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[De La Rive writes thirty years later: "There is a special resistance due to the mere fact of the passage of the current from a solid into a liquid, or from a liquid into a solid. We call this resistance the resistance to passage. It always takes place while a liquid is being traversed by an electric current; for in order to put this liquid into the circuit, solid conductors called electrodes must necessarily be employed. This resistance to passage . . . is the result of the electro—chemical phenomena which in virtue of the decomposing action of the current necessarily occur on the surfaces of the solid conductors that are in contact with the liquids in which they are transmitting this current."—Treatise on Electricity. DE LA RIVE. 1856. Vol. ii. p. 73.]

I have distinctly separated the consideration of such galvanic circuits in which no portion undergoes a chemical change. from those whose activity is disturbed by chemical action, and have devoted separate space in the Appendix to the latter.