278 On measuring the relative Tension of Electric Currents. 



citing cells; batteries charged with nitrosulphuric acid or sul- 

 phate of copper are examples." 



A single })air 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 

 battery. 



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 quantity of the electri- 

 city flowing in the primary wire, we are struck with the fact, 

 that whenever the one has increased the other has diminished. 

 No matter what the other conditions may be, whether the com- 

 7nunication is made by a long wire or a short one^ whether the 

 plates are near or far apart, whenever the quantity is di- 

 minished the tension increases, and whenever the quantity in- 

 creases the termoti is diminished. 



The remarkable analogy of the ponderable elastic fluids, 

 which when their volume is diminished, or in other words 

 condensation takes place, experience an increase of tension or 

 elastic force, is here too broadly indicated to be mistaken. 



When I first saw that removing the plates to a greater di- 

 stance apart determined a given rise in the elastic force of 

 the current, for a time it appeared to me that Dr. Faraday's 

 theory of the tension being due to the affinity of the zinc for 

 oxygen must certainly be incorrect. A more extensive ac- 

 quaintance with the facts has reversed that opinion. If the 

 tension be determined by the affinity of the metal for oxygen, 

 which must be a constant force, how comes it to pass that 

 moving the plates to a greater distance apart, can cause it to 

 increase? This apparent paradox when properly understood 

 forms a fine illustration of the truth of the doctrine advanced 

 in the 5th, ?th, and 8th series of that philosopher's researches. 

 In what follows I shall therefore regard those doctrines as 

 established. 



Let us take a given pair of plates, and connect them to- 

 gether by a slender wire. We find that the quantity that the 

 plates generate is diminished, and its tension is increased ; 

 but that this has not happened either by gain of momentum 

 or inductive influence in the channel of communication, and 

 we are compelled to refer the effect to the resistance of the 

 wire, placing the plates and the electrolyte between them in 

 a state of force. If this be the action of a resisting medium, 

 we might suppose that by continually increasing it, we should 



