The X-ray Century

Editor's Note: This writer from McClure's Magazine had the opportunity to visit and interview Professor Roentgen concerning the discovery. The following excerpts are from the extensive article published in April, 1896.

On instruction by cable from the editor of this magazine, on the first announcement of the discovery, I set out for Wurzburg to see the discoverer and his laboratory. I found a neat and thriving Bavarian city of forty-five thousand inhabitants, which, for some ten centuries, has made no salient claim upon the admiration of the world, except for the elaborateness of its medieval castle and the excellence of its local beer. Its streets were adorned with large numbers of students, all wearing either sca rlet, green, or blue caps, and an extremely serious expression, suggesting much intensity either in the contemplation of Roentgen rays or of the beer aforesaid. All knew the residence of Professor Roentgen (pronunciation: "Renken"), and directed me to th e "Pleicher Ring.''

At the door I was met by an old serving-man of the idolatrous order, whose pain was apparent when I asked for "Professor" Roentgen, and he gently corrected me with "Herr Doctor Roentgen." As it was evident, however, that we referred to the same pe rson, he conducted me along a wide, bare hall, running the length of the building, with blackboards and charts on the walls. At the end he showed me into a small room on the right. This contained a large table desk, and a small table by the window, cove red with photographs, while the walls held rows of shelves laden with laboratory and other records An open door led into a somewhat larger room, perhaps twenty feet by fifteen, and I found myself gazing into a laboratory which was the scene of the discove ry--a laboratory which, though in all ways modest, is destined to be enduringly historical.

Professor Roentgen entered hurriedly, something like an amiable gust of wind. He is a tall, slender, and loose-limbed man, whose whole appearance bespeaks enthusiasm and energy. He wore a dark blue sack suit, and his long, dark hair stood straigh t up from his forehead, as if he were permanently electrified by his own enthusiasm. His voice is full and deep, he speaks rapidly, and, altogether, he seems clearly a man who, once upon the track of a mystery which appealed to him, would pursue it with unremitting vigor. His eyes are kind, quick, and penetrating; and there is no doubt that he much prefers gazing at a Crookes tube to beholding a visitor, visitors at present robbing him of much valued time. The meeting was by appointment, however, and h is greeting was cordial and hearty. In addition to his own language he speaks French well and English scientifically, which is different from speaking it popularly. These three tongues being more or less within the equipment of his visitor, the conversa tion proceeded on an international or polyglot basis, so to speak, varying at necessity's demand.

"Now, then,'' said he, smiling, and with some impatience, when the preliminary questions at which he chafed were over, "you have come to see the invisible rays."

"Is the invisible visible?''

"Not to the eye; but its results are. Come in here."

He led the way to the other square room mentioned, and indicated the induction coil with which his researches were made, an ordinary Rhumkorff coil, with a spark of from four to six inches, charged by a current of twenty amperes. Two wires led fro m the coil, through an open door, into a smaller room on the right. In this room was a small table carrying a Crookes tube connected with the coil. The most striking object in the room, however, was a huge and mysterious tin box about seven feet high an d four feet square. It stood on end, like a huge packing-case, its side being perhaps five inches from the Crookes tube.

The professor explained the mystery of the tin box, to the effect that it was a device of his own for obtaining a portable dark-room. When he began his investigations he used the whole room, as was shown by the heavy blinds and curtains so arrange d as to exclude the entrance of all interfering light from the windows. In the side of the tin box, at the point immediately against the tube, was a circular sheet of aluminium one millimetre in thickness, and perhaps eighteen inches in diameter, soldere d to the surrounding tin. To study his rays the professor had only to turn on the current, enter the box, close the door, and in perfect darkness inspect only such light or light effects as he had a right to consider his own, hiding his light, in fact, n ot under the Biblical bushel, but in a more commodious box.

"Step inside,'' said he, opening the door, which was on the side of the box farthest from the tube. I immediately did so, not altogether certain whether my skeleton was to be photographed for general inspection, or my secret thoughts held up to li ght on a glass plate. "You will find a sheet of barium paper on the shelf," he added, and then went away to the coil. The door was closed, and the interior of the box became black darkness. The first thing I found was a wooden stool, on which I resolve d to sit. Then I found the shelf on the side next the tube, and then the sheet of paper prepared with barium platino-cyanide. I was thus being shown the first phenomenon which attracted the discoverer's attention and led to the discovery, namely, the pa ssage of rays, themselves wholly invisible, whose presence was only indicated by the effect they produced on a piece of sensitized photographic paper.

A moment later, the black darkness was penetrated by the rapid snapping sound of the high-pressure current in action, and I knew that the tube outside was glowing. I held the sheet vertically on the shelf, perhaps four inches from the plate. Ther e was no change, however, and nothing was visible.

"Do you see anything?'' he called.


"The tension is not high enough;'' and he proceeded to increase the pressure by operating an apparatus of mercury in long vertical tubes acted upon automatically by a weight lever which stood near the coil. In a few moments the sound of the discha rge again began and then I made my first acquaintance with the Roentgen rays.

