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Johann Puluj (1845–1918): his career and the “invisible cathode rays”

Emilie Těšínská
X-ray pictures of a hand taken by J. Puluj: negative on the left, positive on the right. (From the Archives of the Czech Technical University in Prague, J. Puluj collection, published with permission.)

1. Introduction

This article commemorates the physicist and electrical engineer of Ukrainian origin Johann Puluj (1845–1918), who completed his professional career and life as a Professor of the German Technical University in Prague over the period 1884–1918. It was here, where, at the beginning of 1896, he learned the news about the discovery of X-rays by W. C. Röntgen. This article focuses on the professional career of J. Puluj and his work in Prague, mainly based on written sources in the Prague archives and in the Archives of the University of Vienna. For a comprehensive view of the life and work of J. Puluj, reference has been made to the existing biography [1].

2. Family background, studies and beginning of his scientific career

Johann Puluj was born on 2 February 1845 in Grzymałów (Hrimailiv/Гримайлiв) in the then Galicia, which was part of the Austrian monarchy (today Ukraine). He was born into an Orthodox landowners’ family, and was the oldest of several children.

[Fig. 1]Figure 1. Puluj's native village, Grzymałów, on a postcard from 1900. [Klomm, S. (1937). Monografia antropogeograficzna miasta Grzymałów.]

After graduating from the Tarnopol gymnasium, Puluj continued his studies at the University of Vienna (k. k. Universität in Wien), at first in the Evangelical-Theological Faculty (1866–1869) and then in the Philosophical Faculty, where, in the school year 1872/1873, he achieved the approbation for teaching mathematics and physics at gymnasiums with German as a teaching language [2]. Consequently, he began to work in the Physics Department (Physikalisches Cabinet) of the University of Vienna, led by Professor Viktor von Lang. Puluj started his study of the dependence of internal friction in gases on temperature there; he summed up the results in two essays, which were presented by Professor Lang on 5 February and 23 July 1874 to the mathematics-science class (department) of the Academy of Sciences of Vienna (die Kaiserliche Akademie der Wissenschaften in Wien) to be published [3].

3. Assistant at the Naval Academy in Fiume

From 1 October 1874, Puluj took up the vacant position of assistant to the Chair of Physics and Mechanics at the Naval Academy (k. k. Marine-Akademie) in the then Fiume (today Rijeka).

The Chair was held by Professor Emil Stahlberger. A public selection procedure was announced for the position of an assistant. The annual stipend was 600 guldens plus an apartment in kind (or an annual supplement of 120 guldens for housing). The position was occupied for a period of two years (with the possibility of extension to four years). Applications had to be submitted no later than by 10 September 1874 to the Austrian Ministry of War, at its naval section (Reichs-Kriegs-Ministerium, Marine-Section); university graduation in physics and scientific activity had to have been documented. The selection procedure notice pointed out that in case of candidates with the same qualifications, those who would be able to prove their ability to substitute also for other disciplines, namely descriptive and practical geometry, would be preferred. The naval administration also offered reimbursement of the costs of moving the newly appointed assistant from his former place of work [4].

Puluj was recommended to the position by the Philosophical Faculty of the University of Vienna. Immediately after his arrival, in the winter semester of 1874, he was charged with physics lectures on heat, and in the summer semester, after E. Stahlberger had died unexpectedly on 3 May 1875, with substituting for all the teaching of physics and mechanics [5]. During his work at the Naval Academy, Puluj designed a simple device to demonstrate and measure the mechanical equivalent of heat. He described the principle of the instrument and the results of measurements made with it in two reports sent from Fiume to the Academy of Sciences. At the meetings of the mathematics-science class on 15 April and 10 June 1875, Professor Lang presented them again. The instrument consisted of two main parts, one calorimetric and one dynamometric, which were connected to a simple rotary machine (which at that time was one of the recommended basic pieces of equipment of physics departments of secondary schools). The heat generated by the mechanical friction between the casings mutually inserted in cast-iron cones, one of which was fixed to the rotary machine and the other rotated together with it, was measured. One measurement reportedly only took 30 to 60 seconds. The mechanical heat equivalent values determined by Puluj using this instrument conformed to the value determined by J. Joule and were remarkable for their achieved accuracy [6].


Puluj also sent a statement on the instrument to the German physics journal Annalen der Physik [7]. In 1878, the device was awarded a silver medal at the General International Exhibition in Paris. In his curriculum vitae written in 1911, Puluj stated that the original device was at that time located in the Physics Institute of the German University (k. k. deutsche Karl Ferdinands-Universität) in Prague. A copy made according to this original under his supervision was given to the Deutsches Museum von Meisterwerken der Naturwissenschaft und Technik in Munich [8].

4. Doctorate at the University of Strasbourg

For the professorship at the Naval Academy that became vacant after the death of E. Stahlberger, a public selection procedure was declared with a deadline for filing applications by the end of July 1875. A commencing salary of 1,600 guldens was offered (with the possibility of salary promotion up to 2,800 guldens) as well as a service apartment or housing supplement. Qualification for (and experience in) teaching physics at secondary schools with German as the teaching language was required; knowledge of English or French was desirable and was considered an advantage [9]. The professorship was granted to Peter Salcher, Doctor of Philosophy and formerly a Professor at a secondary school (Oberrealschule) in Trieste, who was three years younger than Puluj [10].

Salcher took up the professorship at the Naval Academy at the beginning of the school year 1875/1876. Thus, Puluj applied to the Austrian Ministry of Culture and Education (k. k. Ministerial für Cultus und Unterricht) for a scholarship for further education at the University of Strasbourg. The scholarship was granted to him in November 1875, subject to his statement that he intended to study for his habilitation and to work for six years at an Austrian university [11]. He left the assistant position at the Naval Academy in Fiume before the end of the year [12]. 

The Kaiser-Wilhelm Universität in Strasbourg was a newly built Imperial-German University in Alsace, which had been annexed to Germany. Puluj started his doctoral dissertation at the Physics Institute, headed by Professor August Kundt. Under the guidance of Kundt and using the instrument Kundt made at his disposal, he continued to study the dependence of internal friction in gases on temperature.

The then dynamic gas theory indicated that the internal friction in gases did not depend on pressure and was proportional to the square root of the absolute temperature. Pressure independence had been experimentally verified (including by measurements by A. Kundt and E. Warburg over a wide range of pressures), but the results of the temperature dependence differed both from the theory and from that of various authors. Puluj carried out measurements of the temperature dependence for room air, carbon dioxide and hydrogen. From 3 January to 2 February 1876, he carried out measurements of 149 samples; he usually did his experiments in the evening or early morning to avoid the disturbing vibrations in the room during daily operation at the institute.

Puluj summed up his results in a treatise dated in Strasbourg in April 1876, which he sent then to the Academy of Sciences in Vienna for publication; it was presented at the meeting of the mathematics-science class on 5 May 1876 [13]. In the treatise, presented as his doctoral dissertation at the University of Strasbourg, Puluj concluded that the internal friction does not depend on the temperature in the same way with all gases. He also mentioned and acknowledged the help of the Professor at the Naval Academy in Fiume, Budisavljević, who carried out calculations for him of the logarithmic decrements using a mechanical calculating machine (Arithmometer). At the end of May 1876, Puluj was awarded the title of “Doctor of Natural Philosophy” in Strasbourg. At that time, he was 31 years old. It is worth mentioning that he worked at the University in Strasbourg almost at the same time as W. C. Röntgen (who was only less than two months younger but at that time already a Professor) [14]. 

[Fig. 3]Figure 3. Puluj's treatise presented as his doctoral dissertation at the University of Strasbourg in May 1876. The title page is shown on the left and the apparatus he used for the measurements on the right. (From the Archives of the University of Vienna, collection PH PA 2041/Puluj, J., published with permission.)

5. Return to the University of Vienna, the position of assistant and habilitation

After completing his doctorate, Puluj returned to Vienna and on 15 June 1876, he applied for his habilitation [i.e. for permission to lecture as a Privatdozent (unsalaried senior lecturer)] in physics at the Philosophical Faculty of the University of Vienna. In the application he stated that he wanted to give lectures on theoretical mechanics, acoustics, optics, magnetism and electricity; in particular, he wanted to offer to the students a well-conceived repetitorium (i.e. a revision course) of lectures “of his highly esteemed teacher, Director Stefan” [15]. He outlined in more detail a program of lectures on theoretical optics that he intended to hold in the next semester, highlighting as the main topics the emission and wave theory of light, interference, bending, polarization and double refraction [16].

