Updated 27 Jan 2005

WIRKSWORTH Parish Records 1600-1900

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New Experiments on Electricity


Abraham Bennet 1789

    In 1789 Abraham BENNET, who was Curate of Wirksworth, published a book called "New Experiments on Electricity". Bennet, soon to become a Fellow of the Royal Society, had an impressive list of 408 subscribers who backed the printing of his book, which was important in the early understanding of the Theory of Electricity. There seemed to be no transcription of the book on the Internet, and as I had inherited a copy of this rare book from my grandfather I decided to produce a transcription and put it on my website. Enquiries to
    Transcriber's note: spelling or punctuation not understood is marked: [?]. Links have been inserted to ease reading on the Internet. Transcribed at Eadar Dha Fhadhail (Ardroil), Isle of Lewis in the Outer Hebrides, Scotland, January 2005]

Transcribed at

Ardroil Jan 05
Outer Hebrides

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PAGE: v, x, xv, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140: PAGE



    A description of a doubler of electricity by which a very small quantity of electricity may be augmented till it becomes sensible by common electrometers, or visible in sparks.

    The great importance of a machine for the purpose of detecting very small quantities of electricity has occured to many electricians, as by such an assistant it is to be hoped that important discoveries may be made in the atmospheric electricity as well as in chemical experiments, wherein it may be suspected that electricity is combined with other substances. And many curious and well contrived electrometers have been made from the time that Mr Canton first used his pith balls, till Mr Cavallo substituted fine wires and balls suspended in a glass: but these as well as my gold leaf electrometer were incapable of discovering such very small communications of electricity as were made sensible by Mr Volta's condenser, which by means of a thin coated electric is capable of receiving a much greater quantity of the electrical fluid than a common insulated conductor of the same dimension, which fluid becomes sensible by separating the positive and negative sides of the charged plate. On this ingenious contrivance Mr Cavallo made a very


    considerable improvement by transferring the electricity contained in the upper plate to another condenser of smaller dimension, as explained in the philos. trans. vol. 72.

    Yet notwithstanding the very great sensibility of this apparatus, atmospheric electricity cannot always be discovered by it, for instance, when the negative state of falling rain is nearly equal to the positive state of the air thro' which it falls.

    The following instrument (which from its peculiar manner of augmenting small quantities of electricity I have named the electrical doubler) will render much smaller quantities of electricity sensible than the above mentioning double condenser, unless the first condenser exceeds the dimension of the second as much as shall render its power equal to a given number of operations of the doubler, and so far they may be consider'd as the same instrument, for the doubler is only a condenser multiplying its capacity in geometrical progression: but this capacity augments so quickly that a double condenser equal to its power at the twentieth operation must be 40 yards in diameter if the doubler and smaller condenser be only 2 inches.

    The sensibility of the doubler was evinced by an electro-meteorological diary kept for above a month, during which time I never failed to collect and distinguish atmospheric electricity. This diary I undertook at the request of my friend, Dr Darwin, who hoped some important atmospheric discoveries might be made thereby, and which


    accompanied my description of the doubler presented to the Royal Society by the Dean of Lincoln, and printed in the philos. trans. vol. 77.

    This instrument in its first and simplest construction consists of two polished brass plates with insulating handles. The handle of one is fixed on the side of the plate, and the other on the middle, and standing perpendicularly, see plate 1st.

    The plates are varnished on the underside, and the handles are made of mahogany, and fixed to the plates by insulating nuts of glass cover'd with sealing wax.

    The method of collecting electricity from the atmosphere, and continually augmenting it till it became sensible, was thus performed.

    In dry weather I carried into the open air a lighted torch not liable to be easily blown out, or a small lantern with a lighted candle in it, to the bottom of which was fixed by means of a socket an insulating handle of glass cover'd with sealing wax. In the other hand was carried a coated phial. Then elevating the flame a little higher than my head I applied it to the knob of the phial, holding it in this situation about half a minute. By this means I have found that more electricity may be collected than by an exploring wire insulated and fixed to the top of a church steeple, as practised by F.Beccaria. Having thus collected a sufficient charge I return'd into the house and applied the knob of the phial to the cap of the gold leaf electrometer, upon which I placed the plate (b) touching it with the forefinger


    stretched over the insulating nut; by this operation the electricity contained in the phial spreads upon the cap which serves as the condensing plate, and electrifies the plate (b) contrarily, because it is connected with the earth, and the varnish is interposed as a charged electric. The phial being now removed and the forefinger lifted up, the plate (b) is separated from the cap, and the plate (c) placed upon its upper side and touched by stretching a finger over the nut of its insulating handle, this last plate is then electrified contrary to (b) and the finger being removed, and the plate (c) separated from (b) it will be evident to electricians that the electricity of the cap and that of the plate (c) will be of the same kind, and nearly of equal quantity, so that the original charge is now doubled.

