change places with each other; because, according to the laws of tension observed with respect to metals, this transposition would, it is true, alter the individual tensions, but not their sum.
2. The intensity of a galvanic current continues the same, although a part of the circuit be removed, and another prismatic conductor be substituted in its place, only both must have the same reduced length, and the sum of the tensions in both cases remain the same; and vice versâ, when the current of a circuit is not altered by the substitution of one of its parts for a foreign prismatic conductor, and we can be convinced that the sum of the tensions has remained the same, then the reduced lengths of the two exchanged conductors are equal.
3. If we imagine a galvanic circuit always constructed of a like number of parts, of the same substance, and arranged in the same order, in order that the individual tensions may be regarded as unchangeable, the current of this circuit increases, the length of its parts remaining unaltered, in the same proportion in which the sections of all its parts increase in a similar manner, and the sections remaining unaltered, in the same proportion in which the length of all its parts uniformly decrease. When the reduced length of a part of the circuit far exceeds that of the other parts, the magnitude of the current will principally depend on the dimensions of this part; and the law here enounced will assume a much more simple form, if, in the comparison, attention be solely directed to this one part.
The conclusion arrived at in II. 2. presents a convenient means for the determination of the conductibility of various bodies. If, for instance, we imagine two prismatic bodies, whose lengths are and , their sections respectively and , and whose powers of conduction are and , and both bodies possess the property of not altering the current of a galvanic circuit when they alternatively form a portion of it, and both leave the individual tensions of the circuit unchanged, then
consequently
