OF ARTS AND SCIENCES. ' 163 



second or less), the battery seems to regain almost instantly its origi- 

 nal electromotive force. Indeed, it is evident from the numbers given 

 ill Tables I., II., III., IV., and V., that the polarization — which, as is 

 well known, increases and diminishes m the case of any given simple 

 element with the intensity of the currents which pass through the 

 cell — must almost instantly respond to any decrease in the density 

 of the current. Of course, if a battery of water cells is short-circuited 

 for a number of seconds or minutes, the polarization slowly increases, 

 and the battery becomes " tired," and after the circuit is broken it 

 must be allowed to rest for a number of minutes, or even hours, 

 before it gets back its lost power. 



From the fact that the lines in Fig. 9 are not straight, it appears 

 that the sudden falling off in the electromotive force of the cells when 

 the circuit is closed is not wholly due to a polarization, which is at 

 every instant simply proportional to the density of the current then 

 flowing. 



We shall not discuss further the subject of polarization in water 

 cells until we have published the results of some observations made 

 with other kinds of battery. 



Jefferson Physical Laboratory, 

 Cambridge. 