    I then apply the edge of the plate (c) to the side of the cap, and placing (b) as before, and touching it again, the electricity of (c) as well as that of the cap, both act upon the plate (b) and the intensity of its contrary electricity becomes equal to both; then removing (c) which comes away unelectrified; I take off my forefinger from (b) and lift it up, and placing (c) upon it I proceed as before, thus continuing to repeat this doubling process till the gold leaf diverges sufficiently to examine the quality of its electricity; or if the gold leaf be first taken out, the process may be continued till sparks appear.

    In rainy weather the knob of the phial was applied to the insulating handle of an umbrella, or to


    a torch carried under it, and in this manner I continued to examine atmospheric electricity, till I constructed a more convenient apparatus described in section the eighth.

    To prove that the electricity is doubled, it may be observed that the gold leaf opens to about twice the distance at each operation, and the application of the plate (c) to the side of the cap, or to a wire placed in it, does not diminish the divergency of the gold leaf tho' in this situation their electricity is diffused over double the quantity of surface, and admitting that the charge is doubled every time, which is not far from the truth whilst the intensity is weak, the twentieth operation will augment the first quantity of electricity above 500,000 times, and this process even with a doubler in its original and most imperfect state may be performed in less time than a minute.



    Improvements of the electrical doubler, with experiments made to discover the causes and obviate the inconvenience of its adhering or spontaneous electricity.

    Some time after the construction of my doubler of electricity described in the philos. trans. vol.77, and in the above section, I found that on performing the doubling process a sufficient number of times, it always produced electricity without previous communications, even after every method likely to prevent it had been tried; yet this impediment was not so great as to render the instrument useless, for the adherent or spontaneous electricity in the beginning of the process, when the instrument was cautiously used, being very small, was easily overcome by that which was communicated in atmospheric experiments, and in case of doubt the atmospheric electricity was distinguishable by applying the bottle which collected it, to the two first plates alternately as mention'd in my description of the instrument

    However to deprive the doubler entirely of its adherent or spontaneous electricity, was thought a desirable circumstance, as its sensibility wou'd then be much greater, and consequently it might with


    more certainty be applied to the discovery of new electrical facts, and which in this and the next section I hope will be sufficiently proved.

    Dr Darwin, at the desire of Lord G A Cavendish, made the first attempt with two plates moving two others by a lever, so as to bring them exactly to the same position in each operation. This contrivance he soon improved by another instrument in which the plates stood vertically and moved by rack work in a direction exactly parallel to each other. With this I tried whether the plates wou'd act without any resinous substance, and found that the interposed air was a good substitute, and hoped that now since it was not necessary to varnish the plates, nor bring them into contact, the spontaneous electricity supposed to arise from the accidental friction of the plates wou'd not be produced. This instrument was sent to Mr Partington, and the improvement of placing the plates near together without varnish was soon after mention'd to him in a letter.

    That I might accurately try whether the instrument wou'd be improved by this omission of varnish, I made a doubler which consisted of three plates standing vertical and parallel, the middle plate sliding backwards and forwards between the two others. The connection between the two external plates was performed by lifting up the sliding handle, and the distance of approach was adjusted by screws which stopped the foot of the middle plate any where between actual contact and the space of


    half an inch. When this doubler was completed and its insulating pillars entirely deprived of adhering electricity by melting the surface of the sealing wax which covered them, the doubling process was tried, and it produced negative electricity at about ten operations, so that this instrument tho' free from all accidental excitement was yet possessed of spontaneous electricity. But when I counted the doublings and applied an insulated candle to the first and second plates alternately, I cou'd easily collect and distinguish atmospheric electricity in a small room, tho' the doors and windows were shut, this I tried upon the supposition that the air would not be entirely deprived of its electricity by passing through small openings.

    The next improvement I had in contemplation was a revolving doubler, and before I had finished my contrivance, I was informed that Mr Nicholson had made one on the same principles, and intended to send it to me, I therefore attempted nothing more till I received his very elegant and useful instrument, which is much the best mode of constructing my doubler hitherto attempted.

