New Experiments on Electricity
by
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

Frontpage Subscribers Contents Introduction Section 1 Section 2 Section 3

Section 4 Section 5 Section 6 Section 7 Section 8 Plates Translation

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NEW EXPERIMENTS on ELECTRICITY wherein the causes of Thunder and Lightning as well as the constant state of Positive or negative Electricity in the Air or Clouds, are explained; with Experiments on clouds of powders and Vapours Artificially diffused in the Air. also A Description of A Doubler of Electricity, and of the most sensible Electrometer yet constructed with other New experiments and Discoveries in the Science, Illustrated by Explanatory Plates. By the Rev.A Bennet, F.R.S. Curate of Wirksworth, Derbyshire Derby Printed bt John Drewry 1789 To the Reverend Dr Richard KAYE, F.R.S. & F.S.A Dean of Lincoln and Trustee of the British Museum This Work is Dedicated by His obliged Humble Servant Abraham Bennet

The AUTHOR takes this opportunity of expressing his most sincere thanks to his subscribers, and especially to the following ladies and gentlemen who have liberally encouraged his work, and recommended it to their numerous and respectable friends. Mr Adams Mathematical Instrument maker to his Majesty, and optician to his Royal Highness the Prince of Wales. Sir Joseph Banks, Baronet, F.R.S. Mr G Bladon Mr J Chatterton Erasmus Darwin, MD, FRS The Rev The Dean of Lincoln Mr Fox, surgeon Philip Gell, esq Mrs Gell Captain Gell Philip Gell, esq, Wirksworth Rev Mr Greville Charles Hurt, esq Mr Jackson Miss Jones Samuel Lankford, esq Mr More, Sec SA Thomas Percival, MD, FRS J H Pigot, MD Rev Joseph Priestly, LLD,FRS &c Mr John Southern Mr William Strutt, jun Josiah Wedgwood, esq, FRS & FAS LIST of SUBSCRIBERS A Rev Mr Acheson Mr James Adam Rev Dr Adamthwaite Dr Aldrich Mr Allen Sir John Anstruther, Bart Sir Richard Arkwright Miss Arnold Francis Ashby, esq Mr William Atkinson Mr Isaac Atkinson Alexander Aubert, esq, FRS and FSA B Mr A B Mr John Bailey Jos Bainbridge, esq Mr Barr, Surgeon John Barker, esq Thomas Barker, esq Mr Barker Mr H Barlow John Barnard, esq Rev Benj Barnard Mr Miles Barnard Rev T Barnes, DD Sir Brooke Boothby, Bart Rev William Becher, BD Mrs Becher Sir Richard Brooke, Bart Lady Brooke Thomas Brooke, esq, MP Mrs Brooke Miss Bird Matthew Boulton, esq, FRS Mr Matt.Robinson Boulton Mr Beard Rev Theophilus Buckeridge Principal Surrogate of the Diocese of Lichfield Rev Charles Buckeridge Mr Ch Broad J Buxton, esq Brooke Boothby, esq Mr John Birch Mr Brant John Blackburne, esq, MP T P Bonnell, esq Mr Burman, Surgeon Mr Brock Mr Brigham Mr Boot Mr John Beaumont Mr Joseph Boden Mr John Birtles Dr Blagden, Sec R S R H Bennet, esq Mr Blount, Surgeon Mr Brooke Rev Thomas Bingham Mr F Burton Mr William Bakewell Mr Biddulph Mr H Brown Rev Wm Blackwall, MA Francis Bradshaw, esq Mr Beaumont, Surgeon C Right Hon Lord G Cavendish Henry Cavendish, esq, FRS Rt Hon Lady Ann Margaret Coventry Rev Archdeacon Clive Mrs Clive Sir Foster Cunliffe, Bart Lady Cunliffe Dr Crompton Mr John Cox Rev James Hadley Cox Miss Cox Miss J Cox Mr William Cantrell Samuel Crompton, esq Mr Peter Clare Mr Samuel Cooper Thomas Charleton, esq Rev Mr Chapman James Chadwick, esq Mr Caldwell Rev Benjamin Clay, MA Mr Cropper Rev Mr Cusson Rev James Cooke Robert Cheney, esq Mr Clapham Rev T Clarke Mr Hollis Clay Mr Cockshutt Rev D'Ewes Coke Mr Clarke D His Grace the Duke of Devonshire Alexander Dalrymple, esq FRS.FSA Ac R Sc Holm Soc C Dagson, esq Mr Jennings, Deritend. Mrs Darwin Mr Darwin, Attorney Mrs Dawson Mr Thomas Dobbs Mr John Dovaston Rev Mr Darwall Mr William Dobinson C Davies, esq William Dewis, esq Mr Thomas Dicken, Jun E The Hon & Right Rev Lord Bishop of Ely George Errington, esq T W Edge, esq Mrs Edge Dr Eason Francis Evans, esq Mr John Eginton Mr Francis Eginton Mr William Evans Mr Elliot F His Royal Highness Ferdinand Archduke of Austria, Governor of Milan, &c Sir William Fitzherbert Lady Fitzherbert Mr Finch Richard French, esq Samuel Fox, esq Mr Edward Fox Mr William Fox T Ferriar, MD Mr Robinson Foxley Mr Field Mr John Fell, Surgeon Mr Christ.Fuller, Attorney Rev Mr Freeman Mr W Frankland Miss Fletcher Samuel Frith, esq G Samuel Galton, esq, FRS Sam Galton, jun, esq, FRS Mr Goodwin, Surgeon Mrs Goodwin Robert Grimshaw, esq Thomas Gould, esq Mr Thomas Gell Robert Greaves, esq Mrs E Grimshaw Mr Gill, jun Attorney Right Hon Henry Grattan Rev Edmond Gregory, MA Mrs Temperence Gell Mrs Gould Mr Graham Mr F Geast H Right Hon Lord Harrington Right Hon Lady Harrington Sir Henry Harpur, Bart Lady Frances Harpur Henry Harpur, esq John Hatsell, esq Mr James Hatsell Mr Hands Mr Hands Robert Holden, esq Mr Hadley, Surgeon Mr Haden, Surgeon Francis Hurt, esq Mann Horsfield, esq Dr Hunter Rev John Le Hunt T H Hodges, esq Mr Thomas Henry, FRS Mr Ch Heywood Mr Rich Hall, Surgeon Mr Thomas Hadfield Rev Benj Holland Mr William Harrison, Surgeon Mr Jos Hart Mr John Holmes Rev George Holcombe Rev William Hodson, Fellow of Trinity Coll, Cambridge Rev Christ. Hunter, Fellow of Sidney Coll, Cambridge Mr Horrocks, Attorney Mrs Hurt, sen Mr Harding Mr John Hunt Rev Mr Hurst Rev Mr Holmes Mrs Hopkinson Rev Mr Hudson Mr Holland Mr James Hulme Mr Joseph Hall Rev E Heathcote Mr Heberden C G Hudson, esq Rev C S Hope I & J Mr Ince, Attorney William Johnson, esq Dr Johnson R A Johnson, esq, FRS Mrs Johnson Miss Johnson Mr P Johnson Mr James Jones Mr Augustus Jackson Nathan Jackson, esq K James Keir, esq, FRS Mr Thomas Kershaw L Chevalier Landriani Sherbrooke Lowe, esq Mr John Little Mr Penny Lloyd Robert Lowe, esq Mrs R Lowe Mr Leaper, Attorney Mr Locket, Attorney Edward Leacroft, esq John Leacroft, esq Mr Thomas Lomas Mr J A de Luc John Loyd, of Hofoclunos, FRS & FAS Mr Sampson Lloyd, jun Miss Sarah Longden Rev C Lawrence Mr Lattufiere M Edward Mundy, esq, MP Right Hon Lady Middleton F N C Mundy, esq Mrs Mundy Francis Mundy, Jun, esq Major-General James Murray Sir William Musgrave, Bart Mr Moscati, General director of the hospitals at Milan William Milnes, esq Rev Mr Moore Rev John Moore Mrs Moore Rev