In 1903, Blondlot, a distinguished physicist who was one of 8 physicists who were corresponding members of the French Academy of Science announced his discovery while working at the University of Nancy 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 it the N-ray 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 exception that they were not emitted by green wood and 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", American physicist Robert Wood, who had a reputation as a popular "debunker" in the period, was prevailed upon by the journal Nature to travel to Blondlot's laboratory in France to investigate further. Wood suggested that Rubens go since he had been the most embarrassed when the Kaiser asked him to repeat the French experiments and then after two weeks he 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. He 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, published in Nature, suggested that N-rays were a purely subjective phenomenon, with the scientists involved having recorded data that matched their expectations. By 1905 no one outside Nancy believed in N-rays even as 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 an 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 were recorded some 50 years before in another country by the Baron von 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. However, this spread of nearly identical pathological science in history shows the phenomena to have greater breadth than the usually assumed patriotic self-deception.
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 citizens of Nancy and members of the faculty at the university did not remember having heard about N-rays or Blondlot.