    This doubler consists of two insulated and immoveable plates about two inches in diameter, and a moveable plate also insulated which revolves in a vertical plane parallel to the two immoveable plates, passing them alternately. See plate 2.

    The plate A is constantly insulated and receives the communicated electricity. The plate B revolves, and when it is opposite the plate A, the


    connecting wires at the end of the cross piece D must touch the pins of A and C at E F, and a wire proceeding from the plate B must touch the middle piece G, which is supported by a brass, wooden, or other conducting pillar in connection with the earth. In this position if electricity be communicated to the plate A, the plate B will acquire a contrary state, and passing forwards, the wires also moving with it by means of the same insulating axis, the plates are again insulated till the plate B is opposite to C, and then the wire at H touches the pin in C, connecting it with the earth, and communicating the contrary state of electricity to that of B but of the same kind with that of A. By moving the handle still further B is again brought opposite to A, and the connecting wires joining A and C.[?] they both act upon B, which is connected with the earth as before, and nearly double its intensity, whilst the electricity of C is absorbed into A; because of the increased capacity of A, whilst opposed to B, capable by its connexion with the earth of acquiring a contrary state sufficient to balance the influential atmospheres of both plates.

    Thus by continuing to revolve the plate B, the process is performed in a very expeditious and accurate manner.

    The ball (I) is made heavier on one side than the other, and screw'd upon the axis opposite to the handle, to counterbalance the plate B, which may therefore be stopped in any part of its revolution.


    Yet notwithstanding the convenience and accuracy of this doubler it always produced spontaneous electricity, even after all the resinous substances used in its construction had been melted over a candle, and after standing a long time with its plates in connection with the earth. I therefore conjectured that this spontaneous electricity was not owing to accidental friction, but to the increased capacity of approximating parallel plates which might attract and retain their charge tho' neither of them were insulated. To prove my hypothesis I first endeavoured more effectually and speedily to deprive the instrument of the electricity last communicated, and that I might know whether this spontaneous charge supposed to arise from the increased capacity of the parallel plates, wou'd be always of the same kind.

    To effect this deprivation I connected the plates A and C together by a wire hooked at each end upon two small knobs on the backs of the plates, the middle of the same wire touching the pillar which supports the doubler. Another wire was hooked at one end upon the back of the plate B, and at the other end to the brass ball which counterbalances this plate. Thus all the plates were connected with the earth, and by turning the handle of the doubler, it might be discharged of electricity in every part of its revolution.

    After often trying this method of depriving the doubler, I observed that its spontaneous charge was almost always negative. I then touched A and C with a positively charged bottle, and turned the


    doubler till it produced sparks for a long time together; and after this strong positive charge I hooked on the wires as above, and revolved the plate B about an hundred times, which so deprived the doubler of its positive electricity that when the wires were taken off, it produced a negative charge at about the same number of revolutions which it required before.

    The positively charged bottle was again applied, and the wires being hooked upon the plates, as before, B was revolved only fifty times, yet this was found sufficient to deprive it of its positive charge, and in many experiments five or six revolutions were sufficient; but I never thought it safe to stop at so few, and have therefore generally turned the handle forty or fifty times between every experiment.

    Lest electricity adhering to the electrometer shou'd obstruct the above experiments, I did not let it stand in contact with the doubler during its revolutions, but touched the plate A with the cap of the electrometer, after I supposed its electricity was become sufficiently sensible: but left even this contact shou'd communicate any electricity, I made a cap for my electrometer of shell lac, having a small tin tube in the center, to which the gold leaf was suspended within the glass, and a bent wire was fixed to the top which might easily be joined to the plate A of the doubler, and thus the gold leaf was more perfectly insulated, and the electricity cou'd


    not be diffused over so large a surface. The glass which insulates the plates and cross piece of the doubler was also cover'd with shell lac.

    The doubler and electrometer being now well insulated, I proceeded to try the following experiments to ascertain whether the spontaneous electricity was attracted by the approximation of uninsulated parallel plates.


    The doubler was deprived of electricity by revolving the plate B forty times with brass wires hooked to all the plates, and during this deprivation the electrometer was connected with the plate A by means of a brass wire. I then took off the wires whilst the plate B stood between C and A, in the upper part of the plane of its revolution; and turning the handle towards the right hand, the gold leaf open'd negatively about a quarter of an inch, with twenty-one revolutions.


