194 Prof. Marianini's Examinatio7i of an Experiment 



ance to this experiment, declaring it of itself demonstrative. 

 And as after such a judgement it may be believed by some 

 that I am of the same opinion, and that for this reason I have 

 been silent on the subject, I think it incumbent on me to dis- 

 cuss it in this article, which may therefore be considered as a 

 continuation of the foregoing memoir 4th. 



The experiment now under consideration is that in which, 

 by agitating with a feather the liquid in which are immersed 

 the zinc and the copper of a voltaic pair, the electric current 

 is strengthened. And to explain such increase of strength. 

 Professor Faraday observes that the neutralized acid stratum 

 adhering to the zinc is removed, the acid stratum in contact 

 with it is renewed, and thence the chemical action acquires 

 new force. 



By stirring with a feather the liquid in which the voltaic 

 pair is immersed, the neutralized acid stratum adhering to the 

 zinc is removed when the electromotor has been a short time 

 in action ; but when the electric current operates for some 

 time, half an hour, for example, the greater part of the neu- 

 tralized acid stratum remains still adhering to the zinc, not- 

 withstanding the agitation of the liquid. I will suppose, then, 

 that an experiment is here treated of in which the circuit is 

 completed only for a few minutes, in which case, by this agi- 

 tation, the neutralized acid stratum covering the zinc is in 

 great part removed. 



By means of the above-mentioned operation, if it is per- 

 formed when the electric circuit is interrupted, the current is 

 considei'ably strengthened when the circuit is again completed; 

 but whenever the circuit is completed many times, and espe- 

 cially when the liquid is water, acidulated or strongly saline, 

 the liquid may be agitated with a feather as much as may be 

 desired, since the electric current does not acquire more 

 strength, as is shown by the constantly decreasing deviation 

 of the galvanometer. And this is very natural, since if on 

 the one hand, the agitation of the liquid removes some of the 

 neutralized acid stratum from the surface of the zinc, the elec- 

 tric current causes it to adhere again, and probably in greater 

 quantity than the agitation of the liquid subtracts. It is other- 

 wise, if, instead of stirring the liquid with a feather, the sur- 

 face of the zinc is lightly scraped with the angle of a plate of 

 glass; since, in that case, detaching from the metal more neu- 

 tralized acid than that which the current causes to adhere to 

 it in the same time, the electric current is in a degree visibly 

 strengthened. But here it is said that the current is strength- 

 ened by agitating the liquid with a feather ; we will therefore 