A commission consisting of Professors J. Stefan, J. Loschmidt, L. Boltzmann and V. v. Lang was established to assess Puluj's application. The Commission (or more precisely, its three members Stefan, Boltzmann and Lang) met on 24 June 1876. It unanimously recommended that Puluj be allowed for further habilitation procedure, i.e. for a colloquium and a lecture on probation. On the same day, their opinion was submitted to the Professorial Collegium (board) of the Philosophical Faculty. Further habilitation steps, however, were delayed by the requirement to supplement Puluj's application with the original doctoral diploma and its nostrification (i.e. recognition as equivalent to a doctoral diploma from an Austro-Hungarian university); at least a two-year interval between the doctorate and the habilitation was also required. The habilitation colloquium was held on 7 July 1877. Meanwhile, at the suggestion of Professor Lang, Puluj was appointed an assistant to the Physics Department (from October 1876), and he supplemented his habilitation application with some more scientific publications. The habilitation lecture on probation followed on 11 July 1877. Puluj offered three topics: 1. On the radiometer, 2. On the diffusion of gases, 3. On the mechanical theory of heat. The commission opted for the third one. Both the colloquium and the lecture given by Puluj were recognized as fully sufficient. This successful habilitation procedure was then reported by the Dean of the Faculty to the Ministry of Culture and Education, which by a decision of 6 September 1877 agreed to both the nostrification of Puluj's doctoral diploma and his admission as a Privatdozent of physics at the University of Vienna [17].

After returning to the University of Vienna, Puluj continued his studies of internal friction in gases, vapours and gas mixtures, diffusion of gases. From these topics, he then went on to study phenomena in low-pressure gases in discharged (vacuum) tubes; in the period 1877–1882, he presented to the mathematics-science class of the Academy of Sciences in Vienna four communications on radiometers and four communications on “radiant electrode matter” [18].

Puluj rejected the hypothesis of a fourth state of aggregation of matter, pronounced by the British physicist and chemist Sir William Crookes in his lecture “On Radiant Matter” at the Annual Meeting of the British Association for the Advancement of Science in Sheffield on 22 August 1879, to explain phenomena in highly evacuated cathode tubes (e.g. the creation of a dark space near the cathode). Puluj called the Crookes hypothesis “transcendental” with an inclination to spiritism. With reference to works of the German physicist Johann W. Hittorf on conducting electricity in gases, Puluj offered a more natural (materialistic and mechanical) explanation based on the idea of the “radiant matter of electrodes,” i.e. of physical particles mechanically released from the electrodes that are charged with negative electricity, moving in a straight line at high speed, and together with the residual molecules of the gas mediating the conduction of electricity between the electrodes of the discharge tube [19]. This was before the discovery of the electron as the primary bearer of negative electricity. The lecture by W. Crookes also awoke a prompt and lively interest of physicists in the Czech lands. In 1880 a paper entitled (in Czech) “On the Fourth Aggregate State or Radiant Matter” appeared in the Journal of Czech Mathematicians and Physicists. The paper was written by the assistant of physics at the Czech Technical University František Čecháč “using the material that W. Crookes had sent to him most willingly at a kind intercession of the Professor of Physics at the Czech Technical University in Prague K. V. Zenger” [20].

Puluj supported his idea and interpretation of phenomena in vacuum tubes by a series of experiments, to which he alone designed several sophisticated “vacuum apparatuses” in the Physics Department of the University of Vienna. Their production was taken over by the company F. O. R. Goetze of Leipzig. Puluj mentioned the cooperation with this company in his letter to Professor Lang on 25 July 1879 (written in Krieglach, Styria). In the letter, he wrote that the mechanic Robert Goetze from Leipzig had just made a radiometer with a cylindrical glass casing according to his own (Puluj) design; the price of one piece was 12 Marks. Puluj ordered one piece and asked Professor Lang whether he was also interested in buying a specimen for his radiometric collections [21].

Puluj’s vacuum apparatuses were introduced in 1881 at the first international electrical exhibition (Exposition internationale d'Électricité) in Paris. In particular, the Puluj cathode tube with a fluorescent screen placed between the cathode and an anode that emitted very intense light aroused the interest of both experts and natural science lovers. Puluj was awarded a diploma for his participation in the exhibition. Some of the devices he presented there remain in the Conservatoire National des Arts et Métiers in Paris.

[Fig. 4]Figure 4. The Puluj phosphorescent lamp. It consisted of a simple glass tube having in the center an obliquely placed elliptical plate of mica covered with calcium sulfide. Below the mica plate was a disc of aluminium of the same diameter as the section of the tube, which served as the cathode (-). Above the mica plate was the much smaller anode (+). The light of the phosphorescent lamp was sufficiently brilliant to light a room, and it was possible to read even at some distance from it [Puluj, I. (1889). Radiant electrode matter and the so-called Fourth State, l. c., pp. 293–294, Fig. 51].

In 1882, Puluj received a grant from the Academy of Sciences in Vienna to continue his work on discharges in dilute gases [22]. The strong interest he encountered in Paris prompted him to publish a collected edition of his papers on the radiant matter of electrodes [23]. The dispute with the opinions of such an authority as W. Crookes subsequently became an impulse to translate this edition into English. The translation, according to the text modified by the author concerning new knowledge, was published in 1889 in the series Physical Memoirs, selected and translated from foreign sources, which began to be published by the Physical Society of London. In the same volume, a translation of three papers by J. W. Hittorf on the conduction of electricity in gases was published, to which Puluj referred in particular. Translations into English were done by the British physicist, chemist and astronomer Warren De la Rue, who was also interested in the issue of electrical discharges in low-pressure gases; he died before the translation was published [24]. 

The Puluj collected edition was published in English during his time working in Prague. Related to this was an appended chapter (dated in Prague in February 1888), in which Puluj drew attention to an article by the Professor of General and Analytical Chemistry at the German Technical University in Prague, Wilhelm F. Gintl, of January 1880, where Gintl also critically commented on the Crookes' concept of radiant matter and which had previously escaped Puluj's attention [25].

[Fig. 5]Figure 5. Puluj's treatise on "radiant electrode matter": the 1883 edition in German is on the left and a copy of the Physical Memoirs of 1889 (with the translation of the treatise into English) dedicated by Puluj to the Library of Prague Technical Universities on the right. (National Library of Technology in Prague, Rare Books and Special Collections, published with permission.)

6. Practical work in the electrical engineering industry

The appointment of Puluj as assistant at the Physics Department of the University of Vienna was extended twice for another two years (which was the permitted maximum), until the end of September 1882. In the suggestions for extending his assistant service, Professor Lang stated with words of praise that Puluj had performed his assistant duties with enthusiasm, published numerous scientific papers and was a skilled experimenter [26]. 

Working at the University of Vienna in the circle of leading physicists of that time was stimulating for Puluj’s career. Yet, his financial situation was uncertain and not great. His assistant salary amounted to 700 guldens a year, a sum that was not easy to live on in Vienna at that time. The income from his lectures as Privatdozent was dependent on the number of enrolled students, which was usually less than ten, and the enrolment fees were usually not even enough to cover the costs of preparing the lectures [27]. 

Puluj repeatedly turned to the Ministry of Culture and Education with the request for a “fair financial reward” for his teaching and scientific activities at the university. Both Professor Lang and the Professorial Collegium warmly supported his application. But ministerial support was sparse and little. Puluj's financial situation would have been improved by his appointment as a secondary school teacher in a university city where he could continue his lectures and scientific work. However, Puluj applied for such a position without success [28]. 

Though the substance of electricity was still unknown (electricity being still taken to be a fluidum), electricity was already successfully applied in technical practice. In 1882, after six years as an assistant and with the knowledge he had acquired, Puluj went into electrical engineering practice. From 1882 to 1883, he was employed as technical manager for the production of Geisler tubes at the Vienna office of the firm Ganz & Co. in Budapest; the company participated in installing the electric lighting at the electrical exhibition held in Vienna in 1883. Then, by the end of 1883, Puluj became a technical consultant to the Austrian arms factory (Waffenfabrik-Aktiengesellschaft) in Steyr; the factory chief executive, Joseph Werndel, decided to organize an electrical exhibition in Steyr in 1884 and commissioned Puluj with the task of building and managing a new bulb factory.

