Scientific American Supplement, No. 288, July 9, 1881

Excerpt: ...being exactly regular, are sufficiently well represented within practical limits by the formula: (2) A = - a'i + b'i, of the same form as the expression E: E = - ai + bi, of the heating of the thermometer electrode. Further, every cause which affects the coefficients, a or b, also affects in the same way a' and b' such causes being the greater or less dilution of the solution, the nature of the salt, etc. It is, therefore, impossible not to be struck by the direct relation of the thermic and mechanical phenomena of which the negative electrode is the origin. The following is the explanation which I offer: The thermometer indicates the mean temperature of the liquid just outside it; this temperature is not necessarily that of the metal which incloses it. The current, propagated almost exclusively by the molecules of the decomposed salt, does not act directly to cause a variation in the temperature of the dissolving molecules; these change heat with the molecules of the electrolyte, which should be in general hotter than those when a heating is noticed and colder when a cooling is observed. Suppose it is found, in the first case, that the metal, at the moment when it is deposited, is hotter than the liquid, and, consequently, than the thermometer; it becomes colder immediately after the deposit, and consequently contracts; the deposit is compressed. The reverse is the case when the metal is colder than the liquid; the deposit then dilates. If this hypothesis is correct, the excess, T, of the temperature of the metal over the liquid which surrounds the thermometer should be proportional to the contraction, A, represented by the formula (2), and the neutral point, I', of the contraction corresponds to the case where the temperature of the metal is precisely equal to that of the liquid. It might be expected, perhaps, from the foregoing, that I' = I; this would take place if the excess of temperature of the metal, measured by the contraction, were...