Thorax (1968), 23, 676.

Was Wilhelm Roentgen a German or a Dutchman?What was his relation to The Netherlands?

W. A. H. VAN WYLICK

From the Catholic Hospital, Hilversum, The Netherlands

Roentgen's father, the draper Friedrich ConradRoentgen, was a German born at Lennep, nearCologne, in 1800. His only son, Wilhelm Conrad,was also born at Lennep in 1845. After complet-ing his training at school and at the university,Wilhelm Conrad worked at several Germanuniversities as an assistant, later as a private lec-turer, and finally as a professor. In Wtirzburg(Bavaria) on 8 November 1895 he discovered'rays of a new type' which he called X-rays, andthese rays made him world-famous within a fewweeks. In 1900 he was appointed professor inMunich, the Bavarian capital, and in Munich hedied in 1923 after an emeritus period of threeyears.

In the light of these facts, could there be anydoubt about his German nationality ? As a pro-fessor in German universities he held an office ofState and must have had German nationality.Assuredly this was the case, but nevertheless hewas not a German citizen during an importantperiod of his life. He lived in The Netherlandsfrom the third to the twentieth year of his life.

It is on this period of the great physicist's life,and on the relationship he maintained with TheNetherlands through many years until his death,that this paper intends to focus attention; andin considering this period and this relationship weshall also come to know and appreciate Roentgenas a person.

Roentgen's mother, Charlotte ConstanceFrowein, was a Dutchwoman. When she marriedFriedrich Conrad Roentgen in his native city,Amsterdam, a local daily paper published theannouncement at the foot of this page.The young couple established themselves at

Friedrich Conrad's place of residence, but threeyears after the birth of their only son, Wilhelm

Conrad, they decided to emigrate to The Nether-lands. On 23 May 1848 Friedrich Conrad visitedthe Registrar's Office at Lennep and in thepresence of the Registrar signed a documentstating that, with a view to his intended emigra-tion to The Netherlands, he had surrendered hisPrussian nationality.The family went to live at Apeldoorn (Province

of Gelderland), which for almost two centurieshad had a special reputation among the Dutchmunicipalities because it was (and is) the site ofthe royal residence 'Het Loo'. The King, and inearlier times the Stadtholder, lived in this castlefor many months of the year. The residence hadbeen built in the years 1685-89 by Willem III,Stadtholder of The Netherlands and King of Eng-land. In Roentgen's days it was the residence ofKing Willem II (died 1849) and King Willem III(1817-90), whose daughter Queen Wilhelmina(born 1880) died there in 1962.At that time a foreigner who had been a

resident of The Netherlands for six years andhad no intention of leaving the country shortlywas 'put on equality' with Dutch citizens andgranted the same rights and duties, with the excep-tion of the right to vote and to elect (which atthat time did not mean much). Therefore thestatement that Friedrich Conrad Roentgen'sfamily acquired Dutch citizenship after a fewyears' stay at Apeldoorn is hardly contestable.And, as such, Wilhelm Conrad had obligationsalso with regard to the national militia. However,he was never on active military service because atthat time the law exempted the only son of afamily from conscription. The King's Com--missioner for the Province of Gelderland con-firmed this in a document which Wilhelm receivedshortly before his marriage on 24 November

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Was Wilhelm Roentgen a German or a Dutchman ? What was his relation to The Netherlands ? 677

