Prosper-René Blondlot (July 3, 1849 - November 24, 1930) was a French physicist, best remembered for his mistaken identification of N rays, a phenomenon that subsequently 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 tens 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 established 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.

Little is known about Blondlot's later years. William Seabrook stated in his Wood biography “Doctor Wood”,[1] that Blondlot went insane and died, supposedly as a result of his exposure: “This tragic exposure eventually led to Blondlot's madness and death”. Using an almost identical wording this statement was repeated later by Martin Gardner, possibly without having investigated into the subject: „Wood's exposure led to Blondlot's madness and death“.[2] Note, however that Blondlot continued to work as a university professor in Nancy until his early retirement in 1910.[3] He died at the age of 81; at the time of the N-ray affair he was nearly 60 years old.


1. ^ Seabrook William: Doctor Wood, Modern Wizard of the Laboratory Harcourt Brace, New York 1941

2. ^ Martin Gardner, Fads and Fallacies in the Name of Science (Popular Science); Dover Publications, 1957, ISBN 0486203948

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

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