Robert Lageman: "New Light on Old Rays: N Rays"
Rene Blondlot: N-Rays ~ A Collection of Papers Communicated to the Academy of Sciences
Scientific American: "Photographic Records of the Action of N-Rays"
William Seabrook: The Great N-Ray Delusion
Goodle Search Results (Excerpts)
Marcel Ascoli: "Les Rayons N"Rene Blondlot"

See also: Dobler/Telluric Photography

Professor Rene P. Blondlot

American Journal of Physics 45 (3): 281-284 (March 1977)

"New Light on Old Rays: N Rays"

Robert T. Lagemann
(Dept of Physics and Astronomy, Vanderbilt Univ., Nashville TN)

During the period 1903-1906, some 120 trained scientists published almost 300 articles on the origins and characteristics of a spurious radiation, the so-called N rays. Some new explanations are advanced for the extensive false observations and the deductions made from these observations. These are based on visits to Nancy, France, where the purported discovery was first announced and after which the rays were named, on an interview with a former assistant who knew some of the principals involved in the case, and on new archival information. Some of the misleading statements in the subsequent literature and oral history dealing with N rays are challenged, and additional information is provided on the original discoverer, Rene Blondlot.


Mistakes in the process of discovery are not rare in physics and the other sciences. Of special interest to physicists is the purported discovery of N rays in 1903 by Rene Blondlot, a professor of physics at the University of Nancy, France. Here is a case unequalled in the number of scientists actively involved and the number of notes and papers published in the scientific journals of the day by scientists qualified by education, academic appointment, and reputation to belong to the community of scholars. Some 120 scientists published almost 300 articles on the topic during the years 1903-1906, and the original discoverer himself published 26 articles and a book (Ref. 1) before halting, while one of his colleagues published no fewer than 38 reports in the same three-year period -- all on "rays" which have never since been observed. (Ref. 2)

American physicists, if aware of the case at all, are usually limited in their knowledge to the information found in an account by de Solla Price (Ref. 3) and a popular biography of the American physicist, R.W. Wood (Ref. 4). It is the purpose of this present contribution to correct certain notions about this case presented in that biography, add information gathered during visits to the city where the first experiments took place, and provide a bibliography, especially of references not likely to be discovered by or available to US physicists.

The Purported Discoveries

That such a protracted series of publications could be possible is largely explicable from the fact that the observations of the alleged radiation consisted of subjective viewing by the eye of very feeble and often flickering sources of light, with all the attendant physiological effects and difficulties of reproducing observations (Ref. 5). In his first experiments (Ref. 6), when he thought that x-ray tubes were a source of N rays, Blondlot used as a detector a small spark whose increased brightness was thought to be an indicator of the impinging rays (see Fig. 2). Later he used a low-intensity gas flame as a detector. He soon found additional sources of N rays besides x-ray tubes: (1) Auer and Nernst burners (mixtures of rare earth salts heated to incandescence), (2) the flame of an annular gas burner (but not of a Bunsen burner), 3) a piece of sheet iron or silver heated to dull redness, and (4) the Sun. He found new detectors: (1) a small flame of gas flowing from a small orifice which in turn could be better observed by noting its reflected image from a ground-glass plate, and (2) surfaces covered with a properly prepared deposit of calcium sulfide, which having first been made phosphorescent by sunlight, revealed increased light emission upon exposure to N rays. The difficulty of making uniform films of calcium sulfide mixed with collodion and ether led to confusion in observation, or so it was thought, and in his book Blondlot provided instructions and a sheet bearing 25 calcium sulfide deposits for the reader to use to observe N rays. To observe spectral lines of N rays, he packed a narrow slit with calcium sulfide, moved the slit along in the region of the expected dispersed beams, and when the sulfide showed increased phosphorescence, a line was pronounced present.

Furthermore, he found that N rays could be stored in certain materials. They traversed platinum 4 mm thick, but not rock slat 3 cm thick. They passed through dry cigarette paper but not through the wetted paper. Certain solids in compression emitted the rays, as when a walking cane was bent by the hand and held near the eyes, and the "strengthening action" of the N rays on the retina allowed faintly luminous objects to be seen better. A file of tempered steel held near the eyes allowed surfaces and contours to be seen, as for instance the dial of a clock in a darkened room. He discovered N1 rays, which lessened the luminosity of glowing sources. He found the "heavy emission", which was claimed to consist of streams of minute particles ejected form metals and certain liquids and to be subject to gravitational attraction.

The Professor of Biophysics in the School of Medicine, Augustin Charpentier, became especially adept at seeing the new rays. In a single month (May 1904) he published seven papers on the subject. He found that rabbits and frogs gave off the rays, Tendons stretched by muscles gave no effects, but the biceps muscle did. N rays increased the sensitivity of the human to vision, smell, taste and hearing. Soon he found the rays from living matter were somewhat different from the N rays, and he called them "physiological rays". These latter could even be transmitted along wires. Thus a small copper plate is fixed at the end of a copper wire 90 cm long. At the other end is the phosphorescent screen. When the human body is opposite the plate, the screen lights up, indicating transmission of the radiation through the wire. Both the physiological rays and the N rays were transmitted in this way, he claimed. A long list of medical and biological effects were chronicled in a book published at the time (Ref. 7).

We have described only some of the findings claimed by two of the many investigators. So extensive were the supposed properties that G.F. Stradling required 59 pages simply to enumerate or briefly describe the claims made over a 3-year period (Ref. 8). At the same time there were those who could not reproduce the effects claimed. Such recognized physicists as Rayleigh, Langevin, Rubens, and Drude, for example, reported failure. Indeed, within a month after Blondlot’s first announcement, there appeared the first report of failure. But it is the nature of scientific discovery for the world of science to accept the findings of trained, reputable scientists until such time as their results may be disproven by others. Blondlot was a physicist of experience and accomplishment. At the time he was one of 8 physicists who were corresponding members of the French Academy of Science (Ref. 9). He had acquired a doctorate in physics from the Sorbonne in 1881 with a thesis on electric cells and laws of polarization of such cells. He had joined the faculty at Nancy in 1882. In 1893 and again in 1899, he had received prizes from the Academy (Ref. 10).

Similarly, P.M. Augustin Charpentier was a scientist of good reputation, with the title of Professor of Medical Physics at the University of Nancy. His thesis for the M.D. degree had been entitled "Vision with the Different Parts of the Retina", and he had numerous publications in the field of ophthalmology and physiology, including one, for example, on "Physiological Conditions Influencing Photometric Measurements" (Ref. 11). Here, if anyone, was a man who should have been wary of the mistakes that would be possible during observations of flickering, low-intensity luminous sources. Many other observers who reported success were as experienced as Blondlot and Charpentier.

Wood’s Exposure

The purported finding of a new radiation had, of course, been discussed at meetings of physics societies. There the reaction was almost uniformly one of disbelief, based often on futile attempts made sometimes with specific instructions furnished by Blondlot himself. It was while attending such a meeting in Europe, after having failed to obtain positive results in his own laboratory at John Hopkins, that the American physicist R. W. Wood decided to visit Nancy during the summer of 1904 and ask the discoverer to show him the experiments. The story of his visit is told in various places (Ref. 12). It suffices to say here that during one demonstration, while Blondlot was finding spectral lines in a refracted beam of N rays, he was doing so with an essential part of the apparatus missing. At the beginning of the observations and in the darkness, Wood had placed the necessary prism in his pocket and then replaced it before the room lights were turned back on. Wood’s report signaled the end of the N-ray affair.

Some Explanations

When it became evident that some physicists could not observe the rays, Blondlot invited a few to visit his laboratory, and in the appendix of his book he made suggestions for successful observations. These instructions, themselves not easily followed, provided insufficient aid in observing a phenomenon which did not in fact exist. Hoping the provide objective, convincing evidence, Blondlot took photographs (see Fig. 3) of light sources both when exposed and not exposed to the action of N rays and found those exposed to N rays to have produced a darker negative. But when the nonreality of the rays became apparent, the photographic evidence was explained by his detractors as caused by nonuniform photographic emulsions and poorly controlled exposure time and development. Pierret (Ref. 13) implies that the exposure and development of the plates for equal conditions were not performed by Blondlot but were left to the assistants. In brief, the difficulties introduced by subjective observation of low-intensity sources, whose energy output varied with time, led to spurious results. But this was compounded by the failure of the observers to perform what today we call the controlled experiment, and to apply the classical method of difference and the method of agreement (Ref. 14). Even such psychological factors as can be grouped under suggestibility and hypnosis, and such motivational factors as national pride and the quest for prestige, could have been eliminated or their importance reduced if reproducibility of results and control of the conditions of comparison had been better effected.

Recognition of the inherent difficulty of observation does not alone explain the widespread observations. Deliberate fraud can be ruled out, both because so many different scientists were involved and because they had nothing to gain from reporting findings which could be subjected to confirmation by others. What of deceit on the part of Blondlot’s colleagues and assistants? The two other physicists at Nancy themselves made announcements of N ray discoveries and could not, therefore, be thought to be deceiving or encouraging Blondlot (Ref. 15). And as for his chief assistant, according to Wood, and Pierret, he was not learned enough in science to perpetrate such a deception (Ref. 16). At any rate Blondlot retained his services afterward, and certainly any such deception cannot explain why others in distant laboratories "saw" the effects. For explanations of the involvement of so many persons one might profitably turn to the phenomena of suggestion, hypnosis, and mass hysteria. Such a psychological study waits to be done.

Some New Aspects

A few new aspects to the case have, however, been uncovered by the present writer during visits to the city of Nancy that shed some light on the reasons for the announcement of the original observations by Blondlot. In his book, Seabrook states that "only Frenchmen could observe the phenomena", a minor exaggeration he must have heard from the flamboyant Wood (Ref. 17). But for the record it should be mentioned that J.S. Hooker (Ref. 18), an Englishman, and F.E. Hackett (Ref. 19), a student at the Royal University of Ireland, reported that they had observed the rays. And another non-Frenchman who observed the rays was Leslie Miller, an instrument-maker of London, who so believed in their reality, or at least in the commercial exploitation of the rays, that he made apparatus for observing them which he sold for L. 1,1,0 (Ref. 20). Seabrook is wide of the mark, on the other hand, when he writes: "The tragic exposure eventually led to Blondlot’s madness and death". Actually, Blondlot continued in his post of Professor of Physics for six years after Wood’s disclosure. He retired in 1910 (Ref.21) at the age of 61, before the usual age of retirement. He lived for 20 years in retirement, until his death in 1930 at the age of 81 (Ref. 22). During that period he held the title Professor Honoraires (i.e., emeritus) and continued to live in his large home at 16-18 Quai Claude le Lorrain. He continued to have associations with others at the University, as when for example, in 1909, on the occasion of the unveiling of a monument of his friend, Ernest Bichat, Blondlot made one of the speeches. In 1923, a third edition of his book on thermodynamics appeared, and in November 1927, he wrote a new preface for a third edition of his textbook on electricity (Ref. 23). Certainly his long will, frequently revised to accommodate changing conditions, which was duly accepted and probated upon his death, is one prepared by a sane man (Ref. 24).

Nor is there any evidence that he committed suicide, as is sometimes inferred by those who read Seabrook. Blondlot lived some 26 years after Wood’s exposure. Had he taken his own life, he probably could not have been buried in a Catholic cemetery with the full rites of the Church, as was indeed the case according to newspaper accounts. Cemetery records show he is buried in the Cimetiere de Preville, the central one of the city.

Modern scientists at the University of Nancy know little or nothing about the history of N rays, and those who do are usually reluctant to speak of the mater. Two, however, freely expressed themselves on the impressions they had acquired from colleagues who had been alive at the time or who in turn had known such. One I interviewed was Josef Bolfa, Prof. of Mineralogy and Crystallography, who has long had an interest in the history of the University. His view is that a prominent, but little recognized factor in the discovery was the national and regional pride of the Nancy professors, who were aware of the recent discovery of the cathode rays, x rays, and canal rays by their counterparts in other countries wanted to bring fame to France and exploited the original observations without due regard to firm evidence. Moreover, he said, Nancy has for a long time been a garrison city in the French military system. Repeatedly he used the words, "C’est une erreur".

E. Pierret, with whom I talked, probably has more direct knowledge of the case than anyone else. Retired now from his post of chief assistant in the Department of Physics, he told me he had known the assistants who worked with Blondlot and Charpentier, and he showed me the very prisms and lenses (Ref. 25) used by Blondlot in his investigations. He had talked with Blondlot in 1926, at which time Blondlot did not appear to have lost his intellectual powers. Blondlot, he said, continued to believe in the existence of N ryas after he stopped his active study of them in 1906, and continued to teach for a few years afterward. He never blamed his former assistant for any deception (Ref, 26), but, at the same time, Pierret noted, in the days prior to the N rays studies, one of the assistants had received from Blondlot part of the prize money won by Blondlot for discoveries made in the laboratory and doubtless welcomed the prospect of new awards for the finding of this new, extraordinary radiation, a prospect which might have influenced his observations. It was the custom of the day for an experimentalist to give but general instructions to an assistant, who would be expected to build or assemble apparatus and make many of the observations. This was Blondlot’s custom. Pierret felt also that the assistant responded to the suggestions and authority of the professor and sawmore than the evidence warranted.

A useful summary of the case, entitled "A la Poursuite des Rayons N", was published in 1965 by C. Gelain and H. Geoffrey, who include photographs of some of the prisms and lesnes used by Blondlot as well as a photograph of Blondlot’s laboratory of about 1900 (Ref. 27). Another interesting summary is that of Jean Rosmorduc (Ref. 28). A brief treatment of the case is given by Jean Rostand (Ref. 29), while some of the psychological aspects have been discussed by Y. Galifret (Ref. 30).


It is a pleasure to express my thanks to Mr. Emile Pierret, Prof. Joseph Bolfa, and, especially, Prof. Jacques Touret -- all of the University of Nancy -- for much assistance and fruitful discussions. Part of the study was supported by a grant from the Vanderbilt University Research Council.


(1) R. Blondlot, N Rays: A Collection of Papers Communicated to the Academy of Sciences; Transl. J. Garcin; Longman, Green, London, 1905. French edition, 1904, by Gauthier-Villars, Paris.

(2) See G.F. Stradling, J. Franklin Inst. 164: 57-64 (1907); ibid., 164: 113-130 (1907); ibid., 164: 177-199 (1907). Written at the close of the period of active interest in the rays, this series of three articles gives the most comprehensive recital of the alleged discoveries. Stradling lists 278 references to original articles, resumes, and editorial comment. In addition, he states, there were summaries in 15 other professional and popular magazines.

(3) D. J. de Solla Price, Science Since Babylon (Yale Univ. Press, New Haven CT, 1975), pp. 153-160.

(4) W. Seabrook, Doctor Wood (Harcourt, Brace and World, NY, 1941), pp. 233-239.

(5) The speculations, false starts, spurious results, and confusion attendant upon the study of N rays are similar to those associated with the early observations of radioactivity by Henri Becquerel and others, but of course the N rays were spurious, while the rays of radioactivity were not. See L. Badash, Amer. J. Physics 33: 128 (1965).

(6) R. Blondlot, C.R. Acad. Sci. 136: 284 (1903); ibid., 136: 735 (1903); ibid., 136: 1120 (1903); ibid., 137: 684 (1903).

(7) H. Bordier, Les Rayons N et les Rayons N1; Les Actualites Medicales (Baillere, Paris, 1905).

(8) G.F. Stradling, Ref. 2.

(9) There were also 6 regular members who were physicists, and 4 foreign members: Rayleigh, Hittorf, van der Waals, and Michelson.

(10) Rene Prosper Blondlot was born on 3 July 1849 in Nancy, France, and died in the same city on 24 November 1930. He was the son of Nicolas Blondlot (b. 1808), who held an M.D. degree and was for a long time Prof. of Toxicology in the Faculty of Medicine. In 1893, the French Acad. Awarded him the Gaston Plante prize, in 1899 the LaCaze prize, and in 1904 (with the N ray controversy at its height), the Le Conte prize. He had been elected a correspondent of the Academy in 1894, taking the place of Helmholtz.

(11) A. Charpentier, C.R. Acad. Sci. 103: 130 (1886)

(12) W. Seabrook, Ref.4; Nature 70: 530 (1904); Electr. Review 45: 630 (1904); Phys. Zeitschr. 5: 789 (1904); Rev. Sci.. 2: 536 (1904).

(13) E. Pierret, Bull. Acad. Soc. Lorraines Sci. 7: 240 (1968).

(14) These methods are much used by physicists who, on the whole, are often not aware of their formalization by J.S. Mill and others. However, much as Mill’s canons have been criticized, they would have been useful guides to N ray students.

