Claims of priority - The scientific path to the discovery of X-rays

Abstract

Shortly after Röntgen's publication about a new kind of rays, a dispute about priority claims began. Röntgen was not the first researcher to produce X-rays nor the first to take X-ray images. An analysis of the history of cathode ray research in the 19th century reveals ample evidence that researchers before Röntgen had already produced X-rays, albeit without knowing this. Most of them, for their part, did not claim any priority, some did so rather casually. The German-Hungarian physicist Philipp Lenard, a co-founder of German Physics, considered himself a "true discoverer". It remains to be said, however, that he, like many others before him, failed to recognize the character of the new radiation. It was Wilhelm Conrad Röntgen, with his three scientific publications on X-rays, who laid the foundations for their physical clarification and paved the way for the success story of their application in a variety of fields that continues to this day.

Keywords: 100th anniversary of his death; Canal rays; Cathode rays; Crookes tube; Electron; First X-ray image; Gas discharge; Heinrich Geissler; Hittorf tube; Lenard window; Priority claims; Puluj lamp; Radiating matter; Unipolar vacuum tube; Wilhelm Conrad Röntgen; X-rays.

Figure 1

Michael Faraday by Thomas Phillips oil on canvas, 1841–1842 35 3/4 in. x 28 in. (908 mm x 711 mm) Purchased, 1868 NPG 269. (Michael Faraday – Wikipedia Wikimedia Commons).

Figure 2

Schematic diagram and photograph of a direct current glow discharge showing the following structures: The cathode glow, i.e., the first violet glowing region immediately adjacent to the cathode; the cathode dark space (Hittorfscher Dunkelraum), i.e., the darker band between the two brighter regions adjacent to the cathode, where the electrons already have energy above the maximum of the excitation energy and can no longer excite the gas as efficiently; the negative glow, i.e., the second larger purplish glowing region next to the cathode, whose brightness gradually decreases toward the anode; the Faraday dark space, i.e., the region without glow near the center of the tube; the positive column, i.e., the pink glowing region filling the right side of the tube and representing a plasma with hot electrons. This region is characterized by low electric field strength and vanishing space charge and ensures current transfer between cathode and anode. In the photo, striation, i.e. alternating bright and dark bands, can be seen in the positive column, caused by an instability in the plasma; the anode glow, i.e. the bright layer on the far right in front of the anode (Gas discharge - Category:Gas discharge tube - Wikimedia Commons).

Figure 3

Plate VII ’A continuation of the Experiments on the Attrition of Glass’ and ’Some further Experiments relating to the Electricity of Glass’ from Physico-Mechanical Experiments on various subjects, presented to the Royal Society on October 26, 1709 (Francis Hauksbee – Wikipedia Wikimedia Commons

Figure 4

Julius Plücker (1801–1868). Lithographie von Rudolf Hoffmann, 1856. (Julius Plücker – Wikipedia Wikimedia Commons).

Figure 5

Heinrich Geissler (1814–1879). (Heinrich Geißler (Glasbläser) – Wikipedia Wikimedia Commons).

Figure 6

Johann Wilhelm Hittorf. Taken from the Festschrift on the occasion of Johann Wilhelm Hittorf’s 80th birthday. Leipzig: Barth 1904. Adolf Heydweiller, Münster (Johann Wilhelm Hittorf – Wikipedia Wikimedia Commons).

Figure 7

Gas discharge tube of the Hittorf type. The first experiments with X-rays took place with tubes that were initially still cylindrical. The end of the glass bulb acted as an anti-cathode, but the radiation was still quite diffuse. (Archiv Deutsches Röntgen-Museum).

Figure 8

Crookes shadow cross tube (Crookes tube two views - File:Crookes tube two views.jpg - Wikimedia Commons).

Figure 9

Canal rays: Anode-ray tube showing the rays passing through the perforated cathode and causing the pink glow above it (Anode ray - Wikipedia Wikimedia Commons).

Figure 10

Puluj lamp. Courtesy of Museum Experimentalphysik Innsbruck.

Figure 11

X-ray image of two American coins. (Archiv Deutsches Röntgen-Museum).

Figure 12

Telegram from Tesla to Röntgen dated March 14, 1896 (Archive Deutsches Röntgen-Museum).

Figure 13

Lenard discharge tube (Archive Deutsches Röntgen-Museum).

Figure 14

Wilhelm Hallwachs (1859–1922) (Wikimedia commons. Wilhelm Hallwachs | Niels Bohr Library & Archives (aip.org)).

Figure 15

Advertisement for X-ray tubes by the Gundelach company from May 1896 (Courtesy of Glasmuseum Gehlberg).

Figure 16

Röntgen’s glass plate for investigating permeability with increasing layer thickness (Archiv Deutsches Röntgen-Museum).

Figure 17

Joseph J Thomson (1856–1940) steel engraving from 1896. Taken from The Electrician, 1896 - The Electrician, 1896, p.120 ISBN 0-87942-238-6, (File:JJ Thomson.jpg - Wikimedia Commons) Wikimedia Commons.

Figure 18

Wilhelm Conrad Röntgen in his physics institute in Würzburg portraits by Nicola Perscheid (1864–1930) for the making of the Röntgen Monument by Reinhold Felderhoff (1865–1919), which was erected on the Potsdamer Bridge in Berlin in 1898. (Archiv Deutsches Röntgen-Museum).