104 Dr. G. Gore on the Relation of Volta 



electromotive force of amalgamated zinc in a solution of zinc 

 sulphate by increase of pressure of about two thirds of an atmo- 

 sphere, and observed that it was in any case less than one 

 400,000th of that of one Darnell's cell, = about -0000028 volt 

 (compare exp. 63). He apparently failed to discover the 

 phenomenon of the current by not happening to select a 

 suitable electrolyte. 



General Results. 



On examining Tables I., II., III., and IV. various facts 

 may be observed : — 1st. Currents were produced by using a 

 large variety of metals as electrodes, and by employing various 

 kinds of electrolytes. 2nd. The results varied both with the 

 land of liquid and with that of metal. 3rd. In every one of the 

 cases in which the liquid employed was a diluted acid alone no 

 current was observed, and the addition of a salt to the acid 

 appeared to have no effect unless the salt alone gave a current 

 (compare exps. 19, 20, 24, 45). 4th. Out of 91 experi- 

 ments 41 gave perceptible currents ; probably in many other 

 cases currents were produced, but were too feeble to be 

 detected. 5th. Out of the 41 cases in which a current 

 occurred, in 39 it was in an upward direction and in 2 

 downward. 6th. The current continued many hours without 

 sensible diminution. 7th. In every case the current was 

 extremely small, and required a few minutes to attain its 

 maximum amount. 8th. It was much smaller with a dilute 

 solution than with a concentrated one. 9th. The largest 

 current occurred with zinc in a solution of CI and KC1, prob- 

 ably in consequence of the great chemical energy of the 

 combination and the small amount of resistance. 10th. By 

 adding to a solution of CI some KC1, or to one of Br some 

 KBr, a larger current was obtained than with either liquid 

 singly, probably in consequence of diminution of resistance. 

 11th. Solutions of iodides frequently gave smaller currents 

 than those of bromides, and bromides less than chlorides ; 

 there are, however, numerous exceptions to this statement. 

 And 12th. Vibration of the lower electrode by means of a 

 tuning-fork had no apparent effect upon the maximum 

 current. 



Influence of Equal Pressure at the two Electrodes, 



In order to ascertain whether the current was produced 

 during the absence of any difference of pressure at the two 

 electrodes, I employed one of the usual tubes, 3 metres high, 

 having a porous biscuit-ware diaphragm ^ inch thick near 