1871. Naturally, Roentgen also had a Dutch pass-port, written in the language of diplomacy-French (Fig. 1).

At Apeldoorn young Wilhelm Conrad wasbrought up by his well-to-do parents like anyDutch boy of his class. When he was 5 years oldhe was allowed in a small ceremony to lay thefoundation-stone of the house his parents werehaving built. In 1958 this stone-with the inscrip-tion 'W.R.C. 22.10.1850'-was recovered in thehouse at No. 171 Hoofdstraat. Wilhelm, ofcourse, went to school at Apeldoorn, and whenhe was 17 years old his parents took him toUtrecht, where he was taken into the family of ayoung, ambitious chemist, Dr. Jan WillemGunning, who at that time lived at No. 62 NieuweGracht. Gunning was a lecturer in the Universityof Utrecht and also on the teaching staff of thetechnical school, a private institution of secon-dary education. Roentgen attended this schooland proved himself an excellent pupil. The sevenprogress reports he received at this school canonly be described as exceptionally good. In sub.jects like geometry and stereometry, for example,he never had any marks lower than 'very good'or even 'excellent'; in chemistry, the subjecttaught by Dr. Gunning, his marks were neverother than 'good' or 'very good'. Only in physicswere his marks sometimes less good. The firstwinner of the Nobel prize in physics sometimesreceived marks not exceeding 'reasonable' andoccasionally even 'moderate' and 'very moderate';his final report of 3 May 1867 in fact marked him'very poor' in this subject. In no other report andno other subject had he ever had so poor a mark.

It must have been at this school that Wilhelmrefused to report a friend who had drawn a cari-cature of a teacher on the screen surrounding thestove; when the friend did not reveal himself asthe perpetrator, Roentgen took responsibility forthe offence and was given the severest punishmentthe school could possibly impose-he had toleave the school for good. This must have hap-pened about two months before he would havecompleted the two-year course, and this explainswhy only seven progress reports instead of eightare available. Apparently even his fatherly friend,Dr. Gunning, was unable to prevent this cata-strophe. On the other hand, the importance of thispunishment to Roentgen must not be exag-gerated: the technical school had no finalexamination and Roentgen's excellent progressreports warrant the conclusion that he derivedthe full benefit from this two-year course.

At that time Dr. Gunning advised his youngfriend to refrain from returning to his father'sdrapery at Apeldoorn but to take lessons in Latinand Greek instead in preparation for a matricu-lation examination of the University of Utrecht.Those who had not passed a final examination ata 'gymnasium' (training college) recognized bythe state could gain admission to a university bypassing such an examination. An entry in thestate archives at Utrecht on 14 January 1865shows that Roentgen took this examination . . .

and failed! Four days later he nevertheless regis-tered, but not as a student: as an auditor hestarted to attend lectures in stereometry, analy-tical geometry, physics, botany, zoology, logic,and Latin and Greek.

Early that year Dr. Gunning had to moveto Amsterdam, where he had been appointedprofessor of chemistry.

This event certainly made a deep impression onthe young student, who at that time achievedsomething unusual: he wrote a treatise entitled'Questions concerning the inorganic part of Dr.J. W. Gunning's textbook of chemistry'. It is aneat little book of 58 pages, with some 1,000questions without answers. Its purpose is clearlyexplained in the preface:

'The intensive use made of Dr. J. W. Gunning'sTextbook of Chemistry as a guide to the initial studyof this science, and the many peculiar difficulties Ihave noticed when attending an institution wherechemistry is taught, suggested to me the idea of com-piling a brief scheme which might also be used as arepertory. For it seemed to me that the principaldifficulty for many young people lies in the fact thatthey confuse the various substances and actions. ...'May this publication, rather than doing a disservice

either to Mr. Gunning or to the study of this splendidscience, contribute to its better understanding andappreciation.'At the end of that year (1865) Roentgen

changed his study plans, and made a decisionwhich was to be of the greatest importance forthe rest of his life. Apparently he regarded hischances of passing the matriculation examinationat a second attempt as slight, and he knewthat the Polytechnikum in Zurich acceptedstudents without complete college training. InZurich Roentgen managed to obtain a diplomain mechanical engineering within three years; andwithin another year he had written a thesis en-titled 'Studien uber Gase' which earned him adoctor's degree.

During these years it was undoubtedly still hisintention to return to his 'fatherland', The Nether-lands, for he wrote a request to King Willem III

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FIG. 1. The Dutch passport of Wilhelm Conrad Roentgen.

