14 THE POPULAR SCIENCE MONTHLY. 



Guppy's flight, who glories in being so completely unfettered by 

 scientific prejudices as to be free to swallow anything, however pre- 

 posterous and impossible in the estimation of scientific men, that his 

 belief in " spiritual " agencies may lead him to expect as probable. 



If time permitted, it w^ould be my endeavor to show you, by an his- 

 torical examination of these marvels, that there has been a long suc- 

 cession of ejiidemic delusions, the form of which has changed from 

 time to time, while their essential nature has remained the same 

 throughout ; and that the condition which underlies them all is tJie 

 subjection of the mind to a dominant idea. There is a constitutional 

 tendency in many minds to be seized by some strange notion which 

 takes entire possession of them ; so that all the actions of the individ- 

 ual thus " possessed " are results of its operation. This notion may 

 be of a nature purely intellectual, or it may be one that strongly inter- 

 ests the feelings. It may be confined to a small group of individuals, 

 or it may spread through vast multitudes. Such delusions are most 

 tyrannous and most liable to spread when connected with religious 

 enthusiasm: as we see in the dancing and flagellant manias of the 

 middle ages ; the supposed demoniacal possession that afterward be- 

 came common in the nunneries of France and Germany ; the ecstatic 

 revelations of Catholic and Protestant visionaries; the strange per- 

 formances of the Convulsionnaires of St.-Medard, which have been 

 since almost paralleled at Methodist " revivals " and camp-meetings ; 

 the preaching epidemic of Lutheran Sweden, and many other out- 

 breaks of a nature more or less similar. But it is characteristic of 

 some of the later forms of these epidemic delusions that they have 

 connected themselves rather with science than with religion. In fact, 

 just as the performances of Eastern magi took the strongest hold of 

 the Roman mind when its faith in its old religious beliefs was shaken 

 to its foundations, so did the grandiose pretensions of Mesmer who 

 claimed the discovery of a new force in Nature, as universal as gravi- 

 tation, and more mysterious in its effects than electricity and magnet- 

 ism find the most ready welcome among skeptical votaries of novelty 

 who paved the way for the French Revolution ; and this pseudo-scien- 

 tific idea gave the general direction to the doctrines taught by Mes- 

 mer's successors, until, in the supposed " spiritualistic " manifestations, 

 a recurrence to the religious form took place, which, I think, may be 

 mainly traced to the emotional longing for some assurance of the con- 

 tinued existence of departed friends, and hence of our own future ex- 

 istence, which the intellectual loosening of time-honored beliefs as to 

 the immortality of the soul has brought into doubt with many. 



I must limit myself, however, to this later phase of the history, and 

 shall endeavor to show you how completely the extravagant preten- 

 sions of mesmerism and odylism have been disproved by scientific in- 

 vestigation ; all that is genuine in their phenomena having been ac- 

 counted for by well-ascertained physiological principles; while the 



