Luminosity of the Magnetic Field. 273 



bat they declared it ivas at once obscured when these bodies 

 were held between the eyes of the observers and the magnet, 

 the absolute darkness being of course preserved continuously. 

 When the current was cut off, both the observers simulta- 

 neously exclaimed that the light had disappeared. 



The current was now at irregular intervals made and broken, 

 by means of the commutator in the next room, and the excla- 

 mations of the observers in the dark chamber noted down by 

 those who had charge of the commutator. The commutator 

 worked noiselessly ; and no indication whatever was given of 

 the moment when the current was to be put on or taken off. 

 During the experiments Mr. Smith stood near the magnet, 

 touching one of us, and remote from the curtains which sepa- 

 rated the dark from the lighter room beyond. 



After a few preliminary trials to test the arrangements, a 

 consecutive series of observations extending over an hour 

 was then made by Mr. Smith. From time to time during this 

 period the observers in the next room silently and unexpec- 

 tedly closed or interrupted the current, the intervals being 

 purposely varied from a few seconds to several minutes. In 

 this way fourteen consecutive trials were made ; and in every 

 case except one the exclamations made by Mr. Smith, such as 

 " Now I see it," " Now its gone," were absolutely simultaneous 

 with the movement of the commutator — according to the 

 unanimous report of the witnesses in the adjoining room. In 

 the one exception referred to, a delay of five seconds occurred 

 between the breaking of the current and the exclamation : 

 this, however, may easily have been due to a momentary 

 relaxation of attention on the part of Mr. Smith. The strain 

 on the attention was indeed so severe, that after the fourteenth 

 observation Mr. Smith complained of considerable pain in his 

 eyes and head and was obviously much exhausted. During a 

 succeeding half hour two or three further experiments were 

 made ; but the results were uncertain, and may, I think, be 

 fairly excluded. It may be noted that Mr. Smith and Wells 

 did not at any time appear to have unusual powers of vision 

 for the objects in the darkened room. 



It is obvious that a series of accidental coincidences be- 

 tween the act of closing or opening of the circuit and the 

 exclamation of the observer cannot explain the facts here 

 noted. As there are 3600 seconds in an hour, to hit off any 

 one right moment by pure chance would be very improbable; 

 but the chances against success increase in geometric pro- 

 gression when 14 right moments are successively hit off. The 

 probabilities against mere coincidence as an explanation are 

 therefore many millions to one. 



