142 Remarks on tht Galvanic Battery. 



will gradually recede and stand as before. It appears that 

 wIk'u the .specific gravity of the 8. z. approaches saturation 

 it becomes charged with electricity like a Leyden jar or 

 prime conductor. From numerous experiments, we find 

 q. reaches its maximum when the specific gravity of the 

 s. z. is between 20° and 30° 13. However, for practical 

 purposes the battery gives essentially the same force be* 

 tween 15° and 38° 13. Below 15° 13. the conducting power 

 of the 5. z. is considerably less, and consequently the re- 

 sistance greater, and above 38° B. the resistance is again 

 increased by polarization. The conducting power of s. z. 

 was found to be essentially the same between 30° B. and 

 saturation. At 1° B. it was one-fourth, at 7° one-half 

 and at 14° three-fourths as great as for a saturated so- 

 lution. 



On the use of the negative metal in DanieWs Battery. — The 

 negative metal in Daniell's Battery isonly useful as a con- 

 ductor of the current. 



For the purpose of testing the correctness o[" this con- 

 clusion, experiments were made with the following metals 

 as the negative plate: 1, copper; 2, sheet lead ; 3, sheet 

 iron ; 4, sheet iron tinned (the ordinary sbeet tin) ; 5, sheet 

 zinc; 6, cast zinc. 



The s. c. was a saturated solution, and the 8. z. had a 

 specific gravity of 25° B. The quantity of electricity and 

 the electromotive force was found to be the same for 

 copper, lead, iron and tin. When zinc was used for both 

 the positive and negative metal, the action was somewhat 

 different. For two or three seconds alter immersion in 

 the .?. c. there was a small negative current, after which 

 the galvanometer needle was gradually deflected until it 

 indicated a quantity of electricity nearly equal to the 

 normal condition of the element. It then remained at 

 rest for a few seconds after which it receded and stood at 

 a degree indicating about one-half the quantity. The 



