the kidneys and other organs in that department. The orthopedist finds X-ray invaluable in his studies of bones and joints. In fact, the X-ray is used in nearly every field of diagnosis where formerly the doctor had to guess or feel his way around…

Early X-ray experiments - 1890s (1)

Roentgenologists, or radiologists, or X-ray specialists have developed the art of reading the X-ray picture to a high point, and can spot things that the untrained eye would miss. 

When we think of the x-ray it is usually in connection with doctoring of some kind, but it is also extremely important in industry. Some 4,000 plants in the U. S. are using X-ray in one way or another.

It is primarily an inspection tool, though other uses have been found, too. A good many Government contracts now have a clause requiring X-ray inspection as a guarantee against defects that might become apparent only when the product was used.

Industrial X-ray machines are of all sizes or shapes, some of them specially designed for a particular job. They all depend on the same basic principle — that different substances, or different thicknesses of the same substance, can be penetrated by certain numbers of X-rays, and the variations can be measured accurately.

There is a brewery which has an apparatus that inspects cans on the filling line to see that they are full. An X-ray sends a beam through the can near the top. If the can is full, okay. If it’s under the proper level, the beam, encountering no liquid, passes through to a crystal detector that actuates a blast of air that blows the can off the line. The same principle can be applied to other canned goods.

A candy company uses a fluoroscope to inspect sealed packages to make sure, for example, that a small stone has not slipped in among the peanuts in its candy bars.

Hand and bouquet X-ray - republished in 1953


Cathode ray wonders: Professor Sanford explains Crooke’s Tubes, ether vibrations and X-rays

Waves with a new wiggle: The great thing that Röntgen’s discovery may be, and things that it is not

The San Francisco Call (San Francisco, California) February 18, 1896

Professor Fernando Sanford of the department of physics of the Stanford University has just received a letter from his associate, Professor Carmen, who is now in Berlin, and who has investigated Röntgen’s photographs with his X, or unknown, rays. Professor Carmen doesn’t say very much, but what he does say comes from a scientist.

Birthplace fo the X ray

“I saw Röntgen’s photographs the other day,” writes Carmen in the course of his letter, “and heard Warburg, professor of physics in the University of Berlin, and others discuss them. Lummer had also seen them, and there seems to be no doubt about the reality of the phenomenon.

“The photograph of the hand, in which only the bones and the ring are shown, is very striking. It is, however, not very sharp. A photograph of a magnetic compass in a wooden case, photographed through the case, is very sharp indeed.

We know as much here as any, where, but there is yet no consensus of opinion as to what the phenomenon really is. The natural idea is that they are longitudinal ether waves. They are, however, very faint.”

Photographs in the dark

Professor Sanford is a widely-known physicist, who has made some important discoveries in physical science, the most important of which were his photographs in the dark, with the so-called Hertzian waves, made three years ago, and he is naturally keenly interested in Professor Roentgen’s startling discovery of unseen shadows, not made with light, and of a way to fix them on photographic plates. Sanford has experimented a little with Roentgen’s process, and has secured faint results, but he has not had ready for use the proper apparatus, and is not ready to talk about his experiments.

He talked about Roentgen’s work, however, yesterday, at the university, and explained, in a way that people of ordinary intelligence can understand, what Roentgen’s discovery may possibly be. The scientists are only guessing at the new thing yet, though many have opinions.

Hand X-ray from the February 1896 issue of Photographische Rundschau (Germany)

“The point of chief scientific interest in the matter, which is the theory by which Roentgen and others explain the phenomenon, the papers say little or nothing about,” said Professor Sanford.

“That is, that he has discovered a new form of motion or vibration in the ether – vibrations that are longitudinal instead of transverse to the line of progress. I would not express any definite opinion about it. It would be only guessing, and there is plenty of guessing going on. It is a scientist’s business to guess, but to find out before he talks.

“A large part of the stuff and most of the pictures the papers publish are necessarily fakes. It is but natural that there should be a good deal of slopping over about such a thing, of course.

“It is too early to make any definite predictions as to what scientific or practical value the discovery will have, but it is, of course, a thing of great interest to physicists, and it may extend our knowledge wonderfully.”

Then the physicist led the way into a big laboratory, full of all sorts of costly scientific apparatus, and elucidated somewhat the story of Roentgen’s X-rays.

Early X-ray experiments (1)

Roentgen’s X-rays

The discovery and the process of Professor Roentgen [Röntgen] (call it Rantgen, with a short “a” and a hard “g”) began with a Crooke’s tube, and the professor picked up a Crooke’s tube and connected it by two wires with an induction coil, which was in turn connected with a two-cell battery.

A Crooke’s tube arranged for use is a hollow sealed shell of glass of any size or shape, from which the air has been very nearly but not quite exhausted, and into which run platinum wires connected with the opposite poles of a battery.

