Michael Faraday

“ That these effects may be almost infinitely varied, some being exalted whilst others are diminished, is universally acknowledged; and yet without any doubt of the identity of character of the voltaic currents thus made to differ in their effect. The beautiful explication of these variations afforded by Cavendish's theory of quantity and intensity requires no support at present, as it is not supposed to be doubted. ”

“ If the electricity pass a little way from the wire over the surface of the moistened paper, before it finds mass and moisture enough to conduct it, then the reddening extends as far as the ramifications. ”

“ It is evident that these offer no analogy to cases of true voltaic decomposition, where the electricity only decomposes when it is _conducted_ by the body acted upon, and ceases to decompose, according to its ordinary laws, when it passes in sparks. These effects are probably partly analogous to that which takes place with water in Pearson's or Wollaston's apparatus, and may be due to very high temperature acting on minute portions of matter; or they may be connected with the results in air (322.) . As nitrogen can combine directly with oxygen under the influence of the electric spark (324.) ”

“ If, with a constant pair of points, the electricity be passed from the machine in sparks, a certain proportion of gas is evolved; but if the sparks be rendered shorter, less gas is evolved; and if no sparks be passed, there is scarcely a sensible portion of gases set free. On substituting solution of sulphate of soda for water, scarcely a sensible quantity of gas could be procured even with powerful sparks, and nearly none with the mere current ”

“ Cavendish in his theory of the torpedo; or may we suppose, according to the analogy of the solar ray, that the electrical power, whether excited by the common machine, or by the voltaic battery, or by the torpedo, is not a simple power, but a combination of powers, which may occur variously associated, and produce all the varieties of electricity with which we are acquainted?" At p. 279 of the same volume of Transactions is Dr. Ritchie's paper, from which the following are extracts: "Common electricity is diffused over the surface of the metal;--voltaic electricity exists within the metal. ”

“ If similar ramifications occur at the termination _n_, on the turmeric paper, they _prevent_ the occurrence of the red spot due to the alkali, which would otherwise collect there: sparks or ramifications from the points _n_ will also redden litmus paper. If paper moistened by a solution of iodide of potassium (which is an admirably delicate test of electro-chemical action,) be exposed to the sparks or ramifications, or even a feeble stream of electricity through the air from either the point _p_ or _n_, iodine will be immediately evolved. ”

“ Common electricity is excited upon non-conductors, and is readily carried off by conductors and imperfect conductors. Voltaic electricity is excited upon combinations of perfect and imperfect conductors, and is only transmitted by perfect conductors or imperfect conductors of the best kind. ”

“ But on the other hand it is also true, that the accuracy of Wollaston's experiments has been denied [D] ; and also that one of them, which really is no proper proof of chemical decomposition by common electricity (309. 327.) , has been that selected by several experimenters as the test of chemical action (336. 346.) . It is a fact, too, that many philosophers are still drawing distinctions between the electricities from different sources; or at least doubting whether their identity is proved. ”

“ With regard to thermo-electricity, (that beautiful form of electricity discovered by Seebeck,) the very conditions under which it is excited are such as to give no ground for expecting that it can be raised like common electricity to any high degree of tension; the effects, therefore, due to that state are not to be expected. The sum of evidence respecting its analogy to the electricities already described, is, I believe, as follows:--_Tension._ The attractions and repulsions due to a certain degree of tension have not been observed. ”

“ In this, however, was found no point of discordance between voltaic and common electricity; for when a Leyden battery (291.) was charged so as to deflect the gold leaf electrometer to the same degree, the points were found equally unable to discharge it with such effect as to produce either magnetic or chemical action. This was not because common electricity could not produce both these effects (307. 310.) ; but because when of such low intensity the quantity required to make the effects visible (being enormously great (371. 375.) ,) could not be transmitted in any reasonable time. ”

“ That the electricity was apparently not analogous to voltaic electricity is evident, for the "usual shocks" only were produced, and nothing like the terrible sensation due to a voltaic battery, even when it has a tension so feeble as not to strike through the eighth of an inch of air.
341. It seems just possible that the air which was passing by the kite and string, being in an electrical state sufficient to produce the "usual shocks" only, could still, when the electricity was drawn off below, renew the charge, and so continue the current. ”

“ The water is decomposed at both poles independently of each other, and the oxygen and hydrogen evolved at the wires are the elements of the water existing the instant before in those places. That the poles, or rather points, have no mutual decomposing dependence, may be shown by substituting a wire, or the finger, for one of them, a change which does not at all interfere with the other, though it stops all action at the changed pole. This fact may be observed by turning the machine for some time ”

“ When a wet thread was interposed in the course of the current of common electricity from the battery (291.) charged by eight or ten [A] revolutions of the machine in good action (290.) , and the discharge made by platina spatulas through the tongue or the gums, the effect upon the tongue and eyes was exactly that of a momentary feeble voltaic circuit. ”

“ With these adjustments and the use of iodide of potassium on paper, chemical action is sometimes a more delicate test of electrical currents than the galvanometer (273.) . Such cases occur when the bodies traversed by the current are bad conductors, or when the quantity of electricity evolved or transmitted in a given time is very small. ”

“ On working the machine for a short time only, acid was evolved at _all_ the poles or terminations _p, p, p_, by which the electricity entered the solution, and alkali at the other poles _n, n, n_, by which the electricity left the solution.
322. In all experiments of electro-chemical decomposition by the common machine and moistened papers (316.) , it is necessary to be aware of and to avoid the following important source of error. If a spark passes over moistened litmus and turmeric paper, the litmus paper (provided it be delicate and not too alkaline,) is reddened by it ”

“ In the exhausted receiver the electricity would _strike_ through nearly half an inch of space, and the combined effects of rarefaction and heat were such upon the inclosed air us to enable it to conduct the electricity through a space of six or seven inches.
[A] Elements of Chemical Philosophy, p. 153 275. The instantaneous charge of a Leyden battery by the poles of a voltaic apparatus is another proof of the tension, and also the quantity, of electricity evolved by the latter. ”

“ These effects must not be confounded with those due to the true electro-chemical powers of common electricity, and must be carefully avoided when the latter are to be observed. No sparks should be passed, therefore, in any part of the current, nor any increase of intensity allowed, by which the electricity may be induced to pass between the platina wires and the moistened papers, otherwise than by conduction ”

“ But still those attractions and repulsions are exactly of the same nature as those already referred to under the head _Tension, Voltaic electricity_ (268.) ; and the difference in degree between them is not greater than often occurs between cases of ordinary electricity only. I think it will be unnecessary to enter minutely into the proofs of the identity of this character in the two instances. They are abundant; are generally admitted as good ”

“ When this frame and the two coatings were connected with the discharging train (292.) , an insulated point or ball, connected with the machine when most active, might be brought within an inch of any part of the galvanometer, yet without affecting the needle within by ordinary electrical attraction or repulsion. ”

“ But as no other one has come forward in confirmation, MM. Arago, Ampère, and Savary, not having themselves published (that I am aware of) their admission of the results, and as some have not been able to obtain them, M. Colladon's conclusions have been occasionally doubted or denied ”

“ Animal Electricity | X | X | X | + | + | X | | | |_________________________|___|___|___|___|___|___|___|___|
[A] Many of the spaces in this table originally left blank may now be filled. Thus with _thermo-electricity_, Botto made magnets and obtained polar chemical decomposition: Antinori produced the spark; and if it has not been done before, Mr. Watkins has recently heated a wire in Harris's thermo-electrometer. In respect to _animal electricity_, Matteucci and Linari have obtained the spark from the torpedo, and I have recently procured it from the gymnotus: Dr. ”