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hemispheres on the atmospheric atoms in the two inner b and c extend its influence or disturbance of equilibrium indefinitely in every direction. Let the inner circle, fig. 7, represent a section of such ball, and the spaces between each two adjacent rings, the sections of spherical strata of atmospheric atoms, with their centres coinciding with the centre of the ball.

(52.) The sum of the attractions of the free active electricity of the atoms in any one spherical stratum, for the common matter of those in the next more remote stratum would (if the law be as above stated) equal that between the electricity of the ball and the common matter of the first stratum; and, consequently, the sum of such attractions between any one pair of next adjacent strata, (strata 2 and 3, for instance,) would exactly equal the sum of those between any other pair of strata next adjacent to each other, however distant those pairs of strata might be from the ball, or one pair of strata from the other pair.

(53.) Thus calling the number of atoms in the first stratum = 9, and the sum of their attractions for the electricity of the ball = 1, the forces would stand thus :

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12th.... 144g X 1-144 =

And so forth, for any number of strata whatever.

(54.) But I suppose the attractions exerted by the electricity of the ball on the common matter of the atoms of the first stratum is (contrary to the supposed law) lessened, or partly neutralised, at that and every subsequent stratum, by the attraction between each atom and its own electricity, such attraction tending to an equal diffusion of that electricity over every part of its surface.

(55.) This continual deduction from the original force, I presume, would, at some finite distance, entirely overcome it, and that force would, in that case, be divided equably, though not equally, amongst all the atoms, in a limited spherical space, having the electrified ball for its centre. The ball would thus be opposed by all the surrounding atoms, in a struggle, as it were, for the possession of the electricity added to it. The force of the ball would be exerted on such electricity in a direction towards the ball's centre, and the forces of all the atmospheric atoms exerted on the same electricity, would be from the centre of the ball; but the forces of each stratum after the first, would not be immediate, but be exerted, as before shewn, through the medium or inductive agency of all the strata nearer to the ball; as the lower links of suspended chains do

not act immediately on the higher, but only by communication. through those intermediate.

(56.) Admitting the law and the imaginary conditions above mentioned, and applying them to the balls b and c, fig. 6, the before mentioned preponderant force to the right of mn, or beyond the outer c space, would never be wholly destroyed, however far the balls might recede from each other. Many of the spherical strata of atmospheric atoms, within the influence of each ball, must impinge on and intersect similar spherical strata round the other ball at the plane vx, and prevent the inductive influence of either ball being exerted with the same effect in the portions of its spherical strata, which shall be cut off from the larger portion by the plane v x, and of course prevent the inductive influence of each from being exerted with the same force, on its side nearer to the other ball, as on its remoter side.

(57.) But excluding the law, and even admitting the other imaginary conditions (prop. 50), then the balls will recede only till the inductive force of the electricity of each ball, exerted in every direction, is equalled and balanced exactly by the resisting attractions of the common matter of such balls, and the surrounding atmospheric atoms, for their own several electricities, and perhaps by other retarding or opposing causes.

(58.) Then, also, two perfect spheres of disturbed equilibrium, having the two balls for their centres, will meet at the atom e, without being able to cause its electricity to recede towards the next adjacent atoms, 1, 2, &c., in the plane vx, so as to act upon them by induction.-Vide note at the end.

(59.) The dissipation of electricity, whether positive or negative, from points to atmospheric atoms, is an instance of recession apparently explainable in the same manner, as the recession of one electrified ball from another.

By fig. 3, it is shown how one ball (or atom), as c 2, in its natural state, becomes, by its neighbourhood to an electrified ball, more changed in its electrical condition than another, as c 1; that is to say, by its induction being assisted by, or transmitted to a greater mass of matter, on its side remote from the electrified ball, as by or to d 2 and d 3, and the two lines of balls through which they are supposed to transmit their inductive influence.

(60.) Fig. 4 (19, et. seq.) furnishes a further illustration of this; and the ends of the cylinder are similar in principle to points, especially when we consider such cylinder as becoming more elongated than in the figure, and also reduced in thickness; the whole cylindrical surface approaching the axis fk, and the surface of the right hemispherical termination contracting equally towards its central point k, till the radius of both cylinder and hemisphere are reduced to (say) onefourth of their original length.

(61.) By this change, the number of balls forming the first stratum round the cylindrical part of the cylinder, (supposing them

moveable like the atoms of the atmosphere,) are but about onefourth of the original number; whereby each ball of this smaller number will have to sustain nearly four times the proportional inductive influence before sustained by each ball of the larger number. (62.) By the same change, the number of balls in the first stratum round the hemispherical part of the cylinder, will be reduced to one-sixteenth of the original number; whereby each ball of this smaller number, will have to sustain a far greater proportional inductive force or influence than that before sustained by each ball, of such original or larger number; and also a far greater proportional increase of induction than that sustained by the reduced cylindrical portion of the cylinder.

(63.) A great increase of tendency will therefore be acquired, by the reduced hemispherical end of the cylinder (if electrified positively), to part with its electricity to the stratum of balls next adjacent to it (prop. 15, pp. 10, 11, 12), particularly those about h, where the positive state of the cylinder will be at the highest; and where also the nearest balls will be in the most negative state on the side nearest the cylinder, and the most positive state on the remoter side. When this positive state of the cylinder, and negative state of the nearest half of the balls, (or, which I suppose the same thing, (34,) the atoms of a surrounding atmosphere,) become so great, that the attraction of the balls or atoms for the electricity of the cylinder overcome that of the cylinder itself, a portion of electricity will pass as a spark from the cylinder, to a ball or balls (or atoms) about h (11, 12).

