addticed bi/'Prof.Yaraday in'supporiqf'Dela'Rive's Theory. 201 



troduced between the two plates. In order that such increase 

 of level might not be sensible, I made use for the experiments 

 above described, of rather large cups, so that the two plates of 

 the pair remained distant from each other four centimetres. 



2ndly. In the second place the force of the current is in- 

 creased on the first insertion of the feather, when this being 

 wet, one of the plates is touched with it; because it is as if of 

 these plates another part was immersed in the liquid besides 

 that which is already immersed; and in this case if it is the 

 plate of copper which is touched by the wet feather, the in- 

 crease of force is much greater than when the plate of zinc is 

 touched; and this is very intelligible after what we know re- 

 lative to the voltaic pair with unequal plates*. 



The deviation of the galvanometer which indicates the force 

 of the current, decreases in some degree when the feather is 

 introduced between the two plates, and parallel to them, or 

 but little inclined ; for in this case the feather intercepts 

 part of the current, or, to speak more correctly, obliges part 

 of the current to run through a greater distance before ar- 

 riving at the other plate. 



Whenever the feather is in the liquid, but not between the 

 plates, or if it is between them, remains there so as not to in- 

 tercept the current in any great measure ; in this case, the 

 feather being withdrawn, the current itself slowly diminishes 

 in some little degree. 



Finally, when the feather has been for some minutes im- 

 mersed between the plates, and so as to cause the deviation 

 of the galvanometer to diminish in some degree, and has been 

 left there without agitating the liquid, upon withdrawing the 

 feather, or even only drawing it aside, the deviation is imme- 

 diately seen to increase an equal number of degrees, and the 

 needle to stop above that to which it pointed before the feuther 

 was placed between the plates. 



In one of such experiments, in which the liquid conductor 

 was water very slightly saline, the circuit was scarcely closed, 

 when the needle deviated eighty degrees; after an hour the 

 needle was for several minutes stationary at twenty-eight ; the 

 feather being introduced between the plates, the needle itself 

 moved to twenty-five. After a space of three minutes I re- 

 moved the feather, and the needle oscillated to thirty-three 

 and then stopped at thirty. This is an experiment at first sight 

 very singular, and for which it would be difficult to assign a 

 reason, unless it be remembered that when an electromotor 

 has lost force by the circuit remaining complete for some time, 



• Essay before quoted, §§. 129 and following. — Annahn, cjc, Oct. 1826. 