Thomas Manlove Rev S Murthwaite Mr Macniven John Mitchel, MD Mr Richard Marriot Samuel Martin, esq William Middlemore, esq Mr William Matthews Mr William Mott, Dep Reg and Proctor Richard Molesworth, esq FRS & FAS Wm Marsden, esq, FRS and FAS Free-Mason's Lodges, No 47 and No 189, Macclesfield Mr R Mather N His Grace the Duke of Northumberland Mr Nairne, FRS John Need, esq Richard Norman, esq Mrs Norman Robert Newton, esq S W Nicoll, esq O The Honourable Mr Oliver John Osborne, esq Mr Ogle, King's Light Dragoons P His Grace the Duke of Portland University of Pavia Rev William Pickering Rev Edward Pole Mr George Philips Mr Polehill, King's Light Dragoons T B Parkyns, esq Mr Partington Mr Parkinson, Surgeon Mr Pratt Sacheverell Pole, esq Messrs Pearson and Rollason, Printers Mr Joseph Priestley Richard Pearson, MD Rev Nathaniel Philips Rev R Peryn, MA Q C A Quist, esq R Right Hon Lord Rawdon Lieutenant-General Rainsford Hayman Rooke, esq, FSA Mr Edward Rigby Mr H Richardson, Jun George Robinson, esq Mr Radford, Surgeon Charles Roe, esq S Right Hon Earl of Scarborough Richard Smallbrooke, LLD Chancellor of the Diocese of Lichfield and Coventry Mrs Sherbrooke Miss Sutton Rev T Salmon Mr Stanley Philosophical Society, Derby Union Society, Derby Book Society, Derby New Society, Nottingham Jedediah Strutt, esq Mr William Strutt Mr Stevenson, Surgeon Mr James Simpson, Attorney E S Sitwell, esq Robert Shuttleworth, esq Rev Charles Shuttleworth Mr John Simpson Mr Samuel Simpson William Sherbrooke, esq Miss Coape Sherbrooke Samuel Smith, esq George Smith, esq Mr John Snape Miss Stamford Castel Sherwood, esq William Sheldon, esq Mr Robert Small Mr William Sherwin Henry Sykes, esq T William Tillard, esq Mrs Tillard Miss Tillard Rev Richard Tillard Mr John Thacker John Topham, esq, FRS John Toplis, esq Mr Henry Travis Mr Tibson Mr Toone Rev Robert Thorp R W Disney Thorp, MD Mr Gervase Thorp Mr Twemlow, Surgeon Mr Taylor, Surgeon Mr Trevor V & U Mr Volta, Professor of Nat and Exp Philosophy Charles Upton, esq W Right Hon Lord Willoughby de Broke Right Hon Lady Willoughby de Broke Wm Wilberforce, esq, MP Mrs Wilberforce Miss Wilberforce James Watt, esq, FRS &c Mr James Watt W Withering, MD, FRS Sir John Warren, Bart Rev W U Wray, MA Mr Cecil Bromley Wray Miss Webb Mr George Wheeldon Rev Robert Wilmot Rev John Ward Charles White, esq Mr Wynne Mr Edmond Wheeldon Snowdon White, MD Rev G Walter John Wright, esq Thomas Wright, esq Captain Wright, King's Light Dragoon John Wright, Jun, esq Mr Wright Mrs H Wright Miss Wright Miss Ann Wright Miss S Wright Miss Lucy Wright Ichabod Wright, esq George Wyndham, esq Miss Wyndham Mr Ch Wyat Mr Th Willmore, Jun Mr Robert Watt Mrs W Whitaker Mr John Walker Mr Thomas Wheeldon Paul Webster, esq Mr Wolley, Attorney Mr Ward, Attorney Rev Mr Willey John Wightwick, esq Dr Wilson Mr William Wilson Mr Worral Mr S Woodford Mr Wilson Mr George Wilkinson Mr John Wilcockson Y Mr Nicholas Yarburgh Mr W Young

CONTENTS Introduction, containing a short theory of Electricity SECTION I Description of a gold leaf electrometer Slips of tinfoil increase the sensibility of the electrometer. Exp 1 Slips of tinfoil take off the influence of the cap............ Exp 2 SECTION II Powdered chalk blows upon the electrometer.................... Exp 1 to 7 Some of its varieties explained............................... Exp 7 Experiment to shew the effect of influential atmospheres...... Exp 8 Chalk projected from a brush.................................. Exp 9 The brush electrified contrary to the cloud of powder......... Exp 10 Electrometer charged positively by the influence of a negative cloud of powder.................................. Exp 11 Chalk and dust projected several ways......................... Exp 12 & 13 All powders negative except flour, oatmeal, and minium........ Exp 14 The electricity of powders not owing to friction.............. Exp 15 to 17 Chalk more strongly electrified than flour.................... Exp 18 Flame collects electricity in circumstances where it would not otherwise become sensible............................. Exp 20 to 24 Positive and negative electricity produced by evaporation in several new methods.................................... Exp 26 to 30 Atmospheric electricity collected by a Lantern................ Exp 31 to 32 By water spouted upwards...................................... Exp 33 Heat without effluvium does not dissipate electricity......... Exp 34 Charge of the gold leaf electrometer too small to be dissipated by the sharpest points or edges................ Exp 36 to 38 SECTION III New experiments with M Lichtenburg's large electrophorus. Powderd chalk projected upon the figures in various ways...... Exp 1 to 21 ______________________________________________________________________ vi Minium and sulphur mixed are seperately attracted by positive and negative figures............................. Exp 22 Ramifications and shades explained............................ Exp 23 to 27 The figures indelibly fixed on sealing wax.................... Exp 28 The figures taken off on paper, leather, callico, or linen.... Exp 29 The figures fixed on porcelain................................ Exp 30 The figures preserved by framing the electrophorus............ Exp 31 More ways of varying the figures.............................. Exp 32 to 35 A convenient box for projecting powders without loss.......... Exp 36 An electrical pen............................................. Exp 37 To make circles and other figures more conveniently........... Exp 38 Imitation of Fairy rings...................................... Exp 40 SECTION IV Electricity excited by evaporation Both states of electricity in one experiment.................. Exp 1 Several metals heated and plunged in water.................... Exp 1 to 10 Green vegetables burnt........................................ Exp 11 Dry wood, hay and cinders..................................... Exp 12 to 15 Salts, acids, oil and water................................... Exp 16 to 22 Various substances dropped upon a hot iron.................... Exp 23 to 46 Upon Bell metal............................................... Exp 47 to 48 A more convenient iron, with which more substances were tried................................................ Exp 49 to 63 The ascending vapours examined................................ Exp 64 to 70 SECTION V Description of a doubler of electricity SECTION VI Improvements of the doubler A convenient method of depriving the doubler of its charge. The plates of the revolving doubler absorb more electricity when touched in a parallel position...................... Exp 1 & 2 Uninsulated approximating plates of different substances absorb electricity....................................... Exp 3 to 6 ____________________________________________________________________________ vii The condenser in its original state produces a strong spontaneous charge of electricity........................ Exp 7 SECTION VII Experiments on adhesive electricity By the double contact of hardened steel and soft iron......... Exp 1 & 2 Lead ore and lead............................................. Table 1 Lead and iron wire............................................ Table 2 Lead ore and iron wire........................................ Table 3 Tinfoil and iron wire......................................... Table 4 Zinc and iron wire............................................ Table 5 By single contact of lead ore and zinc alternately............ Table 6 Zinc applied to A and B seperately............................ Table 7 Lead ore applied to A and B seperately........................ Table 8 Suggestions for improving the accuracy of the revolving doubler Adhesive electricity explains the excitation of rubbed electrics SECTION VIII A short theory of atmospheric electricity. Description of a convenient apparatus for observing the state of atmospheric electricity in all sorts of weather Convulsive motion of the gold leaf electrometer, occasioned by a thunder cloud....................................... Obs 1 Positive and negative state of showers........................ Obs 2 A thunder cloud which caused 10 changes of electricity in the space of an hour and a half....................... Obs 6 Clouds and rain............................................... Obs 7 to 12 Serene sky.................................................... Obs 13 Clouds and rain............................................... Obs 14 to 16 Mist.......................................................... Obs 17 Thunder cloud................................................. Obs 18 Rain and mist................................................. Obs 19 to 21 Snow, mist and rain........................................... Obs 22 to 25 Sleet and rain................................................ Obs 26 & 27 ___________________________________________________________________________ viii Snow.......................................................... Obs 28 Mist, snow and sleet.......................................... Obs 29 to 31 Wind and hail................................................. Obs 32 & 33 Thunder cloud................................................. Obs 34 Serene weather................................................ Obs 35 to 38 Heavy shower wholly positive.................................. Obs 39 Experiment in dry air......................................... Obs 40 Thunder cloud................................................. Obs 41 Aurora Borealis............................................... Obs 42 & 43 Ten changes of electricity during a shower.................... Obs 44 A severe shock from a kite string............................. Obs 45 Aurora Borealis............................................... Obs 46 Several clouds positive and negative without rain............. Obs 48 & 49 Snow.......................................................... Obs 50

ix INTRODUCTION By the desire of some of my friends I am induced to prefix a concise theory of Electricity, that the reader may more easily comprehend the Intention and use of the following experiments. 1st. Electricity is an extremely subtle fluid, which pervades metals with astonishing facility. It also pervades water, moist vegetables, animals, and many other substances more imperfectly. These substances are termed perfect and imperfect conductors. But amber, glass, silk, oil, dry air, and some other bodies are impervious to the electrical fluid; and because when rubbed they show signs of electricity adhering to them, it was once supposed, that they were the only bodies which contained electricity, and were therefore termed electrics. That some bodies are conductors and others electrics or non-conductors does not appear to depend on their specific gravity; for gold is the best conductor, and of the greatest specific gravity; and air, which is so much less dense, does not conduct; but charcoal is a good conductor, and lighter than glass, which is an electric. It is not improbable but that this property may depend on the chemical affinity of their component parts with the electrical fluid. If electrics are supposed to have in their composition a large quantity of fixed electricity as limestone contains fixed air, they may be impervious x to any additional quantity of it, because already saturated. 