Puluj did well in his work in the electrical industry. Yet his relations with Director Werndel were strained. Therefore, an offer coming from Prague was taken by Puluj as an opportunity to resolve his troubles.

In Steyr, Puluj became acquainted with František Křižík, the leading Czech electrical engineer and businessman, who invented an automatically regulated arc lamp in 1880. Křižík later stated in his Memoirs that, in Steyr in 1884, he learned from Puluj “to blow bulbs,” which he then tried to introduce at his electrical plant in Karlín (today a district of Prague). He also acted for some time as an intermediary in some difficult communication between Werndel and Puluj [29]. 

7. Professor at the German Technical University in Prague

7.1 Called up to Prague

By the supreme decision of the Emperor Franz Joseph of 8 August 1884 “the Privatdozent at the University of Vienna and Head of Electrical Engineering company Werndel in Steyr, Dr. Johann Puluj” was appointed as an ordinary (full) professor at the Chair of Experimental and Technical Physics in the German Technical University in Prague (k. k. deutsche technische Hochschule in Prag, hereafter DTH in Prague), as of the beginning of the school year 1884/1885 [30]. By that time, he had been released from service at Werndel.

I have not been able to find documents explaining the circumstances by which Puluj was called up to the DTH of Prague. However, the matter was clearly under discussion before the end of 1883. The decisive moment was undoubtedly Puluj's expertise and his willingness to include the teaching of electrical engineering within a single Professorship of Physics. An independent Chair of Electrical Engineering had not been set up at the DTH yet (for economic and budgetary reasons and the lack of teaching and working space); Puluj could hardly anticipate that such an interim state would last for the next 16 years! The Philosophical Faculty of the University of Vienna fully supported the proposal to appoint Puluj as a professor at the DTH [31]. Before taking up his new post, on 2 October 1884, Puluj married 21-year-old Katharina, born Stozicky, in Vienna; the marriage produced five (surviving) children, who were born in Prague [32].

[Fig. 6]Figure 6. Johann Puluj [Stark, F. (1906). Die k. k. deutsche technische Hochschule in Prag 1806–1906. Festschrift zur Hundertjahrfeier, Prag, p. 180] and his wife, Katharina Puluj, born Stozicky. [National Archives in Prague, collection "PŘ Praha II, všeobecná spisovna, 1941–1950", box 9230, sign. P 4129/2, Puluj Katharina b. 1863 (passport No. 23 666 issued on 29. 7. 1924), published with permission.]

Having been appointed professor at the DTH of Prague crowned Puluj's earlier attempts to obtain a civil service post that would allow him to continue his scientific work. He accepted the assignment of duties formulated as a representation of the nominal field (i.e. experimental and technical physics) and also in the field of electrical engineering, fully corresponding to the needs of the relevant school, as recognition of his scientific and technical activities to date. His starting salary at the DTH (i.e. 2,000 guldens plus an efficiency bonus of 480 guldens per year) was lower than the salary he was paid as a consultant and plant manager at Werndel (i.e. a fixed salary of 3,000 guldens per year plus a share in the company profit and an apartment in kind) [33]. However, the final provision in the new post (which occurred in 1889) presumed a salary promotion and entitlement to a retirement pension.

7.2 Taking up the professorship

At the DTH of Prague, Puluj succeeded Professor Adalbert von Waltenhofen (1828–1914), who was by the supreme decision of 1 August 1883 (after 14 years at the DTH) called up to the Technical University of Vienna to extend the teaching of electrical engineering there [34]. In the school year 1883/1884, the vacated Chair was taken over by the assistant Wilhelm Paukert (who then obtained a scholarship for further education in electrical engineering in Germany) [35].

Puluj took on pedagogical and scientific-organizational duties at the DTH with enthusiasm and support from the Minister of Culture and Education, S. Conrad von Eybesfeld. As Puluj stated in his later biography, thanks to the minister's liberality, a new electrical laboratory and engine room were furnished in the main building of the DTH in Husova Street in Prague already in 1884/1885. In addition, all the rooms of the existing Physics Department (Physikalisches Institut) were adapted, and another workshop for fine mechanics was furnished, in addition to the existing workshop for gross mechanical works, and positions for one mechanic and one servant were established [36].

[Fig. 7]Figure 7. The old DTH building in Husova Street, Prague (Die k. k. deutsche technische Hochschule in Prag 1806–1906. Festschrift zur Hundertjahrfeier, Prag: DTH 1906, s. p.).

Teaching physics was a part of the compulsory curriculum of virtually all the fields of study in the first two years. This included a lecture on general (experimental) physics and a lecture on technical physics supplemented with practical seminars. Electrical engineering, which Professor Waltenhofen began to teach at the DTH, was incorporated into technical physics. However, Puluj introduced separate lectures and seminars in electrical engineering starting from the school year 1885/1886; they were intended for students of higher classes, especially in the field of machine building (mechanical engineering). At first, these lectures were held by Puluj without a requirement for any remuneration. Starting from the school year 1888/1889, he was remunerated for them with 1,000 guldens a year [37].

Rudolf Suchomel became the first assistant to Professor Puluj at the DTH; he held the post from October 1884 for two school years. The position of assistant to the Chair of Experimental and Technical Physics was later changed to the higher position of a constructor (a design engineer). It was not easy to get an expert with the necessary skills to hold the position. The high demands of Puluj were well met by the Doctor of Philosophy Johann Sahulka, who became Puluj's assistant in Prague from 1889 to 1890. Sahulka (1857–1927) studied mathematics and physics at the University of Vienna, and for two years, he also attended lectures in electrical engineering at the Technical University of Vienna. At the DTH, he then passed an electrical engineering examination in 1890 (with Puluj) and in May 1891 applied for a habilitation in electrical engineering there; during the habilitation procedure, on the proposal of Puluj, the subject of the Sahulka habilitation was specified as “venia legendi for alternating currents and their application.” In 1894 Sahulka returned to Vienna, and in 1903 he became Professor of Electrical Engineering at the Technical University of Vienna [38]. 

7.3 Project for a modern institute for physics and electrical engineering

In 1895 Puluj proposed to build a modern institute for physics and electrical engineering at the DTH in Prague. In connection with this and with a grant of 300 guldens from the Ministry of Culture and Education, he went on a study trip to Switzerland and Germany in the summer of 1895. In his report on the trip (submitted to the Ministry on 27 May 1896), he stated that foreign technical universities with magnificent electro-engineering institutes outperformed Austrian technical schools by a full decade [39].

Nevertheless, Puluj did not live to experience a new modern institute for physics and electrical engineering at the DTH, despite his repeated suggestions, urgencies and persuasive arguments (which were commonly recognized as legitimate).

It was at the time of his planning of the new institute, and after returning from the study trip to Switzerland and Germany, that Puluj learned, in early 1896, of the discovery of X-rays by W. C. Röntgen, which was bitter news for him. We shall come back to Puluj’s response to Röntgen's discovery in part 8 at the end of the article. 

7.4 Establishing a Chair of Electrical Engineering

Requirements for the teaching of electrical engineering increased, both in the amount of the curriculum and in the interest of students. This was related to the development of the field and its growing economic importance. Ensuring quality teaching of electrical engineering within a single physics Chair and its confined space in the main building of the DTH in Prague was becoming unbearable. After 16 years, at the threshold of the new millennium, Puluj objected to this situation.

In his letter dated 12 March 1900 and sent directly to the Ministry of Culture and Education, Puluj called for the division of his professorship into a separate professorship for experimental physics and the one for electrical engineering. He noted that his teaching commitment at the DTH at that time included two two-semester courses in physics (general physics and technical physics, totaling 7 hours of lectures per week) and two two-semester courses in electrical engineering (totalling 4 hours of lectures and 3 hours of practical seminars per week); he had taught both disciplines with enormous effort and regardless of his health; he was not able to bear this burden any longer than by the end of the summer semester 1900 [40].

In a personal audience given to Puluj, the Minister of Culture and Education, Wilhelm von Hartel, promised to consider the request. The Professorial Collegium of the DTH fully supported Puluj's demands. Based on the proposal of a commission set up for the case, the collegium recommended: 1) to systematize the Chair of Electrical Engineering as an ordinary (full) professorship and entrust it to Professor J. Puluj, 2) that steps be taken to fill the new Chair of Experimental Physics also by an ordinary professor. The most complicated question, namely where to locate the new Chair of Electrical Engineering, however, was not decided for the moment. 

