164 



Br. J, Burdon-Sandemm 



[June 9, 



that the left lobe is excite-i. The experiment consists in this : By 

 the electrodes near r, an induction shock passes throngh the right 

 lobe. Apparently at the same moment the electrometer, which is in 

 relation witii the 'opposite lobe, responds. I sav apparently, beeanse 

 in reality we know that the response does not begin until about yfg- 

 of a second later. We prove this by a mode of experimentation 

 which is of too delicate a nature to be repeated here. I will explain 

 the mode of action of the instrument used, by a diagram (Fig. 9) 

 which represents a pendulum in the act of swinging from left to 



Fig. 9. 



Diagram oi me pcniuiuin-inc'.'iomt:. Aj, Aj. and A', are the kevs referred to. 

 I. " " " '^ resent respectirelT the primary and secondary coils of the inductorium. 

 T. . ranometer, battery, &c., vrill be easily recognised. 



right. As it does so, it opens in succession three keys, of which the 

 first is interpolated in the primary circuit of the induction apparatus 

 which serves to excite the leaf; the second breaks a derivation wire 

 which short-circuits the electrodes, so that, so long as it is closed, no 

 current passes to the galvanometer, which in this experiment takes 

 the place of the electrometer ; while the third breaks the galvano- 

 metric circuit Consequently the opposite surfaces of the leaf are 

 in c<jmmunication with the galvanometer only between the opening 

 of the sec^jnd and third keys. These three keys can be plaiced at 

 any desired distance from one another. If they are so placed that 

 the galvanometer circuit is closed y^ of a second after excitation, 

 smd opened ^hj ^^ ^ second, and it is foimd that there is no effect, 



