Part 15
Thus in the common experiments, where the vitreous or resinous ether is accumulated by art, metallic bodies have been esteemed the best conductors, and next to these water, and all other moist bodies; but it was lately discovered, that dry charcoal, recently burnt, was a more perfect conductor than metals; and it appears from the experiments discovered by Galvani, which have thence the name of Galvanism, that animal flesh, and particularly perhaps the nerves of animals, both which are composed of much carbon and water, are the most perfect conductors yet discovered; that is, that they give the least resistance to the junction of the spontaneous electric atmospheres, which exist round metallic bodies, and which differ very little in respect to the proportions of their vitreous and resinous ingredients.
Thus also, though where the accumulated electricities are dense, as in charging a coated glass-jar, the glass, which intervenes, may be of considerable thickness, and may still become charged by the stronger attraction of the secondary electric ethers; but where the spontaneous adhesive electric atmospheres are employed to charge plates of air, as in the Galvanic pile, or probably to charge thin animal membranes or cuticles, as perhaps in the shock given by the torpedo or gymnotus, it seems necessary that the intervening nonconducting plate must be extremely thin, that it may become charged by the weaker attraction of these small quantities or difference of the spontaneous electric atmospheres; and in this circumstance only, I suppose, the shocks from the Galvanic pile, and from the torpedo and gymnotus, differ from those of the coated jar.
3. When atmospheres of electricity, which do not differ much in the quantity or proportion of their vitreous and resinous ethers, approach each other, they are not easily or rapidly united; but the predominant vitreous or resinous ether of one of them repels the similar ether of the opposed atmosphere, and attracts the contrary kind of ether.
The slowness or difficulty with, which atmospheres, which differ but little in kind or in density, unite with each other, appears not only from the experiment of Mr. Canton above related, but also from the repeated smaller shocks, which may be taken from a charged coated jar after the first or principal discharge, if the conducting medium has not been quickly removed, as is also mentioned above.
Hence those atmospheres of either kind of electric matter, which differ but very little from each other in kind or quantity, require the most perfect conductors to cause them to unite. Thus it appears by Mr. Bennet's doubler, as mentioned in the Preliminary Proposition, No. VI. that the natural adhesive atmosphere round silver contains more vitreous electricity than that naturally round zinc; but when thin plates of these metals, each about an ounce in weight, are laid on each other, or moderately pressed together, their atmospheres do not unite. For metallic plates, which when laid on each other, do not adhere, cannot be said to be in real contact, of which their not adhering is a proof; and in consequence a thin plate of air, or of their own repulsive ethers exists between them.
Hence when two plates of zinc and silver are thus brought in to the vicinity of each other, the plate of air between them, as they are not in adhesive contact, becomes like a charged coated jar; and if these two metallic plates are touched by your dry hands, they do not unite their electricities, as the dry cuticle is not a sufficiently good conductor; but if one of the metals be put above, and another under the tongue, the saliva and moist mucous membrane, muscular fibres, and nerves, supply so good a conductor, that this very minute electric shock is produced, and a kind of pungent taste is perceived.
When a plate or pencil of silver is put between the upper lip and the gum, and a plate or pencil of zinc under the tongue, a sensation of light is perceived in the eyes, as often as the exterior extremities of these metals are brought into contact; which is owing in like manner to the discharge of a very minute electric shock, which would not have been produced but by the intervention of such good conductors as moist membranes, muscular fibres, and nerves.
In this situation, a sensation of light is produced in the eyes; which seems to show, that these ethers pass through nerves more easily, than through muscular flesh simply; since the passage of them through the retina of the eyes from the upper gum to the parts beneath the tongue is a more distant one, than would otherwise appear necessary. It is not so easy to give the sensation of light in the eyes by passing a small shock of artificially accumulated electricity through, the eyes (though this may, I believe, be done) because this artificial accumulated electricity, as it passes with greater velocity than the spontaneous accumulations of it, will readily permeate the muscles or other moist parts of animal bodies; whereas the spontaneous accumulations of electricity seem to require the best of all conductors, as animal nerves, to facilitate their passage.