The Ministry of Culture and Education and the Ministry of Finance assessed the presented proposals in terms of financial costs. The division of the Chair of Experimental and Technical Physics at the DTH was agreed upon, but the implementation was postponed until 1901 [41]. Having been assured by the Ministry of Culture and Education that the division of the existing Chair of Physics at the DTH would take place from the summer semester of 1901, Puluj assented to the request for teaching of both physics and electrical engineering for another semester. However, at the end of the winter semester 1900/1901, by a letter to the Rectorate of the DTH of 12 February 1901, the Ministry again postponed the division of the Chair to the beginning of the school year 1901/1902. The problem arose, namely around the location of the Chair of Electrical Engineering and the associated costs [42]. 

Puluj responded with a new urgent letter to the Ministry dated 3 March 1901. This time he categorically rejected further representation of both subjects. He wrote that his mental and physical exhaustion was exacerbated by a complicated influenza illness he had suffered in the meantime. He insisted on the division of the Chair of Experimental and Technical Physics from the coming summer semester of 1901. On a question that the Ministry had addressed to him, Puluj expressed his willingness to take over the new Chair of Electrical Engineering but he set his own conditions. If they could not be fulfilled, he intended to keep the Professorship of Physics, with the existing staff. In this case, he recommended that the new electrical engineering Chair was occupied by a full professor “with the necessary qualifications” and that at least one constructor, one laboratory technician and a corresponding subvention were provided to him.

There was evident interest on the part of the Professorial Collegium and the Rectorate of the DTH that Puluj, as a highly renowned expert in electrical engineering, should take over the new Professorship of Electrical Engineering; filling a Chair of Physics with a good specialist seemed easier. The requirements stated by Puluj were generally justified. However, resolving the issue before the beginning of the semester was not possible for an advanced date. For the summer semester of 1901, a temporary solution had to be undertaken. Puluj was willing only to teach physics in that semester. As it was necessary to provide the obligatory teaching of electrical engineering for students of machine building too, Puluj suggested that the constructor at the chair of physics, Robert Mayer, should be appointed as a substitute for the lectures, and possibly to supervise practical seminars. He offered to share a physics auditorium with him. Puluj said that Mayer was an excellent graduate of the DTH (in the machine-building field). He had also studied in London for a year but had only been involved in electrical engineering for one year (since his appointment as a constructor). For the time being, however, he did not have the qualifications to provide full electrical-engineering education. Therefore, this only was an emergency solution for the summer semester of 1901, which was not to continue in the next school year [43]. 

The division of the Chair of Experimental and Technical Physics at the DTH was made on 1 October 1901 based on a decision of the Ministry of Culture and Education of 2 July of the same year. The decision stipulated that one of the two newly created independent Chairs, on which the current Professor, Puluj, would decide, would be systematized as an ordinary professorship, and the other one would be an extraordinary professorship. The Ministry pointed out that there were no financial resources available to systematize a second ordinary professorship. The former positions of the constructor and mechanic were transferred to the Chair of Electrical Engineering. For the Chair of (Experimental) Physics, a systematized assistant post with the annual salary of 1,400 K was established from 1 October 1901. The Chair of Electrical Engineering was awarded an annual subvention of 2,000 K. Lectures, and practical seminars on electrical engineering were supposed to be held as so far in the premises of the physics Chair in the main building in Husova Street; when drawing up the school timetable, however, care had to be taken to ensure that physics and electrical engineering did not interfere with each other [44].

Puluj decided on the Chair of Electrical Engineering (even though not all his requirements were met). Therefore, the Chair of Physics became an extraordinary professorship. Until the filling of this vacant position, Josef Geitler von Armingen, a Privatdozent with the title (not salary) of extraordinary professor at the German University of Prague, was entrusted as a substitute for physics lecturing at the DTH.

7.5 Filling the Chair of Physics

A commission headed by Puluj was entrusted with the task of preparing a proposal for filling the extraordinary physics professorship at the DTH on 17 July 1901. At its first meeting on 7 January 1902, the commission asked Puluj to look for suitable candidates. On 8 April 1902, Puluj presented the professional curricula of five candidates. The commission then drew up a proposal of the usual “triennial,” which was submitted to the Professorial Collegium on 23 June 1902 and with their approval passed to the Ministry on 6 November 1902 by the Rector of the DTH.

In the first place, two “local” candidates were proposed ex aequo (as equal in power): the above-mentioned 31-year-old Josef Geitler von Armingen (a native of Prague) and 37-year-old Josef Tuma, at that time Privatdozent and adjunct of the Physics Institute of the German Technical University in Brno (Moravia). Stefan Meyer, a Privatdozent and assistant of the Physics Institute of the University of Vienna, was nominated in second place. Two other ex aequo candidates were nominated in third place: Anton Lampa, a Privatdozent and assistant of the Physics Institute of the University of Vienna, and Eugen von Schweidler, a Privatdozent and assistant of the Physical Chemistry Institute of the University of Vienna. The Ministry decided on J. Tuma. His advantages included higher age and richer professional experience, and also the order in which Tuma and Geitler were previously proposed to the Professorship of Technical Physics at the German Technical University in Brno (Tuma was second and Geitler the third candidate for that professorship) [45].

The final filling of both Chairs was made by the supreme decision of 18 October 1902: Puluj was appointed ordinary Professor of Electrical Engineering and Tuma as extraordinary Professor of Physics. Each of their teaching duties was defined as a proper representation of the field in the theoretical and practical direction to the extent corresponding to the requirements of the particular technical university, subject to possible later modification [46]. Puluj's salary remained unchanged. Tuma was assessed a commencing salary of 3,600 K plus an efficiency bonus of 840 K per year, and took up the new post on 1 November 1902; five years later he was appointed ordinary professor. J. Geitler continued to work at the German University of Prague until September 1906, when he was appointed ordinary Professor of Physics at the University of Czernowitz in Bukovina (now Ukraine). 

7.6 Professor of Electrical Engineering

As a Professor of Electrical Engineering, Puluj held a two-semester lecture, “General Electrical Engineering,” at the DTH of Prague, which was obligatory for students of machine building and was completed with practical seminars in a laboratory. Also, “on his own initiative” and until 1912/1913 without any remuneration requirements, he gave optional one-semester lectures on selected chapters of electrical engineering; these lectures were intended for students of the field of machine building who had attended the compulsory lecture and were interested in a more in-depth education in electrical engineering because they intended to work in the electrical engineering industry.

In particular, in the school year 1911/1912 Puluj gave optional lectures: "Selected chapters from AC electrical engineering: theory and calculation of transformers and three-phase motors" (1 hour per week in the winter semester), "Special electrical engineering: power plants for lighting and power transmission" (2 hours per week in the summer semester) and "Introduction to electrical engineering machines and devices" (1 hour of lectures and practical seminars in the summer semester).

Puluj had to supervise by himself all the practical seminars because only unqualified persons still applied for the position of constructor (whom he had to train first and who, usually after one or two years, would leave for a better-paid position in industry) [47]. Furthermore, Robert Mayer did not stay as constructor at the DTH for very long. From the beginning of the school year 1903/1904 he took up the post of a teacher of electrical subjects at the German Technical College (k. k. deutsche Staats-Gewerbeschule) in Brno; the commencing payment offered for this post was 2,800 K plus an efficiency bonus of 600 K, whereas as the constructor at the DTH, Mayer drew an annual remuneration of 2,400 K [48].

The proposal for the establishment of the second electrical engineering Chair at the DTH, which was to form the basis for the establishment of an Electrical Engineering Department with an independent second state examination, was submitted to the Professorial Collegium in 1906. Particular negotiations on this issue in the Collegium and with the Ministry, however, did not start until 1916, when it was related to Puluj’s retirement. The establishment of the Electrical Engineering Department subordinate together with the Department for Machine Building to the same dean's office (Abteilung für Maschinenbau und Elektrotechnik) and the Electrical Engineering Institute only became a reality with Puluj's successor. 

7.7. Puluj's last assistant at the DTH in Prague

Puluj's last assistant (paid from the resources arranged for a constructor) was Ing. Johann Wegscheider, who held this post after 1 December 1912 [49]. Just like Mayer, he graduated from the machine-building department at the DTH. He continued to work as an assistant under the guidance of Puluj's successor [50]. During World War I, when he was called up to the army, the student Johann Fukke stood in for him [51].

