In october of 1895, Wilhelm Conrad Ršntgen (1845-1923) who was professor of physics and the director of the Physical Institute of the University of Wurburg, became interested in the work of Hillorf, Crookes, Hertz, and Lenard. The previous June, he had obtained a Lenard tube from Muller and had already repeated some of the original experiments that Lenard had created. He had observed the effects Lenard had as he produced cathode rays in free air. He became so fascinated that he decided to forego his other studies and concentrate solely on the production of cathode rays.
One Friday evening, on November 8, 1895, he worked alone in his laboratory. It was the beginning of the weekend and all of his assistants had gone home. He had set up his experiment using a Crookes tube fitted with an anode and cathode , separated from each other by a few centimeters in the tube. He used a Rhumkoff induction coil to produce a difference of potential of a few thousand volts, knowing that a stream of charged particles would originate in the cathode and would be attracted to the anode.
The laboratory Ršntgen worked in that evening was very similar to all other laboratories of those who worked before him, but the conditions that existed that evening varied in three very important ways. His laboratory was dark, his tube was covered with a light-proof cardboard jacket and a screen of fluorescent material laid on a table a few feet away from the apparatus. While passing the discharge, he suddenly noticed a shimmering light on the table top. He could not believe his eyes, so he again repeated the experiment. He released the discharge many times producing the same results each time. Greatly excited, he realized that the green fluorescence was emanating from the screen. He repeated the experiment again, this time moving the screen further and further away and he still received the same results.
Ršntgen knew the fluorescence could not be produced by the cathode rays since it was well known that they could not penetrate through the wall of the tube. Visible light could not be the stimulus since the tube was covered with a shield which was opaque to light. He boldly hypothesized that he must have been producing some unknown type of radiation.
Ršntgen spent the next eight weeks in his laboratory repeating his experiments. He ate and even slept in his laboratory as he attempted to determine if the rays could penetrate substances besides the air. He placed various objects between the tube and screen and he found that the screen still fluoresced but with different intensities depending on the material being used. When he placed a lead disk, which he was holding, in the cathode ray path he was astonished to find the shadow of the round circle appeared on the screen along with the outline of his thumb and forefinger and within them the bones of his hand! He replaced the screen with a photographic plate and employed his wife Bertha to place her hand on the photographic plate while he directed the rays at it for fifteen minutes. Frau Ršntgen was taken back and somewhat frightened by the first x-ray plate of a human subject which enabled her to see her own skeleton. The feeling to her, as would come to others, was vague premonition or death.
Ršntgen hurriedly prepared his notes so that his first report “On a New Kind of Rays” could be published in the
Proceedings of the Physical Medical Society
of Wurburg on December 28, 1895. The paper consisted of some seventeen numbered paragraphs indicating various observations. Ršntgen described how he created and noticed the fluorescence of the barium platinocyanide screen. He described his amazement at the fact that something had passed through the cardboard surrounding his tube. He then described how he sought to
the transparency of other objects. He wrote on his observations of paper, a One thousand page book, blocks of wood, a sheet of tin foil, a double deck of cards, a single card, and sheets of hard rubber. He described his observation that glass plates of equal thickness behaved in different wars depending on the amount of lead they contained, those with more lead were less transparent. He described testing various metals and his finding that lead seemed to be the most opaque material. Not knowing what these emanations were he uses the term
to describe the rays he was producing.
Ršntgen continued by describing objects which fluoresced besides the screen such as rock salt and ordinary glass. He described an insensitivity of the eye to the rays even when brought close to the tube. He wrote his attempts to pass the rays through a prism finding that no deviation occurred. He told of his attempts to defract the rays by utilizing a magnet. He wrote of his certainty that the rays were emitted from the point on the tube which fluoresced the most. By deflecting the cathode rays, he found the x-ray emanated from a new spot. He continued on to tell of some of the shadowgrams he produced. (Shadows of this type are of extreme sharpness when the source of the ray is narrowed more than those produced by light because the shadows enlarge as a result of defraction, which is almost completely absent with x-rays.) He wrote of how one shadowgram was taken through a door with the discharge apparatus on one side and the plate on the other. He concluded the paper by stating his belief that the rays were not some type of ultraviolet light.
The news spread quickly and the first newspaper report occurred as a result of a “leak”. Ršntgen had sent his friend, Franz Exner, at the Vienna University, some of his first x-ray pictures. Exner in turn showed some of his associates, one of whom was the son of the editor of the Vienna Presse. The young man borrowed the pictures and showed his father who at once realized the news value of the discovery and published an article describing the main facts as he knew them. He also included a prediction of his own of the possible medical value of the new discovery. The article was quickly copied by papers in many other countries and publications soon appeared both in Europe and the United States, even before they appeared in the local Wurburg papers.
Ršntgen was not at all pleased with the notoriety. He described, in a letter to a friend, his disgust at not being able to recognize his own work upon reading the newspaper reports and his sadness that the photographs were not viewed as a means for his discovery, but rather were treated as the main discovery. He described his inability to work free of interruption in his own laboratory.
On January 13, 1896, Ršntgen was called to give a demonstration of his discovery for Kaiser Wilhelm II. From five o’clock until midnight, Ršntgen demonstrated, using limited equipment, showing how the rays penetrated boards of paper and wood, boxes of paper, and other non-living objects. At the end, the Kaiser decorated Ršntgen with the Order of the Crown.