4. In the Galvanic pile of Volta this electric shock becomes so much increased, as to pass by less perfect conductors, and to give shocks to the arms of the conducting person, if the cuticle of his hands be moistened, and even to show sparks like the coated jar; which appears to be effected in this manner. When a plate of silver is laid horizontally on a plate of zinc, the plate of air between them becomes charged like a coated jar; as the silver, naturally possessing more vitreous electric ether, repels the vitreous ether, which the zinc possesses in less quantity, and attracts the resinous ether of the zinc. Whence the inferior surface of the plate of zinc abounds now with vitreous ether, and its upper surface with resinous ether. Beneath this pair of plates lay a cloth moistened with water, or with some better conductor, as salt and water, or a slight acid mixed with water, or volatile alcali of ammoniac mixed with water, and this vitreous electric ether on the lower surface of the zinc plate will be given to the second silver plate which lies beneath it; and thus this second silver plate will possess not only its own natural vitreous atmosphere, which was denser or in greater quantity than that of the zinc plate next beneath it, but now acquires an addition of vitreous ether from the zinc plate above it, conducted to it through the moist cloth.
This then will repel more vitreous ether from the second zinc plate into the third silver one; and so on till the plates of air between the zincs and silvers are all charged, and each stronger and stronger, as they descend in the pile.
If the reader still prefers the Franklinian theory of positive and negative electricity, he will please to put the word positive for vitreous, and negative for resinous, and he will find the theory of the Galvanic pile equally thus accounted for.
5. When a Galvanic pile is thus placed, and a communication between the two ends of it is made by wires, so that the electric shocks pass through water, the water becomes decomposed in some measure, and oxygen is liberated from it at the point of one wire, and hydrogen at the point of the other; and this though a syphon of water be interposed between them. This curious circumstance seems to evince the existence of two electric ethers, which enter the water at different ends of the syphon, and have chemical affinities to the component parts of it; the resinous ether sets at liberty the hydrogen at one end, and the vitreous ether the oxygen at the other end of the conducting medium.
Hence it must appear, that the longer the Galvanic pile, or the greater the number of the alternate pieces of silver and zinc that it consists of, the stronger will be the Galvanic shock; but there is another circumstance, difficult to explain, which is the perpetual decomposition of water by the Galvanic pile; when water is made the conducting medium between the two extremities of the pile.
As no conductors of electricity are absolutely perfect, there must be produced a certain accumulation of vitreous ether on one side of each charged plate of the Galvanic pile, and of resinous ether on the other side of it, before the discharge takes place, even though the conducting medium be in apparent contact. When the discharge does take place, the whole of the accumulated electricity explodes and vanishes; and then an instant of time is required for the silver and zinc again to attract from the air, or other bodies in their vicinity, their spontaneous natural atmospheres, and then another discharge ensues; and so repeatedly and perpetually till the surface of one of the metallic plates becomes so much oxydated or calcined, that it ceases to act.
Hence a perpetual motion may be said to be produced, with an incessant decomposition of water into the two gasses of oxygen and hydrogen; which must probably be constantly proceeding on all moist Surfaces, where a chain of electric conductors exists, surrounded with different proportions of the two electric ethers. Whence the ceaseless liberation of oxygen from the water has oxydated or calcined the ores of metals near the surface of the earth, as of manganese, of zinc into lapis calaminaris, of iron into various ochres, and other calciform ores. From this source also the corrosion of some metals may be traced, when they are immersed in water in the vicinity of each other, as when the copper sheathing of ships was held on by iron nails. And hence another great operation of nature is probably produced, I mean the restoration of oxygen to the atmosphere from the surface of the earth in dewy mornings, as well as from the perspiration of vegetable leaves; which atmospheric oxygen is hourly destructible by the respiration of animals and plants, by combustion, and by other oxydations.
6. The combination of the electric ethers with metallic bodies, before mentioned appears from the Galvanic pile; since, according to the experiments of Mr. Davy, when an acid is mixed with the water placed between the alternate pairs of silver and zinc plates, a much greater electric shock is produced by the same pile; and an anonymous writer in the Phil. Magaz. No. 36, for May 1801, asserts, that when the intervening cloths or papers are moistened with pure alcali, as a solution of pure ammonia, the effect is greater than by any other material. It must here be observed, that both the acid and the alcaline solution, or common salt and water, and even water alone, in these experiments much erodes the plates of zinc, and somewhat tarnishes those of silver. Whence it would appear, that as by the repeated explosions of the two electric ethers in the conducting water, both oxygen and hydrogen are liberated; the oxygen erodes the zinc plates, and thus increases the Galvanic shock by liberating their combined electric ethers: and that this erosion is much increased by a mixture either of acid or of volatile alcali with the water. Further experiments are wanting on this subject to show whether metallic bodies emit either or both of the electric ethers at the time of their solution or erosion in acids or in alcalies.