7.8 Retirement

In the school year 1914/1915 (on 2 February 1915), Puluj reached the age of 70, which was – at that time – the age limit for holding a university teaching office. At a meeting of the Professorial Collegium on 18 January 1915, the decision was made to ask him to hold his teaching office for one more honorary school year. The Rector, J. Tuma, however, disagreed and attached his separate votum to the proposal presented to the Ministry. He argued that Puluj's successor should be provided with the opportunity to get involved as soon as possible in the establishment of the Electrical Engineering Department and the Electrical Engineering Institute. While the Ministry listened to this argument, it nevertheless complied with the proposal to extend Puluj's mandate at the DTH in Prague – given his merits “and not to endanger his health.”

[Fig. 8]Figure 8. House in Prague-Smíchov, now Presl (at Puluj's time Fibich) Street No. 1268, the last residential address of Puluj and his family. The plaque remembering Puluj was placed on the house in 1930. (Photo credit: E. Těšínská, January 2020.)

Puluj retired on 30 September 1916. In this context, upon the supreme decision of 28 October 1916, he was bestowed Komturkreuz des Franz-Joseph-Ordens [52]. He was assessed a pension of 11,840 K, which, however, he did not enjoy for long. He did not live to the age of 73, nor to the end of the World War and the collapse of Austria–Hungary. He died on 31 January 1918. He and his wife (who died on 8 August 1945, after World War II) are buried in the cemetery in Prague's Smíchov, Malvazinky.

[Fig. 9]Figure 9. Grave of Puluj and his wife at the cemetery in Prague's Smíchov, Malvazinky. (Photo credit: E. Těšínská, January 2020.)

Puluj's successor at the Chair of Electrical Engineering at the DTH of Prague became Friedrich Niethammer (1874–1947), formerly Professor of Electrical Engineering at the German Technical University (k. k. deutsche Franz-Joseph-Technische Hochschule) in Brno. He took up the position from 1 March 1917 [53].

7.9 Career posts and social honours

During his work at the DTH in Prague, Puluj held responsible academic positions. He worked in expert committees and associations, and as an expert, he continued to cooperate with industry. In the academic year 1888/1889, he held the office of Rector of the DTH. He was a member of the examination committee for civil engineers and architects, and chairman of the scholarship committee for outstanding academic achievement. He was a sworn expert in Electrical Engineering at the Commercial Court for Bohemia. He participated in the construction of power plants in Bohemia, Moravia and elsewhere. As an invited expert, he also endorsed the project of the Prague municipal power plant with a single AC central power station. He was an honorary member of the Elektrotechnischer Verein in Vienna. He was awarded the title of Court Councillor (Hofrat) and a gold medal at the Jubilee Exhibition (Kaiser Franz-Josef Jubiläums-Ausstellung) in Prague in 1908.

8. Puluj's response to the discovery of X-rays

The sensational news of Röntgen's discovery of X-rays also reached Prague in early January 1896. On 7 January, for example, the German newspaper Bohemia reported on it by reprinting a piece of news from the Vienna newspaper Die Presse [54]. The author of the news was the Austrian physicist Ernst Lecher, son of the editor of the newspaper Die Presse and from 1 October 1895, Professor of Physics at the German University in Prague (where he succeeded Ernest Mach). Lecher learned about the discovery of X-rays by Röntgen in Vienna on 5 January from the professor of the University of Vienna, Franz Exner, his former teacher [55]. Three weeks later, on 24 January, Ernst Lecher delivered a lecture, “On the new discovery of Professor Röntgen (including demonstrations)” to the Prague Association of German Medical Doctors. Incidentally, it was Lecher who succeeded Puluj as Professor Lang's assistant at the University of Vienna in 1882. However, there were also other communication channels, through which people at the Prague universities could learn about Röntgen’s discovery. Their response to the discovery was similar to elsewhere in the world. In the physics and electrical engineering departments of both the Czech and German Prague universities, Röntgen's experiments were immediately repeated, and X-rays, their origin and properties, subjected to further investigation. X-ray images of various objects were produced in cooperation with experts or amateurs in the field of photography. A possibility to use X-rays in medicine was the subject of special interest (though initially also with scepticism). These first experiments were reported at meetings of learned societies and professional associations; apart from that, lectures and demonstrations were also organized for the general public [56].

On 17 January 1896, the Professor of Electrical Engineering at the Czech Technical University in Prague, Karel Domalíp, reported, probably as the first one in Prague, on his experiments with X-rays at a meeting of the mathematical-science class of the Czech Academy of Emperor Franz Joseph for Sciences, Literature and Art. He presented an X-ray picture of a human hand there, which he took at the Institute of Physics and Electro-Engineering of the Czech Technical University on 11 January [57]. It was allegedly the third object photographed “under the cathode light according to Professor Röntgen's method” at that institute using a Crookes tube with a platinum cross inside, connected to the anode, and a side cathode in the shape of a concave mirror (the first two photographed objects were a thermoelectric pile and a metallic ornament) [58]. The picture was photographically processed (he developed a negative and produced a positive) by the Privatdozent of Technical Chemistry (from 1899 the Professor of Fermentation Chemistry and Photography) at the Czech Technical University in Prague, Karel Kruis [59]. This successful picture was subsequently published in the Czech popular science journal Živa [60] and then also reproduced in other magazines.

[Fig. 10]Figure 10. Karel Domalíp (1846–1909), Professor of Electrical Engineering at the Czech Technical University in Prague (on the left) [Časopis pro pěstování matematiky a fyziky, 1910, Vol. 39, s. p.] and the X-ray picture of a hand made by K. Domalíp in cooperation with the chemist K. Kruis on 11 January 1896 [Živa, časopis přírodnický, Vol. 4, 1896, s. p.].

K. Domalíp (1846–1909) was a professional counterpart of Puluj at the Czech Technical University in Prague. He had studied mathematics and physics at the Philosophical Faculty of the University in Prague (at that time not yet divided into Czech and German), where he was one of the students of E. Mach. After his studies, in 1871–1876, he worked as an assistant to A. von Waltenhofen at the DTH in Prague, where he completed his habilitation for theoretical physics in 1875. In 1884 he made his habilitation for electrical engineering at the Czech Technical University in Prague, where, in 1891, he was appointed extraordinary professor (and in 1893 ordinary professor). In the meantime, in the years 1875–1891, he was employed as a secondary school teacher [61].

Puluj was somewhat disappointed about the news of Röntgen’s discovery of X-rays, which overshadowed all previously made pioneering works on cathode rays, namely his own valuable contributions. Based on the archives being at my disposal, I am not able to document Puluj's early experiments and alleged X-ray pictures he had made (unknowingly) with his lamp before Röntgen’s discovery. For this interesting, but sensible question, I prefer to refer to the existing biographical literature and their sources for the moment [62]. I limit myself here just to Puluj's immediate response to Röntgen's discovery.

During January–February 1896, in the Physics Department at the DTH, Puluj verified the emergence of and the photography by "invisible cathode rays" using his old lamp with a fluorescent screen. He achieved very successful images. Consequently, he focused on the location of X-ray formation in the cathode tube and on the origin of the X-rays. He reported on the results of his experiments, as before, to the Academy of Sciences of Vienna.

At the meeting of the mathematics-science class of the Vienna Academy on 6 February 1896, it was recorded that Professor J. Puluj sent eight photographic reproductions of pictures he had made in the DTH Physics Department in Prague with his vacuum apparatuses. In the accompanying commentary, Puluj stated that he had been encouraged to do so by a lively interest that was aroused in the widest circles by the photographic effects of the invisible cathode rays discovered by Professor Röntgen. The pictures he presented, he continued, showed a "not insignificant" progress over other reproductions known to him and showed what use this method of photography would find in surgical practice (see photos at the start of this article). He added that on 2 February, he managed to photograph a two-month-dead baby in this way; the reproduction to be sent later to the Academy clearly showed not only the details of the chest but also the entire spine up to the head; the newborn head could not be displayed due to the small size of the photo plate. He added that the head of an adult human, however, could not be displayed with the radiation provided by the current cathode tubes [63].

On 8 February 1896, just six weeks after Röntgen presented his discovery of X-rays, Puluj published his own findings in the French journal La Nature in Paris.