2dly. Electricity adheres to the surface of electrics much more strongly than to the surface of conductors, and hence when two such substances are rubbed together, part of the natural quantity of fluid belonging to the conductor adheres to the electric. Without this property of electricity its existence might never have been discovered, but first on rubbing amber and then other electrics some of its effects were observed, and after gradual improvements the present electrical machines were constructed, and various other dicoveries made. 3dly. Electricity is a very elastic fluid, so that it may be condensed or accumulated upon any substance, whose connection with the earth is cut off by the interposition of an electric. This is termed insulation. Electricity, thus accumulated, repels the natural electricity of the surrounding air, disposing it to recede, which is then termed an electrical atmosphere, whose density according to the demonstration of the Earl of Stanhope, in his learned principles of electricity is proved to be in the inverse ratio of the square of the distance. An accumulation of electricity which disposes that of the surrounding air to be repelled is termed a positive electrical atmosphere. But if the same insulated body be deprived of its natural quantity of this fluid, it disposes the surrounding air to absorb more electricity, and this also produces an atmosphere which is termed negative. xi If light conducting substances as bits of gold leaf be brought within an electrical atmosphere, they become attracted towards the electrified body: for the density of the electrical atmosphere increases towards the centre, and the power of its attraction being proportionate to its density, whatever light conducting substances are immersed in the extreme parts will move towards the centre till they touch the electrified body and receive a part of its electricity. When the gold leaf has touched the electrified body, which thus attracted it, and has received from it a part of its electricity it becomes repelled; because the superinduced electricity will attract a quantity of air to form round itself another atmosphere, whose electricity it tends to repel like the body which was first electrified, and therefore either the light substance will move off till it comes into the air whose electricity is not repelled by the influence of the first electrified body, or a double quantity of air must be attracted into the same space, or lastly the intensity of the electrical atmosphere between the two bodies must diminish, which always happens when the two electrified bodies are immoveable. The same effects will take place whether the atmosphere be positive or negative, for every substance has a strong tendency to absorb its natural quantity of electricity, as it has to emit or dissipate a superfluous quantity. This explanation of electrical repulsion easily applies to the divergency of cork or pith balls or the still lighter shreds of gold leaf used in the several kinds of sensible electrometers. xii The electrical attraction and repulsion of light substances may be illustrated by cork balls or other light bodies swimming on water, which adhering round them is raised above or depressed below the common level, and causes the corks to be attracted towards or repelled from each other. When two cork balls are equally moistened and the adhering water is raised above the level surface, or when both the corks are dry and the surrounding water is depressed below the level surface, the corks are attracted, which may not seem to agree with the case of electrification, for two equally electrified bodies repel each other, but if two light bodies were electrified in a perfectly exhausted glass, where the air could not interfere, it is probable that they would not repel but attract each other, from the tendency in fluids to unite and form one globular mass, as two globules of clean quicksilver unite when brought into contact. Two light substances electrified in the open air repel each other, because their electricity strongly attracts the air, which coming between pushes them asunder, and in like manner the two corks swimming on water will be repelled, if one of them be made to raise its surrounding atmosphere of water above the common surface, and the other to depress it; for in this case the level surface may be considered as a third substance flowing in and attracted by each cork to complete its atmosphere, which pushes the corks asunder. This experiment may be conveniently tried, by pressing two bits of thin writing paper upon a round hole about half an inch in diameter, xiii so as to make the paper concave; then let the edges be pared, and they will form two small paper cups, which are to be placed upon the surface of a bason of water; let a little fine sand be put into these cups that the edges of the paper may be depressed below the level surface of the water, and then the two loaded cups will approach, and at last come into contact with each other, then let the edge of a moistened piece of paper be placed in the direction of a tangent line between the cups, and they will suddenly recede to the distance of several inches. Every method of condensing or rarifying the electrical fluid may be explained by the principle of adhesive attraction: but I shall here only mention the practical method of rubbing a stick of sealing wax or rather a glass tube about five inches long covered with sealing wax upon a woollen cloth, for the purpose of trying the quality of electricity communicated to an electrometer. It is well known that the sealing wax thus rubbed is excited negatively, that is the natural electricity of the sealing wax is left upon the woollen, and its atmosphere being brought so near as to touch the atnosphere of the electrometer the gold leaf will either diverge wider or collapse; if it diverges more, its electricity is negative like that of the sealing wax; but if it collapses, it is positive. 4thly. Electricity may be accumulated in a much greater degree upon one side of a thin electric as a plate of glass or a bottle, if the opposite side be connected with the earth by means of a conductor, for xiv as electricity is condensed on one side of the glass the natural electricity is rarified on the other, and the restoration of the equilibrium between the two sides, causes the effect termed an electrical shock, and that the fluid may be more speedily diffused over or discharged from the surface of the glass it is coated with tinfoil except near the edges. Fluid electrics may also be charged, but because the charge might otherwise soon break through, the two coatings must be farther distant from each other, except when the quantity of electricity is small. There is one remarkable difference between the charge of a solid and a fluid electric, which is, that the charge principally adheres to the surface of the solid electric and not to its coating: but when a plate of air is charged it adheres to its coating: on this consideration was founded the