The first and only demonstration before a scientific group occurred on January 3, 1896. He gave an introductory review and then demonstrated the penetration powers of the x-ray. After his formal lecture, he invited a colleague, Professor R.A. von Kolliker, the famous anatomist and embryologist, to have his hand photographed. Von Kolliker was so impressed that he called for a round of cheers and proposed that the new rays be designated Ršntgen rays.
Ršntgen was a sincere and humble man of great modesty and he lid not wish his rays to bear his name. As offers of honor came to him, Ršntgen found them so very distasteful that he sought refuge in Italy in March, after the publication of his second paper. The Kingdom of Bavaria offered him the Royal Order of the Crown. The offer also meant that the word “von” would be placed before his name and he would be considered nobility. He accepted the invitation, but declined the symbol of status, the “von”. Later, in 1896, he accepted the Rumford gold medal of the Royal Society and in 1901 he would be the first to receive the Nobel Prize for physics, but he bequeathed the Nobel prize money to scientific research at Wurburg.
Just as incidents of honors were high, as was excitement, the saturation point was quickly reached by the public and interest began to wane. However, the shock of looking at a shadowgraph (as x-ray pictures came to be called) of one’s hand or head produced sensations of death and those who did not understand, saw the x-ray as an invasion of privacy. Cartoonists and jokers saw in this new discovery an area for new humor. From cartoons which appeared in the printed media, it seems clear that the general public did not receive Ršntgen’s discovery very well. The general concept seemed to indicate that Ršntgen’s photography was similar to that of regular photography, except that it was believed to penetrate every thing including flesh, clothing, bones, etc . . . In researching, mention is often made of the fact that
magazine often carried many jokes and cartoons pertaining to the subject. A London firm even advertised the sale of x-ray proof suits in one magazine. One New York newspaper report announced that the College of Physicians and Surgeons was using x-rays to reflect the diagrams directly on to the students’ brains, making a more enduring impression than the normal method of learning. In New Jersey, the misconceptions spread to the House of Representatives floor when one legislator forbade the use of x-rays in opera glasses.
Ršntgen spent the ten weeks after his first publication pursuing new lines of investigation and the second paper was submitted in March, 1896. Ršntgen knew that x-rays were capable of discharging electrified bodies and he felt certain that it had been x-rays, not cathode rays in Lenard’s experiments which had passed through the aluminum window. Ršntgen wanted an atmosphere free from electrostatic forces from the vacuum tube, from the induction wires, and the air which was near the discharge apparatus. He built a sheet metal cabinet approximately seven feet high and four feet square in order to create a more permanent dark room and eliminate the need to drape the laboratory with ineffective curtains and blinds. On one side he inserted a thin aluminum disk approximately eighteen inches in diameter for the rays to pass through. He also covered the wall with lead paint. He placed the discharge apparatus on the outside of this wall. He placed a zinc door on the opposite side, which allowed him to enter and exit. (This apparatus, without his knowing, would also provide Ršntgen the needed protection from x-ray radiation.)
His second paper described his discovery that electrical bodies were discharged more quickly if the rays were more intense. He described finding no difference between positive and negative electricity or conductors or insulators. Secondly, when an electric conductor was surrounded with a solid insulator, such as parafin, the radiation had the same effect as would result from an exposure of the insulating material to earth. He wrote next of surrounding the insulating material with a conductor connected to earth, noting the radiation produced no action which can be detected. These observations lead him to conclude it was the air through which the x-rays had passed which possessed the power to discharge the electrified bodies.
Ršntgen described next how he set up an experiment to show that it might be possible to discharge bodies by exposing them to air which had been exposed to x-rays. He wondered why the air lost this property. (We know the ions recombine in a short time, especially upon collision with a surface.) The paper concluded with the observed effects of an x-ray on other gases and the effects of different cathodes concluding that platinum was the best material to use to make a cathode.
Ršntgen’s third and final paper on the subject was published one year later in March, 1896. It contained still more information on experiments he had conducted. Ršntgen described his finding that any substances subjected to x-rays would themselves emit x-rays. He termed this secondary radiation. Ršntgen found that with
, the emission was uniform over a hemisphere on a target, while with
and a thin target, some radiation appeared from the back of the target. He concluded with a number of comparative opacity to x-rays of various substances in different thicknesses.
Ršntgen went on to accept a position to head the Philosophical Faculty of the University of Munich. Here he issued seven more communications over the next seventeen years, most of which covered his former interests. In a letter to his cousin in America in 1912, he wrote about making a possible trip. However, his frail wife’s health worsened, World War I broke out and the trip was never taken. His feelings for his country remained strong and when the call for gold came to be melted into buillion, he turned in his decorations, including the Rumford medal. This, it is said, he later regretted.
At the end of the war in 1919, there was bitter political unrest and considerable inflation. Ršntgen, on a fixed income, struggled to adjust to the daily rise in costs. To add to his sadness, within the year of the armistice, he lost his wife and became increasingly lonely. He continued to work until his retirement in 1920 and even then two rooms were set aside in which he continued to work. By 1923, he still walked to the laboratory but he complained that his sight and hearing were proving inadequate for observations. On February 10, 1923, he died in Munich at the age of seventy-eight of carcinoma of the intestines. In accordance with his will, his body was cremated and his papers and personal correspondences were burned. His personal belongings were auctioned off and the proceeds were turned over for educational uses.
Have students read the selection on Ršntgen contained in the slide packet and complete the worksheet in this unit.