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ably heated; and if a glass pane be heated till mentioned the equal repulsion in cases of poit begins to grow soft, and in that state be sitive and of negative electricity, as a phenoheld between the wire of a charged phial, and menon difficult to be explained. I have somethe discharging wire, the course of the elec- times, too, been inclined, with you, to resolve trical fluid wilī not be through the glass, but all into attraction; but besides that attraction on the surface, round by the edge of it.” seems in itself as unintelligible as repulsion,
By this last experiment of Mr. Canton's, it there are some appearances of repulsion that appears, that though by a moderate heat, thin I cannot so easily explain by attraction; this glass becomes, in some degree, a conductor for one instance. When the pair of cork balls of electricity, yet, when of the thickness of a are suspended by flaxen threads, from the end common pane, it is not, though in a state near of the prime conductor, if you bring a rubbed melting, so good a conductor as to pass the glass tube near the conductor, but without shock of a discharged bottle. There are other touching it, you see the balls separate, as beconductors which suffer the electric fluid to ing electrified positively; and yet you have pass through them gradually, and yet will not communicated no electricity to the conductor, conduct a shock. For instance, a quire of for, if you had, it would have remained there, paper will conduct through its whole length, after withdrawing the tube; but the closing so as to electrify a person, who, standing on of the balls immediately thereupon, shows wax, presents the paper to an electrified prime that the conductor has no more left in it than conductor; but it will not conduct a shock its natural quantity. Then again approacheven through its thickness only; hence the ing the conductor with the rubbed tube, if, shock either fails, or passes by rendering a while the balls are separated, you touch with hole in the paper. Thus a sieve will pass a finger that end of the conductor to which water gradually, but a stream from a fire en- they hang, they will come together again, as gine would either be stopped by it, or tear a being, with that part of the conductor, brought hole through it.
to the same state with your finger, i. e. the It should seem, that to make glass perme- natural state.
But the other end of the conable to the electric fluid, the heat should be ductor, near which the tube is held, is not in proportioned to the thickness. You found that state, but in the negative state, as appears the heat of boiling water, which is but 210, on removing the tube; for then part of the nasufficient to render the extreme thin glass in tural quantity left at the end near the balls, a Florence flask permeable even to a shock leaving that end to supply what is wanting Lord Charles Cavendish, by a very ingenious at the other, the whole conductor is found to experiment, has found the heat of 400 requi- be equally in the negative state. Does not site to render thicker glass permeable to the this indicate that the electricity of the rubbed common current.
tube had repelled the electric fluid, which “ A glass tube, (See the Plate) of which was diffused in the conductor while in its nathe part C B was solid, had wire thrust in tural state, and forced it to quit the end to each end, reaching to B and C.
which the balls were suspended? Iown I find "A small wire was tied on at D, reaching it difficult to account for its quitting that end to the floor, in order to carry off any electri- on the approach of the rubbed tube, but on city that might run along upon the tube. the supposition of repulsion; for, while the
“ The bent part was placed in an iron pot; conductor was in the same state with the air, filled with iron filings; a thermometer was also i. e. the natural state, it does not seem to me put into the filings: a lamp was placed under easy to suppose, that an attraction should sudthe pot; and the whole was supported upon denly take place between the air and the naglass.
tural quantity of the electric fluid in the con“The wire A being electrified by a ma ductor, so as to draw it to, and accumulate it chine, before the heat was applied, the corks on the end opposite to that approached by the at E separated, at first upon the principle of tube ; since bodies, possessing only their nathe Leyden phial.
tural quantity of that fluid, are not usually “But after the part C B of the tube was seen to attract each other, or to affect mutuheated to 600, the corks continued to sepa- ally the quantities of electricity each contains. rate, though you discharged the electricity by There are likewise appearances of repulsion touching the wire át E, the electrical ma- in other parts of nature. Not to mention the chine continuing in motion.
violent force with which the particles of wa. “ Upon letting the whole cool, the effect ter, heated to a certain degree, separate from remained till the thermometer was sunk to each other, or those of gunpowder, when 400.”
touched with the smallest spark of fire, there It were to be wished, that this noble philo- is the seeming repulsion between the same sopher would communicate more of his expe- poles of the magnet, a body containing a subriments to the world, as he makes many, and tle moveable fluid in many respects analogous with great accuracy.