contrivance of the doubler of electricity hereafter described. That some quality of accumulated electricity should act through electrics which are impervious to the fluid itself, and cause their natural electricity to expand so as to produce an electrical atmosphere; or repel the natural electricity on the opposite side of an electric in the case of charging the leyden bottle, are facts which have long been admired, and though most of the extraordinary effects of electricity depend on this property, yet I think it has never been very satisfactorily explained. If the elasticity of fluids in general was clearly understood, I doubt not but this difficulty would be surmounted, and if the opinions of Des Cartes on this subject were verified by experiments xv they might gain credit, notwithstanding the general fallacy of his principles. Rara corpora illa sint, inter quorum partes multa intervalla existunt, corporibus aliis repleta. Ut cum videmus spongiam aqua vel alio liquore turgentem. Etsi cum aer aut aqua sit rarefacta, non videamus ullos ipsorum poros qui ampliores reddantur, nec ullum novum corpus, quod ad illos replendos accedat; non est tamen rationi tam consentaneum, aliquid non intelligibile effingere, ad eorum rarefactionem verbotenus explicandam, quam ex hoc quod rarefiant, concludere, in ipsis esse poros, sive intervalla quae ampliora redduntur, & novum aliquod corpus accedere, quod ipsa implet; etsihoc novum corpus nullo sensu percipiamus. Nulla enim ratio nos cogit ad credendum, corpora omnia quae existunt debere sensus nostros afficere. Des Cartes Prin. Philos. Par.2. Sect.6. [See Translation into English] What is here said of the rarefaction of air and water may be applied to the rarefaction of electricity, that is there appears no way of accounting for it but by the supposition of another fluid strongly adhering to and mixed with it, and which is sufficiently subtle to pass thro' glass. On this hypothesis it is easy to conceive such mixed fluid accumulated in a bottle by the action of an electrical machine, and as the charge goes on and the fluid is condensed by being forced into a less space than it xvi would otherwise occupy, the fluid which can pass thro' glass is forced out and would rarify all the surrounding electricity, by uniting with it, like heat diffused amongst colder bodies, but being everywhere insulated, it is confined, except on the outside of the bottle, where because the surface is connected with the earth its electricity can pass off. Light is so constantly emitted or excited by electrical sparks and so readily passes thro' glass that it might reasonanly be suspected to be combined with the electrical fluid and be the cause of its electricity, but some experiments do not seem to favour this supposition particularly Sect.2d. Exp.34. By these few principles the chief effects of electricity as far as they are yet known may be in some measure explained; but it is impossible to aquire an adequate knowledge of it without an attentive performance of experiments: for altho' I believe electricity is entirely subject to the same laws with every other substance, yet because it hath some quantities in a very high degree as subtilty, elasticity and adhesive attraction, and others scarcely at all as gravitation and solidity, it is very difficult without experiments to become impressed with a just notion concerning them. Since the performance of experiments is so necessary to those who wish to aquire a more accurate knowledge of electricity, I beg leave here to suggest that the gold leaf electrometer, may without partiality to my own contrivance, be recommended, as the first instrument to be used, and the contents of xvii the following sections may serve for introductory lessons as well as any other. And if the more laborious and troublesome part of the science shou'd not be approved, there is sufficient scope for instructive varieties in the use of the electrometer and doubler without more cumbersome machinery, so that the author hopes, that ladies as well as gentlemen, who have honoured him with their patronage, will here find some amusement

18 NEW EXPERIMENTS, &c SECTION I Description of a gold leaf electrometer This instrument principally consists of two narrow slips of gold leaf suspended in the middle of a hollow cylindrical glass. The foot A Plate 1, may be made of metal or wood, and about three inches high, that there may be convenient room to handle the instrument without touching the glass. The cylindrical glass B in which the gold leaf is suspended may be about five inches high, and two inches in diameter. The cap C is made of metal, and flat on the top, that the various substances whose electricity is to be examined may be conveniently placed upon it. The diameter of the cap is about an inch more than that of the glass, and its rim D is about an inch broad and hangs parallel to the glass to keep it clean and dry. Within this is a circular rim about half as broad as the other, made to go over or within the glass, and is therefore lined or covered with leather, or other soft substances, to make it fit close, and thus 19 NEW EXPERIMENTS, &c. the cap may be easily taken off to repair any accidental happening to the gold leaf. Within this rim and in the centre of the cap a tube is fixed, wherein the peg E is placed. To the peg, which is made round at one end and flat at the other, two slips of gold leaf F are fastened with paste, gum water or varnish. If gold leaf is used it may be shorter than silver leaf. The gold is much more sensible, but the silver is easier to cut and less liable to be accidentally torn. I have mostly used gold about two inches long, tapering to a fine point and fastened to the peg at the broad end. The breadth of the upper end of the gold is about one fifth of an inch, which keeps the slips more exactly parallel, and the electrical repulsion is more sensible when the points are narrow, as I have observed when an accidental very narrow slip hung by the side of two parallel ones, the narrow slip always moving first. Without the glass the gold leaf would be so agitated by the least motion of the air that