On the Phcenomena of the Electropkorus. 297 



I shall close my account of the phoenomena with the ex-' 

 perinients of Mr. Morgan, which 1 have reserved for the 

 last place, because it appears to me that in general his theory 

 to explain them is the most inteHigible of any. 



" Let the cover he placed upon the excited cake, con- 

 necting the cover at the same time, by any conducting sub- 

 stance, with the ground : let the connection v.ith the ground 

 be suddenly broken, and the cover raised by its glass handle. 



'•' 1. A spark will strike to any conducting body brought 

 near the cover. (See No. 13.) 



" 2. The cover will always be in the opposite state to the 

 excited cake," i. e. while removed. (See No. 13.) 



In the insulated electrophorus a pith ball electrometer 

 attached to the sole. 



" 1 . After the hand has been laid on the cover in con- 

 tact with the sole, not the least signs of electricity are dis- 

 coverable on the removal of the cover ; i. e. in the sole. 



'^ 2. The same effect is produced by connecting the sole 

 and cover with an insulated discharging-rod. 



*' 3. 7"he cover is then only charged when the commu- 

 nication between itself and the sole is continued to the 

 ground : the sole electrometer docs not separate till the 

 cover is raised : remove the cover and the pith ba'1.3 di- 

 verge ; replace the cover undischarged, they instantly close, 

 but when the cover is discharged and then replaced, ihe di- 

 vergence is continued.''' 



This is not consistent with experiments No. 9, 10, 11. 



In attempting the explanation of these plia;nomena it is 

 necessary to keep in mind that the eflfecls are of a compound 

 nature, combining the double operation of an electric, both 

 excited and charged : it will therefore be desirable to con- 

 sider the appearances separately of charged and excited elec- 

 trics ; and 111 the investigation of the first of these I avail 

 myself of the observations of Mr. Miluer, — in the second, 

 of Mr. Morgan. 



" 1. Let a plate of crown glass be placed between two 

 circular plates of brass rounded at the edges, and let the 

 whole be insulated; the lower plate on a glass stand, with 

 a brass chain to connect it, when wanted, with the table: 

 Jet another insulated stem be appended to the up|)er plate. 

 Ill the hist place, bend a piece of brass wire into such a 

 shape that it may stand perpendicularly on the ujiper plate j 

 ^nd let the ui)pcr extremity of this wire be formed mto a 

 hook, that it may at any time be removeil by a silk string 

 %vi(h()ut destroying ttie insulation of the plate." 



Observation,' — It is obvious that this disposition of the 



apparatus 



