AND WITH DISTANCE OF THE PLATES. 81 



wire being introduced, and the slender one taken away, the needle came again to zero. 

 But I suppose, if the long wire had impressed more tension on the current than the 

 slender one, either by momentum or otherwise, more electricity should have passed the 

 secondary wire when it was used, which is not the case. 



284. Again, I took a copper wire 242 feet long and T V inch in diameter, and adjusted 

 to it a fine iron wire as before : the extremities of this wire were tinned; it was 12? inches 

 long. Either of these wires being used as a discharger, brought the needle to the same 

 point of the scale. On using the secondary wire and the long wire together, I adjusted 

 the needle accurately to zero, and then passing the current through the fine wire and 

 secondary wire, it came again to zero. And this was repeated often, and so near was 

 the adjustment, that, when an assistant turned first one and then the other wire on, it 

 could not be told which was in action, or whether the current had come along the long 

 or the short wire. A long wire, therefore, impresses no sort of change on a current, 

 but merely serves as an obstacle ; for, in the first case, we had one wire sixteen times 

 louger than the other, and in this we have a wire more than 230 longer than the one 

 with which it is compared, yet the tension has increased only to the same amount in 

 both. 



2 So. And the same results were obtained by the voltameter. 



286. The current that flows in a simple closed voltaic circle may be resisted in two 

 ways : 1st, the length of the wire connecting the plates may be increased, as in the 

 foregoing experiments ; 2d, the connecting wire remaining of constant length, the dis- 

 tance of the plates may be increased : the result is the same in both cases, a rise of tension. 



TABLE D. 



So that, whether we obstruct the current by lengthening the connecting wire or by 

 increasing the distance of the plates, the general effect is the same, the tension imme- 

 diately rises ; that increase of tension being due to the plates themselves, and not to the 

 channel of conduction. This brings us to the third proposition, 



287. " That there are two different methods of accomplishing these disturbances, and 

 thereby of raising the elastic force of a current. 1st. That tension may be augment- 

 ed by the sacrifice of quantity ; VOLTA'S plan of a reduplicated series, and HENRY'S rib- 

 and coil in its condition of equilibrium, being examples. 2d. By the introduction of 

 new affinities in the exciting cells ; batteries charged with nitrosulphuric acid or sul- 

 phate of copper are examples." 



288. A single pair of plates, under the influence of a long wire, or the spiral coil, 

 presents a remarkable analogy to Volta's pairs arranged in reduplicated series. In point 

 of fact, they may be considered as scarcely differing from each other either in mode of 

 action or in effect The study of the single pair under this condition reveals at once 

 the theory of the voltaic action. 



289. If we inspect tables B, C, D, we are at once furnished with the fundamental 

 fact which is the basis of explanation. When we compare together the tension and 



L 



