On the PhcB7iomena of the Elect rophorus. 295 



handle, but without touching the cover, and again sepa- 

 rated from the cake, no electricity whatever is observed in 

 the cover." 



Observation. — ^This last remark is not true, as will be 

 seen by reference to experiments No. 9 and 10 : it is true, 

 indeed, that the electricity is seldom strong enough to yield 

 a spark. 



** 2. But if the cover be touched while on the cake, a 

 sharp pungent spark is obtained from it; and if at the same 

 time the sole be touched with the thumb, a very sensible 

 ehock is felt in the finger and thumb. (See No. 12 and 15.) 

 ** 3- After .this the electrophorus appears quite inactive, 

 and is said to be dead, neither sole nor cover giving any 

 sign of electricity.'" (See No. 15.) 



This «tate of 4eath or neutrality lasts,, however, but a 

 fhort time, especially in the cover, which soon occasions 

 the pith baills to diverge negatively. 



*' 4. When the cover is raised to some distance from the 

 cake (k^€!eping it parallel therewith), if it be touched v\hile 

 in this situation a smart spark flies to some distance be- 

 tween it and -the finger; more remarkably from the upper 

 side, w^iid £1111 more from its edge; which will even throw 

 off sparks iajto the air if it be not rounded off. As this di- 

 minishes the jdesircd effects, it is proper to have the edge so 

 roimd(;d. This spark is not so sharp as the former, and 

 resembi-es -ttiat from any electrified conductor." (See 

 Kg. 13.) 



Some importance seems attached to the preservation of 

 a parallel direction in elevating the cover ; but I have never 

 found any diminution of effect by removing the cover late- 

 rally, or in any other direction : I may remark, that the 

 fiensatiou occasioned by the passage of the spark is too in- 

 (distinct to enable the operator to judge satisfactorily of the 

 quality or kind of electricity. 



*' S. The electricity of the cover when thus raised is of 

 the opposite kind to that of the cake, or positive. (See 

 No. 13,) 



" 6. The electricity of the cover while lying on the cake, 

 i« the same with that of the cake, or negative. (Sec No. y, 

 11, and 14.) 



" 7. The appearances recited under the propotiitions num- 

 bered 2, 3, 4, may be repeated for a long time without any 

 sensible diminution of their vivacity. The instrument has 

 been known to retain its power undin)inishcd even for 

 nionthj. This makes it a sort of magazine of electricity, 

 and we can take off the electricity of the cake and of the 

 '1" 4 cover 