X. _Of the two Magnetic Ethers._
1. Magnetism coincides with electricity in so many important points, that the existence of two magnetic ethers, as well as of two electric ones, becomes highly probable. We shall suppose, that in a common bar of iron or steel the two magnetic ethers exist intermixed or in their neutral state; which for the greater ease of speaking of them may be called arctic ether and antarctic ether; and in this state like the two electric fluids they are not cognizable by our senses of experiments.
When these two magnetic ethers are separated from each other, and the arctic ether is accumulated on one end of an iron or steel bar, which is then called the north pole of the magnet, and the antarctic ether is accumulated on the other end of the bar, and is then termed the south pole of the magnet; they become capable of attracting other pieces of iron or steel, and are thus cognizable by experiments.
It seems probable, that it is not the magnetic ether itself which attracts or repels particles of iron, but that an attractive and repulsive ether attends the magnetic ethers, as was shown to attend the electric ones in No. II. 9. of this Note; because magnetism does not pass through other bodies, as it does not escape from magnetised steel when in contact with other bodies; just as the electric fluids do not pass through glass, but the attractive and repellent ethers, which attend both the magnetic and electric ethers, pass through all bodies.
2. The prominent articles of analogical coincidence between magnetism and electricity are first, that when one end of an iron bar possesses an accumulation of arctic magnetic ether, or northern polarity; the other end possesses an accumulation of antarctic magnetic ether, or southern polarity; in the same manner as when vitreous electric ether is accumulated on one side of a coated glass jar, resinous electric ether becomes accumulated on the other side of it; as the vitreous and resinous ethers strongly attract each other, and strongly repel the ethers of the same denomination, but are prevented from intermixing by the glass plane between them; so the arctic and antarctic ethers attract each other, and repel those of similar denomination, but are prevented from intermixing by the iron or steel being a bad conductor of them; they will, nevertheless, sooner combine, when the bar is of soft iron, than when it is of hardened steel; and then they slowly combine without explosion, that is, without emitting heat and light like the electric ethers, and therefore resemble a mixture of oxygen and pure ammonia; which unite silently producing a neutral fluid without emitting any other fluids previously combined with them.
Secondly, If the north pole of a magnetic bar be approached near to the eye of a sewing needle, the arctic ether of the magnet attracts the antarctic ether, which resides in the needle towards the eye of it, and repels the arctic ether, which resides in the needle towards the point, precisely in the same manner as occurs in presenting an electrised, glass tube, or a rubbed stick of sealing wax to one extremity of two skewers insulated horizontally on wine-glasses in the experiment ascribed to Mr. Canton, and described in No. IX. 1, of this Additional Note, and also so exactly resembles the method of producing a separation and consequent accumulation of the two electric ethers by pressing a cushion on glass or on sealing wax, described in No. 4 of this Note, that their analogy is evidently apparent.
Thirdly, When much accumulated electricity is approached to one end of a long glass tube by a charged prime conductor, there will exist many divisions of the vitreous and resinous electricity alternately; as the vitreous ether attracts the resinous ether from a certain distance on the surface of the glass tube, and repels the vitreous ether; but, as this surface is a bad conductor, these reciprocal attractions and repulsions do not extend very far along it, but cease and recur in various parts of it. Exactly similar to this, when a magnetic bar is approximated to the end of a common bar of iron or steel, as described in Mr. Cavallo's valuable Treatise on Magnetism; the arctic ether of the north pole of the magnetic bar attracts the antarctic ether of the bar of common iron towards the end in contact, and repels the arctic ether; but, as iron and steel are as bad conductors of magnetism, as glass is of electricity, this accumulation of arctic ether extends but a little way, and then there exists an accumulation of antarctic ether; and thus reciprocally in three or four divisions of the bar, which now becomes magnetised, as the glass tube became electrised.
Another striking feature, which shows the sisterhood of electricity and magnetism, consists in the origin of both of them from the earth, or common mass of matter. The eduction of electricity from the earth is shown by an insulated cushion soon ceasing to supply either the vitreous or resinous ether to the whirling globe of glass or of sulphur; the eduction of magnetism from the earth appears from the following experiment: if a bar of iron be set upright on the earth in this part of the world, it becomes in a short time magnetical; the lower end possessing northern polarity, or arctic ether, and the higher end in consequence possessing southern polarity or antarctic ether; which may be well explained, if we suppose with Mr. Cavallo, that the earth itself is one great magnet, with its southern polarity or antarctic ether at the northern end of its axis; and, in consequence, that it attracts the arctic ether of the iron bar into that end of it which touches the earth, and repels the antarctic ether of the iron bar to the other end of it, exactly the same as when the southern pole of an artificial magnet is brought into contact with one end of a sewing needle.
