The apparatus which we have described, pro duces, with diminished intensity, the decomposi tion of water, and the other physical or chemical effects obtained from the ordinary pile. By vary ing the order and the number of the discs of card and of copper, Ritter obtained various interesting results. In this manner, he observed, that of all the ways in which a number of heterogeneous conduc tors can be disposed, the arrangement in which there is the fewest alternations, is the most favour able for the transmission of electricity. If we con struct, for example, a pile with sixty-four discs of copper, and sixty-four discs of moistened card, ar ranged in three masses, so that all the cards may form an uninterrupted series, terminated on each side by thirty-two metallic plates, this pile will conduct very well the electrisity of the column of Volta, and will consequently be charged very little, if at all in a permanent manner. Interrupt now the humid conductors by a plate of copper, and the conducting faculty will already seem to diminish; more frequent interruptions will weaken it still more; and by multiplying them in this man. ner, we at last obtain a system in which the conduc tibility is scarcely sensible. Such are the phenome na which led Ritter to imagine that a weak elec tricity suffers some resistance in passing from one surface to another ; a resistance which produces no effect except in this state of weakness; for by a gular property, a degree of electricity sufficiently powerful to overcome it, opens a perfectly free pas sage, and discharges itself entirely.
We have seen that, in changing the distribution of the elements in a secondary pile, its conducting faculty can be changed at pleasure; and it was na tural to think that such modifications would vari ously influence the chemical and physiological ef fects produced. To examine the consequences pro gressively, Ritter varied the arrangement of a given number of humid and solid conductors, from the separation into two groups to the most numerous al ternations. The following are the results which he has obtained.
A very small number of alternations gives a too easy passage to the electrical current of the primitive pile, if it be sufficiently powerful. The apparatus, then, is not charged in a permanent manner; and the chemical and physiological effects do not make their appearance. By multiplying the number of alternations, while the primitive pile remains the same, the secondary pile begins to be charged. It communicates electricity to the electrometer. It disengages from the water some bubbles of gas ; but it gives no shock in human organs. The num ber of alternations increasing still more, the electri cal charge increases, and we obtain the decomposi tion of the water, the shock, the spark, and the pe culiar taste. But, at a certain limit of alternations, the chemical and physiological effects cease to in crease, although the total electrical charge remains the same, or even continues to augment. Beyond this point, the charge is always produced; but the other effects decline. The disengagement of the bubbles ceases first, and afterwards the shock. We then arrive at the other extreme of ' a very im perfect conductibility ; and the progression with which these phenomena are extinguished, the elec trical charge remaining always the same, affords a final and conclusive proof of what we have above advanced regarding the manner in which they de pend upon the velocity of transmission.
From the same principles, the reason will appear why the apparatus of Ritter is better adapted than any other for exhibiting clearly and distinctly these two kinds of action. In the ordinary pile, the quan tity of free electricity increases with the number of plates, and balances the resistance which arises from the alternations ;_ while, in the secondary pile, the repulsive force of the electricity at the two poles can never surpass that of the primitive pile ;, and the re sistance which the alternations produce is wholly employed in. modifying the discharge of the same quantity of electricity.
In fine, if the column of Volta is thus enabled to charge the secondary pile of Ritter, it owes this far culty to the circumstance of the repulsive force of the electricity at, its poles being extremely weak, and nearly imperctptible. A more povterfhl electri city, such, for example, as that of the ordinary elec trical machines, would pass entirely through the sys tem of conducting bodies, which forms the se condary pile, and could not consequently produce any of the effects which result from its accumulation.
The differences which subsist in the chemical agency of ordinary piles, on account of the magni tude of their plates, occur also in the secondary piles. The nature of the cards, their thickness, the 'nature of the solution with which they are moistened ; the order, in fine in which we in termix them, and a variety of Other trifling circum stances, modify these effects in a thousand different ways, 'which it would be equally useful and curious to examine.
The secondary pile being, as we have mentioned above, formed with a single metal and a moistened substance, would seem, at first sight, incapable of possessing electricity of itself; and its own action, in 'fact, before we have charged it, is ticarcely percep •ible. But it may yet commonly be rendered sen sible, by bringing the muscles and the nerves of a frog in communication at their two extremities.
By considering the process by which the electri city, developed by 'our machines, 'discharges itself through bodies of different kinds, we find, that those which seem to conduct it best, still oppose to its pas sage a sensible resistance. Hence, it is to be conceiv ed, that if we could attenuate sufficiently the energy of the electricity, without losing, at the same time, the possibility of recognising its presence, we should ob.. Min for every body, and even for the best conduc tors, certain limits, at which the transmission would become very slow, or would cease altogether to take place. The electromotive apparatus, furnishing an inexhaustible source of electricity, with a repulsive force, which may be rendered extremely feeble, unites all the conditions the best adapted for this kind of research. It has, accordingly, led to the dis covery of various phenomena in the conducting qua lities of liquids, with which our ma chines could never have made us acquainted.