to the electric fluid. If two magnets are so You know I have always looked upon and 'suspended by strings, as that their poles of
the same denomination are opposite to each when more matter of the same kind was adother, they will separate, and continue so; ded to the smallest parcel, so as to make it or if you lay a magnetic steel bar on a equal to the biggest. By all the laws atsmooth table, and approach it with another traction in matter, that we are acquainted parallel to it, the poles of both in the same with, the attraction is stronger in proportion position, the first will recede from the second to the increase of the masses, and never in so as to avoid the contact, and may thus be proportion to the difference of the masses. I pushed (or at least appear to be pushed) off should rather think the law would be, “ That the table. Can this be ascribed to the attrac- the electric fluid is attracted strongly by all tion of any surrounding body or matter draw- other matter that we know of, while the parts ing them asunder, or drawing the one away of that fluid mutually repel each other." from the other? If not, and repulsion exists Hence its being equally diffused (except in in nature, and in magnetism, why rnay it not particular circumstances) throughout all other exist in electricity? We should not, indeed, matter. But this you jokingly call “electrimultiply causes in philosophy without neces- cal orthodoxy.” It is so with some at present, sity; and the greater simplicity of your hypo- but not with all; and, perhaps, it may not althesis would recommend it to me, if I could ways be orthodoxy with any body. Opinions see that all appearances would be solved by are continually varying, where we cannot it. But I find, or think I find, the two causes have mathematical evidence of the nature of more convenient than one of them alone. things: and they must vary. Nor is that vaThus I might solve the circular motion of riation without its use, since it occasions a your horizontal stick, supported on a pivot, more thorough discussion, whereby error is with two pins at their ends, pointing contra- often dissipated, true knowledge is increased, ry ways, and moving in the same direction and its principles become better understood when electrified, whether positively or ne- and more firmly established. gatively: when positively, the air opposite Air should have, as you observe, “its share to the points being electrised positively, re- of the common stock of electricity, as well as pels the points; when negatively, the air oppo- glass, and, perhaps, all other electrics per se. site to the points being also, by their means, But I suppose, that, like them, it does not electrised negatively, attraction takes place easily part with what it has, or receive more, between the electricity in the air behind the unless when mixed with some non-electric, heads of the pins, and the negative pins, and as moisture for instance, of which there is so they are, in this case, drawn in the same some in our driest air. This, however, is only direction that in the other they were driven. a supposition; and your experiment of restor
-You see I am willing to meet you halfway, ing electricity to a negatively electrised pera complaisance I have not met with in our son, by extending his arm upwards into the brother Nollet, or any other hypothesis-maker, air with a needle between his fingers, on the and therefore may, value myself a little upon point of which light may be seen in the night, it, especially as they say I have some ability is, indeed, a curious one. In this town the in defending even the wrong side of a ques- air is generally moister than with us, and tion, when I think fit to take it in hand. here I have seen Mr. Canton electrify the air
What you give as an established law of the in one room positively, and in another, which electric fluid, " That quantities of different communicated by a door, he has electrised the densities mutually attract each other, in order air negatively. The difference. was easily to restore the equilibrium,” is, I think, not discovered by his cork balls, as he passed out well founded, or else not well expressed. Two of one room into another.-Père Beccaria, large cork balls, suspended by silk strings, and too, has a pretty experiment, which shows both well and equally electrified, separate to that air may be electrised. Suspending a a great distance. By bringing into contact pair of small light balls, by flaxen threads, to with one of them another ball of the same size, the end of his prime conductor, he turns his suspended likewise by silk, you will take globe some time, electrising positively, the from it half its electricity. It will then, in- balls diverging and continuing separate all deed, hang at a less distance from the other, the time. Then he presents the point of a but the full and the half quantities will not needle to his conductor, which gradually appear to attract each other, that is, the balls drawing off the electric fluid, the balls apwill not come together. Indeed, I do not proach each other and touch, before all is know any proof we have, that one quantity drawn from the conductor; opening again as of electric fluid is attracted by another quan- more is drawn off, and separating nearly as tity of that fluid, whatever difference there wide as at first, when the conductor is reduced may be in their densities. And, supposing to the natural state. By this it appears, that in nature, a mutual attraction between two when the balls came together, the air surparcels of any kind of matter, it would be rounding the balls was just as much electrised strange if this attraction should subsist strong- as the conductor at that time; and more than ly while those parcels were unequal, and cease the conductor, when that was reduced to its
natural state. For the balls, though in the parts of the wire burning holes in the floor natural state, will diverge, when the air that on which they fell, has proved the same with surrounds them is electrised plus or minus, regard to the electricity of nature. I was too as well as when that is in its natural state and easily led into that error by accounts given, they are electrised plus or minus themselves. even in philosophical books, and from remote I foresee that you will apply this experiment ages downwards, of melting money in purses, to the support of your hypothesis, and I think swords in scabbards, &c. without burning the you may make a good deal of it.
