1901.] on the Besponse of Inorganic Matter to Stimulus. 629 



intensity of response is very much modified by the effect of varying doses 

 of chemical reagents. For example, with a *25 per cent, strength ot potash 

 solution, the response was 57 divisions ; but the increase of this strength to 

 *75 and upwards completely abolished all response. 



3. It may be urged that the electro-motive effect is due in some way to 

 (1) the friction of the vibrating wire against the liquid, or (2) some unknown 

 surface action at the point in the wire of the contact of liquid and air surfaces. 

 It is, however, to be remembered as regards (1), that the amount of this fric- 

 tion is exceedingly small ; the movement of the wire at the lower fixed end 

 being zero, that at the upper end is through an angle of about 180°. (2) 

 Variation of surface, similarly, must be almost non-existent under the arrange- 

 ments adopted for experiment. 



Both these questions may, however, be subjected to a definite and final 

 test. When the wire to be acted on is clamped below, and torsional vibration 

 is imparted to it, a strong molecular disturbance is produced. If now it be 

 carefully released from the clamp, and the vibration repeated as before, there 

 could be little molecular disturbance due to torsion of the wire, but the 

 liquid friction and surface variation, if any, would remain. The effect of any 

 slight disturbance outstanding owing to shaking of the wire would be relatively 

 very small. 



We can thus determine the effect of liquid friction and surface action by 

 repeating experiments with and without clamping. In a tin wire cell (with 

 interposed external resistance equal to 1,000,000 ohms), the wire A was sub- 

 jected, to a series of vibrations through 180°, and a deflection of 210 divisions 

 was obtained. A corresponding negative deflection resulted on vibrating the 

 wire B. Now A was released from the clamp, so that it could be rotated 

 backward and forward in the water by means of the handle. On vibrating 

 the wire A no measurable deflection was produced, thus showing that neither 

 water friction nor surface variation had anything to do with the electric 

 action. The vibration of the still clamped B gave rise to the normal strong 

 deflection. 



As all the rest of the circuit was kept absolutely the same in the two 

 different sets of experiments, these results conclusively prove that the electro- 

 motive variation is solely due to the molecular disturbance produced by 

 mechanical vibration in the acted wire. 



The question of surface action again can be finally disposed of if we take 

 a cell (with external high resistance) and tilt it backwards and forwards. 

 This will produce a great surface variation, yet little or no current will be 

 detected. But vibration of the wire will produce the normal strong response. 



The same strong response is obtained, further, when the air surface is 

 completely abolished, vibration being communicated to a completely^immersed 

 wire by means of an ebonite clip-holder. 



A new and theoretically interesting molecular voltaic cell may thus be 

 made, in which the two elements consist of the same metal. Molecular dis- 

 turbance is in this case the source of energy. A cell once made may be kept 

 in working order for a considerable time by pouring in a little vaseline to 

 prevent evaporation of the liquid. 



I shall now proceed to describe in detail the response curves 

 obtained with metals, and as a substance which gives good results 1 

 shall take tin. The records given in this paper were obtained, some 

 by following the galvanometer deflection with a pencil, others by 

 direct photography, and have been exactly reproduced. The gal- 



