Luminosity of the Magnetic Field. 271 



electric discharge in rarefied air. This peculiar luminosity was 

 only to be seen in a perfectly darkened room, and even then 

 was only visible to certain persons. Since the publication of 

 Reichenbach's elaborate investigations on this subject nume- 

 rous attempts have been made by competent observers to see this 

 luminous smoke; but ihese attempts have generally resulted in 

 failure*; and amid the few cases of success that are recorded 

 (such as by the late Professor Gregory and by Dr. Ashburner) 

 I can find no evidence that proper precautions were taken to 

 avoid the effects of imagination, of deception, or of chance. 

 It is not surprising therefore that the discovery claimed by 

 Reichenbach has been very generally discredited among scien- 

 tific men in all countries. It has, however, always seemed to 

 me very difficult to explain away the abundant, and in some 

 cases weighty, testimony which Reichenbach adduces — such as 

 the evidence of Professor Endlicher, and others in high social 

 position, who in their normal healthy condition describe these 

 appearances in minute detail, the luminosity they assert 

 springing into existence whenever the magnet was excited, as 

 if a phosphorescent cloud had suddenly been created over the 

 magnetic poles. 



Affirmative statements of this kind, however foreign to our 

 present knowledge, are surely worthy of respectful inquiry ; 

 and though my own attempts to see the glare have been en- 

 tirely unsuccessful, I prefer to think some of the necessary 

 conditions of the experiment— such as extreme sensitiveness 

 of the retina — have been absent in my case, rather than con- 

 clude from my want of success that the phenomenon has no 

 existence. 



Considerations such as these led the recently formed Society 

 for Psychical Research to appoint a Committee to repeat 

 Reichenbach's experiments with the object of testing their 

 accuracy, when a wide range of individuals were examined. 

 As a member of that Committee I have lately been present at 

 a course of experiments, where a remarkable verification was 

 afforded of the fact that, to certain eyes, a faint luminosity 

 accompanies the creation of a powerful magnetic field. The 

 evidence, so far as it goes, seems to me so absolutely unex- 

 ceptionable that I venture to ask you to place on record a 

 brief statement of the facts so far obtained. The positive 

 evidence afforded by the experiments now to be described 

 cannot be annulled by the fact that on subsequent occasions 

 the trials were, as I am informed, less successful. It is, I 



* See, for example, Dr. W. H. Stone's very careful and excellent ex- 

 periments described in the St. Thomas's Hospital Reports (1880), vol. x. 

 p. 100. 



