Manual of mental and physical tests : a book of directions compiled with special reference to the experimental study of school children in the laboratory or classroom / by Guy Montrose Whipple.
- Guy Montrose Whipple
- Date:
- 1910
Licence: In copyright
Credit: Manual of mental and physical tests : a book of directions compiled with special reference to the experimental study of school children in the laboratory or classroom / by Guy Montrose Whipple. Source: Wellcome Collection.
450/566 page 424
![A. ILLUSORY WARMTH—RESISTANCE-WIRE METHOD Apparatus.—Stop-watch. Special warmth-tester; The warmth-tester consists of a wooden box, open at the end facing E, and provided, on the top, with porcelain sockets for four electric lamps, wired in multiple, and with a snap switch by which the current (105-110 volt, D. C.) may be turned on or off. The wiring is purposely left visible, and leads conspicuously from the lamps to a coil of No. 24 German-silver wire, 1 m. long, which is wound, without covering, about a flat piece of hard rubber, 3 X 10 cm. This resistance coil is fastened to the front of the box, in such a manner that it may be easily reached by S, without exposing his fingers to the warmth of the lamps on the top of the box. A concealed cir- cuit leads to a noiseless switch, underneath the box, which can be operated by E without S’ s knowledge. By means of this switch, E may shunt the current through the coil, or cut the coil out entirely, without affecting the illumina- tion of the lamps.1 Preliminaries.—Find an arrangement of lamps such that, when the current passes through the coil, warmth becomes perceptible in 8 to 10 sec. Four 8-C. P. carbon-filament lamps generally prove satisfactory. If necessary, use one or more 16 C. P. lamps. A more powerful illumination, with the same heating effect in the coil, may be secured by the use of tantalum or of tungsten lamps. Method.—Give S the following instructions: “I want to test your ability to perceive warmth. Hold this coil of wire gently between your thumb and two fingers, like this [illustrating]. You will see that the coil is connected with these electric lamps, so that, when I light them, a current of electricity can flow through the coil and warm it—it is made of German-silver wire, and offers a slight resistance to the current. There is nothing at all to be afraid of. You can’t feel any shock from the current, nothing but a slight warmth. Watch carefully, and, the moment that you feel warmth, say 'now.’ ” Without attracting S’s attention, close the secret coil-switch, so that no current passes through the coil. After a preliminary ‘ready,’snap the lamp-switch rather ostentatiously; start the stop- watch at the same instant, and lean forward in an attitude of expectancy, keeping one hand on the lamp-switch, as if awaiting 1 In default of a 110-volt circuit, a resistance-wire apparatus may be contrived with a battery, after the plan described by Seashore, though the absence of the illuminated lamps alters the experimental conditions.](https://iiif.wellcomecollection.org/image/b28083179_0450.jp2/full/800%2C/0/default.jpg)
