280 Prof. J. C. Bose. On Electromotive Wave [May 21, 



along from the other end towards N, the wire being mechanically 

 stimulated during the test. The galvanometer spot remains quiescent 

 as long as the exploring contact is over normal areas. But as soon as 

 it touches the zone on which is impressed the invisible image of 

 physico-chemical change, the differential effect of stimulus at once 

 reveals it by producing a vigorous movement of the galvanometer spot. 

 At Nj there was no movement, but there was an upward movement of 

 response when the explorer came over " Carbonate." As the explorer 

 passed on to N 2 there was a cessation of movement, but when it reached 

 the area marked " Oxalic" there was a vigorous movement downwards 

 (fig. 3). 



Interference Effects. 



I have already described a case of interference in the galvanometric 

 effect when the two points A and B in similar molecular conditions are 

 simultaneously acted on by the same mechanical stimulus. Under 

 these conditions the electric variation at the two points continuously 

 balance each other, and there is no resultant effect. 



When one point is acted on by a chemical reagent, not only is its 

 electric excitability changed, but its time relations — its latent period, 

 the time-rate of its acquiring the maximum electric variation, and the 

 recovery from the effect of stimulus — will also be modified. Using the 

 block method, we may place a drop of excitant IS^COg on A and 

 depressant KBr on B. On simultaneous vibration of A and B, the A 

 effect being relatively much stronger than B effect, the resultant would 

 be an upward deflection. But on shifting the balancing clamp away 

 from A (thus decreasing the stimulation intensity of A and increasing 

 that of B) we may find a point where the A effect is equal and oppo- 

 site to the B effect. But owing to change of time relations, simulta- 

 neous vibration of A and B will no longer give a continuous balance ; 

 instead we obtain a diphasic variation. The diphasic curve thus 

 obtained is exactly the same as the resultant curve deduced from the 

 algebraic summation of the A and B curves obtained separately. 



Continuous Transformation from Positive to Negative through an Inter- 

 mediate Diphasic Response. — In the following record, fig. 4, I succeeded 

 in obtaining a continuous transformation from positive to negative 

 phase by continuous change in the relative sensitiveness of the two 

 contacts. I found that traces of after effect due to application of 

 Na 2 C03, even after it is washed off, remain for a time, the in- 

 creased sensitiveness conferred disappearing gradually. Again, if we 

 apply Na 2 C0 3 solution to a fresh point, the sensitiveness gradually 

 increases. There is another interesting point, viz., that the beginning 

 of response is earlier when the application of Na 2 C0 3 is fresh. In the 

 experiment whose record is given, the wire is held at one end, and 

 successive uniform vibrations imparted to the wire as a whole at inter- 