(15) In 1905, at the height of the N ray controversy, there were two professors of physics at Nancy, Rene Blondlot and Ernest Bichat. This unusual arrangement (of more than one) was brought about by Bichat’s added duties as Doyen (Dean) of the Faculty of Sciences. Bichat died in 1905; a life-size statue of him presently stands before a science building of the University. A third scientifically trained member of the department was Camille Gutton, who at the time was Maitre de Conferences (in charge of the teaching duties of the department). Upon Blondlot’s retirement, Gutton was made Prof. of Physics, and upon Bichat’s death he was made Dean, upon the condition that he not persist in expressing a belief in the reality of N rays.

(16) During my interview with him, Pierret declined to reveal the name of Blondlot’s assistant.

(17) Seabrook also has Blondlot announcing his discovery "in the late autumn of 1903", whereas in his paper of 23 March 1903, C.R. Acad. Sci. 136: 735 (1903), the discoverer used the words "n-rays", which were later changed to "N-rays".

(18) J.S. Hooker, Lancet 1:686 (1904); ibid., 2: 1380 (1904).

(19) F.E. Hackett, Sci. Trans. Roy. Soc. Dublin 8: 127 (1904); Nature 70: 167 (1904); ibid., 70: 583 (1904).

(20) L. Miller, Electrician (Lond.) 52: 788 (1904), an advertisement; Lancet 1: 610 (1904); ibid., 1: 831 (1904); ibid., 1: 1150 (1904).

(21) Pierret, in Ref. 13, states that in November 1909, Blondlot chose to retire from his University post. "It has been said", writes Pierret, "that he [resigned] at the instance of a committee of inquiry". Probably the retirement became effective about September 1910.

(22) See C’est Republicain (daily newspaper of Nancy) for 27 Novemeber 1930. Also Biographique des Membres et Correspondants de L’Academie des Sciences; (Gauthier-Villars, Paris, 1954).

(23) E. Bichat and R. Blondlot, Introduction a l’Etude de l’Electricite Statique at de Magnetisme (Gauthier-Villars, Paris, 1927).

(24) The will is to be found in Archives Departmentales/Archives Historiques/Centre de Documentation Administrative/Service Educatif in Nancy. Blondlot never married and at his death had no close living relatives. A portion of his estate was divided among servants and friends, but the largest part, his house and garden of about 1.65 acres, was given to the city of Nancy to serve, in the case of the garden, as a place of rest for the townspeople and, in the case of the house, as a place where young people could come to obtain advice about job and educational opportunities. They are in use today for the purposes intended. The entire estate was valued at over one million francs. As a consequence of his beneficence, the city bestowed on him a special title. The park adjacent to his former home bears the inscription Pac Blondlot above the entrance. A street in the city is also named after him.

(25) The writer saw and handled these items. There were 5 prisms which appeared to be made of aluminum, silver, clear (transparent) quartz, smoky quartz, and wood. The height of each was about 6 cm. The faces of each approximated squares. One prism (Ag?) of which I drew the base by drawing a pencil along the edges as I held it on a piece of paper, had a prism angle of about 29*. The others appeared to the eye to be somewhat smaller, all with a prism angle of perhaps 22*. A metal plano-convex lens of aluminum measured 7 cm in diameter. I estimated the curvature of its convex face to be about 30 cm radius. Pierret did not show me, if indeed they were in his possession, the 60* and 90* aluminum prisms used by Blondlot. Pierret became an assistant in the department about 1928. One day while taking an inventory of the contents of a laboratory, he came upon the materials used in the N-ray work. Another assistant, said Pierret, warned him not to touch them or to speak of the subject to the professor in charge. In 1962, when he retired from the post of Maitre de Conferences, the materials came into his possession.

(26) This belief is also expressed in Pierret’s article on the subject. See Ref. 13, p. 254.

(27) C. Gelain and H. Geoffrey, Ing. Ind. Chim. 41: 7 (1965).

(28) J. Rosmorduc, Rev. Hist. Sci. Leurs Appl. 25: 13 (1972).

(29) J. Rostand, Error and Deception in Science (Basic, NY, 1960).

(30) Y. Galifret, Courr. Ration. 9: 191 (1963).

"N-Rays ~ A Collection of Papers Communicated to the Academy of Sciences

With Additional Notes and Instructions for the Construction of Phosphorescent Screens


Rene Prosper Blondlot

Professor, University of Nancy

Translated by J. Garcin
Longmans, Green and Co.( London, New York and Bombay ) 1905

(a) Preliminary Notice

The present volume contains the memoirs on the subject of "N" rays, communicated to the Academy of Sciences by Prof. R. Blondlot. The papers have been reprinted exactly as they were originally published in the Comptes Rendus of the Academy. The notes at the end were added later, with the object of throwing light on certain points which were obscure at the time the papers were communicated to the Academy.

The title of the first memoir in this collection, "On the Polarization of X-Rays", will hardly cause astonishment when it is realized that the study of the X rays led the author to recognize the existence of radiations of a totally different character. To these he gave the name of "N" rays. Before the distinction of these two kinds of radiation was made, some confusion was bound to arise between the phenomena appertaining to each. In particular, the preliminary researches which the author had made on the velocity of propagation of X rays apply in reality not to X rays, but to N rays. He had found that the velocity of propagation was the same as that of Hertzian waves, and consequently of light. Since the properties of N rays, taken in their entirety, do not leave any doubt that these rays are a variety of light, this determination of their velocity is nothing more than a verification of an assured fact. Nevertheless, this verification seemed not altogether superfluous; it proves at least that the experiments have been carried out with care.

Table of Contents

(1)  On the Polarization of X Rays
(2)  On a New Species of Light
(3)  On the Existence, in the Radiation Emitted by an Auer Burner, of Rays Transmissible Through Metals, Wood, etc.
(4)  On New Sources of Radiations Transmissible  Through Metals, Wood, etc., and on New Actions Produced by These Radiations
(5)  On the Existence of Solar Radiations Capable of Traversing Metals, Wood, etc.
(6)  On a New Action Produced by N Rays, and on Certain Facts Connected with These Radiations
(7)  On New Actions Produced by N Rays; Generalization of Phenomena Already Observed
(8)  On the Storing of N Rays by Certain Bodies
(9)  On the Strengthening Action of a Beam of Light on the Eyes, When the Beam is Accompanied by N Rays
(10)  On the Property of Emitting N Rays Conferred on Certain Bodies by Compression, and on the Spontaneous and Indefinite Emission of N Rays by Hardened Steel, Unannealed Glass, and Other Bodies in a State of Strained Molecular Equilibrium
(11)  On the Dispersion of N Rays and on Their Wave Length
(12)  On the Photographic Registering of the Action Produced by N Rays on a Small Electric Spark
(13)  On a New Species of N Rays
(14)  On Peculiarities Presented by the Action Which N Rays Exercise upon a Dimly Lighted Surface
(15)  On the Comparative Action of Heat and N Rays on Phosphorescence
(16)  Complementary Notes
(17)  Instructions for Making Phosphorescent Screens
(18)  How the Action of N Rays Ought to be Observed

(1) On the Polarization of X Rays (Feb. 2, 1903) 

Hitherto the attempts made to polarize X rays have remained fruitless. I asked myself whether X rays emitted by a focus tube are not polarized as soon as emitted. I was led to put to myself this question by considering that the conditions of asymmetry which should exist for the polarization of such rays are in this case exactly satisfied. For each ray is generated from a cathode ray, and the two rays define a plane; thus, through each ray emitted by the tube a plane passes, in which, or normally to which, the ray may well have special properties, this being, in fact, an asymmetry characteristic of polarization. Now, if this polarization exists, how can the fact be ascertained? It struck me that a small spark, such as I used in my researches on the velocity of propagation of X rays, might perhaps in this case play a part of analyzer, inasmuch as the properties of a spark may be different in the direction of its length, which is also that of the electric forces producing it, and in directions normal to its length. Starting from this, I arranged an apparatus as shown in the accompanying diagram, so as to obtain a small spark during the emission of X rays.

A focus tube is connected to an induction coil by wires BH, B’H’, covered with gutta percha (Fig.1). Two other wires, also covered with gutta percha, AIc and A’I’c’, terminate at A and A’ in two loops, which surround BH and B’H’ respectively; a bit of glass tubing, not shown in the figure, keeps each loop separate from the wire which it surrounds. The wires AI, A’I are then twisted together, and their sharply pointed end, c and c’, are fixed opposite each other, at a very small distance, adjustable at will, so as to form a small spark gap. By virtue of this disposition, the electrostatic influence exercised by the wires BH and B’H’ on the loops A and A’ produces at each break of the current in the coil a small spark at the gap cc’, at the same time as X rays are being emitted by the tube. Owing to the flexibility of wires, AIc, A’I’c’, the straight line cc’, along which the spark occurs, can be set in any direction we please. A sheet of aluminum foil, 40 cm square, is interposed between the tube and the spark, so as to prevent any direct influence of the electrodes of the tube on cc’.

In order to define easily the relative positions of the tube and the spark cc’, take three rectangular axes, of which one, Oz, is vertical.

Fix the focus tube so that its length, and consequently, the pencil of cathode rays, coincides with OY, the anticathode being placed near the origin, and sending X rays in the positive direction of OX.

Place the gap cc’ at a point on the positive side of OX, so that its direction is parallel to OY. The spark being properly regulated one observes that the X rays act upon it in such a way as to increase its luminosity, for the interposition of a sheet of lead or glass manifestly diminishes the brightness.

Now, without altering the position of the gap, turn it so that it comes parallel to OZ, i.e., normal to the cathode rays. The influence of the X rays on the spark is then seen to disappear, and the interposition of a lead or glass plate causes no change in its brightness.

X rays have therefore a plane of action, which is the one passing through each X ray and the cathode ray which gives rise to it. If the direction given to the spark gap is intermediate between the two above mentioned, the action is seen to diminish from the horizontal position to the vertical.

The following is another experiment, still more striking: if the spark is made to turn about OX, parallel to plane YOZ, the spark is seen to pass from a maximum brightness when horizontal to a minimum when vertical. These variation of brightness are similar to those observed when a pencil of polarized rays traverse a rotating Nicol’s prism, the small spark playing the part of analyzer. The pencil of X rays presents the same asymmetry as a pencil of polarized light. According to Newton’s definition, it has sides differing from each other; in other words, it is polarized in the complete sense of the term.

The phenomenon is easy to observe when the spark is well regulated; this means that the spark must be very small and faint.

If the focus tube is made to turn about its axis, which is parallel to the cathode rays, the observed phenomena do not change, so long as X rays reach the gap. The plane of action is thus independent of the orientation of the anticathode, being always in the plane passing through the X rays and the generating cathodic rays.

The spark being kept in this plane, and turned round from the position in which it is at right angles to the X rays to that in which it is parallel to them, we observe that the effect of the X rays on the brightness of the spark is a maximum in the first position, and diminishes to nothing in the second.

Now, an X ray and its generating cathodic ray only determine a plane when their directions are different. Again, amongst the emitted X rays, some are in a direction very nearly the same as that of the cathode rays, being those which graze the cathode. One should expect these to be every incompletely polarized; and, indeed the small spark enabled me to confirm this.

I noted several important facts, which, however, I will merely allude to in the present paper. Quartz and lump-sugar rotate the plane of polarization of X rays in the same sense as that of light. I obtained rotations of 40 degrees.

Secondary rays, styled "S" rays, are also polarized. Active substances rotate the plane of polarization of these rays in a sense contrary to that of light. I observed rotations of 18 degrees (Note 2).

It is extremely likely that magnetic rotation also exists for X rays as well as for S rays. Once can also surmise hat the properties of these rays, with reference to polarization, extend to tertiary rays, etc. I intend shortly to publish the results at which I have arrived concerning these different points.

(2) On a New Species of Light (March 23, 1903) 

The radiations emitted by a focus tube are filtered through a sheet of aluminum foil or a screen of black paper, in order to eliminate the luminous rays which might accompany them. While studying these radiations by means of their action on a small spark, I discovered that they are plane-polarized as soon as emitted. I further proved that when these radiations traverse a plate of quartz in a direction at right angles to its axis, or a lump of sugar, their plane of action undergoes a rotation just like the plane of polarization of a pencil of light.

I then asked myself if a rotation could also be obtained by passing the radiations of the focus through a pile of Reusch mica sheets. I observed, in fact, a rotation of from 25° to 30° in the same direction as that of polarized light. This action of a pile of micas made me at once infer that a single sheet of mica must act, and that this action must be depolarization, or, rather, the production of elliptic polarization; this is indeed what occurs. The interposition of a sheet of mica, set so that its axis makes an angle of 45° with the pane of action of the radiations emitted by the tube, destroys their rectilinear polarization, for their action on a small spark remains sensibly the same, whatever be the direction of the spark gap. If a second sheet of mica is interposed, identical with the first, so that the axes of the two sheets are perpendicular to each other, rectilinear polarization is reestablished. This result can also be obtained by the use of a Babinet’s compensator. Consequently we are dealing with elliptic polarization.

Now, if the sheet of mica changes rectilinear into elliptic polarization, such a sheet must be doubly refractive for the radiations thus formed. But if double refraction exists, a fortiori simple refraction must exist; and I was thus led to examine whether, in spite of the fruitless attempts to discover the refraction of X rays, I could not obtain a deviation by a prism. I then arranged the following experiment: a focus tube sends through an aluminum screen a pencil of rays, limited by two vertical slits cut in two parallel sheets of lead, 3 mm thick. The small spark is placed on one side of the pencil at such a distance that it cannot be reached, even by the penumbra; this is ascertained by proving that the interposition of a sheet of lead causes no diminution of its brightness. Now let us interpose in the pencil an equilateral quartz prism, with refractive edge on the side away from the spark. If the prism is properly set, the spark becomes much more brilliant; when the prism is removed, the spark reverts to its former faintness. This phenomenon is certainly due to refraction, for if the setting of the prism is altered, or if the prism is replaced by a plate of quartz, no effect is observed. The experiment may also be carried out in a different manner: the pencil is first made to impinge directly on the spark, then it is deviated by means of the prism, and the brightness of the spark wanes. If, now, the spark is moved laterally towards the base of the prism, it recovers its previous brightness, proving that the rays in question have been deviated in the same sense as rays of light.

 Refraction being thus proved, I at once sought to concentrate the rays by means of a quartz lens. The experiment is unattended with difficulty. An image of the anticathode is obtained, extremely well-defined as to size and distance by a heightened glow of the small spark.

The existence of refraction rendered that of regular reflection extremely probable; as a matter of fact, regular reflection does take place. By means of a quartz lens, or a lens formed by a very thin horn envelope filled with turpentine, I produce a conjugate focus of the anticathode; then I intercept the emerging pencil by a sheet of polished glass, placed obliquely; I then obtain a focus exactly symmetrical, in respect to the plane of reflection, with the one which existed before the glass was interposed. With a plate of ground glass there is no regular reflection, but diffusion is observed.

If one half of a lamina of mica is roughened, the polished half lets pass the radiations, and the other half stops them (note 3)

This allows of the repetition of the refraction experiments under much more precise conditions, by the use of Newton’s arrangement for obtaining a pure spectrum.

From all that precedes, the fact results that the rays which I have thus studies are not Roentgen rays, since these undergo neither refraction nor reflection. In fact, the little spark reveals a new species of radiations emitted by the focus tube, which traverse aluminum, black paper, wood, etc. These are plane-polarized from the moment of their emission, are susceptible of rotary and elliptic polarization, are refracted, reflected and diffused, but produce neither fluorescence nor photographic action.

I had expected to find that amongst these rays some existed whose refractive index for quartz is about 2; but probably quite a spectrum of such rays exists, for in the refraction experiments with a prism, the deviated pencil appears to cover a broad angle. The study of this dispersion remains to be pursued, as well as that of the wavelengths of the rays.

By progressively diminishing the intensity of the current actuating the induction coil, one still gets these new rays, even when the tube no longer produces any fluorescence, and is itself absolutely invisible in the dark. They are fainter, however, in this case. They can also be produced continuously by means of an electric machine giving a spark a few millimeters in length.

At first I had attributed to Roentgen rays the polarization which in reality belongs to the new rays, a confusion which it was impossible to avoid before having observed the refraction, and it was only after making this observation that I could with certainty conclude that I was not dealing with Roentgen rays, but with a new species of light.

It is interesting to collate these remarks with the view expressed by M. Henri Cecquerel, that in certain of his experiments "manifestations identical with those giving refraction and total reflection of light may have been produced by luminous rays which had traversed aluminum" (see Comptes Rendus, t. xxxii, March 25, 1901, p. 739).

(3)  On the Existence, in the Rays Emitted by an Auer Burner, of Radiations which Traverse Metals, Wood, etc. (May 11, 1903) 

A focus tube emits, as I have already proved, certain radiations susceptible of traversing metals, black paper, wood, etc. Amongst these, there are some for which the index of refraction of quartz is nearly 2. On the other hand, the index for quartz of the rays remaining from rock-salt, discovered by Prof. Rubens, is 2’18. This similarity of indices led me to think that the radiations observed in the emission of a focus tube would very likely be near neighbors of the rays discovered by Rubens, and that, consequently, they would be met with in the radiation emitted by an Auer burner, which is the source of such rays. I accordingly made the following experiment: an Auer burner is enclosed in a kind of lantern of sheet-iron, completely closed on all sides, with the exception of openings for the passage of air and combustion gases, which are so arranged that no light escapes; a rectangular orifice, 4 cm wide and 6.5 cm high, cut in the iron at the same height as the incandescent mantle, so that the emerging luminous pencil is directed on the aluminum sheet. Outside the lantern, and in front of this sheet, a double-convex quartz lens is placed, having 12 cm focal length for yellow light, behind which is a spark gap of the kind already described, giving very small sparks. The spark is produced by a by a small induction coil, provided with a rotating make and break device, which works with perfect regularity.