In a report from the following meeting of the mathematics-science class of the Vienna Academy on 13 February 1896, “another remarkable reproduction of a cathode-ray tube picture taken in the DTH Physics Department in Prague led by Puluj” was recorded, namely a photograph of a dead nine-day-old baby. In the same session, a communication by Puluj on the origin of X-rays and their photographic effects was accepted for publication. In it, based on his own experiments, Puluj stated to have confirmed Röntgen's assumption that X-rays came from the glass wall of the discharge tube, which was exposed to visible cathode radiation and which phosphoresced. He further confirmed that a screen covered with calcium sulfide in his lamp (which he constructed 15 years before) not only shined strongly (as described earlier) but also emitted very intense invisible radiation; he stated that with this lamp, clear images of small objects could be recorded on the photographic plate after just two seconds of exposure. Puluj further suggested that all substances that were intensely shining in cathode rays had a strong emission capability even for X-rays. He described several new modifications of his lamp, which he made especially for photography with the invisible cathode rays. He discussed in more detail several clinically interesting cases that he photographed with the new method: a tuberculous hand, a hand with a revolver bullet embedded in the upper bone of the middle finger, the head of a young man with a 6-mm revolver bullet inside for years (yet, even the 1.5-hour exposure failed to locate the bullet), a leg with a small iron tip in the thigh, a dead newborn baby, a healing broken arm of a 13-year-old boy, a hand of a two- and a four-year-old child and a full body picture of a newborn baby. Puluj pointed out the problem with displaying small metal objects in the human or animal body resulting from the divergence of X-rays of the cathode tube, but he was trying to solve this problem. As a success, he mentioned a picture of a "shot guinea pig", in which it was possible to depict  clearly small metal pellets and a bullet. Regarding the way X-rays are formed, Puluj stated his opinion that the conversion of visible cathode radiation to invisible radiation took place through material bodies. Particles mechanically plucked from the cathode, which transferred negative static electricity, balanced their electrical charges when they struck glass walls or other solid bodies, causing molecules and their ether shells to shake. Each point of the glass wall or screen on which the cathode radiation fell became the starting point of the ether waves, which propagated (depending on the type of oscillation and the duration of oscillation) either as visible or as invisible radiation [64].

[Fig. 11]Figure 11. A full body picture of a newborn baby made by J. Puluj in 1896 [The Photogram, 1896, Vol. 3, No. 28 (April), Special supplement, p. 104. Accessible here].

In a supplementary communication, which was adopted for publication at the meeting of the mathematics and science class of the Vienna Academy on 5 March 1896, Puluj described further direct experiments that had confirmed the correctness of the assumption that in Puluj's lamp new radiation was created on the phosphorescent mica screen (namely on the side covered with the phosphorescent substance) rather than at the glass wall or the cathode [65].

Upon making pictures of clinically interesting cases, Puluj cooperated with German university clinics and hospitals in Prague (with Professor G. Pick from the internal clinic, Professor A. Wölfler from the surgical clinic and the pathological anatomist H. Chiari). A short report on the pictures taken by Puluj using his “vacuum apparatuses” was published as early as 31 January 1896 by the German newspaper Prager Tagblatt [66]. In the Czech magazine Světozor, in the 31 January 1896 issue, a reproduction of the above-mentioned picture of a “shot guinea pig” was published. The label stated that the photo was taken using Puluj's lamp by amateur photographers (K.) Paspa and (? E.) Šafařík; on the left front leg of the animal, there were well recognizable "bird" pellets, and behind the right foot, a bullet from a Flobert gun [67].

[Fig. 12]Figure 12. Picture of a shot guinea pig made with "cathode light of Puluj's lamp“ in Puluj's laboratory by photographers Paspa and Šafařík. Pellets can be seen in the left front leg of the animal and a bullet behind its right front leg (Světozor, 1896, Vol. 30, No. 14, p. 143).

On the evening of Saturday 14 February 1896, Puluj gave a lecture on "invisible cathode rays" for the public. A detailed report on the lecture was published on 18 February 1896 in the German newspaper Bohemia. The lecture took place in the physics auditorium in the main building of the DTH in Husova Street. It was widely visited, and “there were even numerous ladies among those present.” It lasted two hours and ended with lively applause from the audience. The financial proceeds from the lecture were donated by Puluj to a fund for supporting poor students of electrical engineering.

[Fig. 13]Figure 13. A cameo with a nacre frame, an X-radiograph made by Puluj in Prague in 1896 (?): negative on the left and positive on the right [published by Lanner, A. (1897). “Die Entdeckung der Rőntgenstrahlen,” Jugendheimat, Vol. 11, p. 141. (Originals preserved in the Archives of the National Museum in Prague, J. Puluj collection.)

As the newspaper report states, Puluj focused at the beginning of the lecture on the work on the cathode rays that preceded Rőntgen’s discovery (that he called a lucky coincidence). He mentioned above all his own experiments performed in the early 1880s by instruments of his own design. During the lecture, Puluj demonstrated how to photograph using "invisible cathode rays". In addition, he showed his previously (referring most probably to 1896) taken images that required more prolonged exposure: skeletons of animals, a child's broken forearm and a skeleton of a newborn baby. Copies of the images were hung on the walls of the auditorium so that those present could better view them. The report stated that all the photographs taken by Puluj using “invisible cathode rays” were photographically processed (and made in multiple copies) by the photographer H. Eckert. Eckert, who had graduated from the Prague Polytechnic School, was a reputable photographer, a member of the Photographic Society in Vienna, and he also collaborated, e.g. on photo documentation of F. Křižík's businesses [68].

[Fig. 14]Figure 14. Interior of Puluj's Physics laboratory at the DTH in 1896 (?). Various cathode tubes can be seen on the upper shelf of the cupboard. Over the desk, Puluj's X-ray pictures are exhibited. [Archives of the Czech Technical University in Prague, J. Puluj collection, published with permission.]

Prior to the public lecture at the DTH, Puluj promised to give a lecture on cathode rays with demonstrations also in the local German Science and Medical Association „Lotos“ (Deutscher naturwissenschaftlich-medizinischer Verein für Böhmen „Lotos“) [69]. Puluj became a regular member of this association immediately after his arrival in Prague in 1884; by the end of 1899, his wife also became a (supporting) member of the association. The association had an interdisciplinary character. Its active core consisted of teachers of Prague’s German universities; E. Mach also was a member and its representative when he was Professor in Prague in 1867–1895. Occasional lecturing was one of the basic duties of the regular members. Puluj gave his first lecture there in 1886 “on two instruments designed for determining the mechanical equivalent of heat and thermal conductivity of mica leaf” [70]. Puluj gave the promised lecture at the Lotos association on 14 March 1896. The lecture entitled „Ueber Kathodenstrahlen und ihre Transformation in die von Rőntgen entdeckten unsichtbaren Strahlen” was announced a day before in the newspaper Prager Tagblatt. The lecture again took place in the physics auditorium in the main building of the DTH in Husova Street. With respect to the limited capacity of the auditorium, it was only reserved for members of the association [71]. It is worth mentioning that on the same day, within a series of popular lectures organized by the Lotos association outside Prague, Joseph Geitler, at that time E. Lecher's assistant in the Physics Institute of the German University of Prague, lectured on X-rays in Plzeň in West Bohemia [72].

Puluj returned to his routine work at the DTH, in which electrical engineering had already outweighed physics. The discovery of X-rays by Röntgen and the several weeks of his own intensive work on X-rays undoubtedly contributed to his increasing physical and mental exhaustion. At about the same time when W. C. Röntgen was awarded the first Nobel Prize in Physics in 1901, J. Puluj was bestowed the new Chair of Electrotechnical Engineering at the DTH (without, however, any increase in his salary).


I would like to thank the management and staff of the cited archives and libraries for their professional and helpful assistance. In particular, I would like to thank Mr Thomas Maisel, Head of the Archives of the University of Vienna, and Mrs Vlasta Měšťánková from the National Archives in Prague, who were very helpful in assisting my search for relevant written sources and illustrations.

It is also my pleasant duty to thank Professor A. M. Glazer, Editor of the IUCr Newsletter, for his kind encouragement, comments and English revision of the text.