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Was Wilhelm Roentgen a German or a Dutchman ? What was his relation to The Netherlands ? 679

in which he asked, on the basis of his Dutchsecondary school education and his Swiss engin-eer's diploma, to be granted authority to teach atDutch secondary schools. On 9 June 1869 theKing did in fact grant him this authority. PerhapsRoentgen had in mind his fatherly friend, Dr.Gunning, who had been a teacher first, then alecturer, and finally a professor. However,Roentgen never made use of the teaching authorityhe was given.At that time he became assistant in physics to

Professor A. Kundt, first in Zurich and sub-sequently in Wurzburg. In 1872 he returned forsome time to The Netherlands, where his parentswere still living. On 19 January 1872 the burgo-master of Apeldoorn performed the ceremony ofhis marriage to a Swiss girl, Anna Berta Ludwig.This marriage, which lasted 47 years and was avery happy one even though there were' nochildren, was solemnized in the Dutch ReformedChurch by the Rev. C. F. Gronemeijer. The Apel-doorn newspaper published the followingannouncement:

invitation. Certainly his reasons for refusing arenot to be found in disagreeable memories of theUtrecht school and his failure to matriculate, butmust be ascribed to his wife. She had no know-ledge of the Dutch language, and was understand-ably reluctant to settle in Utrecht. Roentgen him-self would not have had the slightest difficulty inthis respect; he could easily have given his lec-tures in Dutch, as he indicated politely in hisGerman letter to the Board of Governors.

'Finally, allow me to offer the Governors myapologies for using the German language in thisletter. It is because I fear that I might use somegermanisms in these lines that, against the rules ofcourtesy, I refrain from using the Dutch language.I may add, however, that this fear is perhaps exagger-ated, for in my parents' home the Dutch language wasthe medium of ordihary conversation until mymother's death three years ago.'

Instead of Utrecht it was in Wiirzburg, wherehe had lived before, that Roentgen in 1888accepted an appointment as professor of physics;and it was in Wuirzburg that he wrote his publica-

* Getrouwd:APeLDOOILN, Dt. W. C. RONTGEN

19 3Jnuari 1872. metA. B. LUDWIG.,. -.. ... . .. . ._.

With his young wife Roentgen soon returned toWurzburg, whence he moved to Strasbourg withProfessor Kundt; in 1873 his parents also cameto Strasbourg. At the age of 30, in 1875, he was

appointed professor of physics; and this musthave been the moment when he gave up his Dutch'citizenship', because he entered the service of theGerman state. However, he retained throughouthis life an interest in The Netherlands and hisloyalty to Dutch friends and relatives.

In 1888, after nine years as an ordinary pro-fessor of physics at the University of the State ofHessen, in Giessen, Roentgen had an opportunityto return to The Netherlands. In that year hisformer teacher, Professor Buys Ballot, reached theage of 70, and the Board of Governors of theUniversity of Utrecht tried to persuade Roentgento become Buys Ballot's successor. However,despite the favourable offer of the Governors anddespite emphatic requests by Professor BuysBallot himself, Professor Oudemans, president ofthe faculty of mathematics and physics, and Pro-fessor Engelmann, a German professor of physio-logy in Utrecht, Roentgen did not accept the

tion On a New Type of Ray, which on 28December 1895 astounded the world. All over theworld the notion that it was possible to obtainon a screen the moving image of the bones of aliving human being created a sensation.Among those who received a reprint of Roent-

gen's paper was Hendrik Anton Lorentz, pro-fessor of theoretical physics in the University ofLeyden. He thanked Roentgen in the followingletter:

Leyden, 21 January 1896Esteemed colleague:

Please accept my sincerest thanks for your kindnessin sending me your important publication, and forthe splendid gift attached to it: the marvellous photo-graphs obtained with X-rays. Like all our colleagueshere, I rejoice in your brilliant discovery, which opensup a new field for science. It is my fondest hope thatyou may succeed in elucidating the nature of theseenigmatic phenomena; but even if that should proveto be impossible, science would nevertheless owe oneof its most important triumphs to your work.