The distance p of the lens from the slit being 26.5 cm, one notes, by help of the spark, the existence of a focus of very great sharpness at a distance, p’, of about 13.9 cm. For at this point the spark exhibits a notably greater glow than at the neighboring points, whether in front or behind, above or below, to the right or to the left. The distance of this focus from the lens can be determined within 3 or 4 mm. The interposition of a sheet of lead or glass 4 mm thick causes this action to disappear. By varying the value of p, other values of p’ are obtained, and substituting these values in the lens formula, the number 2.93 is obtained for the refractive index, being the mean value derived from a series of determinations as concordant as the precision of such observations could entitle one to expect. Similar experiments, made with another quartz lens, having a focal length of 33 cm for yellow light, gave for the index the value 2.942.

While pursuing these experiments, I ascertained the existence of three other species of radiations, for which the index of quartz has values 2.62, 2.436, and 2.29 respectively. These indices are all greater than 2, which explains the following fact: if in the path of the rays emerging from the lens a quartz prism of 30 degrees refractive angle is placed, in such a way as to receive these rays in a direction sensibly normal to one of the refracting faces, no refracted pencil is obtained.

The radiations from an Auer burner, transmitted through an aluminum sheet, are reflected by a polished plate of glass in conformity with the laws of regular reflection, and are diffused by a plate of ground glass.

These radiations traverse all the substances whose transparency I tested, with the exception of rock-salt 3 mm thick (note 4), platinum 4 mm thick, and water. A slip of cigarette paper, which is completely transparent when dry, becomes absolutely opaque when wetted with water. Figs. 2 and 3 are reproductions of the impression made in four seconds on a sensitive plate, without any photographic apparatus, before and after wetting the sheet of paper interposed between the lens and the spark. The photoengraving, produced from a paper print, shows in the first case the spark is notably brighter.

These photographic prints are produced by the spark influenced by the rays, and not by the rays themselves, these latter producing no appreciable photographic effect after an hour’s exposure.

Amongst the bodies which are traversed, I may mention tin foil, sheets of copper and brass 0.2 mm thick, a sheet of aluminum 0.4 mm thick, a steel lamina 0.05 mm thick, a silver leaf 0.1 mm thick, a paper booklet, containing 21 gold leaves, a glass sheet 0.1 mm thick, a sheet of mica of 0.15 mm, a plate of Iceland spar of 0.4 mm, a block of paraffin of 1 cm, a beech board 1 cm, a plate of ebonite of 1 mm, etc. Fluorspar is but slightly transparent with a thickness of 5 mm, similarly sulfur 2 mm thick, and glass 1 mm thick. These results I give only as a first indication, for when they were obtained, the co-existence of four different species of radiations, which may have very different properties, was not taken into account (note 5).

It will be highly interesting to investigate whether other sources, and in particular the sun, do not emit analogous radiations to those we are dealing with in the present communication, and also whether the latter produces any calorific action (note 6).

Now, ought these radiations in reality to be considered as akin to the large wave length radiations discovered by Prof. Rubens? Their common origin in the emission of an Auer burner is favorable to such a view, as is also the opacity of rock-salt and of water. But on the other hand, for Auer rays, the transparency of metals and other substances opaque to Ruben’s rays constitute an apparently radical difference between the two sorts of radiations (note 7).

(4)  On New Sources of Radiations Capable of Traversing Metals, Wood, etc., and on New Actions Produced by These Radiations (May 25, 1903)

While investigating whether radiations analogous to those whose existence I mentioned in the emission of an Auer burner are not to be met also in other sources of light and heat, I established the following facts: the flame of an annular gas-burner emits such radiations; the chimney, however, should be removed, on account of the absorption of the rays by glass. A Bunsen burner scarcely produces any. A piece of sheet-iron or silver, heated to dull redness by a Bunsen burner, placed behind them, gives off rays at about the same rate as an Auer burner.

A plate of polished silver was arranged so that its plane made an angle of 45° with the horizontal plane. This plate having been heated to cherry-red by a Bunsen burner, its upper face emitted rays analogous to those of an Auer burner. A horizontal pencil of these rays, after traversing two sheets of aluminum of 0.3 mm total thickness, sheets of black paper, etc., was concentrated by a quartz lens; with the aid of the small spark, the existence of four focal regions was ascertained. I further found that the action on the spark was much more pronounced when the spark was arranged vertically -- that is, in the plane of emission -- than when it was normal to this plane. The new radiations emitted by the polished plate are therefore polarized, as are the light and heat emitted at the same time. The silver plate having been covered with lampblack, the intensity of the emission increased, but the polarization disappeared.

The foregoing leads one to think that the emission of radiations susceptible of traversing metals, etc., is an extremely general phenomenon. First observed in the emission of a focus tube, it was also met in that of ordinary sources of light and heat. For shortness, I will henceforth designate these rays by the name of "N" rays.

[ From the name of the town of Nancy, these researches having been made at Nancy University. ]

I would draw attention to the fact that these N rays comprise a very large variety of radiations; for while those which issue from an Auer burner have refractive indices greater than 2, there are others, amongst those emitted by a Crookes tube, whose index is inferior to 1.52, for if a pencil of these rays is made to impinge on an equilateral quartz prism, parallel to the edges and normal to one of the faces, an emerging pencil is obtained which is very much spread out.

Up to this time the only means of detecting the presence of N rays was by their action on a small spark. I asked myself if the spark should in this case be considered as an electric phenomenon, or only as producing incandescence like a small gaseous mass. If this latter supposition were correct, the spark could be replaced by a flame. I then produced a quite small flame of gas at the extremity of a metal tube having a very small orifice. This flame was entirely blue. I ascertained that the flame could be used to reveal the presence of N rays just like the spark; for when it receives these rays, it becomes whiter and brighter in just the same way. Its variations in glow allowed of four foci being found in a pencil which had passed through a quartz lens; these foci are the same as those detected with the small spark. The small flame behaves therefore, in regard to N rays, just like the spark, save that it does not allow of the observation of polarization phenomena.

In order to study more easily the variations in glow, whether of flame or spark, I examine them through a plate of ground glass, about 25 or 30 mm distant. In this way one obtains, instead of a very small, brilliant point, a luminous patch of about 2 cm diameter, of much less luminosity, whose variations can be far better appreciated by the eye.

The action of an incandescent body on a flame, or that of a flame on another flame, is certainly a common phenomenon. If it has remained unnoticed up to the present, it is because the light of the source prevented the observation of the variations in glow of the receiving flame.

Quite recently I observed another effect of the N rays. It is true that these rays are unable to excite phosphorescence in bodies which can acquire this property under the action of light, but when such a body --- calcium sulfide, for example --- has previously been rendered phosphorescent by exposure to sunlight, if it is then exposed to N rays --- for instance, to one of the foci produced by a quartz lens --- the phosphorescent glow is observed to increase in a very marked fashion; neither the production nor the cessation of this effect appear to be absolutely instantaneous. Of all the actions producing N rays, this is the one which is most easily observed. The experiment is an easy one to set up and to repeat. This property of N rays is analogous to that of the red and infrared rays discovered by Edmond Becquerel. It is also analogous to the action of heat on phosphorus. Nevertheless, I have not noticed as yet an increased rate of exhaustion of the phosphorescent capacity under the action of N rays.

The kinship of N rays with known radiations of large wavelength seems a certain fact. As, on the other hand, the property possessed by these rays of traversing metals differentiates them from all known radiations, it is very probable that they are comprised in the five octaves of the series of radiations, hitherto unexplored, between the Rubens rays and electromagnetic oscillations of very small wavelength. This is what I propose to verify.

(5)  On the Existence of Solar Radiations Capable of Traversing Metals, Wood, etc. (June 15, 1903) 

I have recently proved that the majority of artificial sources of light and heat emit radiations which are able to traverse metals and a great number of bodies, opaque in regard to the spectral radiations hitherto known. It was desirable to ascertain whether radiations analogous to the former --- which, for brevity, I call N rays --- are also emitted by the sun.

As I have shown, N rays act on phosphorescent substances by heightening or stimulating the pre-existing phosphorescence, an action similar to that of red and infrared rays discovered by Edmond Becquerel. I utilized this phenomenon to find out whether the sun sends us N rays.

A completely enclosed dark room has one window exposed to the sun. This is shut by interior, opaque panels of oak, 15 mm thick. Behind one of these panels, at any distance -- 1 meter, for instance -- a thin glass tube is placed, containing a phosphorescent substance, say calcium sulfide, which has been previously exposed for a short time to solar rays. If, now, on the path of the solar rays, which are supposed to reach the tube through the wood, a sheet of lead, or the hand simply, is interposed, even at a great distance from the tube, the phosphorescent glow is seen to diminish; when the obstacle is removed, the glow reappears. The extreme simplicity of this experiment will incite many persons, I hope, to repeat it. The only precaution one need take is to operate with a feeble preliminary phosphorescence (note 9). It is advantageous to arrange permanently a sheet of black paper, so that the interposition of the screen does not change the background on which the tube stands out. The variations in glow are especially easy to catch near the contours of the luminous patch formed by the phosphorescent body on the dark background; when the N rays are intercepted, these contours lose their sharpness, regaining the same when the screen is removed. However, these variations in glow do not appear to be instantaneous. Interposing between the shutter and the tube several sheets of aluminum, cardboard, or an oak board 3 cm thick, does not hinder the phenomenon; any possibility of an action of radiated heat, as such, is consequently excluded. A thin film of water completely arrests the rays; light clouds passing over the sun considerably diminish their action.

The N rays emitted by the sun can be concentrated by a quartz lens; by means of the phosphorescent substance, the existence of several foci is ascertained. I have not yet determined their positions with sufficient precision to speak of them here. The N rays of sunlight undergo regular reflection by a polished plate of glass, and are diffused by ground glass.

The N rays issuing from the sun increase the glow of a small spark and a small flame in the same manner as those emitted by a Crookes tube, by a flame, or by an incandescent body. These phenomena are easy to observe, especially is use is made of an interposed sheet of ground glass, as indicated by me in a preceding communication. The use of a small flame is by far the most convenient and precise of all processes for determining the position of the foci. Operating with the small spark is much harder, because the spark is rarely very regular.

I feel bound to reproduce, textually, here a passage in a letter which M. Gustave le Bon had done me the honor of writing:

"M. Gustave le Bon had indicated, as far back as 7 years ago, that flames emit, independently of the radioactive emanations observed by him, radiations of large wavelength, capable of traversing metals, and to which he had given the name of black light; but while assigning these a place intermediate between light and electricity, he had not exactly measured their wavelength, and the method he had employed to reveal their presence was very uncertain."

The method referred to was the photographic method. Personally, I have not been able to obtain any photographic effect of the rays I have studies.

(6)  On a New Action Produced by N Rays, and on Several Facts Connected with These Radiations (July 20,1903) 

The action of N rays on a small flame gave me the idea of trying whether they did not exercise an analogous action on a solid incandescent body. For this purpose a platinum wire, about 0.1 mm diameter and 15 mm long, was heated to dull redness by an electric current. A pencil of N rays, emitted by an Auer burner, was directed through wood and aluminum screens on this wire, and was concentrated by a quartz lens.

The wire was observed through a plate of ground glass, fixed to the same support as the wire itself, and about 3 cm in front of it. On displacing the wire, several foci were found, just as with other processes employed to detect N rays. The wire being placed at one of these foci, the luminous patch on the ground glass is seen to diminish in brightness when a lead screen, or merely the hand, is interposed; when the obstacle is removed, the light resumes its former brightness. These actions do not appear instantaneous.

I have generalized the former experiments by employing, instead of a wire heated by an electric current, a sheet of platinum 0.1 mm thick, inclined at 45° on the horizontal plane, partially heated to a dark red by a small gas flame placed underneath. A horizontal pencil of N rays, concentrated by a lens, was made to impinge on the under face of the sheet, so as to produce a focus at the heated spot; on the upper face the incandescent patch was observed without interposing ground glass. The variations in brightness are exactly analogous to those of the wire. When observing, through ground glass, the intensity of illumination of the bottom face of the sheet, due to the rays and the flame together quite similar variations are found. Further, the same results are obtained if, instead of making the rays fall on the lower face, or the side on which the flame acts directly, they are directed on the upper face.

The different effects produced by N rays, viz. their action on a spark or flame, and on phosphorescent or incandescent bodies, would lead to the supposition that they might also have a heating effect on the bodies subjected to their action. To test the matter experimentally, I installed a thermopile of Ruben’s connected to an enclosed galvanometer. The action of N rays on this apparatus was absolutely nil, even in the most favorable conditions, though a candle placed 12 meters away gave a deflection of about 0.5 mm on the scale. I conducted the experiment not only with N rays proceeding from an Auer burner, but also with those from the sun on July 3, 1904 [?], at midday. The rays were very intense, for when I placed in front of the thermopile a tube containing calcium sulfide, which had been feebly excited by exposure to the sun, its glow was greatly increased, but was diminished by the interposition of a lead screen or the hand. M. H. Rubens made the same observation, as he was kind enough to write me, his apparatus being much more sensitive even than mine. I nevertheless thought it useful to determine directly whether the incandescent platinum wire was not heated by the action of N rays. To this end, I had recourse to the study of its electric resistance. The current flowing through the wire is produced by 5 accumulators; with the aid of high-resistance rheostats, the intensity is adjusted to make the platinum wire a dull red. The wire is stretched between two massive brass pliers, A  and B, which are connected to the terminals of a capillary electrometer; on one of the connecting wires an adjustable electromotive force is inserted, obtained by shunting a portion of the circuit of an auxiliary battery. This electromotive force is regulated so that the electrometer is at zero. Every variation in resistance of the platinum wire produces a deviation of the electrometer. Now, with N rays playing on the wire, no deviation of the meniscus was observed. The interposition of a lead or wet-paper screen remained without effect on the electrometer, though the wire underwent the usual variations in brightness. This certainly proves that N rays do not raise its temperature. I assured myself moreover that the method was sufficiently sensitive by the following experiment; by means of a wire rheostat, an assistant varied the resistance of a circuit containing the platinum wire and the accumulators, and consequently the strength of the current, but not sufficiently for the observer to perceive a variation in the glow of the wire. In spite of this, the electrometer was deflected three divisions of the micrometer in the eye-piece. The following is another verification: raising the temperature of the wire one degree would alter its resistance in the ratio of about 1.004 to one; the difference of potential between A and B would alter in about the same ratio, since the resistance external to the wire being very great, the current strength does not change. In my experiments this variation would deflect the electrometer by 15 divisions. As absolutely no deviation occurred, and as, moreover, a quarter of a division could have been easily observed, the rise in temperature is certainly very inferior to 1/15 x 1/4 = 1/60 of a degree, and, consequently, quite insufficient to produce the observed increase in glow. It is thus superabundantly established that the increase in glow produced by the rays is not due to a rise in temperature.

In the experiments with a plate of platinum, mentioned above, the increase in glow was apparent on the two faces of the sheet, Given that there is no rise in temperature, this seems paradoxical; for since N rays do not go through platinum, it seemed as if the action should only appear on the side exposed to these rays. To reconcile these results, it was necessary to suppose that N rays, which do not traverse cold platinum, traverse it when incandescent. I then reverted to the apparatus which was destined to show the action of N rays on a small flame, and behind the quartz lens I arranged a platinum sheet larger than the lens. The interposition of a lead screen between the platinum and the source produced no effect on the small flame, and the source produced no effect on the small flame, which verifies the opacity of platinum. The plate being then heated to redness, interposing the screen was seen to diminish the glow of the small flame. N rays issuing from an Auer burner traverse therefore incandescent platinum.

(7)  On New Actions Produced by N Rays -- Generalization of the Phenomena Already Observed (November 2, 1903) 

When a pencil of N rays is directed either on a small spark, flame, or a phosphorescent substance previously exposed to the sun’s rays. Or, again, to a platinum plate heated to dull redness, the light emitted by these various sources is seen to increase in glow. In these experiments, one operates on sources emitting light spontaneously. I asked myself whether one could not generalize these experiments by using a body not emitting light itself, but reflecting that which reaches it from an external source. I consequently carried out the following experiment: a slip of white paper, 15 mm long and 2 mm broad, is fixed vertically to a wire holder; the room being made dark, the slip is dimly lit b projecting laterally on it a pencil of light, emitted by a small flame shut up in a box, in which a vertical slit is pierced.

