Part 18 (1/2)
3. If a metallic point be fixed on the prime conductor, and the flame of a candle be presented to it, on electrising the conductor either with vitreous or resinous ether, the flame of the candle is blown from the point, which must be owing to the electric fluid in its pa.s.sage from the point carrying along with it a stream of atmospheric air.
The manner in which the acc.u.mulated electricity so readily pa.s.ses off by a metallic point may be thus understood; when a metallic point stands erect from an electrised metallic plane, the acc.u.mulated electricity which exists on the extremity of the point, is attracted less than that on the other parts of the electrised surface. For the particle of electric matter immediately over the point is attracted by that point only, whereas the particles of electric matter over every other part of the electrised plane, is not only attracted by the parts of the plane immediately under them, but also laterally by the circ.u.mjacent parts of it; whence the acc.u.mulated electric fluid is pushed off at this point by that over the other parts being more strongly attracted to the plane.
Thus if a light insulated horizontal fly be constructed of wire with points fixed as tangents to the circle, it will revolve the way contrary to the direction of the points as long as it continues to be electrised. For the same reason as when a circle of cork, with a point of the cork standing from it like a tangent, is smeared with oil, and thrown upon a lake, it will continue to revolve backwards in respect to the direction of the point till all the oil is dispersed upon the lake, as first observed by Dr. Franklin; for the oil being attracted to all the other parts of the cork-circle more than towards the pointed tangent, that part over the point is pushed off and diffuses itself on the water, over which it pa.s.ses without touching, and consequently without friction; and thus the cork revolves in the contrary direction.
As the flame of a candle is blown from a point fixed on an electrised conductor, whether vitreous or resinous electricity is acc.u.mulated on it, it shows that in both cases electricity pa.s.ses from the point, which is a forcible argument against the mechanical theory of positive and negative electricity; because then the flame should be blown towards the point in one case, and from it in the other.
So the electric fly, as it turns horizontally, recedes from the direction of the points of the tangents, whether it be electrised with vitreous or resinous electricity; whereas if it was supposed to receive electricity, when electrised by resin, and to part with it when electrised by gla.s.s, it ought to revolve different ways; which also forcibly opposes the theory of positive and negative electricity.
As an electrised point with either kind of electricity causes a stream of air to pa.s.s from it in the direction of the point, it seems to affect the air much in the same manner as the fluid matter of heat affects it; that is, it will not readily pa.s.s through it, but will adhere to the particles of air, and is thus carried away with them.
From this it will also appear, that points do not attract electricity, properly speaking, but suffer it to depart from them; as it is there less attracted to the body which it surrounds, than by any other part of the surface.
And as a point presented to an electrised conductor facilitates the discharge of it, and blows the flame of a candle towards the conductor, whether vitreous or resinous electricity be acc.u.mulated upon it; it follows, that in both cases some electric matter pa.s.ses from the point to the conductor, and that hence there are two electric ethers; and that they combine or explode when they meet together, and give out light and heat, and occupy less s.p.a.ce in this their combined state, like the union of nitrous gas with oxygen gas.
IV. _Acc.u.mulation of Electric Ethers by Contact._
The electric ethers may be separately acc.u.mulated by contact of conductors with nonconductors, by vicinity of the two ethers, by heat, and by decomposition.
Gla.s.s is believed to consist in part of consolidated resinous ether, and thence to attract an electric atmosphere round it, which consists of a greater proportion of vitreous ether compared to the quant.i.ty of the resinous, as mentioned in Proposition No. 4. This atmosphere may stand off a line from the surface of the gla.s.s, though its attractive or repulsive power may extend to a much greater distance; and a more equally mixed electric atmosphere may stand off about the same distance from the surface of a cus.h.i.+on.
Now when a cus.h.i.+on is forcibly pressed upon the surface of a gla.s.s cylinder or plane, the atmosphere of the cus.h.i.+on is forced within that of the gla.s.s, and consequently the vitreous part of it is brought within the sphere of the attraction of the resinous ether combined with the gla.s.s, and therefore becomes attracted by it in addition to the vitreous part of the spontaneous atmosphere of the gla.s.s; and the resinous part of the atmosphere of the cus.h.i.+on is at the same time repelled by its vicinity to the combined resinous ether of the gla.s.s.
From both which circ.u.mstances a vitreous ether alone surrounds the part of the gla.s.s on which the cus.h.i.+on is forcibly pressed; which does not, nevertheless, resemble an electrised coated jar; as this acc.u.mulation of vitreous ether on one side of the gla.s.s is not so violently condensed, or so forcibly attracted to the gla.s.s by the loose resinous ether on the other side of it, as occurs in the charged coated jar.