With my best regards I remain,Truly yours,

H. A. Lorentz.

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W. A. H. van Wylick

Four days later Lorentz discussed Roentgen'sdiscovery at a meeting of the Royal Academy ofSciences in Amsterdam, and showed the x-rayphotographs which Roentgen had sent him. Hewrote about this meeting to Roentgen, and theproceedings of the Academy make mention of thediscussion and Lorentz' demonstration.When in 1901 Roentgen was the first physicist

to receive the Nobel prize, Lorentz sent him hiscongratulations, and Roentgen was so touched bythis gesture that he wrote Lorentz a letter ofthanks in the Dutch language:

Munich, 22 December 1901Esteemed colleague:Many thanks for the kind words you sent me-

words which fill me with great joy and not a littlepride because I hold their author in such high regard.There is indeed a great difference in value betweenthe noisy approval of the crowd and the simplewords of an eminent man of learning. I hope, andI trust, that neither form of approval will make mevain !

With my sincerest compliments I have thehonour to be,

Yours truly,W. C. Roentgen.

In the course of the next few decades the twoworld-famous scientists (Lorentz was awarded theNobel prize in 1902) met regularly and kept intouch by correspondence. When Roentgen cele-brated his seventieth anniversary in 1915-duringWorld War I-Lorentz sent his congratulations,and, in his note of thanks, Roentgen mentionedhis memories of youthful days in The Nether-lands:

. . . and the fact that these wishes came from TheNetherlands, the country I owe so much and whereI spent happy early years, enhanced their value toa considerable extent.He gave expression to fond memories of his

youth in The Netherlands in an official letter on22 May 1907 to Professor J. D. van der Waals,Dutch Nobel prize winner of 1910, who as secre-tary of the Royal Academy of Sciences in Amster-dam had informed him that the Academy hadappointed him a member:' . . . Also I should like to point out that it gave meparticular pleasure to hear of my appointment as amember of the Academy of the country where I spent17 years of my youth, which to me has been a secondfatherland and to which I owe so much in so manyways.

Professor Kamerlingh Onnes, Dutch Nobel prizewinner of 1913, was likewise among Roentgen'sDutch friends, and a number of Roentgen's lettersto him have been preserved. In 1899 Roentgen,

again in Dutch, expressed his thanks after receiv-ing a copy of Communications from the LeydenLaboratory, edited by Kamerlingh Onnes.

While Roentgen was assistant in physics to Pro-fessor Kundt in Strasbourg he befriended a youngDutch physicist, Herman Haga. Haga later be-came professor in Groningen, and the two physi-cists kept up an intensive correspondence after thediscovery of the X-rays. As early as 1899, Hagainformed Roentgen that, according to his experi-ments, the wavelength of the X-rays ought to bebetween 0-1 and 2 5 Angstrom units, 'so that thedesignation "X" for the roentgen rays retains onlyhistorical significance'. This passage shows thatHaga had approximately determined the wave-length of the roentgen rays 13 years beforeM. von Laue!Another of Roentgen's Dutch friends was Hugo

de Vries, Amsterdam professor of botany, who in1901 published his renowned work Die Mutations-theorie. The two came to know each other whenboth were assistants in the University of Wiirz-burg in 1871. In 1897 Roentgen asked de Vriesto come to Wiirzburg to succeed his formerteacher, Professor J. Sachs, but de Vries did notaccept this invitation.When in the early days.of the year 1896 all daily

papers and journals on physics, medicine, techno-logy, and photography published the sensationalnews about the X-rays, Roentgen received manycongratulations from The Netherlands also. Hiscousin, Caroline Frowein, who had married thenotary public, W. Fischer, at Ede (Gelderland),had read in the daily papers 'that you have madesuch a wonderful discovery. Well, my dear Willem,this does not surprise me. Even as a child youused to lie awake at night, pondering what weordinary ignorant people believed to be impossiblethings. My heartfelt congratulations on yoursuccess in obtaining such a brilliant result...Many relatives of Roentgen's father lived in