On the other hand, the rays are produced by the following contrivance: an Auer burner, provided with a sheet-iron chimney, in which a rectangular orifice, 60 mm high and 25 mm broad, has been cut, is enclosed in an iron lantern pierced with an opening placed in front of the chimney orifice, and stopped by a plate of aluminum. In front of this window the small slip of paper is placed, illuminated in the manner indicated above. If, now, the rays are intercepted by interposing a sheet of lead or the hand, the small paper rectangle is seen to darken, and its contours to lose their sharpness; the light diffused by the slip of paper is thus increased by the action of N rays.

The following idea then presented itself: the diffusion of light is a complex phenomenon, in which the elementary fact is regular reflection, and consequently there is reason for ascertaining experimentally whether the reflection of light is, or is not, modified by the action of N rays. For this purpose, a polished steel knitting needle was fixed vertically in place of the slip of paper of the former experiment; at the same time, in a box completely closed, with the exception of a vertical slit cut at the same height as the Auer burner, and stopped up by transparent paper, a flame was disposed so as to light up the slit.. By suitably placing the eye and the slit, the image of this latter is seen formed by reflection on the steel cylinder, and simultaneously the reflecting surface is receiving the N rays. It is then easy to observe that the action of these rays reinforces the image, for if they are intercepted, the image darkens, and turns to a reddish hue. I repeated this experiment with the same success by employing, instead of the knitting needle, a plane mirror of bronze.

The same result is again obtained by reflecting the light on the polished face of a block of quartz. However, when the N rays fall normally on the refracting face, their action on the reflected light disappears, whatever be the incidence of this light, whether it be that their action becomes zero, or simply inappreciable. In order that the light reflected by the quartz may be reinforced by the N rays, it is not necessary that the rays should be directed towards the interior of the quartz; the action still occurs when the N rays traverse the reflecting surface from the inside towards the outside.

All these actions of N rays on light require an appreciable time-interval for appearing and disappearing. I was unable, although I varied the experiment in a great many ways, to observe any action of N rays on the refracted light.

I will here make the following general remark concerning the observation of N rays. The aptitude for catching small variations in luminous intensity is very different in different persons; some see from the outset, and without any difficulty, the reinforcing action produced by N rays on the brightness of a small luminous source; for others, these phenomena lie almost at the limit of what they are able to discern, and it is only after a certain amount of practice that they succeed in catching them easily, and in observing then with complete certainty. The smallness of the effects and the delicacy of their observation must not deter us from a study which puts us in possession of radiations hitherto unknown. I have recently observed that the Auer burner can be advantageously replaced by the Nernst lamp, without a glass, this lamp giving more intense N rays. With a 200-watt lamp, the phenomena are marked enough to be, in my belief, easily visible to any one at the first trial.

(8)  On the Storing-up of N Rays by Certain Bodies (November 9, 1903)

In the course of my researches on N rays, I had occasion to note a very remarkable fact. The N rays were produced by an Auer burner enclosed in a lantern, and after passing through one of the sides of the lantern, formed by a sheet of aluminum, were concentrated by a quartz lens upon phosphorescent calcium sulfide.

This sulfide was tightly packed into a slit cut into a sheet of cardboard 0.8 mm thick; the width of the slit was 0.5 mm and its length was 15 mm. After exposure to sunlight, a small luminous source is thus obtained, which is very sensitive to N rays.

An Auer burner having been extinguished and removed the phosphorescent glow, to my great surprise, remained almost as strong as ever, but was darkened by the interposition of lead, or wet paper, or the hand, between the lantern and the sulfide. Nothing was altered by the suppression of the Auer burner, except that the observed actions grew progressively weaker. At the end of 20 minutes they still existed, but were scarcely noticeable.

Studying closely the circumstances of the phenomenon, I was not long in recognizing that the quartz lens had itself become a source of N rays; for when this was removed, all action on the sulfide ceased, whereas if it was brought nearer the sulfide, even laterally, the latter would become more luminous. I then took a quartz plate 15 mm thick, whose surface formed a square of 5 cm sides, and exposed this to the N rays emitted by an Auer burner through two sheets of aluminum and some black paper. It became as active as the lens; when brought nearer the sulfide, it seemed, according to Bichat’s expression, as if a veil darkening was being removed. A still more marked effect was obtained by interposing the quartz plate between the source and the sulfide, quite close to the latter.

In these experiments, the secondary emission by the quartz is added to the N rays directly emanating from the source. This secondary emission has, indeed, its origin in the whole mass of the quartz, and not at the surface only, for if several plates of quartz be successively placed on top of each other, the effect is seen to increase with each added plate. Iceland spar, fluorspar, barite, glass, etc, behave like quartz. The filament of a Nernst lamp remains active for several hours after the lamp is extinguished.

A piece of gold, laterally brought near to the sulfide while it is being subjected to N rays, increases its glow (note 10). Lead, platinum, silver, zinc, etc. produce the same effects. These actions persist after the extinction of the N rays, as in the case of quartz.

Nevertheless, the property of secondary ray emission only permeates slowly through a metallic mass. Thus, if one of the faces of a sheet of lead 2 mm thick has been exposed to N rays for several minutes, this face alone shows activity; an exposure of several hours is necessary for the activity to reach the opposite face.

Aluminum, wood, dry or wet paper, and paraffin do not enjoy the property of storing N rays. Calcium sulfide, on the other hand, does possess this property. When I put a few grams of sulfide in an envelope, and then exposed the envelope to N rays, I found that its proximity was sufficient to reinforce the phosphorescence of a small mass of previously excited sulfide. This property explains a constant peculiarity that I have previously set forth, viz., that the increase of phosphorescence under the action of N rays takes an appreciable time to appear or to disappear. For, thanks to the storing-up of the N rays, the different parts of a mass of sulfide mutually reinforce their phosphorescence; but since, on the one hand, this reinforcing is progressive, as I have proved, and since, on the other hand, the stored-up provision is not immediately exhausted, the result is that when N rays are made to fall on phosphorescent calcium sulfide, their effect must increase slowly, and that when they are suppressed, their effect can only disappear slowly.

I repeat here that, as a rule, when experimenting with N rays, it is advantageous to replace the Auer burner by a Nernst lamp absorbing about 200 watts.

Pebbles picked up at about 4 p.m. in a yard where they had been exposed to the sun, spontaneously emitted N rays; bringing them near a small mass of phosphorescent sulfide was sufficient to increase its luminosity. Fragments of calcareous stone, brick, etc., picked up in the same yard, produced analogous actions.

The activity of all these bodies still persisted after 4 days, without any sensible diminution. It is, however, necessary for the manifestation of such actions that the surface of these bodies be quite dry; for we know that the thinnest layer of moisture is sufficient to arrest N rays. Vegetable earth was found to be inactive, doubtless on account of its moisture; pebbles taken from several centimeters underneath the surface of the soil were inactive, even after being dried.

The phenomena of the storing-up of N rays, which are the object of the present note, ought naturally to be compared with those of phosphorescence; yet they present a quite distinct feature, as I intend to show shortly.

(9)  On the Strengthening Action of a Beam of Light on the Eyes, When the Beam is Accompanied by N Rays (November 23, 1903) 

While studying the storing-up of N rays by different bodies, I had occasion to observe an unexpected phenomenon. My eyes were fixed on a small slip of paper, dimly lit, about 1 meter distant from me; a brick, one of whose faces had been sun-exposed, having been brought nearly laterally to the luminous pencil, with its sun-exposed face turned towards me, and a few decimeters distant form my eyes, I saw the slip assume a heightened glow; when the brick was removed, or when its non-exposed face was turned towards me, the paper grew darker. To remove all possibility of illusion, I arranged permanently a box closed by a cover and wrapped in black paper; in this completely enclosed box the brick was placed, the dark background on which the slip stood out remained rigorously invariable, but the observed effect remained the same. The experiment can be varied in different ways. For instance, the laboratory shutters being almost closed, and the dial of the clock fixed to a wall which was just sufficiently lighted for the dial, at a distance of 4 meters, to be just perceived as a grey patch with no defined contour, if the observer, without changing his place, directs towards his eyes the N rays emitted by a previopusly exposed brick or pebble, he sees the dial whiten; he can trace distinctly its circular contour, and even succeed in seeingthe hands. When the N rays are suppressed, the dial again grows dark. Neither the production nor the cessation of the phenomenon are instantaneous.

As in these experiments the luminous object is placed very far away from the source of N rays, and as, on the other hand, in order that the experiment may succeed, the rays must be directed, not towards the object, but towards the eye, there can be no question here of an increase in emission of a luminous body influenced by N rays, but indeed of a strengthening of the effect upon the eye, due to the N rays which are superposed on the luminous rays.

This fact astonished me all the more because, since the slightest film of water arrests N rays, it seemed unlikely that they could penetrate into the eye, whose humours contain more than 98.6% of water (Lohmeyer). The small quantity of slat contained in these humours must have rendered them transparent to N rays. But then, in all probability, salt water must itself be transparent. Experiment shows that this is the case, for while a sheet of wet paper completely arrests the N rays, a vase of Bohemian glass, 4 cm thick, filled with salt water and placed in their path, lets them pass without sensible weakening. A very small quantity of sodium chloride is sufficient to render water transparent. What is more, salt water is capable of storing-up N rays, and in the above-described experiments the brick can be replaced by a vase of thin glass, filled with salt water, and previously exposed to the sun’s rays; the effect is very marked. It is certainly due to the salt water, for the empty vase is without effect. This is a unique example of a phosphorescence phenomenon in a liquid body. It is true that the wavelengths of N rays are very different from those of luminous rays, as results from measurements which it is my intention to describe very soon.

The eye of an ox, killed the day before, rid of its muscles and the tissues adhering to the sclerotic, proved to be transparent to N rays in all directions, and became itself active by sun-exposure; it is the storing-up of the N rays by the media of the eye which causes the retardation observed in the appearance and cessation of the phenomena which are the subject to the present note.

Sea water and the stones exposed to solar radiation store up N rays which they afterwards restore. Possibly these phenomena play some hitherto unperceived part in certain terrestrial phenomena. Perhaps, also, N rays are not without influence on certain phenomena of animal and vegetable life.

The following are further observations concerning the strengthening action of N rays on luminous rays.

It is sufficient for the production of the phenomenon that the N rays reach the eye, no matter how, even laterally. This seems to indicate that the observer’s eye behaves like an accumulator of N rays, and that it is these rays accumulated in the eye which act on the retina, jointly with luminous rays.

It matters little whether in these experiments the rays are emitted by a body previously exposed to the sun, or are primary rays, produced for instance by a Nernst lamp.

Sodium hyposulfite, whether solid or dissolved in water, constitutes a powerful accumulator of N rays.

(10)  On the Property of Emitting N Rays, Which is Conferred on Certain Bodies by Compression, and on the Spontaneous and Indefinite Emission of N Rays by Hardened Steel, Unannealed Glass, and Other Bodies in a State of Strained Molecular Equilibrium (December 7, 1903) 

Prof. A. Charpentier kindly undertook to keep me informed with regard to the progress of certain researches of a physiological nature which he is conducting in connection with N rays, unpublished researches which (note 11) promise highly interesting results. These experiments led me to the idea of examining whether certain bodies did not acquire, by compression, the property of emitting N rays. For this purpose I compressed, by means of a carpenter’s press, bits of wood, glass, rubber, etc., and I immediately observed that these bodies had in fact become, during the compression, sources of N rays; brought neat a mass of phosphorescent calcium sulfide, they increased its luminosity; and they can also be used for repeating the experiments which show the strengthening of the action on the retina by light when N rays are acting simultaneously on the eye.

These last experiments may be made in a very simple manner. The shutters of a room should be closed so as to leave just enough light for a white surface standing on a dark background -- for instance, the dial of a clock -- to appear, before an observer 4 or 5 meters distant, like a grey patch with ill-defined contours. If a can stick placed before the eyes is bent, the grey surface is seen to whiten; if the cane is allowed to straighten, the surface grows dark again. Instead of the cane, a slip of plate-glass can be used. If this is bent wither with the press employed in lectures for showing the doubly refractive property of glass acquired by flexure, or simply with the hands. With a suitable amount of light, which may be obtained after a few trials, these phenomena are easily visible. They are not instantaneous, as I have already explained. It is of the utmost importance that this retardation be taken into account when one wishes to study these phenomena; to this may doubtless be ascribed the fact that they have remained so long undetected.

I was then led to ask myself whether bodies which are themselves in a state of strained internal equilibrium would not emit N rays. That they do so in indeed confirmed by experiment. Rupert’s drops, hardened steel, hammer-hardened brass, melted sulfur of crystalline structure, etc., are spontaneous and permanent sources of N rays. One can, for instance, repeat the experiments with the clock dial, employing, instead of a compressed body, a hardened steel tool, such as a chisel or file, or even a pocket-knife, without in any way bending or compressing them; similarly, bringing near to a small mass of phosphorescent calcium sulfide a knife-blade or a bit of unannealed glass is sufficient to increase the phosphorescence Non-hardened steel is without action; a chisel which is successively hardened and softened in turn is active when hard and inactive when the temper is taken out of it. These actions traverse, without any notable weakening, a plate of aluminum 1.5 cm thick, an oak board 3 cm thick, black paper, etc.

The emission of N rays by tempered steel seems to last indefinitely. Some lathe tools and a stamp for leather of the 18th century, which have been preserved in my family, and have certainly not been rehardened since the date of their manufacture, emit N rays like freshly tempered steel. A knife, found in a Gallo-Roman tomb, situated in the district of Craincourt (Lorraine), and dating from the Merovingian epoch, as is attested by the objects found there (glass and earthenware jars, fibulae, belt buckles, etc.), emits N rays just kike a modern knife. These rays originate exclusively from the blade; a test with a file showed that the blade alone is tempered, and that the tailpiece intended to be fixed in a handle is not tempered.

The emission of N rays by this steel blade has thus persisted for more than 12 centuries, and does not appear to have abated.

The spontaneity and the indefinite duration of the emission by steel suggests the idea of assimilating it to the radiant properties of uranium, discovered by M. H. Becquerel, properties which the bodies since discovered by M. and Mme. Curie, viz. radium, polonium, etc., exhibit with so much intensity. Nevertheless, N rays are certainly spectrum radiation; they are emitted by the same sources as spectrum radiation; they are reflected and polarized, and possess well-defined wavelengths, which I have measured. The energy which their emission represents is most likely borrowed from the potential energy corresponding to the strained state of tempered steel; this expenditure is doubtless very slight, since the effects of the N rays are likewise slight, which explains the apparently unlimited duration of the emissions.

An iron plate, bent so as to impress on it a permanent deformation, emits N rays; but the emission ceases after a few minutes. A block of aluminum, fresh-hammered, behaves in an analogous manner; but the time of emission is even shorter. In these two cases the state of molecular strain is transitory, as is also the emission of N rays.

Torsion produces effects analogous to compression.

(11) On the Dispersion of N Rays and on their Wavelength (January 18, 1904) 

To study the dispersion and the wavelengths of N rays, I used methods quite similar to those employed for light. In order to avoid complications which might have resulted from the storing-up of N rays, I used exclusively prisms and lenses of aluminum, a substance which does not absorb their rays.

The following is the method employed to study dispersion. The rays are produced by a Nernst lamp, enclosed in a lantern of sheet-iron, pierced with an opening, which is shut by aluminum foil; the rays from the lamp which pass through this opening are sifted by a deal board 2 cm thick, a second sheet of aluminum, and two leaves of black paper, so as to eliminate radiations foreign to N rays. In front of those screens, and at a distance of 14 cm from the lamp filament, a large screen of wet cardboard is arranged, in which a slit has been cut 5 mm wide and 3.5 cm high, exactly opposite the lamp filament. In this way I obtain a well-defined pencil of N rays; this pencil is received on an aluminum foil prism whose refractive angle is 27° 15’, placed so that one of its faces is normal to the incident pencil.

It is, then, possible to prove that from the other refractive face of the prism several pencils of N rays, horizontally dispersed, emerge. For this purpose a slit 1 mm broad and 1 cm high, cut in a sheet of cardboard, is filled with calcium sulfide rendered phosphorescent; by displacing this slit, the position of the dispersed pencils is determined without difficulty, and the deviations being known, their refractive indices are deduced. This is the method of Descartes. I thus established the existence of N radiations, whose indices are respectively 1.04, 1.19, 1.29, 1.36, 1.40, 1.48, 1.68, and 1.85. In order to measure with more exactness the first two indices I made use of another aluminum prism having an angle of 60°, I again found for one of the indices the same value, 1.04; and for the other, 1.15 instead of 1.19.