3. The magnetic and electric ethers agree in the characters above mentioned, and perhaps in many others, but differ in the following ones. The electric ethers pass readily through metallic, aqueous, and carbonic bodies, but do not permeate vitreous or resinous ones; though on the surfaces of these they are capable of adhering, and of being accumulated by the approach or contact of other bodies; while the magnetic ethers will not permeate any bodies, and are capable of being accumulated only on iron and steel by the approach or contact of natural or artificial magnets, or of the earth; at the same time the attractive and repulsive powers both of the magnetic and electric ethers will act through all bodies, like those of gravitation and heat.
Secondly, The two electric ethers rush into combination, when they can approach each other, after having been separated and condensed, and produce a violent explosion emitting the heat and light, which were previously combined with them; whereas the two magnetic ethers slowly combine, after having been separated and accumulated on the opposite ends of a soft iron bar, and without emitting heat and light produce a neutral mixture, which, like the electric combination, ceases to be cognizable by our senses or experiments.
Thirdly, The wonderful property of the magnetic ethers, when separately accumulated on the ends of a needle, endeavouring to approach the two opposite poles of the earth; nothing similar to which has been observed in the electric ethers.
From these strict analogies between electricity and magnetism, we may conclude that the latter consists of two ethers as well as the former; and that they both, when separated by art or nature, combine by chemical affinity when they approach, the one exploding, and then consisting of a residuum after having emitted heat and light; and the other producing simply a neutralised fluid by their union.
XI. _Conclusion._
1. When two fluids are diffused together without undergoing any change of their chemical properties, they are said simply to be mixed, and not combined; as milk and water when poured together, or as oxygen and azote in the common atmosphere. So when salt or sugar is diffused in water, it is termed solution, and not combination; as no change of their chemical properties succeeds.
But when an acid is mixed with a pure alcali a combination is produced, and the mixture is said to become neutral, as it does not possess the chemical properties which either of the two ingredients possessed in their separate state, and is therefore similar to neither of them. But when a carbonated alcali, as mild salt of tartar, is mixed with a mineral acid, they presently combine as above, but now the carbonic acid flies forcibly away in the form of gas; this, therefore, may be termed a kind of explosion, but cannot properly be so called, as the ethereal fluids of heat and light are not principally emitted, but an aerial one or gas; which may probably acquire a small quantity of heat from the combining matters.
But when strong acid of nitre is poured upon charcoal in fine powder, or upon oil of cloves, a violent explosion ensues, and the ethereal matters of heat and light are emitted in great abundance, and are dissipated; while in the former instance the oxygen of the nitrous acid unites with the carbone forming carbonic acid gas, and the azote escapes in its gaseous form; which may be termed a residuum after the explosion, and may be confined in a proper apparatus, which the heat and light cannot; for the former, if its production be great and sudden, bursts the vessels, or otherwise it passes slowly through them; and the latter passes through transparent bodies, and combines with opake ones.
But where ethers only are concerned in an explosion, as the two electric ones, which are previously difficult to confine in vessels; the repulsive ethers of heat and light are given out; and what remains is a combination of the two electric ethers; which in this state are attracted by all bodies, and form atmospheres round them.
These combined electric atmospheres must possess less heat and light after their explosion; which they seem afterwards to acquire at the time they are again separated from each other, probably from the combined heat and combined light of the cushion and glass, or of the cushion and resin; by the contact of which they are separated; and not from the diffused heat of them; but no experiments have yet been made to ascertain this fact, this combination of the vitreous and resinous ethers may be esteemed the residuum after their explosion.
2. Hence the essence of explosion consists in two bodies, which are previously united with heat and light, so strongly attracting each other, as to set at liberty those two repulsive ethers; but it happens, that these explosive materials cannot generally be brought into each other's vicinity in a state of sufficient density; unless they are also previously combined with some other material beside the light and heat above spoken of: as in the nitrous acid, the oxygen is previously combined with azote; and is thus in a condensed state, before it is brought into the contact or vicinity of the carbone; there are however bodies which will slowly explode; or give out heat and light, without being previously combined with other bodies; as phosphorus in the common atmosphere, some dead fish in a certain degree of putridity, and some living insects probably by their respiration in transparent lungs, which is a kind of combustion.