1. Gajda, R. & Plazko, R. (2001). Johann Puluj – Rätsel des universalen Talents. Ľwiw: EuroWelt-Verlag. Complementary (but not well documented) data on Puluj, his family, colleagues and students in Prague can also be found e.g. in “Hofrat Prof. Dr. Johann Puluj, einst Rektor der K. K. Deutschen Technischen Hochschule zu Prag”. Prager Nachrichten, Beilage Alma Mater Pragensis, 1977, Vol. 28, No. 10, 3–6; No. 11/12, 4–7.

2. Verordnungsblatte für den Dienstbereich des Ministeriums für Cultus und Unterricht (hereafter: Verordnungsblatte f. MfCU), 1873, No. 18 (15 September 1873), p. 519 (Verzeichnis der von der k. k. wissenschaftlichen Gymnasial-Prüfungscommission in Wien im Studienjahre 1872/73 approbirten Gymnasial Lehramtscandidaten, Puluj Johann).

3. Anzeiger der Kaiserlichen Akademie der Wissenschaften (hereafter: Anzeiger d. AdW), mathematisch-naturwissenschaftliche Classe (hereafter: math.-naturwiss. Cl.), 1874, Vol. 8, No. 4, 24–26; No. 20, 160–162.

4. Beilage zum Verordnungsblatte f. MfCU, 1874, No. 28, p. 87 (Concurs-Ausschriebungen).

5. Archiv der Universität in Wien (Archives of the University of Vienna, hereafter: AdUW), sign. PH PA 2041, Puluj Johann (Ivan) (2. 2. 1845–31. 1. 1918), 1875–1884, box 98 (V. v. Lang, Bericht ad Z. 605, 3. 7. 1876).

6. Puluj, J. (1875). “Ueber einen Schulapparat zur Bestimmung des mechanischen Wärmeäquivalentes”. Anzeiger d. AdW, math.-naturwiss. Cl., Vol. 12, No. 10, 85–86; Puluj, J. (1875). “Beitrag zur Bestimmung des mechanischen Wärmeaequivalentes”. Ibid., Vol. 12, No. 14, p. 128.

7. Puluj, J. (1876). “Ueber einen Schulapparat zur Bestimmung des mechanischen Wärmeaequivalentes”. Ann. Phys. Vol. 233, 437–446.

8. Národní archiv v Praze (National Archives in Prague, hereafter: NA Prag), fond MKV/R (Ministry of Culture and Education in Vienna), box 1374 (Hofrat Dr. Johann Puluj, Professor der k. k. deutschen technischen Hochschule in Prag, Curriculum vitae, 17. 11. 1911).

9. Beilage zum Verordnungsblatte f. MfCU, 1875, No. 12, 61–62 (Concurs-Ausschreibungen).

10. Salcher, P. (1892). Geschichte der k. u. k. Marine-Akademie. Pola.

11. AdUW, sign. PH PA 2041, l. c. (MfCU Z. 18309, 18. 11. 1875).

12. Beilage zum Verordnungsblatte f. MfCU, 1875, No. 23, p. 133 (Concurs-Ausschreibungen).

13. Puluj, J. (1876). “Über die Abhängigkeit der Reibung der Gase von der Temperatur (Als Inauguraldissertation vorgelegt der mathem.-naturwiss. Facultät der Universität zu Strassburg in Elsass).” Sitzungsberichte d. AdW, II. Abt., Vol. 73, May 1876, 40 pp. The communication appeared in the issue of May (1876), which, however, had to be published with a delay as the addendum at the end of Puluj's communication was dated in Vienna on 20 July 1876. Cf. ibid., Nachschrift, p. 40.

14. W. C. Rőntgen (1845–1923) assumed the post of A. Kundt's assistant at the University of Strasbourg on 1 April 1872, and within a year he made his habilitation for physics there. From 1 May 1875, Rőntgen was appointed professor of mathematics and physics at the Academy of Agriculture (Landwirtschaftliche Akademie) in Hohenheim by Stuttgart. He came back to the University in Strasbourg in autumn 1876 where he succeeded Emil Warburg in the Professorship of Physics. Cf. Fölsing, A. (1995). Wilhelm Conrad Röntgen. Aufbruch ins Innere der Materie, pp. 333–334. München u. Wien: Carl Hanser Verlag (Zeittafel).

15. Józef Stefan (1835–1893), mathematician, physicist (and also a poet) of Slovenian origin; professor of higher mathematics and physics, director of the Institute of Experimental Physics and in 1876–1877 Rector of the University of Vienna; in 1875–1885 also Secretary of the mathematics-sciences section of the Academy of Sciences of Vienna. Cf.

16. AdUW, sign. PH PA 2041, l. c. (J. Puluj to the Professorial Collegium, Wien 15. 6. 1876).

17. AdUW, sign. PH PA 2041, l. c. (J. Puluj, Habilitation-Akten).

18. Puluj, J. (1880). “Strahlende Elektrodenmaterie. Abhandlung I–IV.” Sitzungsberichte d. AdW, math.-naturwiss. Cl., Vol. 81, 861–922; Vol. 83, 402–420, 696–708; Vol. 85, 871–881. On Puluj's communications on radiometers cf. L'Annunziata, M. F. (2016). Radioactivity: Introduction and History. From the Quantum to Quarks, 2nd edition. Amsterdam: Elsevier.

19. In his second communication on the “radiant matter of electrodes”, J. Puluj summarised his views as follows (quoted in German): “Nach meiner Ansicht bestehen die von der negativen Elektrode in gasverdünnten Raume ausgehenden Strahlen nicht aus elektrischen Teilchen des zurückgebliebenen Gases, das nach Crookes in einem eigenthümlichen ‘übergasigen’ Zustand, dem vierten Aggregatzustand, sich befinden soll, sondern aus Kőrpertheilchen, welche durch den elektrischen Strom von der negativen Elektrode losgerissen, mit statischer negativen Elektricität geladen und mit sehr grosser Geschwindigkeit in den gasverdünnten Raum fortgeschleudert werden. Damit kein Zweifel über die Natur der Kathodenstrahlen obwalte, nenne ich sie ‘strahlende Elektrodenmaterie’”. Cf. Puluj, J. (1881). “Strahlende Elektrodenmaterie. II. Abhandlung.” Sitzungsberichte d. AdW, Vol. 82, p. 402.

For a broader context see e.g. Lehmann, O. (1898). Die elektrischen Lichterscheinungen oder Entladungen bezeichnet als Glimmen, Büschel, Funken und Lichtbogen, in freier Luft und in Vacuumröhren (unter Berücksichtigung von Entladungen ohne Lichterscheinung und der Entstehung des Lichtes, des elektrischen Strahlen, Kathodenstrahlen, Röntgenstrahlen etc., zum Theil auf Grund eigener Experimentaluntersuchungen bearbeitet), pp. 534–535. Halle a. S.: Verlag von Wilhelm Knapp 

20. Čecháč, F. (1880). “O čtvrtém stavu aggregačním čili o hmotě zářící.” Časopis pro pěstování matematiky a fysiky, Vol. 9, 180–190 (in Czech).

21. AdUW, sign. AT-UAW/131.131, Lang, Viktor von (Nachlassfragment 1859–1920), box 1238, Korrespondenz mit Puluj Johann, 1879–1880 (J. Puluj to V. v. Lang, Krieglach, 27. 7. 1879).

22. Sitzungsberichte d. AdW, 1882, Vol. 85, p. 14 (Sitzung vom 30. März 1882).

23. Puluj, J. (1883). Strahlende Elektroden-Materie und der sogenannte vierte Aggregatzustand (86 pp.). Wien: Druck und Verlag von Carl Gerold's Sohn.

24. Puluj, J. (1889). “Radiant Electrode Matter and the so-called Fourth State”. Physical Memoirs, selected and translated from foreign sources, Vol. 1, Part 2, pp. 233–331. London: Physical Society of London.

25. Puluj, J. (1889). “Radiant Electrode Matter...”, l. c., pp. 329–331 (“Professor Gintl´s Views of Radiant Matter”). Puluj referred to an offprint: Gintl, W. (1880). “Studien über Crookes strahlende Materie und die mechanistische Theorie der Elektricität”. Prag (8 p.).

26. AdUW, sign. PH PA 2041, l. c. (J. Puluj, Assistenten-Akten).

27. AdUW, sign. PH PA 2041, l. c. (J. Puluj to the MfCU, 7. 3. 1879).

28. AdUW, sign. AT-UAW/131.131, l. c. (J. Puluj to V. v. Lang from Kharkov, Russia, 27. 9. 1880).

29. Křižík, F. (1952). Paměti, pp. 98–99 (in Czech). Praha: Technicko-vědecké vydavatelství.

30. NA Prague, fond České místodržitelství (k. k. Statthalterei für Bőhmen in Prag, hereafter: ČM) 1884–1890, všeobecné (general), box 3681 (MfCU Z. 15829, 15. 8. 1884); Beilage zum Verordnungsblatte f. MfCU, 1884, No. 17, p. 85.