In order to control the results obtained by the prisms, I determined the indices by producing, by means of an aluminum lens, images of the lamp filament, and measuring their distances from the lens. The lens, which is plano-convex, has a radius of curvature of 6.63 cm, and an aperture of 6.89 cm. The slit of the wet screen is widened so as to form a circular opening 6 cm in diameter; the lens is placed at a known distance ( p cm) from the incandescent filament, and by means of the phosphorescent sulfide, the position of the conjugate images of the filament is determined. The following table gives the values of the indices found, both with the prism and the lens: ---

27° 15’ ~ 60°
1.85 ~ "
1.68 ~ "
1.48 ~ "
1.40 ~ "
1.36 ~ "
1.29 ~ "
1.19 ~ 1.15
1.04 ~ 1.04

P = 40 ~ p = 30  ~ p = 22 cm
1.86 ~ 1.91 ~ 1.91
1.67 ~ 1.66 ~ 1.67
1.50 ~ 1.44 ~ 1.48
1.42 ~ 1.42 ~ 1.43
1.36 ~ 1.36 ~ 1.37
1.36 ~ 1.31 ~ "
1.20 ~ " ~ "

Here is another verification of these results: if for the fourth index the mean value 1.42 is adopted, one works out that for an aluminum prism of 60°, the incidence giving the minimum deviation is 45° 19’, and that this deviation is 30° 38’; the observed deviation was 31° 10’. With the same incidence, the calculated deviation of the radiation, whose index is 1.67, is 57° 42’; the observed deviation was 56° 30’.

I now pass on to the determination of wavelengths.

By means of the above-described arrangement for studying dispersion by the prism of 27° 14’, refracted pencils are obtained, each of which is sensibly homogeneous. If we make the pencil we wish to study impinge on a second screen of wet cardboard, pierced with a slit 1.5 mm wide, we can isolate a narrow portion of this pencil.

On the other hand, a piece of aluminum foil is fixed to the moving radial arm of a goniometer, so that its plane is normal to the arm; in this foil a slit is cut only 0.07 mm wide, and filled with phosphorescent calcium sulfide; the goniometer is arranged so that its axis is exactly underneath the slit of the second wet cardboard. By turning the arm, the path of the pencil is exactly marked out, and one can verify that it is quite unique, and is accompanied by no lateral pencil, such as diffraction could eventually produce in the case of large wavelengths.

A grating is then placed in front of the slit of the second wet cardboard (for instance, a Brunner grating of 200 lines per mm). If, now, the emerging pencil is explored by turning the arm which bears the phosphorescent sulfide, the existence of a system of diffraction fringes is confirmed, just as with light, only these fringes are much closer together, and are sensibly equidistant. This already indicates that N rays have much shorter wavelengths than luminous radiations.

The angular distance of the fringes, or what amounts to the same thing, the rotation of the arm corresponding to the passage of the phosphorescent slit from one luminous fringe to the next, is very small. It is therefore determined by the method of reflection, with the aid of a divided scale and telescope, a plane-mirror being fixed to the arm. Moreover, one measures, not the distance between tow consecutive fringes, but that between two symmetrical fringes of a high order -- for example, that between the tenth fringe on the right, and the tenth fringe on the left. From these measures of angle, and from the number of lines per millimeter of the grating, the wavelength can be deduced by the known formula.

Each wavelength has been determined by three series of measurements, effected with three gratings, having respectively 200, 100, and 50 lines per millimeter.

The following table exhibits the results of these measures:

Indices ~ 200 lines/mm ~ 100/mm ~ 50/mm ~ Probable Values

1.04 ~ 0.00813 ~ 0.00795 ~ 0.00839 ~ 0.00815
1.19 ~ 0.0093 ~ 0.0102 ~ 0.0106 ~ 0.0099
1.4 ~ 0.0117 ~ " ~ " ~ 0.0117
1.68 ~ 0.0146 ~ " ~ " ~ 0.0146
1.85~ 0.0176 ~ 0.0171 ~ 0.0184 ~ 0.0176

Being desirous of controlling these determinations by the use of a quite different method, I had recourse to Newton’s rings. These being produced, in yellow light, for instance, of one passes from one dark ring to the following, the variation of optical retardation in air is one wavelength of yellow light. If, now, with the same apparatus and the same incidence, rings are produced by means of N rays, and the number of these rings comprised between two dark rings in yellow light is counted, we shall obtain the number of times which the wavelength of N rays is contained in the wavelength of yellow light. This methods, applied to rays of index 1.04, gave the values of 0.0085 instead of 0.0081 found by the gratings; and for the index 1.85, the value 0.017 instead of 0.0176. Though the ting method is inferior to the grating method, on account of the uncertainty attending the exact position of the dark rings in the experiment, an uncertainty which is due to the necessity of rendering these rings very wide, the concordance of the numbers obtained by the two methods constitutes a valuable control.

In the tables given above I have retained all the decimals occurring in the calculation of the numbers deduced from observation. Although I cannot with certainty indicate the degree of approximation of the results, I believe, nevertheless, that the relative errors do not exceed 4 percent.

The wavelength of N rays are much smaller than those of light. This is contrary to what I had imagined for a moment, and contrary to the determinations which M. Sagnac thought he had deduced from the position of the multiple images of a source, obtained with a quartz lens, images attributed by him to diffraction. I had previously observed that while polished mica lets N rays pass, roughened mica stops them, and also that whereas polished glass reflects them regularly, ground glass diffuses them. These facts were already an explanation that N rays could not have large wavelengths. If we desire to study the transparency of a body, we must take care that the surface is well polished. Thus I had at first classed rock salt amongst opaque substances, because the specimen I used, having been sawn from a large block, had remained unpolished; in reality, rock salt is transparent.

The radiations of very small wavelength, discovered y M. Schumann, are to a very great extent absorbed by air; N rays are not. This implies the existence of absorption bands between the ultraviolet spectrum and N rays. The wavelength of N rays increases with their refractive index, contrary to what occurs with luminous radiations.

If the increase in brilliancy of a small luminous source by the action of N rays is to be attributed to a transformation of these radiations into luminous radiations, this transformation is in conformity with Stokes’law.

 (12) Registration by Photography of the Action Produced by N Rays on a Small Electric Spark (February 22, 1904) 

Though N rays have no intrinsic action on the photographic plate, it is nevertheless possible to utilize photography to reveal their presence and study their action. This object is attained, as I showed as long ago as May 11, 1903, by making a small, luminous source act for a determined period on a sensitive plate, whilst this source is subjected to the action of N rays, and then repeating the experiment for the same interval of time and under the same conditions, save that the N rays are suppressed. The impression produced is notably more intense in the first case than in the second. As an example of the application of this method, I gave at the time two photoengravings, whose comparison shows that water, even when used in very thin films, arrests N rays issuing from an Auer burner. Since then I have extended the experiments to the registration of actions produced by N rays from various sources, and I have perfected the process, as will be shown.

A small, luminous spark is the most appropriate luminous source for this kind of investigation: for, on the one hand, it is very actinic, and, on the other, it can be maintained as long as necessary at the same intensity. Although it is impossible to obtain absolute steadiness of glow in the spark, since these variations are not produced symmetrically, their influence should disappear in the total impression received by the plate, even after a very short exposure. I contrived, besides, to eliminate even still more completely this cause of perturbation, by repeatedly alternating the experiments, as I will proceed to show.

Figure 4 represents a horizontal section of the apparatus employed. AB is the photographic plate, 13 cm wide; E is the spark enclosed in a cardboard box, FGHI, open only on one side facing the plate, and allowing the spark to act on one half, OB, of the plate only; CD is a lead screen wrapped in wet paper, rigidly connected with the frame which holds the plate. The N rays, proceeding from any source, form a pencil, having the direction NN’. With this arrangement the N rays are arrested by the screen CD; the spark, while it acts on half-plate OB, is sheltered from the rays.

Figures 4, 5 ~

Now impart to the frame containing the plate a translation to the right equal to half its length (Figure 5); the other half, AO, of the plate takes the place formerly occupied by OB; and this time the screen CD, carried along with the frame in this movement, is no longer interposed in the path of the rays. The half-plate AO therefore receives the action of the spark while subjected to the rays.

This being understood, the experiment is as follows: first the plate is kept in the first of the above-indicated positions during 5 seconds, then in the second position also for 5 seconds; it is then brought back to the first position, and the double operation just described is repeated several times.

After an interval of time equal to an even multiple of 5 seconds -- for instance, 100 seconds -- each of the half-plates has been exposed to the spark for an equal period, only, while AO was exposed, N rays were in action, and while OB was exposed there were none.

Thanks to an arrangement of guides and buffer-stops, the to-and-fro motion of the frame can be executed with perfect certainty and regularity, in spite of the darkness. A metronome is used to regulate the action.

The spark is produced by a small induction-coil, known as du Bois-Reymond’s chariot apparatus; it strikes between two blunt points of platinum-iridium, carefully machined and polished. These are fixed to the two jaws of a pair of wooden pliers which tend to close by elasticity, and are kept apart by a micrometer screw. At a distance of about 2 cm from the spark, and facing the plate, a plate of ground glass is fixed. As I have previously mentioned, the light of the spark produces on this plate an extensive luminous patch, much easier to observe than the naked spark, and giving on the photographic plate impressions of much more regular form. The regulating of the spark is the delicate part of the experiment. The induced current must first be adjusted, by modifying the primary current on the one hand, and the position of the secondary coil on the other, till the spark becomes very small. The points are washed in alcohol, then a slip of dry paper is drawn between them, for the purpose of drying and repolishing their surface; then the micrometer screw s turned so as to make the spark as short as possible, yet without incurring any risk of the points touching by any chance vibration, which would make it disappear intermittently. By a methodical process of trial and error, which sometimes demands much time and patience, one succeeds in getting a spark both regular and very feeble; it is then sensitive to the action of N rays. If one directs on it a pencil of these radiations, proceeding from any source, one sees the patch on the ground glass increase in size and glow; at the same time its central part becomes more luminous, appearing wrapped in a kind of nimbus. One can then proceed with the photographic experiment. I made about 40 such experiments, employing in turn, as sources of N rays, a Nernst lamp, compressed wood, hardened steel, Rupert’s drops, etc. I have varied the experiments in different ways -- for example, by changing the side of the screen CD, by using a zinc screen transparent to N rays, etc. Several eminent physicists, who have been good enough to visit my laboratory, have witnessed them. Of these 40 experiments, one was unsuccessful: the rays were produced by a Nernst lamp, and instead of the expected unequal impressions, two sensibly identical images were obtained. I believe this failure, unique, be it remarked, to be due to an insufficient regulation of the spark, which, doubtless, was not sensitive. Figure 6 is a photo-engraved reproduction of the prints obtained with and without N rays issuing from a Nernst lamp.

Figures 6, 7

Figure 7, similarly, shows the result of an experiment with N rays, produced by two large files.

Though the photogravures are far from rendering in a satisfactory manner the aspect of the originals, they nevertheless show the influence of N rays on a photographic impression.

I give further (Figures 8 and 9) the reproduction of photographs, showing that N rays, issuing from a Crooke’s tube, are polarized.

These photographs date from the month of April 1903. They were not obtained by the method of reiterated alternation of exposure, as this method is difficult to apply to this case; but the experiments have been repeated a great number of times with the most minute precautions, and the constancy of the results is an absolute guarantee of their worth.

From my communication of May 11, 1903, and from what precedes, it is clear that from the beginning of my researches on N rays, I had succeeded in recording their action on the spark by an objective method.

Figures 8, 9


(13)  On a New Species of N Rays (February 29, 1904) 

Observations made during a very complex experiment, which I owe to Dr. Th. Guidloz, led me to suspect the existence of a variety of N rays, which, instead of increasing, on the contrary, diminished the glow of a feeble luminous source. I undertook to search for rays of this type amongst those emitted by a Nernst lamp. While previously studying the spectrum of this emission, produced by an aluminum prism, I had not met with such radiations. I consequently thought that there were reasons for studying anew, and still more minutely, the feebly deviated part of the spectrum. On exploring this region, by means of a narrow slit filled with phosphorescent calcium sulfide, I ascertained, without any difficulty, that, in certain azimuths, the glow of the spark diminished under the action of the rays, and increased, on the contrary, when they were intercepted by a wet screen. These were, in fact, the looked-for radiations; I will call them N1 rays.

Although the aluminum prism of 27° 15’ I used previously is suitable for these experiments, nevertheless, in order to increase the dispersion, I used an aluminum prism of 60°, and afterwards another of 90°. With the help of the latter, I very carefully studied the feebly deviated part of the spectrum. The prism was arranged so that the angle of incidence was 20°; for each radiation, the deviation was measured and the refractive index deduced; then the wavelength was determined by means of a Brunner grating of 200 lines per millimeter, by the process already described. The following table gives the numbers which result from this study, and were used for constructing the diagram (Figure 10), in which the abscissae stand for the wavelengths and the ordinates for the indices diminished by unity.

Nature of Rays ~ Indices ~ Wavelengths

N1 ~ 1.004 ~ 0.003
N ~ 1.0064 ~ 0.0048
N1 ~ 1.0096 ~ 0.0056
N ~ 1.011 ~ 0.0067
N1 ~ 1.0125 ~ 0.0074
N ~ 1.029 ~ 0.0083
N ~ 1.041 ~ 0.0081

Each of the divisions marked on the axis of abscissae corresponds to 0.001, and each of the divisions marked on the ordinate axis corresponds to an excess over unity equal to 0.01.

In spite of all the care with which the experiments were executed, the deviations are so small, and, consequently, the indices so near to unity, that the table and diagram can only be regarded as a preliminary indication of the behavior of the dispersion in the very slightly deviated part of the spectrum. An important consequence arises from these measures, viz. points corresponding to N rays, and those corresponding to N1 rays, are all situated on the same curve, within the limits of experimental error. The study of radiations still less refrangible than those I have dwelt on appeared to me impracticable. To avoid confusion, I was obliged to adopt a very large scale for the ordinates; this is why I could not plot on the diagram the results of my former measurements of the more refrangible N rays. These results give points situated on a branch of the curve, starting from the topmost point on the right, and rising almost vertically, with a feeble inclination from bottom to top, and from right to left, and a slight convexity turned upwards.

Certain sources seem to emit N1 rays exclusively, or, at least, these rays predominate in the emission. This is the case with copper and silver wire, and with hard-drawn platinum wire. M. Bichat has observed that ethylic ether, when brought to the state of forced extension, by the process discovered by M. Berthelot, emits N1 rays. When this state of strain ceases, whether spontaneously or under the action of a slight blow, the emission of N1 rays immediately disappears.

N1 rays can be stored up like N rays. For instance, one need only bring a bit of stretched copper wire in proximity to a lump of quartz to make the quartz emit N1 rays for some time after.

Figure 10

(14)  On Peculiarities Presented by the Action Exercised by N Rays on a  Dimly Lighted Surface (February 2, 1904) 

Consider a phosphorescent screen, or, more generally, a dimly lighted surface. If this surface is viewed normally, one notices that the action of N rays is to render it more luminous; if, on the contrary, the surface is viewed very obliquely, nearly tangentially, the action of N rays is to render it less luminous. In other words, the action of N rays increases the quantity of light normally emitted, while it diminishes the light emitted in a very oblique direction. If one looks at it in an intermediate position, no appreciable effect is observed. This explains the fact, observed in all N ray experiments, that only the observer placed exactly in front of the sensitive screen perceives the effect of these rays. It also shows how illusory it would be to try to make an audience witness these experiments; the effects perceived by different persons, depending as they do on their positions with regard to the screen, would certainly be contradictory or imperceptible. The rays I have called N1 rays have an inverse action on all cases to that of N rays; they diminish the light emitted normally, and increase the light emitted tangentially. M. Mace de Lepinay (see C.R. cxxxvii, p. 77, January 11, 1902) has found that sound vibrations increase the glow of a phosphorescent screen as seen by an observer viewing it normally. I have noticed that if the screen is viewed tangentially, the phosphorescence is seen to decrease under the action of the sound waves. The action of a magnetic field or of an electromotive force on a feebly luminous surface, discovered by M. C. Gutton (see C.R., cxxxviii, p. 268, February 1, 1904), presents the same particularities.

To sum up, in all the above-mentioned  actions, the modification undergone by the luminous emission consists in a change in its distribution along the different directions comprised between the normal and the tangent plane to the luminous surface.

(15)  On the Comparative Action of Heat and N Rays on Phosphorescence (March 14, 1904) 

I have recently indicated that, whilst the action of N rays increases the quantity of light emitted by a phosphorescent screen in a normal direction, it diminishes the quantity of light emitted very obliquely. As is well known, heat also acts on phosphorescence, whose brilliance it temporarily increases. When investigating whether this action of heat offered the same peculiarities as that on N rays, with regard to the direction of the emitted light, I found that, on the contrary, heat produces an increase in brilliancy in all directions comprised between the normal and the tangent plane. Hence we are in a position to distinguish between the effects produced on phosphorescence by heat on the one hand, and by N rays, sound waves, magnetic and electric fields on the other.