The Netherlands also. One of them, the painterLouise Constance Adrienne Roentgen, drew apastel portrait of the great physicist when hevisited her parents in Deventer (Fig. 2).Among the many letters Roentgen received

from The Netherlands after his discovery, the onefrom his former fatherly friend and teacher, Pro-fessor Gunning, of Amsterdam (Fig. 3), held avery special appeal for him:

Amsterdam, Andrieskade, 9 February 1896.There are X-rays also in the human heart, which

steadily illuminate what time and space tend to ob-scure. You and your kind parents continue to live inour memory, and it is seldom that a 27th of March(that is Roentgen's birthday) passes without our

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Was Wilhelm Roentgen a German or a Dutchman ? What was his relation to The Netherlands? 681

thinking of you. We take great pleasure in assuringyou of this now that we have reason to send youour special congratulations. May that which you havegiven the world, and which will keep your personvisible even in the obscurity of the future, enhancemankind's good fortune in spiritual as well as inmaterial terms.

Your friends of Nieuwe Gracht/Schalkesteeg,Prof. J. W. Gunning and P. A. Gunning-Pierson.The letter in which Roentgen replied to these

congratulations is among the finest he ever wrote.Written when he had reached the peak of hiscareer, it also symbolizes the height of Roentgen'srelationship with The Netherlands.

Sorrento, 1 April 1896Esteemed Sir and Friend:Among the many surprises and congratulations I

have recently received, there was hardly one so valu-able and fond to my heart as the one you sent me.Your words are proof to me that you are still think-ing of me in friendship, although by my behaviour inrecent years I have forfeited my right to expect this.Many times I have thought: if only I knew that theold friendship is still strong enough, I would write:Pater, peccavi. Take me into your heart again. I havewanted to write you that your place in my heart hasnever been empty, and that I have never forgottenwhat I owe you both.

FIG. 3. Portrait ofProfessor Dr. Jan Willem Gunning.

'9 * It grieves me to know that my dear, unforgettableparents, who were so proud of their son, are nolonger alive to witness my success. But my heart

.-~, rejoices in gratitude at the thought that the dearpeople, who, after my parents, exerted the greatestinfluence on my upbringing and in whose house Ispent so many years as if I were their child, may nowknow that their love and also the concern they havefelt for my sake have not been entirely futile. I donot wish to write down in detail all that I have tothank you for, but please be assured that I have notforgotten even the slightest of these many things.

It would give me great pleasure if I might receivemore detailed and more exhaustive information aboutyou and yours. Perhaps you could find a little timefor a further message when the opportunity presentsitself.

FiG. 2. Portrait of W. C. Roentgen, drawn by L. C. A. Esteemed Sir and friend, let me once more assureRoentgen in Deventer. you and your honoured wife of my sincerest gratitude

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for your interest and your kindness in re-opening our

correspondence.With the most cordial compliments from my wife

and myself to you and your dear family I am,

Your grateful W. C. Roentgen.

It is difficult to conceive of a contrast greaterthan this: while the daily press and the journalsof many branches of science hail the success of a

great physicist who has suddenly attained world-wide fame, Roentgen tenders his apologies withthe words from the Gospel According to St. Luke:'Pater, peccavi'.

It is likewise difficult to conceive of a greaterharmony between the pinnacle of scientificachievement-the discovery of the roentgen rays-and the highest of human motives-gratitudetowards parents and teachers.

BIBLIOGRAPHYDessauer, F. (1945). Wilhelm C. Rdntgen. Die Offenbarung einer

Nacht. Olten, Switzerland.Glasser, 0. (1933). Wilheln Conrad Rontgen and the Early History

of the Rontgen Rays. Thomas, Springfield, Ill.

- (1958). Dr. W. C. R5ntgen. 2nd ed. Thomas, Springfield, Ill.Van Wylick, W. A. H. (1966). Rdntgen en Nederland. Hoeijenbos,

Utrecht.Zehnder, L. (1935). W. C. Rontgen: Briefe an L. Zehnder. Rascher,

Zurich.

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