    The doubler was deprived of electricity, as before, and whilst the plate B stood parallel to the plate A, the brass wires were taken off, then turning the handle forwards, the gold leaf open'd a quarter of an inch negatively at the sixteenth revolution.

    These experiments were repeated about thirty times, and on different days, without any considerable difference in the results; the number of


    revolutions being always greater when the plates set out from a single position than when the wires were taken off whilst A and B were parallel.

    The plate B is placed at the distance of 1-16th of an inch from the other plates, and remains the same in the following experiments. It may be necessary to note the circumstances, for doubtless the number of revolutions, if not other results wou'd vary, if the plates were placed nearer or farther asunder.


    A copper plate thirteen inches in diameter having its surface rather convex, was furnished with an insulating handle of oiled glass, four inches long and baked till the oil was well hardened. One end of the glass was fixed into a copper socket in the middle of the plate, and the other end into wood, that it might not be necessary to touch the electric part of the handle. This copper-plate was placed upon a mahogany table, and the doubler being deprived of its electricity, the plate B was placed parallel to A, so that B was connected with the earth, then the copper-plate was lifted up, by its insulating handle, and applied to the plate A, and lastly, the plate B being revolved only five times, the gold leaf diverged negatively to the distance of a quarter of an inch.


    Lest accidental friction against the mahogany table shou'd be objected, I lifted up the copper-plate,


    and after touching it with the point of a needle, I applied it to the doubler, as before, and found that the doubler did not produce its spontaneous electricity at less than 15 revolutions; then touching the plate again, I lower'd it till a part of its convex surface touched the surface of some water contained in a large dish, and lifting up the plate, I applied it to the doubler, which caused the gold leaf to diverge negatively at five revolutions, as in experiment 3d.


    The plate B of the doubler was placed a little beyond its former position, so that its wire did not touch the middle piece, and consequently tho' most of its surface was parallel to the plate A yet it was insulated. The copper plate was then applied to B after it had touched the water as in the last experiment, and at the same time the plate A was touched by a brass wire, to connect it with the earth. About five revolutions produced a very sensible positive divergency of the electrometer, as might be expected in consequence of the negative charge being communicated to B instead of A.


    By a frequent repetition of the foregoing experiments I was fully convinced of the attraction of electricity by approximating parallel plates: but hitherto the charge was negative, and suspecting that other substances might have a positive affinity with


    the fluid, and especially if my conjectures concerning projected powders and vapours were true; I therefore cover'd the surface of the copper plate with a mixture of gum water and minium, also with gum water and wheat flour, and found that these substances when dried upon the surface of the copper, changed its electricity, so that when it was applied to the plate A, as in experiment 3d, it produced a positive charge, and when applied to B, as in experiment 5th, it produced a negative charge, as might be expected if the painted copper plate by its uninsulated approximation to the surface of the mahogany table or water absorbed a positive charge.


    To render the electricity of approximating plates more conspicuously sensible, I ground a brass plate three inches diameter with emery till it would adhere to the surface of a piece of black marble. This plate and marble therefore constitute a condenser in its original state. The marble being moderately warmed I pressed the brass plate upon its surface with the point of a brass wire, then lifting it up by its insulating handle I applied it to the cap of the electrometer, which caused the gold leaf to strike the side negatively.

    I hope it will now appear evident by the precautions and experiments mentioned in this section, and from the known laws of electricity.

    1st. That the doubler in its present state may be deprived of accidental or communicated electricity.


    2dly. That the principal cause of its spontaneous charge, is the attraction of electricity by the approximation of its parallel plates.

    3dly. That this charge may be positive or negative, according as the plates, or touching wires are composed of substances which have a greater or less adhesive affinity with the electrical fluid.

    4thly. That the causes of spontaneous electricity are common to the condenser both in its original and improved state, and to the doubler, and equal in them all as far as they are equal in their dimensions and powers.

    5thly. That since the doubler may be composed of very small plates, and yet its power be equal to that of a very large condenser, its spontaneous electricity will be more easily overcome by a communicated charge than that of a condenser of equal power, and therefore experiments performed with it will be less liable to equivocal results; and lastly from these considerations I have ventured to presume that the instrument may be advantageously used and applied to the discovery of new and interesting facts in the science of electricity.



    Experiments on the adhesive electricity of metals and other conducting substances.