Hence as weak differences of the kinds or quant.i.ties of electricity do not very rapidly change place, if the cus.h.i.+on be suddenly withdrawn, with or without friction, I suppose an acc.u.mulation of vitreous electric ether will be left on the surface of the gla.s.s, which will diffuse itself on an insulated conductor by the a.s.sistance of points, or will gradually be dissipated in the air, probably like odours by the repulsion of its own particles, or may be conducted away by the surrounding air as it is repelled from it, or by the moisture or other impurities of the atmosphere. And hence I do not suppose the friction of the gla.s.s-globe to be necessary, except for the purpose of more easily removing the parts of the surface from the pressure of the cus.h.i.+on to the points of the prime conductor, and to bring them more easily into reciprocal contact.
When sealing wax or sulphur is rubbed by a cus.h.i.+on, exactly the same circ.u.mstance occurs, but with the different ethers; as the resinous ether of the spontaneous atmosphere of the cus.h.i.+on, when it is pressed within the spontaneous atmosphere of the sealing wax, is attracted by the solid vitreous ether, which is combined with it; and at the same time the vitreous ether of the cus.h.i.+on is repelled by it; and hence an atmosphere of resinous ether alone exists between the sealing wax and the cus.h.i.+on thus pressed together. It is nevertheless possible, that friction on both sealing wax and gla.s.s may add some facility to the acc.u.mulations of their opposite ethers by the warmth which it occasions. As most electric machines succeed best after being warmed, I think even in dry frosty seasons.
Though when a cus.h.i.+on is applied to a smooth surfaced gla.s.s, so as to intermix their electric atmospheres, the vitreous ether of the cus.h.i.+on is attracted by the resinous ether combined with the gla.s.s; but does not intermix with it, but only adheres to it: and as the gla.s.s turns round, the vitreous electric atmosphere stands on the solid resinous electric ether combined with the gla.s.s; and is taken away by the metallic points of the prime conductor.
Yet if the surface of the gla.s.s be roughened by scratching it with a diamond or with hard sand, a new event occurs; which is, that the vitreous ether attracted from the cus.h.i.+on by the resinous ether combined with the gla.s.s becomes adhesive to it; and stands upon the roughened gla.s.s, and will not quit the gla.s.s to go to the prime conductor; whence the surface of the gla.s.s having a vitreous electric atmosphere united, as it were, to its inequalities, becomes similar to resin; and will now attract resinous electric ether, like a stick of sealing wax, without combining with it. Whence this curious and otherwise unintelligible phenomenon, that smooth surfaced gla.s.s will give vitreous electric ether to an insulated conductor, and gla.s.s with a roughened surface will give resinous ether to it.
V. _Acc.u.mulation of electric ethers by vicinity._
Though the contact of a cus.h.i.+on on the whirling gla.s.s is the easiest method yet in use for the acc.u.mulation of the vitreous electric ether on an insulated conductor; yet there are other methods of effecting this, as by the vicinity of the two electric ethers with a nonconductor between them.
Thus I believe a great quant.i.ty of both vitreous and resinous electric ether may be acc.u.mulated in the following manner. Let a gla.s.s jar be coated within in the usual manner; but let it have a loose external coating, which can easily be withdrawn by an insulating handle. Then charge the jar, as highly as it may be, by throwing into it vitreous electric ether; and in this state hermetically seal it, if practicable, otherwise close it with a gla.s.s stopple and wax. When the external coating is drawn off by an insulating handle, having previously had a communication with the earth, it will possess an acc.u.mulation of resinous electric ether; and then touching it with your finger, a spark will be seen, and there will cease to be any acc.u.mulated ether.
Thus by alternately replacing this loose coating, and withdrawing it from the sealed charged jar, by means of an insulating handle; and by applying it to one insulated conductor, when it is in the vicinity of the jar; and to another insulated conductor, when it is withdrawn; vitreous electric ether may be acc.u.mulated on one of them, and resinous on the other; and thus I suspect an immense quant.i.ty of both ethers may be produced without friction or much labour, if a large electric battery was so contrived; and that it might be applied to many mechanical purposes, where other explosions are now used, as in the place of steam engines, or to rend rocks, or timber, or destroy invading armies!
The principle of this mode of acc.u.mulating the two electric ethers in some measure resembles that of Volta's Electrophorus and Bennet's Doubler.
VI. _Acc.u.mulation of electric ethers by heat and by decomposition._
When gla.s.s or amber is heated by the fire in a dry season, I suspect that it becomes in some degree electric; as either of the electric ethers which is combined with them may have its combination with those materials loosened by the application of heat; and that on this account they may more forcibly attract the opposite one from the air in their vicinity.
It has long been known, that a siliceous stone called the tourmalin, when its surfaces are polished, if it be laid down before the fire, will become electrified with vitreous, or what is called positive electricity on its upper surface; and resinous, or what is called negative electricity on its under surface; which I suppose lay in contact with somewhat which supported it near the fire.