78 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



surfaces of air (465. 471.) and water (493.), against which I have effected electro- 

 chemical decomposition, is subject to doubt. In place of the term pole, I propose 

 using that of Electrode^, and I mean thereby that substance, or rather surface, whether 

 of air, water, metal, or any other body, which bounds the extent of the decomposing 

 matter in the direction of the electric current. 



663. The surfaces at which, according to the common phraseology, the electric 

 current enters and leaves a decomposing body, are most important places of action, 

 and require to be distinguished apart from the poles, with which they are mostly, and 

 the electrodes, with which they are always, in contact. Wishing for a natural standard 

 of electric direction to which I might refer these, expressive of their difference and at 

 the same time free from all theory, I have thought it might be found in the earth. If 

 the magnetism of the earth be due to electric currents passing round it, the latter must 

 be in a constant direction, which, according to present usage of speech, would be from 

 east to west, or, which will strengthen this help to the memory, that in which the sun 

 appears to move. If in any case of electro-decomposition we consider the decomposing 

 body as placed so that the current passing through it shall be in the same direction, 

 and parallel to that supposed to exist in the earth, then the surfaces at which the elec- 

 tricity is passing into and out of the substance would have an invariable reference, and 

 exhibit constantly the same relations of powers. Upon this notion we purpose calling 

 that towards the east the anode^, and that towards the west the cathode^ ; and 

 whatever changes may take place in our views of the nature of electricity and elecr- 

 trical action, as they must affect the natural standard referred to in the same direction, 

 and to an equal amount with any decomposing substances to which these terms may 

 at any time be applied, there seems no reason to expect that they will lead to con- 

 fusion, or tend in any way to support false views. The anode is therefore that sur- 

 face at which the electric current, according to our present expression, enters : it is 

 the negative extremity of the decomposing body; is where oxygen, chlorine, acids, &c., 

 are evolved ; and is against or opposite the positive electrode. The cathode is that 

 surface at which the current leaves the decomposing body, and is its positive extre- 

 mity ; the combustible bodies, metals, alkalies, and bases, are evolved there, and it is 

 in contact with the negative electrode. 



664. I shall have occasion in these Researches, also, to class bodies together ac- 

 cording to certain relations derived from their electrical ^.ctions (822.) ; and wishing 

 to express those relations without at the same time involving the expression of any 

 hypothetical views, I intend using the following names and terms. Many bodies are 

 decomposed directly by the electric current, their elements being set free ; these I 

 propose to call electrolytes^. Water, therefore, is an electrolyte. The bodies which, 



* ijkeKrpov, and oZos a way. 



t ava upwards, b^os a way ; the way which the sun rises. 

 X Kara downwards, oZos a way ; the way which the sun sets. 

 § ii\€Krpov, and Xvw solvo. N. Electrolyte, V. Electrolyze. 



