PSYCHICAL RESEARCH. 507 PSYCHOLOGICAL APPARATUS. most notable investigations of the society have been those conducted by Kichard Hodgson, J. H. Hyslop, and others on the 'trance medium,' Mrs. Leonora Piper, of Boston, Massachusetts. The society's most conspicuous work was the census of hallucinations, which it carried on from April, 1889, to May. 1892. The following ijuestion was asked: "Have you ever, when be- lieving yourself to be completely awake, had a vivid impression of seeing or being touched by a living being or inanimate object, or of hearing a voice — «hich impression, so far as .you could dis- cover, was not due to any external physical cause?" To this question exactly 17,000 answers were received, and a report thereon of about 400 pages was issued, embracing tabulated results and explanatory and discussional maltcr. (Pro- rccdiiir/s, vol. x. ) Of the 17,000 answers 1G84. or 9.9 per cent., were affirmative; of the 8.372 answers of men 655, or 7.8 per cent., were affir- mative; of the 8628 answers of women 1029. or 12 per cent., were affirmative. The committee announced that it could make from this report one important deduction: that between the death of a person and the simultaneous apparition of that person to another person, at a distant spot, there is some connection. The society is governed by a coiuicil of 24 members, who elect the officers and the new members. Meetings are held about once a month and are reported in the Proceedings, published montlilv. The first president was Henry Sidg- wick, who served 1882-84 and also 1888-92. The first vice-presidents were Arthur .James Balfour, W. F. Barrett. John R. Holland, Richard H. Hutton. Rev. V. Stainton Jloses. Roden Noel, Balfour Stewart, and Hensleigh Wedgewood. Other presidents have been: Balfour Stewart, 1885-87; Arthur James Balfour, 189.3; William James, 1894-95; Sir William Crookes, 1896-99; Frederic W. H. Myers, 1900; Sir Oliver J. Lodge, 1901-02. Other prominent members have been Ednumd Gurney. Lord Rayleigh. Frank Podmore, and J. J. Thomson. An American branch, estab- lished in 1895. includes in its membership .Josiah Rovce, William Romaine Xewbold. Richard Hodg- son, and J. H. Hyslop. In 1902 the English society had about 900 members, and the Ameri- can branch about 500. PSYCHOLOGICAL APPARATUS. The ap- paratus cra|)loyed in a well-equipped psychological laboratory falls into the following main divis- ions : ( 1 ) Physiological models of the sense or- gans and the brain; (2) demonstration appara- tus, for use in the lecture room before a large audience; (3) drill apparatus, for class work with students in the laboratory; and (4) re- search apparatus for the investigation of new problems, generally built, in part at least, within the laboratory. To these four classes may be added (5) certain anthropometrical instruments (see Anthropometry), such as those which measure the diameter of the pupil, or the force and steadiness of muscular action; (C) appa- ratus for the observation of the habits and faculties of the lower animals, such as a micro- scope, with special attachments for work on the protozoa ; mazes of wire or wood, to test the formation of habits in reptiles or small mam- mals: aquaria; cages, whose fastenings are de- signed to test the intelligence of their occupants; and (7) simple instrinnents for use with chll- VOL, XVI.— 33. dren or defective persons, designed to test sensa- tion, perception, feeling, action, attention. Psychological instruments proper, i.e. the pieces included in classes (3) and (4), may be divided again into two great groups, as qualita- tive and quantitative. The object of a quali- tative instrument is to demonstrate a fact. Sup- pose, e.g. that we have a black 1)ox, with ground- glass front, containing a gas-lamp, and that there are two sets of grooves behind the glass, the front set for the insertion of a black wooden shutter, and the rear set for the insertion of a second glass, colored. We light the lamp, pull up the shutter, and let the observer stare at the colored glass, which he sees through the ground- glass front. After thirty seconds we drop the shutter, and the ob.server sees, on the dark gray of the ground glass, a 'negative after-image' of the original color. If the colored glass was green, he now sees a colored patch of deep pur- ple. We have performed a qualitative experi- ment upon the vjsual after-image; we have demonstrated its existence, but we have not measured its duration, or its intensity and extent as compared with the intensity and extent of the green stimulus. Had our apparatus been so constructed that we could take these nieasire- ments, the experiment would have been quanti- tative. The instruments designed for quantitative work are of two kinds: those which furnish a direct scale-reading, and those which show the course of a bodily or mental process, with all its variations, as a function of time elapsed. In- struments of the former type are familiar to evers' one. The mercury thermometer, e.g. is a physical instrument, which allows one to deter- mine the temperature of a room by noting the point on th? scale of degrees that has been reached by the head of the colunm of mercury. Instances from psychology' would be the a-sthesi- ometer, which tells us how many millimeters apart two points must be set down upon the skin, with a given intensity, if they are to be perceived separately as two, and not run together in a single blurred perception ; the chronoscope, from the dials of which we can read olT our re- action time in units of a thousandth of a second ; and the protractor of the color wheel or color mixer, which tells us the number of degrees or half-degrees by which we have varied the com- position of a parti-colored rotating disk. In all these cases we have a scale of conventional units, from which we can read cur resilts. Instru- ments of the second type are those employed by the 'graphic method.' The essential feature of this method is that it furnishes a curve the ab- scissse of which are time imits (seconds, or fifths or tenths of seconds), while the varying heights of the ordinates show the variations of the Ijrocess under observation. The process may be bodily, as when we trace the curve of breathing, in order to see how it changes with change in our mental state: or it may be mental, as when we have recourse to the grai)hic method to record the fluctuations of attention (q.v. ). PsTcnor.oGic.L Acof.sTics. The least notice- able intensity of auditory sensation is measured by some form oi acoumeter. The stimulus is given by the dropping of a tiny hammer upon a steel bar. by the fall of a cork or pith ball upon a glass plate, etc. Either the sound is kept con- stant, and the observer notes the distance at
