256 Mr. J. Prideaux on the Theory of Voltaic Action. 



The plates being dipped in water, to remove any foreign 

 material, or fugitive impression at the first contact with 

 moisture, the ends of the wires were connected with a multi- 

 plier, and the plates plunged into H, — Deflection . . 40° 



Left in H until the needle had receded to ... . 25°, 



Then taken out and plunged into G, — Deflection . 40°. 



As the plates occupied only the middle of the glass, and 

 the backs were varnished, it was probable that but little of the 

 charge, perhaps only the part immediately between the faces 

 of the plates, had suffered electrical change. The needle was 

 therefore allowed to recede to 28°, when the plates were lifted 

 out and replaced in the same liquid, — Deflection . . 38°, 



but unsteady. After receding to 30°, 



removed to H, — Deflection again . 40°. 



After receding to 20°, taken out and replaced, — Deflec- 

 tion 40°, 



but receded quickly. 



Washed and placed in G, — Deflection 42°. 



Taken out, washed, and left all night in the air. In the 



morning plunged into H, — Deflection 42° : 



So that washing produced the same deflection as hanging all 

 night in the air. 



Receded in 15 minutes to 20°. 



37. It then became a question whether the mere disconti- 

 nuance of electromotion, without moving the plates, might 

 not allow the reaction of the natural affinities, and thus restore 

 the action. 



The needle having fallen back, as above stated, to . 20°, 

 the connexion through the multiplier was severed. Re-con- 

 nected after 10 minutes 42°, 



but fell back, in 10 minutes connexion, to 18°. 



Disconnected 5 minutes ; on re-connexion .... 30°. 



Again disconnected 10 minutes; on re-connexion . 30°. 

 The face of the copper covered with small bubbles ; doubt- 

 less hydrogen gas. Detached 2 minutes to wipe away the 

 bubbles with a feather, — Re-connected 35°. 



The plates had now continued two hours and a half in the 

 solution, and the zinc was black with suboxide; yet simply 

 washed and placed in H, — the Deflection was . . . 37°. 



It is unnecessary to occupy more space with the further 

 variations of this experiment, all which give the same result. 



38. But one circumstance must not be passed over. Hang- 

 ing in the air two or three hours gave a deflection of 45°, 

 which fell back to 35° so rapidly as to allow only time for 

 turning to the desk and writing the figures ; whilst remaining 