The following is another case in which the effects are different. Take a rectangular cardboard screen, 5 cm high and 12 cm long, for instance, coated very uniformly with calcium sulfide, and rendered very feebly phosphorescent. If the temperature of a portion of the screen is raised, this part becomes more luminescent than the rest. If, instead of this, we let fall on one half of the screen a pencil of N rays, proceeding, for example, from a Nernst lamp, we find no sensible increase in its glow; but if in front of this half-screen a small opaque object is placed, for instance, a small key or a bit of metal foil, cut off by daylight, this is seen to come out very strongly on the luminous background, while if it is placed on the half not receiving the N rays, its outline is vague and indeterminate, and seems even to disappear at times. By shifting slowly the object on the screen, its passage from one half-screen to the other is rendered visible by changes in the boldness of its outline. If instead of viewing the object normally, we observed it very obliquely, the phenomena are reversed.

(16)  Complementary Notes 

(1) As mentioned in the Preliminary Notice, and as will be seen in the later communication, the properties attributed in the present paper to X rays, belong not to these rays, but to a new kind of rays, to which I have given the name of N rays. The experiments are correct, and the rectification only applies to the nature of the rays which have been studied.

(2)  What I attributed then to S rays is, in reality, die to diffused N rays. The rotation of the plane of polarization of N rays by active substances is perhaps very great, since their wavelengths are very small. It may be, then, that the angles I have observed are merely the remainders obtained by subtracting 360° once or several times from the real rotations. For the same reason, the rotations in a contrary direction could be apparent only. Investigation on this point remains still to be carried out; the operations should be conducted successively on each of the homogeneous pencils resulting from the dispersion of a pencil of N rays by an aluminum prism. The existence of magnetic rotary polarization has recently been shown by M. H. Bagard, whose investigations are still in progress (C.R., cxxxviii).

(3) Unpolished mica arrests a pencil of N rays; these are not, however, absorbed, but only diffused, as in the case of light.

(4) Rock salt is in reality transparent. What has at first misled me was that the plate of salt I used, having been sawn out of a large block, had remained unpolished. In this state it was only translucent, whether for N rays or for light. When polished with wet paper, it becomes transparent both for N rays and light; when the polish disappears, it becomes translucent again.

(5)  As I state in the text, these rough data on the transparency of different substances will have to be completed by new experiments methodically conducted. I have since found that copper continues to transmit N rays emitted by a Nernst lamp, even when used in thickness of 65 cm; that, similarly, glass is very transparent, etc. M. Bichat has studied the transparency of various bodies; in particular, he has ascertained that the opacity of a sheet of lead is due to the fact that it is superficially covered with oxide and carbonate. Metallic lead lets pass certain of the N radiations (see C.R. cxxxviii, p. 548, February 29, 1904).

(6)  See the communication of May 25 and June 15, 1903.

(7)  I have since found that, on the contrary, N rays have much shorter wavelengths than those of light (See my communication of January 18, 1904).

(8)  See note (7) above.

(9)  The phosphorescence may be intense, provided it be not at its maximum.

(10) The piece of gold must of course be also receiving the N rays.

(11)  These researches have since been communicated to the Academy of Sciences (See C.R. cxxxvii, p. 1049, December 24, 1903).

(12)  According to some experiments which I have made with an aluminum lens on rays issuing from a knife-blade, these should have very large indices. M. Charpentier has found that wet cardboard transmits these rays. These questions remain to be studied.

(17)  Instructions for Making Phosphorescent Screens Adapted for the Observation of N Rays 

(1) If one proposes only to ascertain the production of N rays in given circumstances, a phosphorescent screen, made as follows, may be used with advantage: some powdered calcium sulfide is mixed with collodion, diluted with ether, so as to form a very thin paste; then, with a water-color brush, drops of this paste are painted on blackened cardboard, so as to produce stains several millimeters in diameter, close to each other. The screen then presents the aspect of a spotted fabric. If, after being exposed to light, it is examined in a dark room, and in perfect silence, some of the spots will appear less luminous than the others. Usually, some will not seem to be sharply separated from their neighbors, but will form a sort of confused nebula less visible than the rest. Now, if one speaks aloud...

[Missing text: I lost pp.80-81 of my photocopy -- ed.]

(18)  How the Action of N Rays Should be Observed 

It is indispensable in these experiments to avoid all strain on the eye, all effort, whether visual or for eye accommodation, and in no way to try to fix the eye upon the luminous source, whose variations in glow one wishes to ascertain. On the contrary, one must, so to say, see the source without looking at it, and even direct one’s glance vaguely in a neighboring direction. The observer must play an absolutely passive part, under penalty of seeing nothing. Silence should be observed as much as possible. Any smoke, and especially tobacco smoke, must be carefully avoided, as being liable to perturb or even entirely mask the effect of the N rays. When viewing the screen or luminous object, no attempt at eye-accommodation should be made. In fact, the observer should accustom himself to look at the screen just as a painter, and in particular an "impressionist" painter, would look at a landscape. To attain this requires some practice, and is not an easy task. Some people, in fact, never succeed.

The End

Scientific American (October 14, 1905), p. 299

"Photographic Records of the Action of N-Rays"

The much discussed problem of the existence of N rays could be settled only by an objective demonstration of their effects. As these rays exert no immediate action on photographic plates, Prof. Blondlot some time ago endeavored to obtain indirect photographic records, by taking a view of the same spark first without N rays, and afterward with N rays. In the latter case a more intense impression on the photographic plate was observed. Opponents of the French scientist contended that the electric sparks were not of sufficient constancy to warrant him drawing any definite conclusions from these experiments. Prof. Blondlot therefore continued his efforts in this direction, and in a memoir published in a recent issue of the Revue Generale des Sciences describes a few further experiments where every care has been takes to avoid any uncertainty. These experiments really demonstrate the objective existence of the radiations. The process used was practically the same as that employed previously, but for a telephone inserted in the secondary circuit of the induction coil. The assistant, by keeping the telephone receiver close to his ear, was in a position to check the regularity of the spark throughout the duration of the experiments. If the spark was extinguished owing to an excessive distance of the points, the sound in the telephone was also discontinued. If, on the contrary, the points touched each other, the sound became much more intense. Any irregularities in the spark might thus be detected, and if any were observed during a photographic experiment, the photographs were rejected.

In a series of 35 experiments carried out with every care, 23 tests showed a most striking difference between the images obtained with and without N rays, while 8 tests gave a rather noticeable contrast, and 4 tests a contrast still visible though less marked. All the plates did show the action of N rays, and if the difference between the two photographic impression was not always of the same intensity, this must be ascribed to the impossibility of obtaining an absolutely exact regulation of the small spark.

It is of great importance that exceedingly feeble sparks should be employed, the brilliancy of which be little more than the minimum luminous intensity capable of producing some impression on the plate. Under these conditions a small variation in luminous intensity will result in a great variation in the intensity of the photographic image, while in the case of a stronger illumination only a very small variation is obtained.

In the experiments referred to, the N rays were produced by a Nernst lamp enclosed in a sheet-metal lantern. The N rays traversed successively an aluminum foil constituting the front wall of the latter, a pinewood plank 2 cm in thickness, another aluminum foil, an aluminum lens, a zinc foil, a piece of whitewood 2 cm in thickness, an aluminum foil, constituting an electric screen to protect the spark, and finally the wall of the pasteboard box inclosing the spark.

With all these experiments one second or more has been allowed for the total duration of the exposure made without N rays so as to make sure that this exposure was somewhat longer than the other. Instead of simply taking two successive exposures with and without N rays, another method, consisting in cross-wise fractional photography, has been chosen in some instances. The exposure with N rays was made either before or after the other, and the experiments were varied in many other ways. Metal screens were used so as to eliminate any disturbances likely to be produced by electrical influence. Checking experiments were made, from time to time either by withdrawing the moist paper or by moistening it with salt water, when equivalent images were obtained in each case.

These experiments seem to be free from any objection. While the results practically agree with those obtained in connection with former researches, the following interesting fact was discovered incidentally:

If N rays be made to strike the primary spark of a Hertz oscillator, the secondary spark will decrease in brilliancy. This shows that N rays modify the electric phenomenon itself, and the intimate alteration of the spark is doubtless the cause for which the photographic experiments on the action of N rays is used as illuminant, whereas no result is obtained with other sources of light.

"The Great N Ray Delusion"

by William Seabrook

Excerpted from: "Random Walk through Physics"; condensed from "Dr. Wood: Modern Wizard of the Laboratory", by William Seabrook (Harcort Brace, 1941).

In the last autumn of 1903, Professor R. Blondlot, head of the Department of Physics at the University of Nancy, member of the French Academy, and widely known as an investigator, announced the discovery of a new ray, which he called N ray, with properties far transcending those of the x-rays. Reading of his remarkable experiments, I attempted to repeat his observations, but failed to confirm them after wasting a whole morning. According to Blondlot, the rays were given off spontaneously by many metals. A piece of paper, very feebly illuminated, could be used as a detector, for, wonder of wonders, when the N rays fell upon the eye they increased its ability to see objects in a nearly dark room.

Fuel was added by a score of other investigators. Twelve papers had appeared in the Comptes rendus before the year was out. A. Charpentier, famous for his fantastic experiments on hypnotism, claimed that N rays were given off by muscle, nerves, and the brain, and his incredible claims were published in the Comptes, sponsored by the great d'Arsonval, France's foremost authority on electricity and magnetism.

Blondlot next announced that he had constructed a spectroscope with aluminum lenses and a prism of the same metal, and found a spectrum of lines separated by dark intervals, showing that there were N rays of different refrangibility and wave length. He measured the wavelengths. Jean Becquerel claimed that N rays could be transmitted over a wire. By early summer, Blondlot had published twenty papers, Charpentier twenty, and J. Becquerel ten, all describing new properties and sources of the rays.

Scientists in all other countries were frankly skeptical, but the French Academy stamped Blondlot's work with its approval by awarding him the Lalande prize of 20000 francs and its gold medal for the discovery of the N rays'.

In September (1904) I went to Cambridge for the meeting of the British Association for the Advancement of Science. After the meeting some of us got together for a discussion of what was to be done about the N rays. Professor Rubens, of Berlin, was most outspoken in his denunciation. He felt particularly aggrieved because the Kaiser had commanded him to come to Potsdam and demonstrate the rays. After wasting two weeks in vain attempts to duplicate the Frenchman's experiments, he was greatly embarrassed by having to confess to the Kaiser his failure. Turning to me he said, Professor Wood, will you not go to Nancy immediately and test the experiments that are going on there?' Yes, yes', said all of the Englishmen, that's a good idea, go ahead.' I suggested that Rubens go, as he was the chief victim, but he said that Blondlot had been most polite in answering his many letters asking for more detailed information, and it would not look well if he undertook to expose him. Besides,' he added, you are an American, and you Americans can do anything ...'

So I visited Nancy, meeting Blondlot by appointment at his laboratory in the early evening. He spoke no English, and I elected German as our means of communication, as I wanted him to feel free to speak confidentially to his assistant.

He first showed me a card on which some circles had been painted in luminous paint. He turned down the gas light and called my attention to their increased luminosity, when the N ray was turned on. I said I saw no change. He said that was because my eyes were not sensitive enough, so that proved nothing. I asked him if I could move an opaque lead screen in and out of the path of the rays while he called out the fluctuations of the screen. He was almost 100 percent wrong and called out fluctuations when I made no movement at all, and that proved a lot, but I held my tongue. He then showed me the dimly lighted clock, and tried to convince me that he could see the hands when he held a large flat file just above his eyes. I asked if I could hold the file, for I had noticed a flat wooden ruler on his desk, and remembered that wood was one of the few substances that never emitted N rays. He agreed to this, and I felt around in the dark for the ruler and held it in front of his face. Oh, yes, he could see the hands perfectly. This also proved something.

But the crucial and most exciting test was now to come. Accompanied by the assistant, who was by this time casting rather hostile glances at me, we went into the room where the spectroscope with the aluminum lenses and prism were installed. In place of an eyepiece, this instrument had a vertical thread, painted with luminous paint, which could be moved along in the region where the N ray spectrum was supposed to be turning a wheel having graduations and numerals on its rim. Blondlot took a seat in front of the instrument and slowly turned the wheel. The thread was supposed to brighten as it crossed the invisible lines of the N-ray spectrum. He read off the numbers on the graduated scale for a number of the lines, by the light of a small, darkroom red lantern. This experiment has convinced a number of skeptical visitors, as he could repeat his measurements in their presence, always getting the same numbers.

I asked him to repeat his measurements, and reached over in the dark and lifted the aluminum prism from the spectroscope. He turned the wheel again, reading off the same numbers as before. I put the prims back before the lights were turned up, and Blondlot told his assistant that his eyes were tired. The assistant had evidently become suspicious, and asked Blondlot to let him repeat the reading for me. Before he turned down the light I had noticed that he placed the prism very exactly on its little round support, with two of its corners exactly on the rim of the metal disk. As soon as the light was lowered, I moved over towards the prism, with audible footsteps, but I did not touch the prism. The assistant commenced to turn the wheel, and suddenly said hurriedly to Blondlot in French, I see nothing; there is no spectrum. I think the American has made some derangement.' Whereupon he immediately turned up the gas and went over and examined the prism carefully. He glared at me, but I gave no indication of my reactions. This ended the seance.

Next morning I sent off a letter to Nature giving a full account of my findings, not, however, mentioning the double-crossing incident at the end of the evening, and merely locating the laboratory as `one in which most of the N-ray experiments had been carried out'. La Revue scientifique, France's weekly semipopular scientific journal started an inquiry, asking French scientists to express their opinions as to the reality of the N rays. About forty letters were published, only a half dozen backing Blondlot. The most scathing one by Le Bel said, `What a spectacle for French science when one of its distinguished savants measures the position of the spectrum lines, while the prism reposes in the pocket of his American colleague!'

The Academy at its annual meeting in December, when the prize and medal were presented, announced the award as given to Blondlot for his life's work, taken as a whole.'

"Fooling Students into not Fooling Themselves"

Four activities designed to engage students in the methods of science by showing how personal experience is not always to be trusted.

by Raymond Hall

Expectation Bias and Seeing Things

Here is a short account of a famous instance of expectations bias, or just plain jumping to conclusions. In 1903, during a time of major discoveries of many new forms of radiation, Professor Rene Blondlot of the University of Nancy reported the discovery of a remarkable new radiation he labeled N-rays10. He claimed these rays were emitted by all things except green wood and some treated metals, and had similar penetrating properties akin to X-rays. A number of other French scientists had corroborated his findings by duplicating his experiments. In one experimental arrangement, the N-rays were said to refract through a metal prism, and that a spectrum of dark and light N-ray bands could be cast. Instead of an eyepiece the spectrometer had a vertical thread treated with luminous paint. N-ray bands were detected by Blondlot, determining by eye the faint glow of the string as an assistant called out angles and rotated the prism through a set of intervals.

The journal Nature sent American physicist James Wood to investigate the amazing claims of the N-ray experiments. Wood was invited into Blondlot’s lab for a demonstration, and while waiting in the dark for Blondlot’s eyes to adjust, Wood quietly removed the metal prism from the apparatus. Although the prism was in Wood’s pocket, thus completely disabling the apparatus, Professor Blondlot nevertheless called out the presence and absence of N-rays exactly where he had reported and expected them to be (Ref. 11).

The detection mechanism of Blondlot’s experiment had an unfortunately large subjective aspect, that of visually distinguishing a very feeble illumination, literally on the threshold of detection. Could Blondlot’s strong expectation to see the string glow really manifest in his perception, so that he really saw a glow when none were present? Many have come to this conclusion.

In the case of Blondlot, perhaps the expectation came from his considerable investment in his own hypothesis, or was reinforced by his lab assistants not wanting to contradict their esteemed professor. Whatever the case, the lesson for the students is that his experimental procedure screamed out for the application of a blinded test. If Blondlot had asked his assistant to do in a controlled fashion what Wood had imposed on him, N-rays may never have seen the printed page.

There are other instructive and entertaining incidents in the annals of physics, one of which I highly recommend is the story of Martin Fleischmann and Stanley Pons' announcement of cold fusion in 1989.  The account as told in Robert Park's book Voodoo Science13 gets to the very heart of the problem: signal on the threshold of detection above noise, subversion of peer review, lack of use of control samples (what is the result if you do not use heavy water in your vessel?), and of course a wide berth for expectation bias.

The human pitfall of expectation bias is sometimes referred to as wishful thinking, and plays a role in the acceptance of many questionable beliefs including N-rays, cold fusion, ancient astronauts, claims of perpetual motion ("over unity") devices, and many alternative healing claims, to name a few.

11. Robert W. Wood, "The N-rays", Nature 70, (1904) 530-531.

"Reasons to Challenge Digital Fingerprint Evidence"

California Law Review (January, 2002)

Sir Isaac Newton failed to report absorption lines in the prismatic solar spectrum, though they would have been clearly visible with the apparatus he was using. The most likely explanation for his failure to see them is that he held theoretically based expectations that such phenomena should not exist. Because he believed they did not exist, he failed to see them, or at least to note their presence.