it would be entirely useless, and if electricity should be communicated to the sides, the gold would be attracted and torn, therefore two pieces of polished tinfoil G H are fastened with varnish on opposite sides of the internal surface where the gold leaf may be expected to strike, and are connected with the foot of the electrometer. The breadth of the tinfoil at the foot is one fourth of the circumference of the glass, and it terminates in a point towards the cap, about as high as the peg to which the gold leaf is fastened. It is 20 NEW EXPERIMENTS broad at the bottom, because there the points of the gold leaf are most liable to strike the glass, and being made narrow upwards does not prevent the repulsion from being easily observed. These slips of tinfoil, not only carry off superfluous electricity, but serve other important purposes, as will appear from these two experiments. EXPERIMENT 1 Upon a supposition that the gold leaf was attracted by the tinfoil, I suspended it in the open air, without a glass, and when electrified I brought two wire near it, and the gold leaves open'd wider, till they touched and collapsed, then upon bringing the wires still nearer they again diverged, which proved that the two pieces of tinfoil were useful to increase the sensibility of the instument. EXPERIMENT 2 I fastened the gold leaf to the inside of an iron mortar hanging by a silk string with the mouth downwards, and though I communicated to it as much electricity as it would receive, the gold leaf did not diverge till a wire was introduced, which first caused the points to open, and then the higher part of the gold, as the wire came nearer to the place where the gold was fastened. This experiment shews that the tinfoil takes off the influence of the cap which would otherwise diminish the repulsion of the gold leaf. The upper end of the glass is covered and lined with sealing wax, at least as low as the outermost rim, 21 ON ELECTRICITY to render its insulation more perfect, for sealing- wax does not collect moisture from the air so soon as glass. In performing this operation, the glass shou'd be gradually heated over a candle till it will cause the wax to flow uniformly over the surface, for if it be covered whilst the glass is cooler than the wax it will not insulate so perfectly. The foot may be about three inches and an half in diameter at the bottom, that the instrument may stand sufficiently firm. An electrometer of this kind has been carried from Birmingham to London; another from Wirksworth to York, and a third from Wirksworth to Etruria in a portmanteau on horseback, yet without injury; it is therefore easy to make electrometers less in every dimension, especially in diameter, whereby their sensibility is increased, and inclose them in a proper case to carry in the pocket, to observe the atmospheric electricity whilst on a journey, or on the top of a mountain. For some purposes it may be also necessary to make them larger. In many experiments I have used one about five inches in diameter, which shew'd the changes in the atmospheric electricity more distinctly than a smaller electrometer whose gold leaf would sooner strike the sides The broad cap of this large electrometer was also very convenient for placing upon it red hot crucibles or vessels of water in experiments on evaporation.

22 NEW EXPERIMENTS SECTION II Experiments on clouds of powders and vapours artificially diffused in the air, and other experiments illustrating the principles of electricity, and shewing the great sensibility of the gold leaf electrometer. EXPERIMENT I Powder'd chalk was put into a pair of bellows and blown upon the cap of the electrometer, placed at the distance of about six inches, which electrified it positively. See Plate 3 fig 7 EXPERIMENT II Powder'd chalk was blown from the bellows towards the electrometer placed at the distance of three feet, which caused the gold leaf to diverge negatively EXPERIMENT III The cap of the electrometer was moistened, and the powder'd chalk blown upon it at the distance of six inches, which electrified it negatively, contrary to the dry cap at the same distance. EXPERIMENT IV Two electrometers were placed with their caps about an inch asunder, the one moist and the other dry, and a stream of powder from the bellows at the distance of six inches was made to pass between the caps, which electrified the one positively, and the other negatively. 23 ON ELECTRICITY EXPERIMENT V If a bunch of wire, feathers, or silk, were placed in the bellows, the electrometer was negatived at the same distance which produced a positive state without them; also blowing gently with the bellows without the iron pipe, (by which means the powder was more than widely diffused in the air) had the same effect. EXPERIMENT VI A red hot stone was placed upon an insulating stand connected with the electrometer, and when powder'd chalk was blown upon it from the bellows within the distance of six inches, it became strongly and permanently negative. EXPERIMENT VII If the person who blows the powder'd chalk into the air from the bellows be insulated by standing upon a stool with glass feet, and after blowing touch the cap of the electrometer, the gold leaf will diverge positively. When the bellows produced positive electricity on the dry cap, or negative on the moist one, the cap was permanently electrified: but the negative state of the powder, blown at the distance of three feet, was not communicated; the gold leaf collapsing as the powder passed away. Since the moist cap or hot stone produce a negative state of electricity within six inches, the one by detaining the powder, and the other attracting its 24 NEW EXPERIMENTS electricity by means of hot effluvia, it appears that the whole stream is properly negative: but the powder continues to deposit electricity as it passes out of the bellows, and tho' it has lost some in its way, yet it will electrify the cap positively whilst thus in the act of changing its state. To exemplify this let two metal balls be insulated, and let one of them receive a spark, then bring it near the second ball, and it will cause the