(64.) These electrified balls (or atoms) will then, for an instant, be in a similar situation, with respect to the electrified cylinder, as each of the electrified balls in figs. 5 and 6, is to the other; and will, for the reasons there explained, recede from the cylinder. Other next adjacent balls or atoms will supply their places; become similarly electrified, in the same manner, recede to make room for others, and so on as long as the electricity is sufficiently intense, to pass in a spark to the balls or atoms about h.

(65.) The converse, so far, applies pretty accurately to the negative state of electricity.

(66.) There is, however, a peculiarity in the positive discharge, from a point into the atmosphere not applying to the negative; the former giving a brush-like mass of light, the latter a light generally compared to a star; the explanation of which appears to me to be indirectly connected with the doctrines of the recession.

(67.) The chief cause of the difference I apprehend to be, that in the former case, a large reservoir of electricity, containing more than its natural share, is pouring itself upon a number of smaller ones, containing already their natural share; while in the case of negative electricity, several small reservoirs, containing their natural share of electricity only, are pouring that small quantity into a large reservoir deprived of a portion of its natural share. In the

former case, the absolute quantity of electricity in motion, from any one atom to any other of the air, is far greater than in the latter. In the latter case, the natural quantity, at most, is in motion; in the former, the natural quantity, with a considerable addition.

(68.) When the first atmospheric atom at h, on the line ho (fig. 4), reduced as before mentioned, and representing the end of a long blunt pointed body, has become positively electrified, it acts for an instant like a most attenuated point to the electrified body; its mobility being far less than that of electricity, (and electricity, I suppose, possessing homogeneous attraction and momentum), more of the electricity is enabled to follow the first portion, and pass on over such first atmospheric atom before it has had time to recede, using it as a stepping-stone to the second; that to the third, and so on, as to other more distant atmospheric atoms, about the line h o, according to the intensity of the electrification, the size of the point, &c.

(69.) These electrified atoms, having receded the breadth of one atom, a new one has also been simultaneously drawn into the place of the first; serves in like manner, as a stepping-stone to the stream of electricity; in like manner recedes, and so of others.

(70.) At different distances, (increasing with the increase of the rounded end of the body), this principal spark branches out into several ramifications, to which the above observations, also partly apply.

(71.) When the same body (fig. 4), reduced as before mentioned (60,) is electrified negatively, the quantity of electricity passing at once from the atmospheric atoms into the negatively electrified body, is limited to the small natural quantity in the first few strata of atoms; for, though the first stratum may act sufficiently, by induction, to draw sparks from the second stratum, the second from the third, &c., yet these effects must be less than in the case of positive electricity, and be rapidly diminished by distance and the consequent increase in the number of atoms, in the remoter strata, to be acted upon, by induction, by the smaller number in the nearer strata. The line of sparks, or stream of electricity, must be limited to the natural quantity, at the most, belonging to the atmospheric atoms through which it passes, while the stream from a positive point, to the line of atomspheric atoms, through which it passes, (and even its ramifications,) might well be conceived to be many times larger, and consequently able to act inductively upon, and pass in a continuous spark to, a much more distant stratum of atmospheric atoms, especially when aided by the concentrating power of its own homogeneous attractions.

(72.) The negatively electrified body, appearing from the deficiency in the quantity of electric fluid to be incapable of thus transmitting its negative state to, or rather of drawing the electric fluid from, any great distance, even by using the atmospheric atoms as stepping-stones, it is necessary that every atom, in order to be

come electrified, should approach near to the point, and transfer its small contribution, either immediately to the point or to some atom very near it.

(73.) The atoms near to, and immediately in front of, the point, having become negative in a degree, according to their distance, and incapable of further transmission of electricity by spark; and being more immobile than the electricity, the atoms around the point, and around those atoms nearest to it, and already electrified, pour their electricity into the point (and perhaps into such nearest atoms in front of it), at all or nearly all angles, with the axis of the long conducting body, and then recede, and pass off in the stream of electrified particles, whose general direction is, in the axis of the body, prolonged.

(74.) The view I have taken, that the lesser depth of film is the cause of the less free and distant discharge of negative electricity, is favoured by some variations I tried on the common experiment of piercing a card with the positive and negative points of the discharger, placed at a distance from each other, in contact with the opposite surfaces of the card.

I have for some years supposed that the current of a battery, in all cases, begins both from the positive and negative surfaces simultaneously; so that one end of the connecting conductor becomes negative by deduction from its natural portion of electricity by the negative surface of the battery with which it is in contact, and the other end positive, by an additional portion of electricity, received by it from the positive surface with which that is in contact, and that the conductor would offer a less resistance to the deeper or positive current, so that the meeting of the two states in the conductor would be nearer to the negative than the positive surface of the battery. I also supposed that the same causes, operating more decidedly to the disadvantage of the negative state of electricity on an imperfect conductor, like a card, might be the cause why the perforation was always at the negative point. With these views, and in order to give the negative conductor time to abstract a portion of the shallow natural film of electricity from the negative surface of the card, before the positive surface should be affected by additional electricity from the positive point, I made the connection between the negative point and the battery, a few inches only in length, and also insulated, while that between the positive point and the battery was many feet long, and connected with a fender, the floor, &c. &c. I also made the card damp, to facilitate the negative electrification of the surface. On making the discharges, I obtained perforations of the card at above an inch from the negative point, when the points were 23 inches apart. Height of intensity, as might be expected, also helps this removal of the perforation from the negative point.

(75.) The electrical fly is but the converse example of the recession of electrified atmospheric atoms from a point. The points

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