284' Mr. Mullins's Observalioiis on the 



forded a free passage to the electric fluid, I concluded that my 

 object would be fully attained by their employment in the vol- 

 taic circuit. I accordingly prepai'ed a very thin calf's bladder, 

 and having placed in it a coil of thin sheet copper, with a small 

 quantity of solution of sulphate of copper, I immersed both in 

 an earthenware pot containing a cylinder of zinc fitting close 

 to its inner surface, and distant from the surface of die copper 

 an inch and a quarter, and a sufficient quantity of diluted sul- 

 phuric acid, in the proportion of 5 of the acid to 100 of water ; 

 and on testing the power of this battery with the voltameter, I 

 found that the first deflection suffered very little diminution 

 for several hours, though I had made no alterations in the 

 fluids used, nor in any way disturbed the arrangement (in this 

 experiment the pot used was only two and a half inches in 

 diameter and three deep). In a second experiment, made 

 with the same battery and with the same solutions, having 

 connected it with an electro-magnet of the horse-shoe form, 

 four inches in length and five eighths in diameter, the mag- 

 net sustained SO lbs. attached to the keeper for three hours. 

 Having thus proved the possibility of obtaining a continuous 

 and equally powerful current for a long period, it next be- 

 came a question whether the power could not be still further 

 increased and prolonged by the use of other conducting li- 

 quids in contact with the same quantity of metallic surface ; 

 and after a long course of experiments upon the nature of che- 

 mical action on metals in voltaic connexion, and the compara- 

 tive effects of different electrolytes of different degrees of 

 strength, — the results of which I consider sufficiently important 

 to form the subject of another paper, — I found that of the va- 

 rious acid, alkaline, and saline solutions tested, muriate of 

 ammonia in the proportion of 5 parts of the saturated solu- 

 tion to 100 of water, gave me the best conducting fluid, com- 

 bined with the least injurious action on the zinc surface ; in 

 fact, so slight that, after several days of constant action, the 

 zinc plate, which was amalgamated, was scarcely corroded or 

 reduced in thickness. 



It next became important to examine what connexion ex- 

 isted between the power produced and the distance between 

 the zinc and copper; and it appeared natural to conclude that 

 tlie more remote the surface of the copper from that of the 

 zinc, the less would be the effect produced on completing the 

 circuit ; but, as I was aware that great diversity of opinion ex- 

 isted upon this subject, with the view of fully satisfying myself 

 with respect to the best mode of construction of voltaic batte- 

 ries, I prepared an apparatus by means of which I was en- 

 abled most accurately to measure the increase or diminution 



