58 Notice of Faraday s Discoveries in Electro-Chemical Decomposition. 



must not be understood as involving any adhesion to the tlieory of a single 

 fluid, but merely as affording a convenient conventional formula, which will 

 be equally a])plicable, although we consider these opposite polar forces as 

 two dastmct poivcrs, (fluid is a purely hypothetical term,) which latter view 

 is assuredly the conclusion of those who have applied to the subject the 

 highest resources of mathematical analysis. Still, however, these polar 

 powers, as they neutralise each other, may be very conveniently expressed 

 by the terms positive and negative ; and though two currents, or progres- 

 sions in oj)posite directions, of either polar force towards the pole where 

 it is manifested externally, must be implied on this hypothesis ; still we 

 may most conveniently confine onr attention to one only of these currents, 

 since to embrace both would merely double the correlative terms of our 

 formulcC, and necessarily lead to the same results. 



Mr. F. names the conducting wires attached to the poles of the electro- 

 motive apparatus, electrodes — paths of electricity. M. Ampere had before 

 proposed to call them rheophores, conductors of currents. 



If any body be made to conduct an electrical current, he calls the ex- 

 tremity of such body by which the current enters, the anode, (the way up,) 

 and that by which it issues, the cathode, (the way down.) 



By introducing into these terras the ideas of ascent and descent, Mr. F. 

 has very conveniently employed expressions which necessarily suggest the 

 great primary principle of electro-magnetism, namely, that a magnet is 

 equivalent to the axis of a circular electric current, the north pole being 

 on the left hand, and the south pole on the right hand of the direction of the 

 electric current. But we must remember, that the north and south poles, 

 as they are called, of a magnetic compass needle, are in truth opposite to 

 those of the great terrestrial magnet which attract them ; therefore the 

 north terrestrial pole (equivalent to the south pole of a magnetised needle) 

 must be dextral, and the south terrestrial pole sinistral, with reference to 

 such a current. But if we suppose an electrical current established round 

 the earth, and proceeding from east to west, in the direction of the ap- 

 parent course of the sun, (which is believed with much probability to cause 

 such a current) the north and south terrestrial poles would necessarily be 

 placed as they are placed, from the mere influence of that current. Mr. F. 

 has therefore employed the terms anode and catode, ascent and descent, as 

 suggesting the analogy of the great terrestrial electric current, from the 

 rising to the setting sun. 



Mr. F. uses the verb to electrolyze, for, to decompose a body by 

 electricity j and the noun electrolyte, for a body capable of undergoing 

 such decomposition. He denominates the constituents evolved by such 

 decomposition, according as they are evolved at the opposite extremities 

 of the electrolyte, with reference to the direction of the electric current, 

 anions, (going upwards,) if evolved at the anode ; and cations, (going 

 downwards,) if evolved at the catode. 



Thus it has long been known that acids are generally determined to the 