    Having fully proved by a frequent repetition of experiments, that the positive or negative spontaneous charge of the doubler depended upon the absoption or repulsion of the electrical fluid by the approximation of its parallel plates, and that by applying larger plates covered with minium or flour, its electricity might be changed at pleasure, it easily occured, that if the spontaneous electricity in the beginning of the process was sufficiently weak, the mere contact of metals or other substances having a different adhesive affinity with the electrical fluid might also change it, and a new and interesting employment for the doubler be discovered.

    This supposed effect of contact was confirmed by the following experiments, in which the doubler and electrometer were deprived of electricity, and used with the precautions and improvements mentioned in the last section


    The spontaneous charge of the doubler having been negative, and being deprived of this charge by the usual method, the plate B was placed parallel


    to the plate A, but so that B was not connected with the earth. The plate A was then touched with the blade of a knife, and the plate B at the same time touched with the point of a soften'd iron wire. With sixteen revolutions the gold leaf diverged about one third of an inch positively.


    The doubler being deprived of electricity as before, and the plate B placed as in the last experiment, the knife was applied to B instead of A, and the soft iron wire to A instead of B, which opened the gold leaf negatively at 15 revolutions.

    These experiments were repeated very often, and the electricity changed each time, being always positive in the plate touched by the knife.

    To distinguish so minute a difference of adhesive electricity, as that which might be supposed between two metals so nearly alike as harden'd steel and soft iron, wou'd appear incredible had not the frequent repetition of experiments confirmed it.

    Being now well convinced of this fact I tried many other substances with various success, sometimes the charge wou'd change regularly for a long time together, by applying the opposed substances to A and B alternately, as in the above experiments; and sometimes with other substances the charge wou'd be quite uncertain.

    But to remedy the uncertainty of the influence of metals or other substances as far as possible, and


    to exhibit the effects of adhesive electricity to advantage, I made tables of experiments in which the substances to be tried as were applied to A or B are mentioned in the first and second columns, the number of revolutions in the third, and the state of electricity in the fourth.

    The number of revolutions necessary to cause a divergency of the gold leaf sufficiently sensible, is by no means offer'd as an accurate measure of the strength of adhesive electricity, but at present I know of no better a way of comparing its effects,[?]


    Lead Ore    Lead    Revolutions   Electricity
      A          B       15            P
      A          B       14            P
      A          B       14            P
      A          B       14            P
      A          B       14            P



    Lead     Iron Wire  Revolutions   Electricity
      A          B       13            N
      A          B       13            N
      A          B       16            N
      B          A       16            P
      B          A       20            N


    Lead Ore Iron Wire  Revolutions   Electricity
      A          B       15            P
      A          B       22            P
      A          B       17            P
      A          B       16            P
      A          B       17            P



    Tin-foil  Iron Wire Revolutions   Electricity
      A          B       16            N
      A          B       13            N
      A          B       13            N
      A          B       12            N
      A          B       13            N


    Zinc    Iron Wire   Revolutions   Electricity
      A          B       16            N
      A          B       15            N
      A          B       15            N
      A          B       15            N
    | A          B       16            N
    | A..........B.......17............N
    | A          B       15            N
      B..........A.......22............P |
      B          A       21            P |
      B..........A.......17............P |


    In the above five tables every experiment was made by double contact, and since the state of electricity was evidently changed, (except in a few instances) whenever the two opposed metals were applied alteenately to A or B, there remained no doubt of the influence of these metals. Yet it was not very apparent whether it was the positive state of the one metal or the negative state of the other which prevailed. I therefore tried the effect of single contact, choosing two metals whose electricity appeared to be contrary, and touching A, C, and the cross piece, whilst B stood single in the upper part of its plane, with a positive metal in one experiment, and with a negative metal in the next, or, or [?] applying the same metal to A, C, and the cross piece in one experiment, and to B in another, but in this last case B stood in the lower part of its plane. The reason of varying the position of B was, that the plate intended to acquire a contrary state to that produced by contact, might first be brought into connection with the earth; thus when A, C, and the cross piece had been touched, B came from its higher position into connection with the earth when brought parallel to A, and might then become contrarily electrified; and when B had been touched in the lower part of its revolution, C became connected with the earth when B was parallel to it.



