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vent its intrusion into them than sandstone can prevent the intrusion of water when immersed in it.
From the universal extent of this fluid it is evident that every substance or body which is porous must be full of it, and that all are surrounded with it; that wherever the balance or equilibrium is disturbed by any means, it will have a tendency to regain its former state ; and with all the celerity which the nature of the fluid is calculated to produce. This fluid and electricity is supposed to be the same; but its effects are differently modified by the means taken to accumulate and discharge it: that the sun, and planets, and stars are surrounded with it; and that its extent is commensurate with the universe.
From the different texture of substances it must be evident that some will admit it much more freely, and part with it much more readily than others; just as some kinds of stone and sand imbibe and part with water much more readily than others. In considering these substances it must be recollected that the porous nature of many bodies admit water and air, and other gases, and that the galvanic fluid will occupy the pores in the air and water that are in these substances, and such other pores as may be impervious to the water, air, &c.
It is evident the different bodies must have different capacities for holding the galvanic fluid; some will hold double, treble, or more of it than others. It is found that metals admit and part with galvanic electricity readily, or that they are good conductors of it. What should be the cause of this property is not very obvious. If those are the best conductors which are most easily oxidable, would not this indicate that it is on account of the greater quantity of galvanic electricity they contain ? But be this as it may, it does not affect the theory here proposed, for it will not be doubted or denied that the different substances have different capacities for galvanic electricity, in the same way as they are allowed to have for caloric. Admitting then that the same kinds of matter, and some kinds of metals, have the property of transmitting, or what is the same, of admitting and parting with galvanic electricity quicker than others, and that the fluid is universal ; I shall attempt to describe how all the different galvanic phenomena may be accounted for by the known laws of matter.
In the galvanic trough the zinc plate is a better conductor of galvanic electricity than the copper one, that is, it admits and parts with it quicker. The diluted acids also are supposed to bave their full share of galvanic electricity, and the plates and acids are so arranged that the zinc plate being of greater capacity for the galvanic Auid than the acid; therefore, a part of the galvanic electricity is taken from the acid and absorbed by the zinc in each of the divisions, by which the zinc is so overcharged as to communicate part to the copper. The copper becomes thereby over charged, and again communicates it to the acid in the next cell; so that a continual circulation of the galvanic electricity will go on till it accumulates at the right hand acid, so as to admit no more from the copper, and the copper to admit no more from the zinc, and a state of equilibrium be induced, But if now a wire is used to connect the ends of the trough, the superabundant fluid at the right hand cell of acid will flow to the acid at the left hand cell along the wire; then it will again be communicated to the zinc, the copper, and the acid in each division, and form a circular stream till the acid or plates get oxidized, when it will cease to flow.
To make the operation more plain, suppose the zinc and copper plates soldered together, and put into the trough before the acid is put in, and that these plates are each as full as their capacities would permit, and in a state of equilibrium with respect to each other; but that the zinc admitted and parted with the electricity quicker than the copper, the acid being then poured into the trough between the plates, and as it does not hold the galvanic fluid in the same state of equilibrium with the plates of zinc or copper, it either communicates some of its electricity to the plates or admits it from them. Suppose that it possesses a surplus, and communicates it to the plates, each of the plates will admit a quantity proportioned to their capacities; but they may have different capacities as well as different powers for admitting and parting with it quickly; and we are here to suppose that the zinc admits it much quicker than the copper, and that, consequently, the zinc is saturated with it first or soonest, and is transmitting it to the copper before the copper has received all that it could admit from the acid, and that this has been going forward in all the divisions. The consequence would be that the acid would be deprived of a great quantity of its electricity in each trough, or division; and that the zincs being saturated before the copper, they would be giving the electric fluid to the copper, at the same time that the copper would be receiving it on the other side from the acid; but before the copper is in equilibrio with the acid and the zinc, the acid having parted with the galvanic fluid to both the zinc and copper, is reduced to the equilibrium of the copper, before the copper is in equilibrium with the zinc. The zinc, therefore, continues to pour it into the copper at the same time it is continuing to take it from the acid : the acid is by this means robbed of its galvanic fluid, and its equilibrium is also prevented; and the copper begins to give back to the acid, the acid to give to the zinc, and the zinc to the copper in the next cell, and so on till the whole would come to an equilibrio by the right hand acid, and the zinc having imparted as much to the copper as to put them in equilibrio, and the others in the same way. But suppose a wire or other conductor now to connect the extreme cells of the trough, by which the circuit would be completed, no influence would take place till the equilibrium was destroyed by some means, and the means is the acid which liberates the galvanic fluid from the zinc plates, and supplies it to the copper ; the acid, at the same time, conducts it from the copper to the zinc, and is the medium by which it passes.
But, according to this hypothesis, if water were used in place of acid, the galvanic influence should still take place, if the equilibrium is destroyed by the water being put into the trough of a different capacity for the galvanic Auid, as it imparts it quickly to the zinc and slowly to the copper. The water not acting chemically, or very slightly so, upon the plates, no vibration, or only a very slight one, is produced ; and the galvanic fluid is not propelled to the different ends of the trough with the same celerity as when the acid is used. If, however, the equilibrium was allowed to obtain among the water and metals, and no chemical action to take place, then no galvanic effect would be produced, because there would be complete rest: but the contact of the metals themselves has a chemical effect, and so would pure water have upon them, but only in a slighter degree than acid, and a current of galvanic Auid would still flow along the connecting wire, but only in a less sensible stream.
According to this theory any other substance beside metals might be employed in the trough, if the one was a better conductor of electricity than the other, and arranged in a certain order.
In chemical science it has been the study of the chemist to ascertain and point out the different affinities that bodies have to each other; to show which are the strongest; what are the laws that regulate the composition and decomposition of bodies, and to discover the cause of affinity and repulsion when bodies are brought into certain positions with respect to each other.
