174 



SCIENCE, 



[Vol. XII. No. 297 



The Employment of Mica in Condensers. — Most of the 

 condensers supplied for electrical measurements are made of sheets 

 of tinfoil, separated by thin layers of mica. It is important to know 

 whether the capacity of a condenser made in this way is constant, 

 or whether it varies with the duration and amount of the charge- 

 M. Klemencic has studied the specific inductive capacity of mica' 

 on which the capacity of the condenser depends. He used two 

 sheets of the mineral .5 of a millimetre and .i of a millimetre in 

 thickness respectively, making two condensers with them, and com- 

 paring their capacity with that of a standard air-condenser, using 

 different periods of charge and discharge, and different electro- 

 motive forces. The following table gives the results obtained : — 



M. Klemencic also studied a condenser of .15 microfarads capacity 

 formed of 19 sheets of mica of 15 centimetres square, with tinfoil 

 between them. In the following table the figures under i^ represent 

 the time of charge ; under t^, the period between charge and dis- 

 charge. In one case 12 Bunsen cells were used in charging ; in the 

 other, I Daniell. 



The numbers in the different columns are the ratios of the capacity 

 of a standard air-condenser to those of the mica-condenser. If we 

 take the values for /j = .3 s., and i^ = 60 s., we will have about the 

 actual case in practice, and none of the other values differ from it 

 by more than one per cent : so, if M. Klemencic's results are correct, 

 we can depend upon mica-condensers within that limit. 



MENTAL SCIENCE. 



Association by Contrast. 



M. Paulhan {Revve Sciejiiifique, Sept. i) calls attention to the 

 widespread application of the law of contrast. This law he formu- 

 lates as saying that every psychic state tends to be accompanied 

 (simultaneous contrast) or followed (successive contrast) by an 

 opposite state. An excellent instance of it in sensation is that of 

 complementary colors ; but it is equally applicable to feelings, 

 thoughts, and beliefs. A physiological homologue is shown in the 

 fact that a contraction of a muscle is not accomplished without the 

 simultaneous innervation of its antagonistic muscle. The flexors 

 are always opposing the extensors, and vice versa, and it is a prop- 

 erly adjusted opposition of the two that results in an accurately 

 co-ordinated movement. In the higher psychic states the state 

 must usually be long, and maintained with some difficulty, to have 

 the contrast appear. In all hesitation we see a balancing of op- 

 posites, each argument pro at once calling up a parallel argument 

 contra. The introduction of a new set of ideas at once arouses an 

 opposite train of familiar thoughts. Objections that at first seem 

 trivial and not worthy of attention gather force by brooding over 



them. Again : all knowledge is relative, and epithets must be 

 compared with their opposites : ' little ' suggests ' big,' and ' big ' 

 is only relative to the ' little.' People differ very much in the read- 

 iness with which they take suggestions, in the difficulty with which 

 the opposite train of thoughts arises. In hypnotism this ' contrast- 

 ing ' power is at a minimum, and very rarely does a concept sug- 

 gest its opposite. In normal natures combativeness plays very 

 variously important rSles. Morbid instances of this mode of men- 

 tal action are also to be found. Griesinger records a case of a lady 

 constantly saying just the opposite of her intentions. Some insane 

 patients personify these contrast associations into internal voices 

 controlled by rebellious spirits constantly suggesting the opposite 

 of what they ought to do. Kussmaul describes a state as dys- 

 phrasia in which the emotion is opposed to the words expressing' 

 it, and so on. All this illustrates the wide scope of this association- 

 by contraries, which same trait we recognize in its extreme moral- 

 intellectual side as contrariness. 



The principle of successive association finds an equally broad 

 field of application. Its elusory illustrations are particularly good' 

 in sight (complementary colors, after-images), but are also present 

 in taste (as when any thing tastes sour after eating sweets) and m 

 almost all types of sensations. But we can find the same law in 

 emotional states. Depression is the recognized after-effect of too- 

 jovial dissipation. In hypnotism there seems to be a definite al- 

 ternation from one emotion to its opposite, that suggestion, or, ac- 

 cording to some, the stimulation of a magnet, can excite. In fact^ 

 all such phenomena can be regarded as governed by the universal 

 law of rhythm, one state recurring at regular intervals, filled in. 

 with states of an opposite character. Sleeping and waking, in- 

 spiration and expiration, illustrate the physiological aspect of the- 

 law. Darwin brings the sentiment of remorse following upon, 

 cruelty under the same law. 



Under marked conditions such alternations of emotion are ex- 

 tremely frequent, and lie at the root of the hysterical diathesis. 

 Periodic insanity showing exaltation followed by depression, the- 

 assumption of unworthy habits by most respectable patients, pas- 

 sionate outbreaks in peaceably disposed patients, — all these are 

 not infrequent. Cases of dual consciousness are perhaps only in- 

 tensified instances of such successive contrasts. In incipient in- 

 sanity the dearest relations are often the objects of most intense 

 antipathy. 



Such phenomena of successive contrast as depend for their effect 

 upon the presence of an interval since the experience was last 

 made, are equally varied, and equally numerous. Eating after 

 long hunger, re-union after long separation, success after long: 

 struggle, enjoyment after much care, — all these give especially 

 great pleasure. Pleasures too often partaken of pale, and need the 

 spice of contrast for their relish. Again : a privation always sug- 

 gests a longing. When we are deprived of a convenience, we feel 

 the need of it most. When circumstances prevent the realizatiork 

 of our wishes, the displeasure is at a maximum : witness home- 

 sickness. The fatigue of one set of emotions brings on the opposite 

 set, perhaps ; when continued too long, any state tends to lessen 

 in intensity. Sometimes the feelings flit between sorrow and joy^ 

 and we have a curious mixture of the two, — a selfish comfort and- 

 a trying sympathy. All such considerations suggest, however 

 sketchily, the existence of an underlying psychophysic law that 

 makes the union of opposite psychic states especially significant. 



Hypnotism and Crime. — Hypnotism as an aid to crime has 

 been variously discussed in France from both the medical and the 

 legal side, with the general conclusion that legislation is needed to 

 coventhe most palpable employment of it. The fact that a hypno- 

 tized subject can take and execute a criminal suggestion made by 

 another, and yet be really innocent of any immoral intent, is be- 

 yond all doubt ; and this fact has led observers to the conclusion 

 that the blame must rest upon the giver of the suggestion. An ad- 

 ditional precaution which the true originator of the crime might 

 take would be to give a suggestion forbidding the subject to reveal 

 to any one the name of the suggester or the fact of the suggestion. 

 On the contrary, he was to say and feel that the act was committed) 

 of his own accord. This complicated the legal aspect of the ques- 

 tion very seriously ; but further experiments have shown that the 

 instigator of the crime would not be so entirely safe, after all. M. 