                                               Revolutions  Electricity
    Lead ore applied to A, C, and the cross piece  14         P
    Zinc applied in the same manner................18.........N
    Lead ore                                       13         P
    Lead ore                                       16         P
    Lead ore                                       15         P
    Lead ore                                       14         P

    By experiments of single contact in the above table, it now appears that the adhesive affinity of electricity to lead ore is positive, and to zinc negative.



    In which zinc is again tried by applying it to A in the first six experiments, and to B in the six last, and also tried after the interval of several weeks when the air was much more dry.

    Zinc     Revolutions   Electricity
      A        12            N
      A        11            N
      A        10            N
      B        13            P
      B        15            P
      B        12            P



    Lead ore applied to A and B alternately.

    Lead Ore      Revolutions   Electricity
      A              8            P
      B             14            P
      B             15            N
      A............. 8............P
      A              7            P
      A              7            P
      A............. 7............P

    From these experiments it appears that the adhesive electricity of the lead ore was not always so strong as to overcome the spontaneous charge of the doubler.


    Gold, silver, copper, brass, regulus of antimony, bismuth, tutenag, mercury, various kinds of wood, and stone, were tried by this method of single contact and appear'd to cause a positive charge. Tin was negative, and a large piece of zinc much more weakly negative than a thin plate of the same metal used in the above experiments; of these I defer making tables till I have the opportunity of improving the accuracy of the doubler. This may be done several ways which I shall here describe, hoping that some more experienced electrician will approve and execute them before I have leisure.

    1st. In the course of my experiments I found that the force which the touching wires passed the pins on the back of the plates, had some influence on the charge, which was also observed by Mr Nicholson, and it may reasonably be supposed that the adhesive electricity of these wires may have some effect. I wou'd therefore chuse [?] some metal which has the least influence. Gold wire may probably be the best, and instead of small wires to flirt against the pins, let stronger wires move a rowel like that of a spur, and let the cheeks in which the rowel is fixed be made to hold it harder or easier by means of a screw passing thro' the center of the rowel. Thus the contact of the touching wires may be regulated by these screws, and may perhaps so influence the spontaneous electricity, that either A or B may be made to prevail at pleasure or be exactly balanced.

    2dly. It is evident that the capacity of the plates is increased as they approach to each other, and this


    increased capacity will in many experiments cause them to absorb that kind of charge which agrees with their own affinities, or of the touching wires, instead of being influenced by the substances intended to be tried. Let the plate B be moveable upon its axis that it may easily be placed at any distance, between actual contact and the distance of half an inch from the other plates, that a distance may be found which will produce the least spontaneous charge, and be more easily overcome by an intended delicate communication of electricity. It will also be necessary to regulate the distance on account of the dryness or moisture of the air. In dry weather I have found the spontaneous electricity to be sensible at fifteen revolutions or under, and in moist air at about forty, the distance of the plates and contact of wires being the same in both.

    3dly. The spontaneous charge of small plates must be less than that of large ones, so that adhesive electricity communicated by single contact will be more likely to overcome such charge, for which reason principally, as well as for reasons of convenience, small plates are preferable; perhaps the size of a shilling wou'd be sufficient.

    4thly. The plates shou'd not be cover'd with varnish or lacquer, lest they shou'd retain electricity, and to prevent tarnishing, the plates may be gilt, or made of the metal used for reflecting telescopes.

    5thly. The spontaneous charge is produced at fewer or more revolutions according to the velocity or regularity with which the axis of the doubler is


    turned, so that a regular motion wou'd also add to the perfection of the instrument, which might be effected by means of a pendulum, and a vibrating doubler wou'd perform the process as well or better than any other. The wires touching with equal force, and in regular time, wou'd be a considerable advantage with respect to the accuracy of experiments, and a doubler of this construction might be made to continue its motion like a clock, so that insulated vessels containing chemical mixtures or growing vegetables, might be placed so as to receive its superfluous electricity, and be kept in a constant state of electrification.

    I will conclude this section with observing that since electricity, like all other known fluids, adheres with more or less force to different substances, it affords a simple and very satisfactory theory of the excitation of glass and other electrics, used in the construction of electrical machines; for when the silk flap is rubbed by the revolving glass cylinder, it is brought into close contact, and electricity adhering more forcibly to glass is carried forward into the open air, which air having not been render'd negative like the silk, does not counterbalance the surface of the glass, and therefore its capacity being lessen'd, it emits the charge it has just absorbed. The amalgamated cushion assists the process by bringing a surface of a conducting quality and in connection with the earth into closer contact.

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All Rights Reserved.