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Spectacular rediscovery of the original prints of radiographs Roentgen sent to Lorentz in 1896
Insights into Imaging volume 11, Article number: 46 (2020)
Ninety years after the Dutch theoretical physicist H.A. Lorentz died, detailed investigation of his scientific heritage yielded the set of nine original prints of radiographs that W.C. Roentgen made during his experiments and had sent him, among half a dozen other scientists, on January 1st, 1896.
Through communications with different experts and literature research, the author describes these nine prints and how they relate to the first publication Roentgen wrote about his discovery of the X-rays.
The combination of Roentgen’s first publication on his X-ray discovery and the nine radiographs provides insight as to which aspects of the discovery were considered important by Roentgen and how he carried out the experiments to be able to describe these aspects.
W.C. Roentgen did his experiments after his discovery of a ‘new kind of rays’ in a very analytic and orderly manner.
W.C. Roentgen has sent the prints of radiographs related to his publication, combined with the reprint, to a select group of about a dozen internationally renowned scientists while he sent the reprint as such, without the illustrations, to some 80 other scientists.
Only two presumably full sets of the original radiographs are now known in the world.
Since Hendrik Antoon LorentzFootnote 1  passed away (February 4th, 1928), part of his scientific heritageFootnote 2 has been kept at Teylers MuseumFootnote 3, Haarlem, The Netherlands, where Lorentz was the director (since 1909) of the Physics Laboratory of the Teylers FoundationFootnote 4. As this heritage consisted of many books, papers and thousands of reprints, it had never been studied in detail. In the course of 2018, museum workers embarked on this enormous undertaking. Between the pages of an 1896 catalogueFootnote 5 (Fig. 1) of the Leybold Company (Cologne, Germany), they encountered, near the letter L (personal communication with Mrs. T. van der Spek, head curator of the scientific collections and head of the science department at Teylers Museum), a folder containing 13 prints of radiographs. Nine of these radiographs presumably formed the original set that Roentgen had sent to about half a dozen of his scientific colleagues on January 1st, 1896. The other four prints of radiographs did not originate from Roentgen and were of later dates. Two of these prints could be traced back to an X-ray demonstration by a local high school teacher in the city of Tilburg (The Netherlands) on March 18th 1896. Near the letter R in the catalogue, the original reprint  (Fig. 2) of Roentgen’s first publication, which he had sent along with the prints of radiographs, was found. It contained Roentgen’s handwritten note: ‘W.C. Röntgen. Vom Verfasser überreicht mit 9 Photographien’ (W.C. Roentgen. Presented by the author with nine photographsFootnote 6).
Can we discover to whom Roentgen had sent the prints of radiographs and reprints?
Most of the people in Roentgen’s network only received the reprintFootnote 7. The first batch of these had a blue rim on its spine, and the remaining batch had a yellow rim. We only know six names of those who received both the reprint and the set of radiographs in early 1896. They are Franz-Serafin Exner (1849–1926) in Vienna, William Thomson (Lord Kelvin) (1824–1907) in Glasgow, Emil Gabriel WarburgFootnote 8 (1846–1931) in Berlin, Franz Arthur Friedrich Schuster (1851–1934) in Manchester, Henri Poincaré (1854–1912) in Paris and Hendrik Antoon Lorentz (1853–1928) in Leiden. Later, he sent a similar material to a number of German colleagues. Of them, we know the following names: Otto Richard Lummer (1860–1925) in Berlin, Friedrich Wilhelm Georg KohlrauschFootnote 9 (1840–1910) in Strasbourg and Carl August Voller (1842–1920) in Hamburg. Until now, the only presumably complete set preserved is the one that was sent to Schuster. It was donated by his daughter to the Wellcome Collection in London in the 1960s. Roentgen was befriended with Ludwig Luis Albert ZehnderFootnote 10 (1854–1949) in Freiburg but sent him the reprint only. Via his frequent correspondence with Roentgen , Zehnder must have received several prints of radiographs which have been preserved at the German Radiology Museum in Remscheid-Lennep (personal communication with Dr. U. Busch, head curator of the German Radiology Museum in Remscheid-Lennep) or he could have received them from others after Roentgens’s death (personal communication with G.J.E. Rosenbusch).