natural electricity of this second ball to pass off and electrify any substances touching it positively, and this second ball is left properly negative: but let the first ball approach nearer, and notwithstanding its negative state, the second ball will still communicate positive electricity. By this example it is evident that the powder may communicate positive electricity whilst under the influence of some cause which renders it negative; this cause I suppose to be the contact of air, which has a greater or less affinity with the electrical fluid than the powder, and therefore when it is suddenly projected into the air, each particle is disposed by this contact of air to absorb or emit electricity as it leaves the earth, and in passing along, the chalk deposits electricity upon the dry cap, whilst the same powder is aquiring a negative state. EXPERIMENT VIII When the air is not too dry, or when the electrometer has been kept in a damp place, let the gold leaf be made to diverge by holding excited sealing wax near it, and let it continue thus diverging about 25 ON ELECTRICITY half a minute, then suddenly remove the sealing wax and the gold leaf will first collapse, and then open with a contrary state of electricity. This I supposed wou'd have explained the positive cap above-mentioned: but when a ball of metal was insulated in dry weather by a warm tube of glass cover'd with sealing wax, it became quickly and strongly positive when the chalk was blown upon it within six inches. EXPERIMENT IX A piece of chalk drawn over a brush so as to cause a cloud of powder to pass over the cap of the electrometer, produces a negative repulsion of the gold leaf, but without communicating a negative state of electricity. EXPERIMENT X Powder'd chalk laid upon a metal plate placed upon the cap and blown off with the mouth or bellows, electrifies it permanently positive. EXPERIMENT XI If a brush be placed upon the cap, and whilst held with one hand the brush be rubbed with a piece of chalk till a considerable cloud of powder be raised, and then the hand removed, as the cloud disperses the gold leaf will diverge positively. Or if the cap of the electrometer be touched by one person whilst another projects a cloud of powder'd chalk, the same effect will take place. 26 NEW EXPERIMENTS In this experiment a positive state is caused by the influence of the negative cloud. EXPERIMENT XII Powder'd chalk falling from one plate to another placed upon the electrometer, electrifies it negatively. EXPERIMENT XIII A book was chalked upon the edge and suddenly clapped together, powder'd chalk was projected from a goose wing, and the electrometer was introduced into the dust raised from the road by travellers, all which electrified it negatively: but when dust was struck up with a stick very near the electrometer it became positive, which agrees with exp 1 and 2 EXPERIMENT XIV Wheat. flour, oat-meal, and minium produce in every case positive electricity, where chalk and all other powders yet tried are negative; such are red and yellow ochre, rozin, coal ashes, powder'd crocus metallorum, aurum mosaicum, black lead, lamp black, powder'd quick lime, umber, Spanish brown, powder'd sulphut, flour of sulphur, iron filings, rust of iron, sand. Also powders made from dried decoction of dyers woods as well as metallic calces, on the supposition of their similarity to flour or minium and other powders not registered, but none of these last were positive. 27 ON ELECTRICITY EXPERIMENT XV The inside of the bellows pipe was moistened, but this did not alter the electricity of the powders blown thro', therefore its excitation does not appear to depend upon friction in the pipe. EXPERIMENT XVI Air alone blown upon the cap does not electrify it, nor if blown thro' a hole made in a lump of chalk, whence it is not likely that the electricity is excited by friction against the air. EXPERIMENT XVII A lump of chalk was insulated and rubbed upon a brush fasten'd to the cap of the electrometer, in this case both the chalk and brush were positive, and the ascending cloud of powder negative. Hence probably the excitation of the powder is not occasioned by the friction of the chalk against the brush, since the states of the lump and brush were not contrary. EXPERIMENT XVIII Equal Measures and equal weights of powder'd chalk and wheat flour were mixed and projected from a brush, and the electricity of the chalk prevailed. EXPERIMENT XIX Scales of iron were let fall from a plate a considerable height above the electrometer, which caused a cloud of dust to arise from the lower plate, this lower plate was therefore electrified positively, 28 NEW EXPERIMENTS contrary to the state it acquired by sifting the powder or letting it fall more gently EXPERIMENT XX A lighted candle placed upon the electrometer very much increases its sensibility, and is peculiarly useful in collecting atmospheric electricity: but if the communicated electricity is not constantly supplied, it will also soon dissipate its charge in the air. EXPERIMENT XXI A small tube of glass cover'd with sealing wax was slightly excited, and tho' by the influence of its atmosphere it caused the gold leaf to diverge considerably wide, it did not communicate its electricity even when brought so near as to touch the cap; but when a candle was placed upon the electrometer, the electricity was communicated at the distance of twelve inches or more, and when strongly excited it caused a very sensible divergency at the distance of six feet. EXPERIMENT XXII The electrometer with its candle was carried into a room just swept, and the dust diffused in the air caused a very sensible negative repulsion of the gold leaf. EXPERIMENT XXIII The eletrometer with its candle was carried thro' a room adjoining to that wherein the electrical machine had been turned for some time before, (the 29 ON ELECTRICITY door between the Rooms having been left open,) and the air was found very sensibly electrified. The fluid being diffused thro' the air of both rooms. EXPERIMENT XXIV Take a quantity of powder'd chalk, and also a quantity of wheat flour, and put alternately the chalk