31. AdUW, sign. PH PA 2041, l. c. (Dean of the Faculty of Philosophy to the MfCU, Z. 198, 3. 12. 1883).

32. NA Prague, fond Policejní ředitelství Praha II – evidence obyvatelstva (Police Headquarters Prag II – Registry office), Puluj Jan b. 1845.

33. NA Prague, fond MKV/R, sign. 7 Prag, box 241 (J. Puluj to the MfCU, 3. 3. 1901).

34. Beilage zum Verordnungsblatte f. MfCU, 1883, No. 17, p. 76.

35. NA Prague, fond ČM 1884-1900, general, box 3688, sign. 27/13/3 d (Assistant W. Paukert).

36. NA Prague, fond MKV/R, inv. no. 614 (varia), box 1374 (Hofrat Dr. Johann Puluj, ..., Curriculum vitae, 17. 11. 1911).

37. NA Prague, fond ČM 1884–1900, general, box 3681, sign. 27/5/9 d (MfCU Z. 21060/1888, 4. 2. 1889).

38. NA Prague, fond MKV/R, sign. 7 Prag Assistenten, box 257, Sahulka Johann; Osterreichisches Biographisches Lexikon, 1815–1952, Bd. 9 (Lfg. 44, 1987), s. 379.

39. NA Prague, fond MKV/R, inv. no. 614 (varia), box 1374 (Hofrat Dr. Johann Puluj, ..., Curriculum vitae, 17. 11. 1911).

40. NA Prague, fond MKV/R, sign. 7 Prag Elektrotechnik, box 241 (J. Puluj to the MfCU, 12. 3. 1900).

41. Ibid., MfCU Nr. 17926 u. 10.653 / 1900. 

42. Ibid., MfCU Nr. 8026/1901.

43. Ibid., MfCU Nr. 8026/1901 (Extract from the Minutes of the Professorial Collegium of 11 March 1901).

44. NA Prague, ČM 1901–1910, general, box 7598, sign. 27/8/13 d (MfCU to the Rectorate of the DTH in Prague, Z. 8026, 2. 7. 1901). 

45. NA Prague, fond MKV/R, sign. 7 Prag, box 256, Puluj Johann (MfCU Z. 22783, 9. 10. 1902).

46. Ibid., MfCU Nr. 33521/1902. 

47. NA Prague, fond MKV/R, sign. 7 Prag Elektrotechnik, box 241, file MfCU Nr. 6487/1912 (J. Puluj to the MfCU, 3. 2. 1912).

48. Beilage zum Verordnungsblatte f. MfCU, 1903, No. 8, p. 106 (Concurs-Ausschreibungen); Ibid., No. 18, p. 253 (Personalnachrichten). According to a law of 31 December 1896, assistants and constructors at the Austrian technical universities were conferred the status of public servants (subject to the condition they had achieved the required qualification and had Austrian citizenship). The tenure of the post of an assistant or constructor, however, was limited; the appointment to the post was usually for two years and could be extended by two years up to a maximum of six years.

49. NA Prague, fond MKV/R, sign. 28 Deutsche Technik Prag 1888-1919, box 996, Protokole ... (Protokol No. 3, ord. Sitzung, 9. 12. 1912, Punkt 21).

50. Ibid. (Protokol No. 10, ord. Sitzung, 22. 6. 1917, p. 26).

51. Ibid. (Protokol No. 15, ord. Sitzung, 18. 6. 1917, p. 34).

52. Ibid. (Protokol No. 3, ord. Sitzung, 27. 11. 1916, p. 13). 

53. Ibid. (Protokol No. 6, ord. Sitzung, 5. 2. 1917, pp. 12, 13); NA Prag, MKV/R, sign. 7 Prag Professoren, box 255, Niethammer Friedrich.

54. Bohemia, 7. 1. 1896, Vol. 69, No. 6, p. 3 (Mosaik. Eine sensationelle Entdeckung).

55. Cf. Thomas, A. (1897). "The Progress in Radiology in 1896", The Radiology History & Heritage Charitable Trust. An Occasional Newsletter, No. 10, Winter 1897.

56. Těšínská, E., Cuřínová, L., Hlava, A., Spurný, Z. & Žáčková, H. (1995). “The Beginning of Studies and Use of X-rays in the Czech Lands.” Medizinische Physik 95. Rőntgen-Gedächtnis-Kongress, 20.–23. September 1995 Würzburg (ed. J. Richter), p. 24 (H P5). Würzburg: Deutsche Gesellschaft für Medizinische Physik.

57. Domalíp, K. (1896). “O pokusech paprsky Rőntgenovými.” Věstník České akademie císaře Františka Josefa pro vědy, slovesnost a umění, Vol. 5, 80–82 (in Czech).

58. Mikulík, F. (1896). “Objev Roentgenův.” Zlatá Praha, Vol. 13, No. 11, 125 (in Czech, X-ray picture of the hand on p. 132).

59. “K šedesátým narozeninám prof. Karla Kruisa.” Chemické listy pro vědu a průmysl, 1911, Vol. 5, No. 5, 194–200 (in Czech).

60. Živa, časopis přírodnický, 1896, Vol. 6, No. 2 (17. 1. 1896), insert (s. p.).

61. Kučera, B. (1910). “Dr. Karel Domalíp.” Časopis pro pěstování matematiky a fysiky, Vol. 39, 387–395 (in Czech).

62. In existing biographical notes on Puluj (e.g. in Wikipedia), we can read that in 1877, Puluj constructed a cathode ray tube (the Puluj lamp); subsequent refinements led to his creation of the vacuum tube in 1879 (published in 1883). By 1886, he allegedly recorded his first photographic plate of the radiation phenomenon. In his 1889 experiments on electricity and gases, Puluj observed that photographic plates became black when exposed to cathode rays. (A commentary added courtesy of Professor A. M. Glazer.)

63. Anzeiger d. AdW, 1896, Vol. 33, No. 4 (Sitzung vom 6. Februar 1896), 25–26.

64. Puluj, J. (1896). “Über die Entstehung der Röntgen’schen Strahlen und ihre photographische Wirkung.” Sitzungsberichte d. AdW, Abt. IIa, Vol. 105, 228–238; Anzeiger d. AdW, 1896, Vol. 33, No. 5, 33–34. 

65. Puluj, J. (1896). “Nachtrag zur Abhandlung: ‘Über die Entstehung der Röntgen’schen Strahlen und ihre photographischen Wirkung’”. Sitzungsberichte d. AdW, Abt. IIa, Vol. 105, 243–245, 10 pictures; Anzeiger d. AdW, 1896, Vol. 33, No. 7, p. 55.

66. Prager Tagblatt, 31. 1. 1896, Vol. 20, No. 30, pp. 3–4.

67. Světozor, 1896, Vol. 30, p. 143.

68. Bohemia, 18. 2. 1896, Vol. 69, No. 48, p. 2 (“Uiber unsichtbaren Kathodenstrahlen und die Photographie des Unsichtbaren”). During his public lecture J. Puluj allegedly demonstrated among others a radioscopy of a fridge, a living dog, a man and a (masked) woman. Cf. Prager Nachrichten, Beilage Alma Mater Pragensis, 1977, Vol. 28, No. 10, p. 5.

69. Sitzungsberichte des deutschen naturwissenschaftlich-medizinischen Vereines für Böhmen ‘Lotos’ in Prag, 1896, Vol. 16. (N. F.), p. 105.

70. Cf. Těšínská, E. (1997). “Fyzikální vědy v pražském německém přírodovědném spolku ‘Lotos’”. Pokroky matematiky, fyziky a astronomie, Vol. 42, 35–47 (in Czech).

71. Prager Tagblatt, 13. 3. 1896, Vol. 20, No. 72, p. 6.

72. Ibid., 14. 3. 1896, Vol. 20, No. 73, p. 4. 

Emilie Těšínská is a science historian at the Czech Academy of Sciences, Institute of Contemporary History, Prague, Czech Republic. 

28 April 2020

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