The moment the current passed, the paper began to glow. A yellowish-green light spread all over its surface in clouds, waves, and flashes. The yellow green luminescence, all the stranger and stronger in the darkness, trembled, wavered, and floate d over the paper, in rhythm with the snapping of the discharge. Through the metal plate, the paper, myself, and the tin box, the invisible rays were flying, with an effect strange, interesting, and uncanny. The metal plate seemed to offer no appreciable resistance to the flying force, and the light was as rich and full as if nothing lay, between the paper and the tube.

"Put the book up," said the professor.

I felt upon the shelf, in the darkness, a heavy book, two inches in thickness, and placed this against the plate. It made no difference. The rays flew through metal and the book as if neither had been there, and the waves of light, rolling cloud- like over the paper, showed no change in brightness. It was a clear, material illustration of the ease with which paper and wood are penetrated. And then I laid book and paper down, and put my eyes against the rays. All was blackness, and I neither saw nor felt anything. The discharge was in full force, and the rays were flying through my head, and, for all I knew, through the side of the box behind me. But they were invisible and impalpable. They gave no sensation whatever. Whatever the mysterious rays may be, they are not to be seen, and are to be judged only by their works.

"Now, Professor," said I, "will you tell me the history of the discovery?''

"There is no history," he said. ''I have been for a long time interested in the problem of the cathode rays from a vacuum tube as studied by Hertz and Lenard. I had followed theirs and other researches with great interest, and determined, as soon as I had the time, to make some researches of my own. This time I found at the close of last October. I had been at work for some days when I discovered something new.

''What was the date?''

''The eighth of November.''

''And what was the discovery?"

''I was working with a Crookes tube covered by a shield of black cardboard. A piece of barium platino-cyanide paper lay on the bench there. I had been passing a current through the tube, and I noticed a peculiar black line across the paper.''

''What of that?"

"The effect was one which could only be produced, in ordinary parlance, by the passage of light. No light could come from the tube, because the shield which covered it was impervious to any light known, even that of the electric arc.''

"And what did you think?''

"I did not think; I investigated. I assumed that the effect must have come from the tube, since its character indicated that it could come from nowhere else. I tested it. In a few minutes there was no doubt about it. Rays were coming from the t ube which had a luminescent effect upon the paper. I tried it successfully at greater and greater distances, even at two metres. It seemed at first a new kind of invisible light. It was clearly something new, something unrecorded.

"Is it light?"


"Is it electricity?"

"Not in any known form."

"What is it?"

"I don't know."

And the discoverer of the X rays thus stated as calmly his ignorance of their essence as has everybody else who has written on the phenomena thus far.

''Having discovered the existence of a new kind of rays, I of course began to investigate what they would do." He took up a series of cabinet-sized photographs. "It soon appeared from tests that the rays had penetrative power to a degree hitherto unknown. They penetrated paper, wood, and cloth with ease; and the thickness of the substance made no perceptible difference, within reasonable limits." He showed photographs of a box of laboratory weights of platinum, aluminium, and brass, they and the brass hinges all having been photographed from a closed box, without any indication of the box. Also a photograph of a coil of fine wire, wound on a wooden spool, the wire having been photographed, and the wood omitted. "The rays,'' he continued, "pass ed through all the metals tested, with a facility varying, roughly speaking, with the density of the metal. These phenomena I have discussed carefully in my report to the Wurzburg society, and you will find all the technical results therein stated.'' He showed a photograph of a small sheet of zinc. This was composed of smaller plates soldered laterally with solders of different metallic proportions. The differing lines of shadow, caused by -the difference in the solders, were visible evidence that a n ew means of detecting flaws and chemical variations in metals had been found. A photograph of a compass showed the needle and dial taken through the closed brass cover. The markings of the dial were in red metallic paint, and thus interfered with the ra ys, and were reproduced.'' Since the rays had this great penetrative power, it seemed natural that they should penetrate flesh, and so it proved in photographing the hand, as I showed you.

"There is much to do, and I am busy, very busy," he said in conclusion. He extended his hand in farewell, his eyes already wandering toward his work in the inside room. And his visitor promptly left him; the words, "I am busy,'' said in all since rity, seeming to describe in a single phrase the essence of his character and the watchword of a very unusual man.

In the Nov. 1, 1895 edition of The X-ray Century we examined the history of gas discharge tubes.

In the Nov. 8, 1895 edition of The X-ray Century we were there when Prof. Roentgen discovered a new kind of ray.

In the Dec. 1, 1895 edition of The X-ray Century we looked at the investigation which led Dr. Roentgen to write this paper.

In the Jan. 1, 1896 edition of The X-ray Century we read Prof. Roentgen's first paper describing the new kind of ray.

In the Feb. 1, 1896 edition of The X-ray Century we watched the word spread around the world.

In the March 1, 1896 edition of The X-ray Century we saw the first uses of x-rays for diagnostic purposes in several different countries.

In the April 1, 1896 edition of The X-ray Century we looked on as Becquerel discovered radioactivity.

The next edition of The X-ray Century will be published on June 1.