The bulb of an incandescent electric light is a pretty good Crooke’s tube. The one that Professor Sanford picked up was made to show extra effects. It was of two compartments — one a small one — between which there was free connection through a slender glass tube bent double and then into the form of a cross.

Air or fluid passing between the compartments would go up, around and back through the cross. The professor set the current at work and instantly the Crooke’s tube became a thing of beauty. Around one of the wire ends at one end of the tube, there appeared a purple glow that was simply a mass of fluorescence in the vacuum. The wire itself gave out no light.

Early science experiments - How X-rays were discovered

At the other end of the tube was a much smaller fluorescence. The glass cross glowed with a beautiful greenish light, which seemed to stream through the cross but not leave it.

Now, this Crooke’s tube, as it lay there glowing with its strange light, was ready to produce one of Roentgen’s photographs if things had been fixed right around it.

The history of how X-rays were discovered

Vibrations of some sort — those X rays — were surely beaming from it in all directions, shining through the box on which the tube lay, as sunlight would shine through a glass case, and if the reporter had possessed a sense capable of perceiving those rays he might have seen before him the skeleton of the professor of physics as one might see iron or wooden bones in a glass manikin when the white sunlight shone through it.

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An accidental discovery

But now don’t think that this pretty light, the vibrations that the human eye is capable of perceiving, would have anything to do with the Roentgen photograph.

Scientists would have said so, until Roentgen accidentally discovered something the other day — that arrangement of battery, induction coil and vacuum was setting up different kinds of vibratory motions that variously rolled out through the surrounding ether, air and solid substances, as a big turbine wheel, for instance, might cause all sorts of heavy and light, slow and rapid, shakings through the water and the mill.

If that arrangement had been set up before a scientist a few centuries ago the only phenomenon he would have perceived would have been the glow of light, because the particular vibrations producing it are the only ones of the lot that man happens to have a sense to perceive.

Early X-ray experiments (3)

Since a century and more ago when man learned by experiment to recognize the electric current by its effect on something besides sense, the ordinary force of the electric current would have been recognized in that simple arrangement of Professor Sanford’s.

That makes two things that would have been the limit of the forces of nature which man would have perceived that arrangement on the laboratory table setting into activity up to a very few years ago.

Then Hertz found a new sort of vibrations proceeding from an induction coil and especially from the neighborhood of an electric discharge and these are now called Hertzian waves.

They are not light, heat, or the electric current. They are vibrations that flow outward from their source like light from a thing that glows, and until Hertz stumbled on them so recently nobody ever dreamed that such things were bustling about in the universe.

How X-rays were discovered

Distinct vibrations

And now comes Professor Roentgen with the discovery that from this arrangement described there proceeds what is believed to be a kind of vibration more distinct from the other sorts than the Hertzian waves are from light.

No sense can perceive it, and it is being recognized and studied by its effects, noticed now for the first time. It illustrates how little man is capable of perceiving. This was the way Professor Sanford talked over his Crooke’s tube:

“There are many peculiar phenomena which take place in Crooke’s tube, and they have been studied for about fifteen years. If the air is entirely exhausted, there can be no spark produced in one.

“They are generally exhausted to from the one-thousandth to the one ten-thousandth part of an atmosphere. The end of the wire connected with the negative pole of the battery is called the cathode, and the effect appears to proceed from the cathode. When the current is started the particles of rarefied gas are electrified and driven off from the cathode with great force.

“If there is sufficient gas it becomes luminous through the particles striking each other. When the particles can reach the walls of the tube and pound against them, they set up a fluorescence in the glass. Probably they cause the glass to set up light vibrations in the ether.

“The cathode rays are not the X rays of Roentgen, nor are they rays of light. They are the steams of gas particles as they are repelled from the cathode, and it is rather their effect which is talked about.

“If I put certain substances near this tube, they will likewise fluoresce, as has been known for some time. It has not been known that the cathode rays would produce the same effect when the fluorescence was hidden, though it had been discovered that when a tiny sheet of aluminum is set in the tube like a pane of glass the cathode rays striking on this opaque window would produce a fluorescence in a proper substance placed behind it.

“Roentgen accidentally discovered in his laboratory that a sheet of paper moistened with double cyanide of barium and platinum and left near a Crooke’s tube when the tube was covered with a black cloth would show fluorescent effects, showing that the cloth was transparent to the cause of the fluorescence.

“He followed this discovery with his experiments. The effects secured can hardly be explained by any knowledge or theories held before. The rays from the Crooke’s tube, which produced Roentgen’s new fluorescent effects and later his photographic effects after passing through wood and flesh, are, of course, not light, and they are not Hertzian waves evidently.

