In 1903, Blondlot, a distinguished physicist who was one of eight physicists who were corresponding members of the French Academy of Science, announced his discovery while working at the University of Nancy and attempting to polarize X-rays. He had perceived changes in the brightness of an electric spark in a spark gap placed in an X-ray beam which he photographed, and he later attributed to the novel form of radiation, naming this the N-rays for the University of Nancy. Blondlot, Augustin Charpentier, Arsène d'Arsonval and approximately 120 other scientists in 300 published articles claimed to be able to detect N-rays emanating from most substances, including the human body with the peculiar exceptions that they were not emitted by green wood and by some treated metals. Most researchers of the subject at the time used the perceived light of a dim phosphorescent surface as "detectors", although work in the period clearly showed the change in brightness to be a physiological phenomenon rather than some actual change in the level of illumination. Physicists Gustave le Bon and P. Audollet and spiritualist Carl Huter 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, the notable physicists Lord Kelvin, William Crookes, Otto Lummer, and Heinrich Rubens failed to do so. Following his own failure, self-described as "wasting a whole morning", the American physicist Robert W. Wood, who had a reputation as a popular "debunker" of nonsense during the period, was prevailed upon by the British journal Nature to travel to Blondlot's laboratory in France to investigate further. Wood suggested that Rubens should go since he had been the most embarrassed when Kaiser Wilhelm II of Germany asked him to repeat the French experiments, and then after two weeks Rubens had to report his failure to do so. Rubens, however, felt it would look better if Wood went, since Blondlot had been most polite in answering his many questions.
In the darkened room, Wood secretly removed an essential prism from the experimental apparatus, yet the experimenters still said that they observed N-rays. Wood also secretly replaced a large file that was supposed to be giving off N-rays with an inert piece of wood, yet the N-rays were still "observed". His report on these investigations were published in Nature, and they suggested that the N-rays were a purely subjective phenomenon, with the scientists involved having recorded data that matched their expectations. By 1905, no one outside of Nancy believed in N-rays, but Blondlot himself is reported to have still been convinced of their existence in 1926. Martin Gardner, referencing Wood's biographer William Seabrook's account of the affair, attributed a subsequent decline in mental health and eventual death of Blondlot to the resulting scandal, but there is evidence that this is at least some exaggeration of the facts.
The incident is used as a cautionary tale among scientists on the dangers of error introduced by experimenter bias. More precisely, patriotism was at the heart of this self-deception. France had been defeated by the Germans in the Franco-Prussian War in 1870, and after the major discovery by Wilhelm Röntgen of the X Ray the race was on for new discoveries.
N-rays were cited as an example of pathological science by Irving Langmuir. However, the case is far more interesting than a single event, because nearly identical properties of an equally unknown radiation had been recorded about 50 years before in another country by Carl Reichenbach in his treatise Researches on Magnetism, Electricity, Heat, Light, Crystallization, and Chemical Attraction in their relations to the Vital Force in 1850, and before that in Vienna by Franz Mesmer in his Mémoire on the Discovery of Animal-Magnetism in 1779. It is clear that Reichenbach was aware of Mesmer's work and that researchers in Paris working with Blondlot were aware of Reichenbach's work, although there is no proof that Blondlot was personally aware of it.
A park in downtown Nancy is named after Blondlot. He left his house and garden to the city which transformed it into a public park. This can be seen as appropriate since he made significant contributions to physics before the N-ray debacle. James Randi reported that many citizens of Nancy and members of the faculty at the university did not remember having heard about N-rays or of Blondlot.
See also 
- List of experimental errors and frauds in physics
- Pathological science
- Scientific misconduct
- List of topics characterized as pseudoscience
- Lagemann, R.T. (1977). "New light on old rays: N rays". American Journal of Physics 45 (3): 281–284. Bibcode:1977AmJPh..45..281L. doi:10.1119/1.10643.
- Prosper-René Blondlot (1905). 'N' Rays. translated by Garcin, J. London: Longmans, Green & Co.
- Carroll, R.T. "The Skeptic's Dictionary".
- Guilleminot, H. ""N" rays do not influence the resistivity of selenium nor modify the influence of light upon that resistivity". Archives d'électricité médicale: 243–244.
- Klotz, I.M. (May 1980). "The N-Ray Affair". Scientific American: 130.
- Comptes rendus de l'Académie des sciences: 884–885. 11 April 1904.
- Wood, R.W. (29 September 1904). "The N-Rays". Nature 70 (1822): 530–531. Bibcode:1904Natur..70..530W. doi:10.1038/070530a0. "After spending three hours or more in witnessing various experiments, I am not only unable to report a single observation which appeared to indicate the existence of the rays, but left with a very firm conviction that the few experimenters who have obtained positive results, have been in some way deluded. A somewhat detailed report of the experiments which were shown to me, together with my own observations, may be of interest to the many physicists who have spent days and weeks in fruitless efforts to repeat the remarkable experiments which have been described in the scientific journals of the past year."
- Martin Gardner (1957). Fads and Fallacies in the Name of Science. New York: Dover Publications. p. 345.
- Revue Scientifique. Series 5 2 (22).
- "Parc Blondlot, Nancy".
- James Randi (1982). Flim-Flam! Psychics, ESP, Unicorns, and Other Delusions. Unknown parameter
Further reading 
- Ashmore, M. (1993). "The Theatre of the Blind: Starring a Promethean Prankster, a Phoney Phenomenon, a Prism, a Pocket, and a Piece of Wood". Social Studies of Science 21 (1): 67–106. doi:10.1177/030631293023001003.
- http://skepdic.com/blondlot.html and references therein
- Klotz, I M (May 1980). "The N-Ray Affair". Scientific American: 130.
- 50, 100 and 150 years ago, Feb 2004 pg 14, Originally reported in Feb 1904 Scientific American
- Seabrook, William (1941). Doctor Wood, Modern Wizard of the Laboratory. New York: Harcourt, Brace and Company.- See especially Chapter 17, "Wood as a Debunker of Scientific Cranks and Frauds"
- The Rise and Fall of N-Rays
- Randi at Caltech: A report from the Paranormal Trenches, Skeptic vol. 1, no. 1, Spring 1992, pp. 22–31.