The set of nine prints of radiographs
The nine images could be considered as illustrations to the first publication although they were not included in it. Therefore, someoneFootnote 11 wrote the numbers of the corresponding paragraphs on each cardboard frame. For example, in Fig. 3, we read: ‘§ 2 u. 14’ which stands for ‘paragraphs 2 and 14’. There were 17 paragraphs in total. Captions of what the radiographs showed were added as well.
Reactions to the first mailing by Roentgen
As Roentgen had predicted , the reactions came soon. Lord Kelvin wrote a formal thank-you-note on January 6th after having only seen the prints of radiographs, but, after reading the paper, he wrote a second letter on January 17th to express his astonishment .
Lorentz was very impressed by Roentgen’s discovery, especially because it fitted perfectly with his own ideas. Lorentz was of the English school which believed that cathode rays were of a corpuscular character. We can find this vision in the article that Lorentz was asked to write for the Dutch journal ‘De Gids’ which was published on February 19th, 1896 . Lenard, on the contrary, thought that cathode rays were a distortion of the ether and thus had a wave character. Thompson, in 1897, showed that cathode rays were electrons, thus particles, but, in the end, the supporters of the wave theory had it partly their way at the introduction of the quantum theory: electrons have also wave character.
The radiographs which Exner received were instrumental in spreading the news about Roentgen’s discovery as Exner showed them to the young physicist Ernst Lechner (1856–1926) who told his father (editor of the Viennese newspaper ‘Die Presse’), who published the news on January 5th, 1896 .
Reactions to the rediscovery of the prints of radiographs
The rediscovery of the original prints of radiographs resulted in multiple reactions in the Dutch press. The Teylers Museum reacted by putting Roentgens prints of radiographs (as well as the reprint and the other prints of radiographs) on display for a month.
Comparison with other sets of prints of radiographs Roentgen sent to his colleagues
The prints of radiographs of the set sent to Schuster are reproduced on the website of the Wellcome FoundationFootnote 12. The only difference with Lorentz’ set is that the corners of the frame of the radiograph of Bertha’s hand in Schuster’s set are seriously damaged. The remainder of the set is identical to the one sent to Lorentz. Of the prints of radiographs in possession of Zehnder, five have been preserved in the German Radiology Museum in Remscheid-Lennep, among which is the famous radiograph of the hand of Roentgen’s wife Bertha. The four that are missing are our Figs. 4, 6, 7 and 10. However, there is one additional X-ray photograph which was not present in the Lorentz and Schuster sets and which is also clearly an illustration of Roentgen’s first publication. This is an attempt to refract the X-rays with 30 degree vulcanite and aluminum prisms. It refers to paragraph 7 (personal communication with Dr. U. Busch, head curator of the German Radiology Museum in Remscheid-Lennep). Roentgen states that he could not demonstrate that the X-rays were refracted but if they did it would be to a minimal degree. It is not known why this image was sent to ZehnderFootnote 13 and not to Lorentz and Schuster. Zehnder also received a radiograph of Roentgen’s hunting rifle, which was made after Roentgen’s presentation to the German emperor on January 13th, 1896; the reason being that during this visit in Berlin, the general staff had asked Roentgen whether it would be possible to use the X-rays to examine materials, especially those of rifles (personal communication with Dr. U. Busch, head curator of the German Radiology Museum in Remscheid-Lennep). Roentgen made many notes on this photograph explaining what can be seenFootnote 14. It is, obviously, not an illustration of the publication but falls into the same category as the image of the hand (Fig. 3), the doorpost (Fig. 4), the wooden spool (Fig. 6) and the wooden box with a set of weights  which are specifically mentioned in paragraph 14 of the publication. It remains unclear how Zehnder received the prints of radiographs that are now in the Remscheid-Lennep Museum and requires further investigation. We do know  that Zehnder had some of the missing prints of radiographs temporarily in his possession as he borrowed them from Roentgen for a presentation on February 15th, 1896 for the ‘Naturforschende Gesellschaft’ (Society for Nature Research) in Freiburg. These were the wooden spool (Fig. 6), the zinc plate (Fig. 7), the wooden box with a set of weights  and a radiograph of a hand made by PernetFootnote 15 in Zurich.
Availability of data and materials
All figures originate in the Teylers Museum. They are the owner of the copyright.