“His theory is that the gaseous particles, striking against the glass, produce a vibration which sets up waves or vibrations in the ether different from any other kind of motion. He thinks that they are longitudinal ether waves.

Early X-ray experiments (2)

“We have no sense that enables us to take cognizance of the ether as we can of light and heat, but we know that light and radiant heat are vibrations in an elastic medium, and we call that medium the ether. It must pervade all bodies, because some form of radiation can pass through all bodies at a velocity far greater than it would be if the bodies themselves transmitted it.

The ether is as real to physicists as matter. We know only one kind of ether waves, and they are now all included in the term radiation. We know no limit to their lengths. One very small octave in the range of wavelengths we can perceive by the eye as light.

“Now, every kind of ether waves or vibrations that we know anything about can be reflected, refracted and polarized. We also know that all the kinds of ether waves with which we are acquainted are transverse vibrations; that is, the vibrations are back and forth across the line or plane of motion, like waves in water or in a rope when it is shaken, or like the vibrations of a string.

“When we speculate about Roentgen’s rays being longitudinal vibrations in the ether we mean that they are like sound vibrations, in which the vibrations are back and forth on the line of motion without crossing it. In sound vibrations the air goes out on a straight line, stops with a condensation and goes on again. Sound is the only kind of longitudinal vibrations we know anything about.

“It has been recognized by physicists that there is no theoretical reason why there should not be longitudinal waves in the ether, but it has been supposed that the ether was so nearly incompressible that the waves would have almost infinite velocity and length and hence could not be perceived.

“All elastic bodies, solid, liquid and gaseous, transmit, longitudinal waves, and as the ether is an elastic body it would certainly transmit them too. Roentgen has discovered that his new rays cannot be reflected, refracted or polarized, as we can do with all known kinds of ether vibrations. So Roentgen thinks that he has discovered a new kind of radiation. What longitudinal ether waves would do we do not know.”

Early X-ray experiments - 1890s (7)

An important find

“Whatever Roentgen’s discovery may be, it is an important find. Anything that will throw light on electrical phenomena is of value to science. We are calling on the ether to explain heat, light and electrical effects, and probably all effects which we class under chemical and magnetic attractions and repulsions, and even gravitation, as far as we have any hope of explaining it.

“It should be remembered that we have before produced photographs with electrical waves not luminous, and others have done to a certain extent what Roentgen has done and without the aid of light, except, we can refract and reflect the waves which have been presumed to produce the effects.

“In 1893, I produced photographs in the dark with the use of electrical waves, and I have attributed them to the Hertzian waves. It is barely possible that my pictures were due to the X rays.

“A great general misconception about Roentgen’s discovery and its possibilities would be corrected if it were remembered that his rays cannot be reflected by any thing, or refracted by a lens of any substance. Hence no image can be produced. The rays pass through substances transparent or translucent to them and cast shadows on the negative which are fixed there.

“It is wholly the fixation of shadows. The bones of the hand being opaque to the rays cast their shadow on the plate when the rays pass through the hand. The negatives used are prepared for the effect of light. Negatives better adapted to these rays may be expected to be invented.”


As you might imagine, the suggestion from the very early days of X-ray technology to try making your own at home was not the smartest advice.

A modern medical study has shown that an X-ray machine from 1896 actually exposed the body to 1,500 times more radiation than does the tech of today.

In fact, Gerrit J Kemerink PhD, one of the study’s authors, noted, “Many operators of the early x-ray systems experienced severe damage to hands over time, often necessitating amputations or other surgery.”

X-Rays at home

The following simple and inexpensive device for the production of X-rays is described in the Scientific American of June 11, from which we also copy the accompanying [above] illustration:

“The expense of special Crookes tubes, powerful coils and batteries has deterred many from entering this interesting field of experiment; but R. McNeil of this city has recently devised apparatus in which an ordinary incandescent lamp is substituted for the Crookes tube, and an induction-coil of common form is made to supply electricity of sufficiently high potential to produce the X-ray phenomena.

“The lamp, which is a 52-volt, 16-candlepower Sawyer-Man lamp, is made of German or lime glass. For convenience, it is mounted in an insulating standard. The top of the lamp is covered with aluminum foil, which is connected with one terminal of the secondary of the induction coil, and then the bottom is connected with the other terminal of the secondary, as shown. The X ray proceeds from the cathode.

By means of the fluoroscope the shadows of the bones of the hands and feet, also of the limbs, may be seen when they are placed between the instrument and the lamp.

“It has been found in this experiment that when a blue fog appears in the lamp, the vacuum is too low for the best results. By placing the lamp in the house circuit for fifteen or thirty minutes, the high vacuum is restored by the heat, and will remain good for about fifteen minutes.

“The coil is capable of giving a three-inch spark, and the X-ray produced by this simple and inexpensive apparatus is sufficient for making radiographs.”

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