X. SPECIAL COLLECTIONS. 



The instrument consists of a horizontal cylinder, which, on being turned by 

 the hand, moves in a spiral. The cylinder is covered with smoked paper, 

 upon which a tuning fork with 250 vibrations per second, to be struck by a 

 percussion hammer, registers its vibrations by means of a small .steel spring. 

 This tuning fork can slide and rotate on an axis by which it is suspended. 



Without any further complication, the cylinder with tuning fork is sufficient 

 for experiments with the simplified phonautograph, whose spring registers its 

 vibrations next to those of the tuning fork. Two persons A. and B. sit before 

 the phonautograph. A. shouts a short vocal sound, B. repeats it as quickly 

 as possible ; on the line registered by the spring the instants of the shouting of 

 the sound by A. and B. are visible, and the time can be read on the adjoining 

 chronoscopic curve. The experiments to be made are : a. B. knows which 

 vocal A. will produce ; b. B. does not know which vocal (from two, three, or 

 more) A. will produce ; c. B., not knowing Avhich vocal he is going to hear, 

 has to respond only upon a certain one, e.g., on a. The time for the inter- 

 vening psychical processes may be deduced from the times ascertained in the 

 experiments a, b, and c. 



For other experiments the instrument is more complicated. At one end of the 

 cylinder are two rings partly covered with copper, partly with ebonite. On 

 each ring two pair of electrodes rest ; the lower break and close a constant 

 current, the upper an induction current. The electrodes together are attached 

 by a thick glass bar to a horizontal board following the cylinder, moving in a 

 spiral, thus keeping the electrodes on the rings. The induction currents pass 

 the tuning fork. In one series of experiments only the inner ring is used (the 

 outer ring can be moved aside). On this ring quadrants of copper and ebonite 

 alternate. The electrodes rest on copper, the tuning fork is struck, the cy- 

 linder moved half a turn ; at the instant the lower electrodes leave the copper, 

 the induction current makes a hole in the paper on the chronoscopic curve, and 

 a spark is made visible without being audible, or audible without being visible, 

 or, the spark being neither audible nor visible, a shock is felt. The spark passes 

 in a little box suspended on a cross-bar between electrodes with knobs, which 

 are to be moved so far apart that the passing electricity constitutes only one 

 spark. In order to see or to hear the spark, a Leyden jar is inserted in tho 

 circuit ; the shock is felt as unipolar conduction without an inserted Leyden 

 jar. 



On the stimulus being received, it is responded to by the hand moving a 

 copper arm of a Avooden cylinder with registering spring. By this con- 

 trivance, under similar objective and subjective conditions, the physiological 

 time (the time between stimulation and response) can be determined alter- 

 nately for impressions of vision, of hearing, and of touch at various places of 

 the skin. 



A dilemma may be put. Electrodes are applied right and left on the skiL, 

 and the horizontal arm of the wooden cylinder struck in corresponding 

 direction. In a similar manner, by a conventional response, a decision may be 

 made between red and white light. In both cases response may be forbidden 

 for one colour or for stimulation on one side. Instead of responding with the 

 hand, the voice may be used acting on the phonautograph, and the physio- 

 logical time determined in both cases. On the spark passing in the box, and 

 making transparent letters visible, the physiological time for recognising 

 these letters may be registered and compared with the time for simple light 

 perception, etc. 



The second ring has only a small conducting plate, upon which, at the 

 rotation of the cylinder, the constant current is closed and broken, after con- 

 tact with the electrodes of the induction current has followed. Thus, by 

 sliding this second ring, sooner or later after the first spark, a second is 

 made to pass, perforating the chronoscopic line, and at the same time, either 