H.A. Lorentz is one of the greatest theoretical physicists of the Netherlands (Nobel Prize for Physics in 1902 together with Pieter Zeeman). He was professor at Leiden University. Roentgen travelled to Leiden in early 1905 and asked Lorentz to become professor of theoretical physics in Munich  but Lorentz turned this proposal down. Lorentz moved to Haarlem in 1912. (https://en.wikipedia.org/wiki/Hendrik_Lorentz Accessed 4 October 2019)
Lorentz heritage in Teylers Museum consists of papers and books that he brought with him from Leiden plus everything related to his work as director of the Physics Lab at Teylers Museum. The remainder of his archive is located at the North-Holland Archive (www.noord-hollandsarchief.nl).
Teylers Museum is a museum for science and art. Founded in 1778, it is the oldest museum of the Netherlands.
Lorentz was also curator of the physics cabinet of Teylers Museum.
The catalogue was also a guide on how to make radiographs using the equipment of the Leybold Company.
Roentgens mailing actually contained positive photographic prints of his original negative radiographs.
Without including the prints of radiographs, Roentgen sent this reprint to some eighty other scientific colleagues. Among them were three other Dutch scientists: J.D. van der Waals (1837–1923) at the University of Amsterdam, C.H.C. Grinwis (1831–1899) at the University of Utrecht, and H. Haga (1852–1936) at the University of Groningen.
Predecessor of Roentgen in Strasbourg.
Predecessor of Roentgen in Würzburg.
Assistant of Roentgen in Strasbourg and Würzburg and a later colleague of Roentgen in Munich. After Roentgens death, he received the letters he had sent to Roentgen, back, except the ones written in the period of the discovery (Personal communication with Gerd J.E. Rosenbusch).
The handwriting is clearly different from Roentgens handwriting.
The correspondence between Roentgen and Zehnder is archived at the Zentralbibliotek (Central Library) in Zurich, Switzerland. It is possible that somewhere in this correspondence there are referrals to the prints of radiographs that Zehnder received from Roentgen, but it is not possible for this library to perform this research for me (Personal communication with Monica Seidler-Hux, scientific coworker of the manuscript department).
Roentgen sent this X-ray photograph also to the German emperor along with three prints of radiographs of 23 mm thick iron plates; according to a concept of the letter to the emperor which dates back to January 12th 1897 (Personal communication with Gerd J.E. Rosenbusch).
Jean Pernet (1845-1902) was Professor of Experimental Physics at the ETH Zurich (1890-1902).
Van Wylick WAH (1966) Röntgen en Nederland (Roentgen and the Netherlands), vol 42. Thesis University of Amsterdam
De Haas-Lorentz GL, Lorentz HA (1957) Impressions of his life and work. North-Holland Pub. Co, Amsterdam
Röntgen WC (1895) Über eine neue Art von Strahlen (Vorläufige Mittheilung). Sitzungsberichte der Physikalisch-medizinischen Gesellschaft zu Würzburg. 29:132–141
Zehnder LWC (1935) Röntgen. Briefe an L. Zehnder, Rascher, Zurich
Rosenbusch GJE, de Knecht-van Eekelen A (2019) Wilhelm Conrad Röntgen. The birth of radiology. Springer Nature, Cham
Lorentz HA (1896) De door prof. Röntgen ontdekte stralen (The rays discovered by professor Roentgen). De Gids 60:510–528
Würzburg University (1995) Röntgen Rays Centennial. Exhibition on the occasion of the discovery of X-rays in Würzburg on November 8, 1895 (13-2-till 19-11-1995) Würzburg, Exhibition Catalogue, vol viii. Bavarian Julius-Maximillians-Universität Würzburg, Würzburg, p ix
The author is indebted to Mrs. T. van der Spek of Teylers Museum, Dr. U. Busch of the Radiology Museum in Remscheid-Lennep and Prof. Dr. G.J.E. Rosenbusch and G.J. Kemerink for their support in realizing this publication, and Mrs. A. Simon for linguistic support.
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Consent for publication was obtained from the science curator of Teylers Museum, Mrs. T. van der Spek
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Zonneveld, F.W. Spectacular rediscovery of the original prints of radiographs Roentgen sent to Lorentz in 1896. Insights Imaging 11, 46 (2020). https://doi.org/10.1186/s13244-020-00846-x
- First radiographs
- Discovery of X-rays
- W.C. Roentgen’s experiments
- H.A. Lorentz
- Teylers Museum