214 THE N RAYS OF M. BLONDLOT. 



perhiips not sufficiently exc-liulotl from M. Blondlot's experiments. As 

 we have seen, however, M. Bloiidlot does not depend wholly on phos- 

 phorescent screens to observe his rays, and he remarks the difference 

 in sensitiveness of e3'es to minute changes of the intensit}^ of light, so 

 that this negative evidence is not a disproof of the existence of the 

 rays in question. On the other hand, the positive photographic evi- 

 dence afforded in the illustrations given by M. Blondlot, which does 

 not at all depend on phosphorescence, but onl}' on the brightness of the 

 little sparking device, seems to outweigh indications depending merely 

 on sight alone. 



In connection with M. Charpentier's physiological rays, it may be 

 recalled by the reader that a half century ago there was great interest 

 aroused, both in scientific and po})ulai' circles, by the accounts of the 

 so-called " odic force'' of Reichenbach. This was said to be mani- 

 fested as a luminous aureole which appeared to some observers to sur- 

 round certain persons. For some time there was a controversy 

 between those who claimed they could see it and those who certainly 

 could not see it, })ut at length the discussion disappeared from the 

 journals, and the general impression has ])een that no such thing really 

 existed. 



Some persons have thought that these new discoveries of M. Char- 

 pentier and others may in a certain sense revive the old idea of such 

 an aureole thrown out by living people, but the methods of observing 

 the new rays are evidently wholl}^ different. The physiological rays 

 now l>eing discussed can not be seen by the naked e3'e, nor do they 

 ati'ect the photographic plate or any other of the ordinary means of 

 observing light, and they are only to be distinguished indirectly by 

 the augmentation of brightness which they produce in feebly luminous 

 objects. Accordingly, however interesting it may ])e if we know 

 that the living body actually is surroiuided ))y special radiations which 

 it emits in addition to those rays of great wave length which we 

 have long known are emitted b}' every bod}', living or dead, above the 

 temperature of al)solute zero, still so long as our e^^es can not see 

 them they can hardly be supposed to belong in the category of the 

 aureole of Reichenbach. It is to be hoped that they will not, like this 

 asserted aureole, fall into scientific oblivion. 