While Newton failed to see something that did exist, scientists of the early twentieth century saw something that did not exist. First reported by Rene Blondlot in 1903, "N-rays" appeared to make reflected light more intense. So long as they were believed to exist, the effects of N-rays were "observed" by many scientists. Of course, once it was determined that N-rays did not exist, their effects ceased to be observed.

Let us take another example, this time from the history of science. At the turn of the century, Blondlot, a physicist from Nancy, in France, made a major discovery like that of X-rays.3 Out of devotion to his city he called them N-rays'. For a few years, N-rays had all sorts of theoretical developments and many practical applications, curing diseases and putting Nancy on the map of international science. A dissenter from the United States, Robert W. Wood, did not believe Blondlot's papers even though they were published in reputable journals~ and decided to visit the laboratory. For a time Wood was confronted with incontrovertible evidence in the laboratory at Nancy. Blondlot stepped aside and let the N-rays inscribe themselves straight onto a screen in front of Wood. This, however, was not enough to get rid of Wood, who obstinately stayed in the lab asking for more experiments and himself manipulating the N-ray detector. At one point he even surreptitiously removed the aluminium prism which was generating the N-rays. To his surprise, Blondlot on the other side of the dimly lit room kept obtaining the same result on his screen even though what was deemed the most crucial element had been removed. The direct signatures made by the N-rays on the screen were thus made by something else. The unanimous support became a cacophony of dissent. By removing the prism, Wood severed the solid links that attached Blondlot to the N-rays. Wood's interpretation was that Blondlot so much wished to discover rays(at a time when almost every lab in Europe was christening new rays) that he unwittingly made up not only the N-rays, but also the instrument to inscribe them. Like the manager above, Wood realised that the coherent whole he was presented with was an aggregate of many elements that could be induced to go in many different directions. After Wood's action (and that of other dissenters) no one 'saw' N-rays any more but only smudges on photographic plates when Blondlot presented his N-rays. Instead of enquiring about the place of N-rays in physics, people started enquiring about the role of auto-suggestion in experimentation! The new fact had been turned into an artefact....

Wood, who did not believe in N-rays, also tried to shake the connection between Blondlot and his rays. Unlike the former dissenter he succeeded. To dislocate the black boxes assembled by Blondlot, Wood did not have to confront the whole of physics, only the whole of one laboratory....

It is crucial to grasp that these two adjectives ('objective', 'subjective') are relative to trials of strength in specific settings. They cannot be used to qualify a spokesperson or the things he or she is talking about once and for all. As we saw in Chapter 1, each dissenter tries to transform a statement from objective to subjective status, to transform, for instance, an interest in N-rays inside physics into an interest in self-suggestion in provincial laboratories.

"Worlds Without End"

by James Burke

Elsewhere in Europe Wilhelm Rontgen discovered X-rays in 1895, and a year later Antoine Becquerel identified radioactivity. By 1900 alpha, beta and gamma rays had been found. More were expected. In 1903 a distinguished physicist called Rene Blondlot, who was a member of the French Academy of Sciences and a senior figure at Nancy University, announced his discovery of another ray. In honour of his city he called it the N-ray.

Blondlot had found the new form of radiation while looking at the behaviour of polarised X-rays. He had seen that the new rays, which penetrated aluminium, increased the brightness of an electric spark. The rays were also refracted by a prism and it was known that X-rays could not be refracted in this way. Since the scientific community expected new rays to be found, Blondlot's work immediately attracted dozens of young graduates keen to make their name in this new field.

Within three years three hundred papers had been written on the subject, and doctoral theses were being prepared. Not only did the rays traverse material opaque to light, but, extraordinarily, they were given off by the muscles of the human body. Moreover, N-rays heightened perception and they were produced by the human nervous system particularly during intellectual exertion. Was there a relationship between the mysterious N-rays and the psyche? In 1904 Blondlot was awarded the prestigious Prix Lecomte by the Academy of Sciences.

The crucial stage in the experiment proving the existence of N-rays was the brightening of the spark, which Blondlot always insisted had to be feeble. The trouble was that nobody outside the city of Nancy could see differences in the brightness. In September 1904 an American Professor of Physics, R. W. Wood, arrived in Nancy and Blondlot demonstrated the effect for him. Wood, too, was unable to see changes in the spark. He had previously noted that with the equipment currently available the minimum natural variation to which any spark's brightness could be controlled was as much as 25 per cent. Spark brightness was obviously a dubious criterion of measurement. It was when Blondlot used a prism to refract and split the N-rays so as to show the spread of their wavelength that Wood decided to act. While his French hosts were busy in the dark, Wood removed the prism. The demonstrators continued to see the N-rays. Wood published his story the same month. No more N-rays were observed. The discipline collapsed as quickly as it had appeared.

There was never any suggestion that Blondlot was a charlatan. He and his colleagues were victims of the expectation that N-rays would be discovered and when they built instruments to see the rays, they saw them. For a short time this non-existent phenomenon resisted the most stringent tests and methods known to science.

"Distinguishing Science From Pseudo-Science"

by Barry L. Beyerstein
( Department of Psychology ~ Simon Fraser University )

Pseudoscience in Physics:

N-Rays.  One of the best-known examples of esteemed scientists acting like pseudoscientists is found in the career of the French physicist, René Blondlot, around the turn of the 20th century.  On the heels of the discovery of X-rays by the German, Roentgen, French scientists felt pressured to catch up by scoring a breakthrough of their own.  Blondlot, who already had several important discoveries to his name, believed he had observed yet another form of radiation which he named "N-rays" in honour of his institution, the University of Nancy.  Blondlot's "observations" were eventually shown by the American physicist, Robert Wood to have been the joint result of wishful thinking and some subtle distortions that normally occur in visual perception.  These visual aberrations tend to be ignored under ordinary viewing conditions but they stood out against the backgrounds of Blondlot's viewing apparatus.  The discoverers of N-Rays had allowed their hopes and expectations to colour their observations.  Unfortunately, they had failed to include a simple experimental control that would have saved them much embarrassment.  Wood made his point by surreptitiously inserting this control condition into a demonstration provided for him during a visit to Blondlot?s laboratory.  It is interesting to note that there had been a number of independent "replications" of N-rays by respected laboratories; the fact that some others had failed to find the new radiation had piqued Wood?s interest.  His exposé highlights the need for mechanized recording of data, wherever possible, to minimize the all too human tendency to ?see? what we are predisposed to see.  It is this tendency to find what we expect that makes tight experimental controls, independent replication, and careful statistical analyses an absolute necessity in all research.  If honest, well-trained scientists occasionally fall prey to such foibles, it is not hard to understand why pseudoscientists are such frequent victims.

"Pathological Physics"

 There is a very interesting article published in the October 1989 issue of Physics Today [86]  The article is titled "PATHOLOGICAL SCIENCE" and the abstract reads: "Certain symptoms seen in studies of 'N rays' and other elusive phenomena characterize 'the science of things that aren't so. ' "

The introduction to the article starts:

"Irving Langmuir spent many productive years pursuing Nobel-caliber research (see the photo on the opposite page). Over the years, he also explored the subject of what he called "pathological science."  Although he never published his investigations in this area, on 18 December 1953 at General Electric's Knolls Atomic Power Laboratory, he gave a colloquium on the subject that will long be remembered by those in his audience. This talk was a colorful account of a particular kind of pitfall into which scientists may stumble.

Langmuir begins his presentation with:

The thing started in this way.  On 23 April 1929, Professor Bergen Davis from Columbia University came up and gave a colloquium in this Laboratory, in the old building, and it was very interesting....

Langmuir then gives the details of the Davis and Barnes controversial experiment that produced a beam of alpha rays from polonium in a vacuum tube with a hot cathode electron emitter and a microscope for counting alpha induced scintillations on a zinc sulfide screen.  Then Langmuir described the results of a visit he and a colleague, C. W. Hewlett, made to Davis's laboratory at Columbia University.  With regard to the experiment Langmuir states:

And then I played a dirty trick. I wrote out on a card of paper ten different sequences of V and 0. I meant to put on a certain voltage and then take it off again.  Later I realized that [trick wouldn't quite work] because when Hull took off the voltage, he sat back in his chair??there was nothing to regulate at zero so he didn't. Well, of course, Barnes saw him whenever he sat back in his chair. Although the light wasn't very bright, he could see whether [Hull] was sitting back in his chair or not, so he knew the voltage wasn't on, and the result was that he got a corresponding result. So later I whispered, "Don't let him know that you're not reading," and I asked him to change the voltage from 325 down to 320 so he'd have something to regulate. I said, "Regulate it just as carefully as if you were sitting on a peak."  So he played the part from that time on, and from that time on Barnes's readings had nothing whatever to do with the voltages that were applied. Whether the voltage was at one value or another didn't make the slightest difference. After that he took 12 readings, of which about half were right and the other half were wrong, which was about what you would expect out of two sets of values. I said: "You're through.  You're not measuring anything at all.  You never have measured anything at all."

"Well," he said, "the tube was gassy. The temperature has changed and therefore the nickel plates must have deformed themselves so that the electrodes are no longer lined up properly."

"Well," I said, "isn't this the tube in which Davis said he got the same results when the filament was turned off completely?"

"Oh, yes," he said, "but we always made blanks to check ourselves, with and without the voltage on."

He immediately -- without giving any thought to it -- he immediately had an excuse.  He had a reason for not paying any attention to any wrong results.  It just was built into him. He just had worked that way all along and always would. There is no question but [that] he is honest: He believed these things, absolutely....

At the end of that section, Langmuir states:

To me, [it's] extremely interesting that men, perfectly honest, enthusiastic over their work, can so completely fool themselves.  Now what was it about that work that made it so easy for them to do that?  Well, I began thinking of other things. I had seen R. W. Wood and told him about this phenomenon because he's a good experimenter and doesn't make such mistakes himself very often -- if at all. [Wood was a physicist from Johns Hopkins University.] And he told me about the N rays that he had an experience with back in 1904.  So I looked up the data on N rays.[87]

Then Langmuir gave a detailed account of N rays, and how they were discovered in 1903 by a respected French physicist, Rene Prosper Blondlot, at the University of Nancy. The N-rays were supposed to be generated by a hot wire inside an iron tube that has an 1/8 inch aluminum window in it, and the rays are detected by a calcium sulfide screen which gave out a very faint glow in a dark room.  One of the experiments involved a large prism of aluminum with a 60 degree angle.  Wood visited Blondlot's lab and Langmuir recounts the following trick Wood played on Blondlot:

Well, Wood asked him to repeat some of these measurements, which he was only too glad to do. But in the meantime, the room, being very dark, R. W. Wood put the prism in his pocket and the results checked perfectly with what [Blondlot] had before. Well, Wood rather cruelly published that.[88]  And that was the end of Blondlot...

Cleveland Public Library.

Blondlot, R. (René), 1849-1930.

"N" rays: a collection of papers communicated to the Academy of sciences, with additional notes and instructions for the construction of phosphorescent screens; by R. Blondlot ... Tr. by J. Garcin ... With phosphorescent screen and other illustrations.
London, New York and Bombay, Longmans, Green, and co., 1905.

"To Err is Human"

William James

The story of the "discovery" of N-rays in France in 1903 reveals how physics, the "hardest" of the sciences, could be led astray by subjective evaluation. This "new" form of X-rays supposedly could be detected by the human eye in a nearly darkened room. The best physical scientists in France accepted this breakthrough. Within a year of its original "discovery" by Professor R. Blondlot, the French Academy of Science had published nearly 100 papers on the subject.

However, in 1904 the American physicist Robert Wood visited Blondlot's laboratory and discovered, by secretly changing a series of experimental conditions, that Blondlot continued to see the N-rays under circumstances that Blondlot claimed would prevent their occurrence. When Wood published his findings, it became clear that the French scientists had believed so strongly in N-rays that they had virtually hallucinated their existence. Good research can disconfirm theories, subjective judgment rarely does.

Simon Teague comments:

There is little, if anything, to differentiate McCarthyism and Stalinism when it come to such things as purges and informers, all for "the good of the state", but it does not follow from that, that any system which is shown to be flawed should be discarded in its entirety: like a scientific theory open to scrutiny, it should be tested and, if found wanting, revised and updated - unless it is like Blondlot's N-rays, which was  thrown away.
HYLE--International Journal for Philosophy of Chemistry, Vol. 8, No.1 (2002), pp. 5-20


by Henry H. Bauer

N-rays have been referred to innumerable times, but the best scholarly discussions are by Derek de Solla Price (1975) and Mary Joe Nye (1980).

René Blondlot, in France, at the University of Nancy (hence N-rays), announced his discovery of N-rays in 1903: a new form of radiation, emitted by both living and inanimate bodies, able to penetrate aluminum but not lead, able to be refracted by aluminum prisms as light is refracted by glass. For several years, N-rays were studied by scores of scientists in France and hundreds of papers were published. Yet scientists in other countries were not able to reproduce the radiation. An American physicist, Robert Wood, observed the experiments in Blondlot’s lab: in darkness, visual observation was used to detect on measuring scales the spots of light that N-rays produced. Surreptitiously in the darkened room, Wood removed the aluminum prism. The measurements continued to be read out as before. Evidently optical illusion was causing spots of light to be imagined at expected values along the scales. This demonstration convinced almost all the scientific community that N-rays do not exist; but Blondlot and a few others persisted in their belief that N-rays were real.

So presumably what was pathological here was a reliance on visual observation under conditions -- a darkened room -- where optical illusions readily occur. (One modern test for glaucoma is to note over what field of view one can detect flashes of light on a dark background. Anyone who has taken such a test knows that one ‘sees’ some number of flashes that are not actually there.) But Blondlot was a distinguished member of the French scientific establishment. He had been particularly praised for showing that X-rays moved at the speed of light which he had established by the same method of visual observation, in that case variations in the apparent intensity of electric sparks. Blondlot was therefore very unfortunate; but how can he be blamed for continuing to use a technique that had been so successful? "The curious error of N-rays is much more a sort of mass hallucination, proceeding from an entirely reasonable beginning" (Price 1975, p. 159).

Moreover, the facts Blondlot reported were confirmed by a number of his fellow scientists, not only in his laboratory but also elsewhere in France; which gave Blondlot good reason to think his discovery a genuine one. And early in the 20th century, Blondlot was far from alone in looking for new types of radiation. X-rays and radioactivity had been discovered just a decade earlier, and some years before that Hertz had discovered radio waves.

If pathological science is to be regarded as scientific misconduct, then there would need to be some indication that there had been willful deception, or at least quite egregious incompetence. The record does not support indictment of Blondlot on either of those scores. In point of fact, if anyone behaved unethically during this episode, it would seem to be Robert Wood, who deliberately and surreptitiously interfered with the experiments in order to deceive the experimenters; yet I know of no discussion of the case that does anything but praise Wood for his demonstration that N-rays are not real phenomena.

"Who Speaks For Science In Court?"

by Peter Huber
May 3, 1993

There's the famous episode of the N-rays in France at the turn of the century. It is the great classic in bad science -- really intriguing. It's sort of horribly fascinating to watch a René Blondlot, who had been a reasonably good scientist in his time, claim he had discovered these N-rays. The evidence mounted that there was no such thing as an N-ray -- he was, in fact, observing nothing. But year after year he developed more elaborate and comically sad reasons why N-rays were nevertheless there but only he, and nobody else, could see them.

René-Prosper Blondlot

The so-called N rays (or N-rays) were a phenomenon described by French scientist René-Prosper Blondlot, subsequently shown to be illusory.

In 1903, Blondlot, a distinguished physicist working at the University of Nancy, perceived changes in the brightness of an electric spark in a spark gap which he attributed to a novel form of radiation, naming it the N-ray, for the University of Nancy. Blondlot, Augustin Charpontier, Arsène d'Arsonval and many others claimed to be able to detect rays emanating from most substances, including the human body. Physicists Gustave le Bon and P. Audollet and spiritualist Carl Hunter even claimed the discovery as their own, leading to a commission of the Académie des sciences to decide priority.

The "discovery" excited international interest and many physicists worked to replicate the effects. However, notable physicists Lord Kelvin, William Crookes, Otto Lummer and Heinrich Rubens all failed to do so. Following his own failure, US physicist Robert W. Wood was prevailed upon to travel to France to investigate further. His thorough investigations, published in the September 29 1904 edition of Nature, showed that these were a purely subjective phenomenon, with the scientists involved having recorded data that matched their expectations. The incident is used as a cautionary tale among scientists on the dangers of error introduced by experimenter bias.