and flour into the bellows, and blow the powder into the air a few times. It is then easy for another person bringing the electrometer with its candle into the room, to discover whether the chalk or flour was used, the chalk being negative and the flour positive. In like manner if chalk and flour be projected on different sides of a room it may be discovered where the chalk and where the flour were used, or if they were mixed it will shew which prevails. EXPERIMENT XXV No sensible electricity was produced by projecting water, salt, powder'd nitre, or allum, nor by smoke, flame, or explosions of gunpowder. EXPERIMENT XXVI If the small end of a tobacco pipe be made red hot, and the pipe be fixed in a cloven stick, so that the stick may be easily placed in a small hole in the cap of the electrometer, in such a manner that the pipe may be directed towards another electrometer placed about four inches from the end of the pipe, upon putting some water into the pipe head, the 30 NEW EXPERIMENTS steam will suddenly issue out of the small end, and electrify the first electrometer negatively, and the second positively. EXPERIMENT XXVII Spirit of wine, and ether, were tried with the hot tobacco pipe, and the electricity did not differ from water, but this required less heat. Oil and vitriolic acid produced smoke which was not electrified. EXPERIMENT XXVIII Let a cullender or tin funnel be suspended by silk, and put some hot coals in it. Upon throwing water on the coals the ascending vapour will be found electrified positively, and the drops of water falling thro' upon the electrometer will be electrified negatively: but if a second or third quantity of water be poured thro', the drops will sometimes become positive, as will be found more fully tried in another section. EXPERIMENT XXIX Positive electricity is produced by blowing with one's mouth thro' a red hot tobacco pipe upon the cap of the electrometer, by the rarefaction of moisture contained in such air: but dry air blown thro' from clean dry bellows does not electrify it. EXPERIMENT XXX Vapour of water was drawn into the valve of the bellows and blown upon the electrometer thro' the 31 ON ELECTRICITY iron pipe, yet its positive electricity was not destroyed by thus passing thro' the bellows. EXPERIMENT XXXI If a small lantern with a candle in it be placed upon the cap of the electrometer, and exposed to the air in an open place, or not too near high buildings, or trees, it seldom fails to render the atmospheric electricity very sensible. EXPERIMENT XXXII The electrometer was carried into the middle of a field when the weather was clear and frosty, and a small lantern placed upon it, caused the gold leaf to stand open with positive electricity about an inch wide, and when carried up a mount about six feet higher the gold leaf struck the sides; but it gradually collapsed as it came across trees or houses. EXPERIMENT XXXIII A vessel of water was placed upon an insulating stool in the open air, when the weather was dry and clear, then standing upon the same stool I spouted water as high as I cou'd with a small syringe about six times, then upon touching the cap of the electrometer with my finger, the gold leaf opened positively; the atmospheric electricity from a higher stratum of air having charged my body thro' the stream of water. 32 NEW EXPERIMENTS EXPERIMENT XXXIV Red hot glass was brought very near the electrometer and the focus of a concave mirror made to fall upon the cap, neither of which hastened the dissipation of its electricity. Red hot iron draws it off, but not so far as flame. EXPERIMENT XXXV An iron mortar was placed upon the electrometer and red hot cinders were dropped into it whilst electrified positively or negatively, but this did not diminish the divergency of the gold leaf. Bodies of equal surface but different in mass, when placed in the same circumstances are equally charged with electricity, according to the experiments of M. Achard, therefore various substances may be introduced into the mortar or other hollow vessel placed upon the cap of the electrometer, without adding to the quantity of electrified surface, which may be useful in trying various chemico-electrical experiments. EXPERIMENT XXXVI If the electrometer be charged with a small quantity of electricity, and the sharpest pointed needle or edge of a razor be brought within the least visible distance towards the cap, it will not draw off its electricity, but flame draws it off at a considerable distance. This experiment shews that sharp points or edges need not be avoided in the construction of this instrument, or of the doubler, or atmospheric 33 ON ELECTRICITY apparatus described in the following sections, and that a flame is better than a pointed wire for the purpose of collecting atmospheric electricity. EXPERIMENT XXXVII A very light pith ball was put upon the end of a very small wire, and the wire was suspended by a ring to the prime conductor of the electrical machine; also a wire of the same length, but without any pith ball, was suspended in a similar manner, and both were repelled by the electricity communicated to the conductor; but the wire with the pith ball descended first, which also shews that it is more necessary to make the electrometer light than to avoid points and edges. EXPERIMENT XXXVIII A small pin was fasten'd upon the end of a stick of sealing wax and charged with electricity, which was communicated from the pin to a metallic insulated conductor, fifteen inches in diameter, and seven feet long, whose surface was therefore prodigiously larger than that of the pin, yet its electricity caused a very sensible divergency of the gold leaf. This not only shews the sensibility of this electrometer; but assists our conception of the amazing divisibilty and elasticity of this wonderful fluid. [A description of the gold leaf electrometer and most of the above experiments, are printed in the philosophical Transactions for the year 1787]

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Transcribed, compiled, formatted, hyperlinked, encoded, and copyright © 2005, John Palmer, All Rights Reserved.