DEFINITIONS OF NEW TERMS. 79 



like nitric or sulphuric acids, are decomposed in a secondary manner (752. 757.), are 

 not included under this term. Then for electro-chemically decomposed, I shall often 

 use the term electrolyzed, derived in the same way, and implying that the body spoken 

 of is separated into its components under the influence of electricity : it is analogous 

 in its sense and sound to analyze, which is derived in a similar manner. The term 

 electrolytical will be understood at once. Muriatic acid is electrolytical, boracic 

 acid is not. 



665. Finally, I require a term to express those bodies which can pass to the elec- 

 trodes, or, as they are usually called, the poles. Substances are frequently spoken of 

 as being electro-negative, or electro-positive, according as they go under the supposed 

 influence of a direct attraction to the positive or negative pole. But these terms are 

 much too significant for the use to which I should have to put them ; for though the 

 meanings are perhaps right, they are only hypothetical, and may be wrong ; and then, 

 through a very imperceptible, but still very dangerous, because continual, influence, 

 they do great injury to science, by contracting and limiting the habitual views of 

 those engaged in pursuing it. I propose to distinguish these bodies by calling those 

 anions* which go to the anode of the decomposing body; and those passing to the 

 cathode, cations -f- ; and when I have occasion to speak of these together, I shall call 

 them ions. Thus, the chloride of lead is an electrolyte, and when electrolyzed evolves 

 the two ions, chlorine and lead, the former being an anion, and the latter a cation. 



666. These terms being once well defined, will, I hope, in their use enable me to 

 avoid much periphrasis and ambiguity of expression. I do not mean to press them 

 into service more frequently than will be required, for I am fully aware that names 

 are one thing and science another J. 



667. It will be well understood that I am giving no opinion respecting the nature 

 of the electric current now, beyond what I have done on a former occasion (283. 517.); 

 and that though I speak of the current as proceeding from the parts which are posi- 

 tive to those which are negative (663.), it is merely in accordance with the conven- 

 tional, though in some degree tacit, agreement entered into by scientific men, that 

 they may have a constant, certain, and definite means of referring to the direction of 

 the forces of that current. 



^ iv. On some general conditions of Electro-chemical Decomposition. 

 669. From the period when electro-chemical decomposition was first effected to the 

 present time, it has been a remark, that those elements which, in the ordinary phe- 

 nomena of chemical affinity, were the most directly opposed to each other, and com- 

 bined with the greatest attractive force, were those which were the most readily 

 evolved at the opposite extremities of the decomposing bodies (549.). 



* aviov that which goes up. (Neuter participle.) t nanov that which goes down. 



X Since this paper was read, I have changed some of the terms which were first proposed, that I might employ 

 only such as were at the same time simple in their nature, clear in their reference, and free from hypothesis. 