N rays were cited as an example of pathological science by Irving Langmuir.
External links and references: and references therein; Klotz, I M (year?) The N-ray affair, Scientific American

René-Prosper Blondlot (July 3, 1849 - November 24, 1930) was a French physicist, best remembered for his mistaken identification of N rays, a phenomenon that subseqeuntly proved to be illusory. Born in Nancy, France, he spent most of his early years there, teaching physics at the University, being awarded three prestigious prizes of the Académie des Sciences for his experimental work on the consequences of Maxwell's theory of electromagnetism. In order to demonstrate, in collaboration with Ernest Bichat, that a Kerr cell responds to an applied electric field in a few 10s of microseconds, he adapted the rotating-mirror method that Léon Foucault had applied to measure the speed of light. He further developed the rotating mirror to measure the speed of electricity in a conductor, photographing the sparks emitted from two conductors, one 1.8 km longer than the other and measuring the relative displacement of their images. He thus estabished that the speed of electricity in a conductor is very close to that of light. In 1903, Blondlot announced that he had discovered N rays, a new species of radiation. The "discovery" attracted much attention over the following year until Robert W. Wood showed that the phenomena were purely subjective with no physical origin. Blondlot lived the rest of his life in comparative obscurity in Nancy where he died.

"Benign Hoaxes -- Wake-up Calls to the Gullible"


Jeanine DeNoma

Based on a talk given by Dr, Barry Beyerstein at the Skeptics Toolbox in Eugene in August of 1998.

Rene Blondlot’s N-Rays

One of science’s most famous hoaxes revealed that a newly discovered form of electromagnetic radiation was in fact a figment of its discoverer and his followers imaginations.

In 1903 physicist Rene Blondlot, a member of French Academy of Sciences and an expert in electromagnetic radiation, published his discovery of N-rays in the scientific journal Comptes rendus. By the following year, more than 50 papers appeared describing the curious properties and sources of N-rays.

N-rays had quite remarkable properties. They passed through materials opaque to visible light, such as metal, wood and paper, yet were blocked by water, which transmits light. Blondlot used an aluminum prism to bend the N-rays and water-soaked cardboard to block them. N-rays were found to emanate from the sun and the typical gas burner, but not from Bunsen burners. Augustin Charpentier, a medical physicist, found that the human body emitted N-rays, especially the nerve and muscle cells. He suggested they could be used in medicine to detect the outlines of organs.

Other researchers challenged Blondlot’s right to be noted as the discoverer of this new ray. Gustave le Bon, also a physicist, wrote Blondlot to say he had discovered a similar radiation seven years earlier. P. Audollet claimed that he, not Charpentier, had been the first to find N-rays were emitted from the body; and a spiritualist, Carl Huter, challenged both Audollet and Charpentier for this credit.

Several laboratories outside of France, however, reported difficulty detecting this new radiation. One physicist having trouble was Robert Wood, a well-respected researcher in the field of optics and electromagnetic radiation from Johns Hopkins University. The British journal Nature sent Wood to France to observe Blondlot’s methods. Wood was an interesting choice because not only was he a noted physicist, he was also well-known as a showman and prankster with a wide range of interests. He had investigated spiritualists for fraud and pursued an interest in using scientific methodologies for solving crimes.

In the first experiment Wood observed, N-rays concentrated by an aluminum lens were said to brighten an electric spark if a hand was passed between the spark and the N-ray source. Wood said could not see any increase in brightness, but Blondlot attributed this to Wood’s lack of visual sensitivity. Wood noted, however, that Blondlot couldn’t correctly identify when Wood’s hand was or was not present.

In Blondlot’s second demonstration, a photographic plate, rather than the eye, was used to detect the increased brightness. Unfortunately, Wood noted, the conditions under which the plate was exposed were subject to "many sources of error." The most serious being that the plate was moved back and forth by hand for five-second exposures under first one condition and then the other. Wood pointed out that unconscious bias by the experimenter, who knew the conditions, could account for the increased exposure clearly visible on the plate subjected to the intensified N-rays. He suggested a series of blinded experiments which would eliminate this source of error. Blondlot dismissed such precautions as unnecessary.

In the third and most famous experiment, Wood was shown how an aluminum prism bent and spread the N-rays into a spectrum. Again, this was detected visually, this time by an increase in brilliancy at certain points along a strip of phosphorescent paint. Wood made a conclusive judgement about the reliability of Blondlot’s observations by surreptitiously removing the prism. Blondlot, not realizing the prism had been removed, continued to report seeing the expected changes.

Wood writes, "I was unable to see any change whatever in the brilliancy of the phosphorescent line...and I subsequently found that the removal of the prism (we were in a dark room) did not seem to interfere in any way with the location of the maxima and minima in the deviated (!) ray bundle".

After a couple lesser tests yielding similar results, Wood left the lab convinced that N-rays were "purely imaginary". Wood’s report was published in Nature on September 29, 1904. Wood carefully avoided naming Blondlot in his report, although it was widely known by researchers in the field whose lab Wood had visited.

Following its publication Blondlot was encouraged to conduct a definitive test to settle the N-ray issue once and for all. Blondlot did not respond to these requests until 1906 when he wrote,"Permit me to decline totally your proposition to cooperate in this simplistic experiment; the phenomena are much too delicate for that. Let each one form his personal opinion about N-rays, either from his own experiments or from those of others in whom he has confidence". Blondlot continued his work on N-rays until his retirement in 1909.

When Blondlot published his discovery of N-rays, the X-ray, alpha and beta "rays", and gamma rays had all recently been discovered. Scientists were primed to expect more discoveries and, initially, most embraced N-rays with excitement. Skepticism set in only when other labs were unable to repeat Blondlot’s observations. Although many French scientists helped debunk N-rays, a small group clung to their belief in the authenticity of N-rays long after the evidence warranted. Personal attachment and French nationalism seemed to motivate this belief. Some French defenders were known to claim that only Latins had the intellectual and visual "sensitivities" to detect N-rays.

N-RAYS.HTM To address the claim by Joseph that when science goes wrong that the scientistists must have committed fraud, I intend to show an instance in which the explanation was not fraud as much as self-deception:

"I want to close this presentation with some parallel examples of scientific claims that turned out to be so much nonsense. Let's go back to 1903 in France. You may have heard of this, if not it really is something you should look up. A prominent scientist - a physicist named Rene Blondlot - startled the world of science with his announcement of the discovery of N-rays. A very well respected man who had won many prizes in science and justifiably so, he was doing experiments by today's standards that were very simple - such as finding the speed of electricity in a conductor. It sounds easy today, but in those days it was a very sophisticated experiment and not all that easily done. Blondlot was in his 70s at the time when he discovered N-rays, named after the town of Nancy, where he was head of the Department of Physics at the University of Nancy."

"What were N-rays? N-rays were allegedly radiation exhibiting impossible properties emitted by all substances with the exception of green wood (wood not dried out) and anesthetized metal. (Metal that had been dipped in ether or cholorophorm did not give out N-rays!) Within a matter of six to eight months of the announced discovery of N-rays, 30 papers had come in from all over Europe confirming the existence of N- rays. Reports were published in journals despite the fact that there were many laboratories reporting failure after failure in replicating the results. Such acceptance was understandable considering that X-rays, which also exhibited unsuspected properties, were by then firmly established."

"What Blondlot had was a basic spectroscope with a prism (not glass, but aluminum) on the inside, and a thread. The narrow stream of N-rays was refracted through the prism and coming out produced a spectrum on a field. The N-rays were reported to be invisible, except when viewed when they hit a treated thread (for example, treated with calcium sulfide). They moved the thread across the gap where the N-rays came through and when it was illuminated that was reported as the detection of the N- rays."

"Before long N-rays were established as factual. Nature magazine was skeptical of the N-rays since laboratories in England and Germany were unable to find them. (Germany had just discovered X-rays the decade before and the French were annoyed that they didn't have a ray.) Nature sent an American physicist named Robert W. Wood from Johns Hopkins University to investigate. Now, I've been accused of skulduggery in my time, but what Wood did was brilliant. When no one was looking he removed the prism from the N-ray detection device and put it in his pocket. Without the prism the machine could not possibly work because it was dependent on the refraction of N-rays by the aluminium-treated prism. Yet, when the assistant conducted the next experiment he found N- rays! He swore they were there."

"When the experiment was over Wood knew it was really over. He was prepared to make his report, and when he went to replace the prism back in the machine, one of the other assistants saw him do this and thought he was actually removing it, and he decided to show Wood up. Thinking Wood had removed the prism (when he had actually put it back), he set up the experiment, could find no lines, and opened the box to show that the prism was not there and to his dismay, there it was! The whole incident blew up. Papers were withdrawn, those that were in the mail were retracted, and N-rays disappeared from the scene."

"How did this happen? How did over 30 papers get published? Not because the scientists who wrote the papers were stupid. Not because they were lying. But because they were deceiving themselves.

Dr. Blondlot was a French physicist who, in 1903, was convinced he had discovered a new type of ray, similar to X-rays. He named them N-rays after his home town of Nancy, where he worked in the university of the same name. He claimed that these rays were emitted by every material, except green wood, and believed he could generate large amounts of N rays by heating a wire and refracting the combination of rays through an aluminum prism, enclosed in the apparatus. The rays could be detected by swinging a metal filament up and down across the invisible spectrum until it glowed slightly. This glow could not be detected by instruments, but required a human's experience to confirm a positive result. Other scientists failed to repeat the experiment.


Well, things went from bad to worse as Blondlot hypothesized that Germanic and American physiology was not as sensitive as latins like himself and his Italian assistant, who found no trouble detecting the rays, and Nature magazine dispatched Dr. Robert Wood from Johns Hopkins University to observe Blondlot's technique. During a pre-demonstration examination of the instrument, Wood secretly removed the prism. Blondlot and his assistants proceeded to spend several hours repeatedly finding N-rays.

Satisfied that the rays were a delusion, Wood was caught replacing the prism, although he managed to place it inside the instrument. Wood picked up a second prism from its storage below the instrument and pretended to have removed the original. Blondlot, thinking the prism was now removed, demonstrated how its absence generated negative results by failing to find the rays for several tries. The original prism, of course, was back inside the instrument. Several of the visiting scientists had been informed of the prism's removal earlier and now knew of its replacement. The results had obviously been entirely in Blondlot's imagination, and he was very embarassed when all was revealed.

Lesson learned?

Generally, scientists prefer to have several things in place for an experiment to have high confidence: falsifiability, repeatability, independant verification, control groups, and double-blindedness. Other factors are important, but failure of these four are problematic. The N-rays ran into trouble almost immediately when only French laboratories could repeat the experiment, complicating independant verification. The experiment was falsifiable and repeatable, but it was certainly not double-blinded: the observer simply had to wave the filament around until he believed he felt a heat increase or saw a glow, but he knew in advance the ray was there somewhere, it was simply a matter of reinterpreting natural variations in perception of light and heat as evidence for their effects on the filament.

What I want to impress on readers is that neither intelligence nor education is protection from deception or self-deception: we can only avoid these types of problems in our lives by being aware of our own mental limitations, since not everybody is like Dr. Blondlot and accidentally making false claims: some people do it on purpose to our disadvantage. Awareness of this is the purpose of skepticism.

"Perceptual Fallacies"

The Blondlot Case and N-rays - famous case in which scientist Rene Blondlot announced the discovery of N-rays, which could be detected by the human eye and were emitted by metals. They apparently increased the brightness. Blondlot claimed that this type of radiation was blocked by lead. Scientists could not reproduce his results because the experiments were entirely subjective. Another scientist named Wood challenged Blondlot while participating in a test of N-rays. He told Blondlot that a lead sheet was in place when it was not, and Blondlot claimed to see the rays. Wood then placed the lead sheet in front of the source of N-rays and Blondlot claimed to see the N-rays. Blondlot's observations depended entirely on his beliefs, and were not correlated to when the sheet was actually in place.

"The Skeptic's Dictionary"

Robert Todd Carroll

René Prosper Blondlot (1849-1930) was a French physicist who claimed to have discovered a new type of radiation, shortly after Roentgen had discovered X-rays. He called it the N-ray, after Nancy, the name of the town and the university where he lived and worked. Blondlot was trying to polarize X-rays when he claimed  to have discovered his new form of  radiation. Dozens of other scientists confirmed the existence of N-rays in their own laboratories. However, N-rays don't exist. How could so many scientists be wrong? They deceived themselves into thinking they were seeing something when in fact they were not. They  saw what they wanted to see with their instruments, not what was actually there (or, in this case, what was not there).

The story of  Blondlot is a story of self-deception among scientists. Because many people have the misguided notion that science should be infallible and a fount of absolutely certain truths, they look at the Blondlot episode  as a vindication of their excessive skepticism towards science. They relish accounts such as the one regarding Blondlot and the phantom N-rays because it is a story of a famous scientist making a great error. However, if one properly understands science and scientists, the Blondlot episode indicates little more than the fallibility of scientists and the self-correcting nature of science.

Blondlot claimed that N-rays exhibit impossible properties and yet are emitted by all substances except green wood and certain treated metals. In 1903, Blondlot claimed he had generated N-rays using a hot wire inside an iron tube. The rays were detected by a calcium sulfide thread that glowed slightly in the dark when the rays were refracted through a 60-degree angle prism of aluminum. According to Blondlot, a narrow stream of N-rays was refracted through the prism and produced a spectrum on a field. The N-rays were reported to be invisible, except when viewed as they hit the treated thread. Blondlot moved the thread across the gap where the N-rays were thought to come through and when the thread was illuminated it was said to be due to N-rays.

Nature magazine was skeptical of Blondlot's claims because laboratories in England and Germany had not been able to replicate the Frenchman's results. Nature sent American physicist Robert W. Wood of Johns Hopkins University to investigate Blondlot's discovery. Wood suspected that N-rays were a delusion. To demonstrate such, he removed the prism from the N-ray detection device, unbeknownst to Blondlot or his assistant. Without the prism, the machine couldn't work. Yet, when Blondlot's assistant conducted the next experiment he found N-rays. Wood then tried to surreptitiously replace the prism but the assistant saw him and thought he was removing the prism. The next time he tried the experiment, the assistant swore he could not see any N-rays. But he should have, since the equipment was in full working order.

According to Martin Gardner, Wood's exposure of Blondlot led to the French scientist's madness and death (Gardner, 345 n.1). But were those who verified Blondlot's N-ray experiments stupid or incompetent? Not necessarily, since the issue isn't one of intelligence or competence, but of the psychology of perception. Blondlot and his followers suffered "from self-induced visual hallucinations" (ibid.).

What is the lesson from the Blondlot episode? James Randi writes: does not always learn from these mistakes. Visiting Nancy recently and speaking on the subject of pseudoscience, I discussed this example and though I was in the city that gave the name to N-rays, no one in the audience had ever heard of them, or of Blondlot, not even the professors from the University of Nancy!  --James Randi at Cal Tech


"Paradigm Builder: N Rays"

by Ian Hawkins

Rays that never were: a form of radiation discovered in 1903 that affects light sources and the human mind.

Rene Blondlot's N-Rays

In 1903, René-Prosper Blondlot was studying the polarization of X-rays, a new form of radiation recently "discovered" by a German Scientist. He was using a hot platinum filament enclosed in an iron tube. A thin aluminum window allowed radiation to escape. He found that radiation escaping his apparatus increased the luminosity of a nearby gas flame. Further investigation showed that the radiation caused a dimly illuminated screen painted with calcium sulfide to brighten visibly. He named the new radiation "N rays" for Nancy, the name of his town and the university he worked at.

Dozens of other Scientists confirmed the existence of N rays. Over 300 papers were published on the subject over the next three years. Aluminum lenses and prisms were used to focus N rays, which were stopped by thin folds of iron. Most things were found to emit N rays: iron, most metals, even human bodies. A brick wrapped in black paper and left in the sunshine became an intense, long-life emitter of N rays, although two bricks produced the same amount of radiation as a single brick. Interestingly, only specially treated metals and wood did not emit N rays. Wood, in fact, absorbed N rays.

Inexplicable and Astounding Properties

N rays themselves, like X rays, are not perceivable to the unaided eye. Most experiments used a screen painted with calcium sulfide to visualize the rays (the CaS would glow ever so slightly). Through these experiments, N rays were found to have a number of peculiar effects. They enhanced vision especially in dimly lit areas. When focused on a flame or spark, the light source glowed brighter. Loud noises made them dissipate while heat made them more effective. They even had a documented effect on the human brain!

The most tantalizing property of their complex structure was that they retained a level of exactness through wide openings not seen with normal radiation, such as visible light or X rays. For instance, a 1/8 inch hole in a pin-hole camera would cause the resulting image to be blurred by about 1/8 of an inch all over. However, N rays passing though openings and prisms separated into spectra with much greater resolution than would be expected.


The beginning of the century marked a crack-down on "unauthorized science" by the Technocracy. The American Scientist Wood was sent to France to unravel N rays and tear them, ripping and screaming, from the scientific paradigm. Some say that the choise of executioners shows how warped the humor of our once-comrades is. Wood claimed that Blondlot and his assistant saw what was not there and that the experiments worked even when Wood removed essential equipment. He even claimed that, at one point, the assistant could not see the effects of the rays when the apparatus was in working condition. He blatantly suggested that the assistant was lying and that Blondlot was deceived. Wood's debunking (Nature, 1904) led to Blondlot's madness and death. Papers on N rays were published after 1904, but they quickly trickled to nothingness. This is one of the many tragedies that lead to the entire defection of the Electrodyne Engineer Convention to the Traditions.