of Electricity in Voltaic Combinations, 283 



which is about five inches high, and is surrounded by a zinc 

 cylinder one fourth of the surface of the copper*, the needle 

 will be deflected to an angle of, say 75°: now, if we remove the 

 first cylinder of zinc and substitute another of twice its surface, 

 we shall find no increased deflection, and therefore no increase 

 of quantity. In like manner, if we go on enlarging the zinc 

 surface until at length it equals that of the copper, the indica- 

 tion of the needle will still be the same, and this though we 

 have added a large proportion of the two solutions for the pur- 

 pose of bringing the entire zinc and copper into contact with the 

 fluids. So far I agree with Mr. Daniell, who also uses small sur- 

 faces of zinc ; but in prosecuting this experiment it will appear 

 that I differ as much from that gentleman's conclusions, if he 

 says that a thin wire of zinc, or a piece of ^inc reduced to the 

 smallest proportions, will produce no diminution of power, as 

 in the former part of the same experiment 1 differed from 

 Marianini, who asserted that the copper should be at least 

 eight times the surface of the zinc in order to produce the 

 maximum effect; for if instead of increasing the zinc surface 

 we now reduce that which was first used, the needle will then 

 diminish its angle and go on retrograding in proportion as the 

 zinc is reduced, thus showing that there is a certain propor- 

 tion between the zinc and copper surfaces which produces the 

 greatest power. Again, with an electro-magnet of sufficient 

 size, the battery described, when in proper order, will lift two 

 hundred weight; add the larger zincs until you bring the sur- 

 faces equal ; the lifting power is no greater than at first. Again, 

 take one of my intensity-sustaining batteries, which consists of 

 three zinc and three copper cylinders one within the other; apply 

 this instrument to the magnetic voltameter, which will give an 

 angle of 86° ; then apply it to Faraday's decomposition volta- 

 meter, and the quantity of the gases produced will be found 

 to be exactly the same, whether the small cylinders of zinc be 

 used or larger ones equal in surface to the copper, and the 

 needle will indicate no greater deflexion in the one case than 

 in the other. Fully convinced, therefore, by the results of 

 these and many other experiments too numerous to detail here, 

 that zinc plates or cylinders about one fourth of the surface 

 of the copper, produce fully as great an effect as if the surfaces 

 were equal, I strongly recommend any student of this branch 

 of science, if he still has any doubts as to the correctness of my 



• It may be well to observe that in charging this battery I use two fluids : 

 one consisting of 1 part of saturated solution of muriate of ammonia to 4 

 of water, in contact with the zinc ; the other, a saturated solution of sul- 

 phate of copper, in contact with the copper; a bladder, or what is better, i£ 

 properly managed, white silk, being interposed between the metals. 



2 O 2 



