that N-rays were causing a small visual reaction, too small to be seen under normal illumination, but just visible when most normal light sources were removed and the target was just barely visible to begin with. N-rays became the topic of some debate within the science community. After a time, American physicist Robert W. Wood decided to visit Blondlot's lab, which had moved on to the physical characterization of N-rays. An experiment passed the rays from a 2 mm slit through an aluminum prism, from which he was measuring the index of refraction to a precision that required measurements accurate to within 0.01 mm. Wood asked how it was possible that he could measure something to 0.01 mm from a 2 mm source, a physical impossibility in the propagation of any kind of wave. Blondlot replied, "That's one of the fascinating things about the N-rays. They don't follow the ordinary laws of science that you ordinarily think of." Wood then asked to see the experiments being run as usual, which took place in a room required to be very dark so the target was barely visible. Blondlot repeated his most recent experiments and got the same results—despite the fact that Wood had reached over and covertly sabotaged the N-ray apparatus by removing the prism. Other examples Langmuir offered additional examples of what he regarded as pathological science in his original speech: The Davis–Barnes effect (1929; after Professor Bergen Davis from Columbia University) Mitogenetic rays (1923; Alexander Gurwitsch and others) The Allison effect (1927; after Fred Allison) Extrasensory perception (1934), where Rhine consciously discarded contrary test results because he felt they could not be correct. Later examples A 1985 version of Langmuir's speech offered more examples, although at least one of these (polywater) occurred entirely after Langmuir's death in 1957: Water dowsing Martian canals (Observed in late 19th century and early 20th century, they turned out to be optical illusions.) Certain reported photomechanical and electromechanical effects Polywater Biological effects of magnetic fields (see magnetobiology and magnet therapy) except magnetoception Newer examples Since Langmuir's original talk, a number of newer examples of what appear to be pathological science have appeared. Denis Rousseau, one of the main debunkers of polywater, gave an update of Langmuir in 1992, and he specifically cited as examples the cases of polywater, Martin Fleischmann's cold fusion and Jacques Benveniste's "infinite dilution". Polywater Polywater was a form of water