462 



SCIENCE. 



[Vol. VIII., No li 



was to decide whether the method of the ' mean 

 gradations,' is applicable to the sensations of 

 brightness. This method consists in presenting 

 two disks composed of different proportions of 

 black and white (and thus, when rapidly revolved, 

 showing different shades of gray), and asking the 

 observer to regulate the amount of black and 

 white in a third disk until it was just as much 

 darker than the one as it was lighter than the 

 other : i.e., to find a gray of a mean intensity. 

 Call the intensity of the darker one x and of the 

 lighter one y, then the arithmetical mean would 

 be ?±^. But if Weber's law (which says, that 

 to produce equal differences of sensation, the dif- 

 ference in the stimuli vary proportionately to the 

 stimulus already present) is true, then yxy would 

 be the intensity that appears to be mean; i.e., 

 X : i/a;?/:: V«^y '■ V- Dr. Lehmann's study is de- 

 voted to discovering all the sources of error in 

 such an experiment. The order of the disks, 

 whether the variable disk should be between the 

 two or not ; the direction and kind of illumina- 

 tion ; the order of experimenting ; and, beyond 

 all, the effect of contrast with the back-ground 

 against which the disks were seen, — were all 

 taken into account. Dr. Lehmann succeeded in 

 measuring quantitatively the effect of contrast (a 

 very valuable result), applied a method of elimi- 

 nating its effect, but finally comes to the purely 

 negative conclusion that the question of the 

 validity of Weber's law is not favored or refuted 

 by his experiments. A real test still remains to 

 be made. His most valuable residt is the study 

 of the great effect of contrast in all such work. 



Joseph Jastkow. 



PROCEEDINGS OF THE ENGLISH SOCIETY 

 FOR PSYCHICAL RESEARCH. 

 To allay at once any feelings of expectancy 

 (which some readers may share with the writer 

 whenever the green cover of a new number of 

 these ' Proceedings ' is caught sight of) it may be 

 well to say that nothing unusually v^^onderful is 

 therein revealed. A considerable portion of the 

 number is devoted to the ' physical phenomena ' 

 connected with spiritualism. Fortunately, through- 

 out most of the discussion the subject is strictly 

 adhered to, and any theory of explanation in- 

 volving assumptions contradictory to the princi- 

 ples of physical science is considered irrevelant. 

 The issiie is, in the main, considered to be whether 

 certain strange phenomena are explicable by what 

 we know of conjuring, oaal-observation, and the 

 psychology of belief, or whether they must be 



Proceedings of the English society for psychical research. 

 Part X, Oct., 1886. London, TrUbner. 



transferred to the category of the unexplained, to 

 be reserved for future study. Can we say 'yes' 

 or 'no' to this alternative, and if not, which of 

 these answers is pointed out as the more probable ? 

 Professor Barrett opens the discussion, and at 

 once records his conviction, "that, at any rate, 

 some of the simpler phenomena of spiritualism 

 are inexplicable by any causes at present recog- 

 nized by science." This conviction is not due to 

 experience gained in the ordinary public seances ; 

 that is considered as largely fraudulent, and evi- 

 dently worthless. But attention is called to a few- 

 cases of private mediutnship, in which all the con- 

 ditions necessary for a scientific test were granted. 

 In the first of these cases, a girl of ten years had 

 the peculiar gift of causing raps to be heard, even 

 when her hands and feet were firmly held ; the 

 raps occurred at certain letters of the alphabet, 

 and displayed a childish intelligence. A word 

 "was misspelled by raps, exactly as the child 

 would have misspelled that word." Professor 

 Barrett concludes that he is ' morally certain ' that 

 hallucination, trickery, or known causes had 

 nothing to do with it, but that it belongs to a 

 ' class of phenomena wholly new to science.' A 

 case is then cited in which a clever boy deceived 

 his father (a distinguished surgeon) and all his 

 family, by pretended spu'itualistic manifestations, 

 for a whole year ; but the ' radical ' difference is 

 pointed out that in this case the trick was dis- 

 covered, in the former case it was not. Professor 

 Barrett, with another private medium, saw tables 

 move, and raps spell out 'pious platitudes,' " such 

 as the medium herself (a Methodist) would be 

 likely to concoct,"' and again considers the phe- 

 nomena as inexplicable. A seance with a paid 

 medium, Mr. Englinton, added to the mystery. 

 Whether further study will support this convic- 

 tion or not, at any rate, says Professor Barrett, 

 more light can be shed on these phenomena by 

 occasionally assuming the possibility of the spii-it- 

 ualistic stand-point ; theorizing is needed as well 

 as observation. 



The paper of Mrs. Henry Sidgwick reports an 

 unusually able investigation of the so-called spirit- 

 ualistic phenomena. It is the account of an ob- 

 server who knows how enormous the possibilities 

 of deception, of mal-observation, and how insidi- 

 ously inference usurps the place of perception. 

 Every one interested in the psychology of illusions 

 should read this admirable exposition of an inter- 

 esting chapter on that subject. 



The phenomena to be explained include raps, 

 levitation of objects, playing on musical instru- 

 ments, psycography and so on. Mrs. Sidgwick 

 speaks from a twelve years" experience with medi- 

 ums, including several of considerable fame. As 



