46. The intensity of the excitement produced by different electrical machines is estimated to be as the relative lengths of the sparks which proceed from their prime conductors respectively. Admitting that the relative intensity were merely as the length of the spark, not as the square of that length, still there would be an infinite difference between the intensity of a voltaic series and that of electrical machines, if measured by this test. Large electrical machines, like that at the Polytechnic Institution, London, give sparks at twenty inches and more; while, agreeably to Gassiott’s experiments, a Groves’s battery of 320 pairs, in full power, would not, before contact, give a spark at any distance, however minute. It follows, that, as respects the species of intensity which is indicated by length of sparks, or striking distance, the difference between the electricity of the most powerful voltaic series and electrical machines is not to be represented by any degree of disparity; it proves that galvanism proper and electricity proper are heterogeneous.

47. It should be recollected that the intensity of galvanic action in a series of 320 pairs, excepting the loss from conduction, would be to that of one pair as 320 to 1.[70] Of course, the striking distance of a battery of one pair would be 320 times less than nothing: 320 below zero.

48. We may infer that the undulatory polarization of ethereo-ponderable matter is the primary, direct, and characteristic effect of galvanic excitement, in its more energetic modifications. Yet, that by peculiar care in securing insulation, as in the water batteries of Cross and Gassiott, ethereal undulations may be produced, with the consequent accumulation of ethereal polarity requisite to give sparks before contact, agreeably to the experiments of those ingenious philosophers.

49. Hence it may be presumed that, during intense ethereo-ponderable polarization, superficial ethereal waves may always be a secondary effect, although the conducting power of the reagents, requisite to the constitution of powerful galvanic batteries, is inconsistent with that accumulation of ethereal polarity which constitutes a statical spark-giving charge.

50. As all the members forming a voltaic series have to be discharged in one circuit, the energy of the effort to discharge, and the velocity of the consequent undulations must be, cæteris paribus, as the number of members which co-operate to produce the discharge. Of course the more active the ethereo-ponderable waves, the greater must be their efficacy in producing ethereal waves of polarization, as a secondary effect, agreeably to the suggestions above made, (49, 36.)

51. Hence, in a battery consisting of one galvanic pair excited by reagents of great chemical energy and conducting power, the electro-magnetic effects are pre-eminent; while De Luc’s electric columns, consisting of several thousands of minute pairs, feeble as to their chemical and conducting efficacy, are pre-eminent for statical spark-giving power, (48.) This seems to be quite consistent; since, on the one hand, the waves of polarization must be larger and slower as the pairs are bigger and fewer; and, on the other hand, smaller and more active as the pairs are more minute and more numerous.

On the perfect similitude between the Polarity communicated to Iron Filings by a Magnetized Steel Bar and a Galvanized Wire.

52. If by a sieve, or any other means, iron filings be duly strewed over a paper, resting on a bar magnet, they will all become magnets, so as to arrange themselves in rows like the links of a chain. Each of the little magnets thus created will, at its outermost end, have a polarity similar to that of the pole (of the magnet) with which it may be affiliated. Of course the resulting ferruginous rows formed severally by the two different poles of the bar will have polarities as opposite as those of the said poles.

53. In an analogous mode, if two wires be made the media of a galvanic discharge, iron filings, under their influence, will receive a magnetic polarity, arranging themselves about each wire like so many tangents to as many radii proceeding from its axis: those magnetized by one wire reacting with such as are magnetized by the other.

54. The affections of the ferruginous particles during the continuance of the current so called are precisely like those of the same particles when under the influence of the bar magnet. The great discordancy is in the fact that the influence of the magnet is permanent, while that of the wire is indebted for existence to a series of oppositely polarizing but transient impulses which proceed toward the middle of the circuit from each side, so as to produce reciprocal neutralization by meeting midway.