inflammable matters that were so near those It was a curious inquiry of yours, Whether melted metals. But men are, in general, such the electricity of the air, in clear dry weather, careless observers, that a philosopher cannot be of the same density at the height of two be too much on his guard in crediting their or three hundred yards, as near the surface relations of things extraordinary, and should of the earth and I am glad you made the never build an hypothesis on any thing but experiment. Upon reflection, it should seem clear facts and experiments, or it will be in probable, that whether the general state of danger of soon falling, as this does, like a atmosphere at any time be positive or nega- house of cards. tive, that part of it which is next the earth will How many ways there are of kindling fire, be nearer the natural state, by having given or producing heat in bodies! By the sun's to the earth in one case, or having received rays, by collision, by friction, by hammering, from it in the other. In electrising the air of by putrefaction, by fermentation, by mixtures a room, that which is nearest the walls, or of fluids, by mixtures of solids with fluids, and floor, is least altered. There is only one by electricity. And yet the fire when prosmall ambiguity in the experiment, which duced, though in different bodies it may differ may be cleared by more trials; it arises from in circumstances, as in colour, vehemence, &c. the supposition that bodies may be electrised yet in the same bodies it is generally the same. positively by the friction of air blowing strong. Does not this seem to indicate that the fire ly on them, as it does on the kite and its existed in the body, though in a quiescent string. If at some times the electricity ap- state, before it was by any of these means expears to be negative, as that friction is the cited, disengaged, and brought forth to action same, the effect must be as from a negative and to view? May it not constitute a part, and state of the upper air.
even a principle part, of the solid substance I am much pleased with your electrical of bodies? If this should be the case, kindling thermometer, and the experiments you have fire in a body would be nothing more than demade with it. I formerly satisfied myself by veloping this inflammable principle, and setan experiment with my phial and syphon, ting it at liberty to act in separating the parts that the elasticity of the air was not increased of that body, which then exhibits the appearby the mere existence of an electric atmo- ances of scorching, melting, burning, &c. sphere within the phial; but I did not know, When a man lights a hundred candles from till you now inform me, that heat may be the flame of one, without diminishing that given to it by an electric explosion. The con- flame, can it be properly said to have commutinuance of its rarefaction, for some time after nicated all that fire? When a single spark the discharge of your glass jar and of your from a flint, applied to a magazine of gunpowcase of bottles, seem to make this clear. The der, is immediately attended with this conseother experiments on wet paper, wet thread, quence, that the whole is in flame, exploding green grass, and green wood, are not so satis- with immense violence, could all this fire ex. factory; as possibly the reducing part of the ist first in the spark? We cannot conceive it. moisture to vapour, by the electric fluid pass- And thus we seem led to this supposition, ing through it, mighi occasion some expan- that there is fire enough in all bodies to sion which would be gradually reduced by the singe, melt, or burn them, whenever it is, by condensation of such vapour.' The fine silver any means, set at liberty, so that it may exert thread, the very small brass wire, and the itself upon them, or be disengaged from them. strip of gilt paper, are also subject to a simi- This liberty seems to be afforded it by the lar objection, as even metals, in such circum- passage of electricity through them, which stances, are often partly reduced to smoke, we know can and does, of itself, separate the particularly the gilding on paper.
parts even of water; and perhaps the immeBut your subsequent beautiful experiment diate appearances of fire are only the effects on the wire, which you made hot by the elec- of such separations ? If so, there would be no tric explosion, and in that state fired gunpow- need of supposing that the electric fluid heats der with it, puts it out of all question, that itself by the swiftness of its motion, or heats heat if produced by our artificial electricity, bodies by the resistance it meets with in and that the melting of metals in that way, is passing through them. They would only be not by what I formerly called a cold fusion. heated in proportion as such separation could A late instance here, of the melting a bell be more easily made. Thus a melting heat wire, in a house struck by lightning, and cannot be given to a large wire in the flame