Sir Humphry Davy was among the first who gave anything like a probable reason why the affinity of bodies might be owing to the influence of the electric Auid. That hypothesis since his time has received a considerable degree of corroboration by several authors: but though all these authors have found from experiment that electricity is intimately connected with every change of chemical action, yet they have not attempted to account for the production of the action, or mode of operation by the presence of the electrical fluid. They find that an action takes place when two or more bodies are brought together, but they have not attempted to show what it is in these bodies which gives rise to the action : the mode of operation is not investigated; they only find that there is weaker or stronger affinities, attractions, or repulsions, and to these they ascribe the effects which take place.
These philosophers have discovered that when a certain arrangement of metals and liquids are placed together, as in the galvanic trough, that certain decompositions and recompositions are the result, by means of a stream of electricity; but they have not shown why that stream should produce such effects, or why it should take place by the metals and liquids being so arranged.
My object in this investigation is to discover what it is in the bodies that is the cause of the changes which is effected by that arrangement. It must proceed from some quality or property in the bodies employed in connection with their arrangement, which enables them to produce a current or stream of electricity. It is found that different kinds of metals will produce this effect; and that different kinds of liquids may also be employed with effect. But the metals must be arranged all in a particular order, and that a medium of communication must be established between the plates by a liquid or other conducting body; and it is found, that were but only one of the plates reversed, the stream of electricity would no longer circulate. How has this apparatus produced this current of electricity is the question to be answered ? That it has produced it is unquestionable. Has its motion in passing through any of the acid solutions been ascertained? Is it propagated by vibrations, updulations, or by a right forward motion in the fluids ? That it is propagated by undulations seems highly probable, because the fluid is stationary and cannot get forward; and as the whole surface of the plate must act on the acid fluid at the same time, the electric Auid will be communicated to every touching particle, and transmitted from it to the one adjoining successively, till it reach the next plate. Whether the electric fuid is transmitted in this way, or whether it is only a system of vibrations communicated from the plates to the acid fluid in the troughs, and by it to the plates in succession, I shall pot at present pretend to know. If it is by vibrations only, then it must be supposed that the air and acid is saturated with the electric fluid; that it is only put in motion by the vibrations; and that the vibrations are so quick as to separate the elements of water, or other substances, at the sharp ends of the wires.
But how does it happen that only one element is evolved at one wire ? Where goes the other ? Does it go to the other wire? If the separation takes place at the positive wire, why does one gas evolve there, and not both gases rise together? Has the stream of electricity a tendency to carry the one gas forward to the other or negative poiot of the wire, and leave the other to rise to the surface ? This seems to be the case from observing the platinum wire : but whether this be the case or not may probably be ascertained by experiment. One thing seems probable, that the electric fluid fills all space in all substances, solid, liquid, and gaseous, and that its circulation or current is caused by a change of temperature in the substances. This change of temperature may be caused by the plate being composed of two metals which have different capacities for caloric by being soldered together; the communication being complete, the heat of the one which has the greater capacity will be flowing into the other continually till it be saturated, and a balance be established. But as there is a communication by means of the acid in the trough for the colder caloric to escape to the next adjoining warmer plate, it will go there, and enter that plate, but that plate being also soldered to another of less capacity for caloric, it will be continually discharging its caloric into that plate, and the plate again into the acid fluid, and so on through the whole trough. ' The two extreme plates having wires fixed to them, the
points of these wires beivg brought near together enables the stream to be completed, or the circuit formed, by which the electric fuid is formed to produce such extraordinary effects.
It may still be asked what makes the stream of electricity circulate, if there is no impelling force or power ? The answer is, that it is owing to the elasticity of the electric Auid, which has a tendency, from its elasticity, to produce an equal state of density in every body, and throughout the universe. The intensity of the Auid is as its density, every particle being the same wherever it is placed, but by its rarity it becomes less hot, and by compression or condensation it becomes concentrated, and has its elasticity and intensity increased in proportion to the compression.
The instance of compressed air in a syringe is a complete proof of this proposition, and instead of condensation, if the air were rarified, without increasing the quantity of caloric, it would feel colder, and it is that which produces heat in thunder storms, and condensation in the lightning.
From this theory it appears that it is the motion of the electric fluid that must produce the changes or effects on the bodies with which it is in contact.
There is a difficulty of accounting for the different capacities and dispositions that bodies have when in contact to contain caloric or electricity (for they are considered the same in different circumstances), and to part with it to the adjoining body with which it is in contact.
It is a fact that different bodies exposed to the same temperature in a room, and which show the same degree of temperature by the thermometer, will change their temperature when brought into new situations in the same room. For instance were a piece of lead and a glass containing water brought into contact, with a piece of damp cloth between them, which had formerly stood at a distance from each other, the lead would part with its cold, or rather the water would part with its caloric to the lead. The lead would absorb caloric, and the water would furnish it in the first instance, but before it took the temperature of the room it would absorb from the surrounding atmosphere the quantity wanted. Whenever two bodies have different radiating powers, then if one have the power of absorbing faster than the other radiates it will contain much heat, but it will probably also part with it quickly. If it absorbs quickly it radiates quickly. A third body may still absorb quicker than either of the two former, and also part with it quicker than either. This disposition will cause a stream of caloric to flow along, so long as the bodies do not approach a state of equilibrium. But if the last is connected so as to radiate upon the first, it will supply it with more caloric than it can absorb, and thus a constant stream will be kept up similar to that by the galvanic apparatus.
The electric spark when taken from a steam boiler is a proof of the theory that all electricity is only caloric in a quiescent condensed state : in that state called positive it is in a higher state of conden