{"collection":"philosophy-ethics","full_text_available":true,"graph_url":"https://unchartedknowledge.5gfusion.net/v2/api/page/gutenberg_60392/graph","html_url":"https://unchartedknowledge.5gfusion.net/v2/page/gutenberg_60392","id":"gutenberg_60392","license":"Public Domain (US)","rights_basis":"gutenberg_metadata_copyright_false","source":"gutenberg","source_url":"https://www.gutenberg.org/ebooks/60392","summary":null,"tags":["Category: Health & Medicine","Category: Philosophy & Ethics","Category: Science - Physics","Electricity -- Early works to 1850","Electrotherapeutics -- Early works to 1800"],"text":"Transcriber\u2019s notes:\n\nThe text of this e-book has been preserved in its original form,\nincluding inconsistent archaic spelling and capitalisation, and use\nof italics.\n\nThe cover image of the book was created by the transcriber and is\nplaced in the public domain.\n\n\n\n\n  A\n\n  TREATISE\n\n  ON\n\n  ELECTRICITY:\n\n  WHEREIN\n\n  Its various _ph\u00e6nomena_ are accounted for, and the\n  cause of the _attraction_ and _gravitation_ of solids,\n  assigned.\n\n  TO WHICH IS ADDED,\n\n  A short account, how the electrical _effluvia_ act\n  upon the animal frame, and in what disorders\n  the same may probably be applied with success,\n  and in what not.\n\n  By FRANCIS PENROSE\n  Surgeon at _Bicester_.\n\n  They who are universally allowed the very greatest, and\n  wisest of men, have been, and still are, intent upon\n  the making of _observations_, and _experiments_: and surely\n  that must be in order to some further end. These would\n  be vain, and wholely useless, were not some reflections\n  made, some conclusions drawn, some theory or hypothesis\n  raised from them.\n\n  _Woodward_\u2019s state of _physick_ and of _diseases_, p. 55.\n\n  _OXFORD_,\n\n  Printed at the THEATRE for SACKVILLE PARKER, Bookseller\n  at _Oxford_, and W. OWEN, at _Homer\u2019s Head, Temple-Bar,\n  London_. MD CC LII.\n\n\n\n\n  ON\n  ELECTRICITY.\n\n\nThe many surprising effects of _electricity_, and the great cures\nperformed by it, one would imagine, should awaken the attention of all\nphilosophers and physicians; but as these cures have been effected by\nrandom experiments, every body has admired, but no body seems to have\nconsidered how, or by what means, they were performed. Whence\n\nNotwithstanding all these surprising _ph\u00e6nomena_, from which many\nhave entertained hopes of a great addition to the healing art; yet\nnot one tolerable account has been given, how, or from what cause,\nthese _ph\u00e6nomena_ proceeded; except what has been done by Mr. _Freke_,\nsurgeon to _Bartholomew hospital_; whose admirable piece shews the\ngreat penetration of its worthy author, with whom I shall join in\nthinking \u201cit may possibly be the beginning of much good.\u201d\n\nOne would think, this silence, on so interesting a subject, _in this\nenlightened age_, can proceed from nothing but a prejudice in favour\nof wrong principles of philosophy: That this is certainly the taste of\nthe present age, M. _Freke_ seems very well convinced; for, at the end\nof his pamphlet, he takes notice of a show-man, who, \u201chaving published\nsome experiments in electricity, and hearing that Mr. _Freke_\u2019s piece\nwas publishing, own\u2019d, he was much affrightened, because of the hard\nfate, as he said, of his booksellers; but, before he had read two\npages, he likewise owned he had recovered his spirits, when he found\nMr. _Freke_ pretended to think for himself, and did not let Sr. _Isaac\nNewton_ think for him.\u201d\n\nNow, if all persons would take the same freedom of thinking for\nthemselves, as Mr. _Freke_ has done, I doubt not but we should soon\nbe as much ashamed of mentioning the _attraction_ of _gravitation_,\nand the _attraction_ of _cohesion_ &c. as we now are of the _occult\nqualities_ of the ancient philosophers; and should perhaps, then\nagree with him, when, speaking of electricity, he says, that \u201cit is a\nsubject which can, with more nobleness and dignity, employ the mind of\nman, than any he can think of, relating to the sublunary part of the\nworld. For by it you may be acquainted with the immediate officer of\nGod Almighty, which he seems to send to all things living: Nay, this\npower, (according to his conception,) seems to be the cause, under\nHIM, both of life and death. And when it may be more fully understood,\nit may afford us means, whereby we may be better enabled to reason\nmore intelligibly, than now we can, concerning various operations in\nnature.\u201d Therefore,\n\nIn the following essay, I shall endeavour to shew,\n\nI. How, and from whence, this electrical fire and force are produced;\nin doing of which I shall make some observations, in order to shew that\nwe may form a more exact idea of most of the great operations of that\ncomplete machine, the universe, from electrical experiments, than can\nbe attained by any other means: I shall also produce some experiments\nwhich demonstrate, that the terraqueous globe has no _attraction_;\nnor a solid body, falling towards the earth, any _gravitation_; after\nwhich, I shall bring other experiments to prove what is the cause of\n_solidity_, and by what means bodies _gravitate_ towards the earth.\n\nII. How this electrical fire and force act upon the animal frame, and\nin what disorders they are likely to be of benefit, and in what not.\n\nI. We are certain, that this electrical fire is produced, either from\nthe glass globe, or the air that surrounds it. As to the glass globe,\nMr. _Freke_ has fully proved it cannot proceed from that; \u201cBecause\nnothing, we know of, can send out of it a quantity of matter, but there\nmust be less of that matter remaining, after it has been so discharged;\nwhereas it cannot be shewn, but that the glass globe, after ever so\nmany times using, remains as fit for the same use, as at first.\u201d From\nhence we assert, that this fire must proceed from the surrounding air\nbeing acted upon by the glass globe; and our inquiry must be, how, and\nby what means, fire is produced by the glass globe being made to act\nupon the air by which inquiry we shall find, that _air_, _light_, and\n_fire_ are of the _same substance_, or _essence_; only differently\nmodified, and appointed for performing different actions: that air (by\nbeing divided or broke to pieces) produces light; and, if that action\nis still encreased, it produces fire. Now as the greatest friction\nor attrition are necessary to produce fire, so fire, when it is once\nproduced, having received the greatest force, of consequence _acts_\nwith the greatest force; and light, with a less; so, wherever there is\nthe greatest quantity of these small particles of air, (which we call\nby the name of fire) in proportion to what we call gross air, there the\naction must be the greatest; by which means the said fire or light will\nexpand itself, \u2019till, by mixing with what we call gross air, it becomes\nof an uniformity with it. Now therefore, as experiments are the sure\nway either of proving or disproving any _hypothesis_; so, to illustrate\nthis, I shall produce some experiments both from Mr. _Freke_, and other\nauthors of unblemished credit, which prove that air is convertible\ninto light and fire, and also that light and fire are convertible back\nagain into air; and likewise, as some parts of the air are present in\nall places and things, that therefore, whenever a violent action either\nof solids or fluids is brought on, there light, fire, or heat, are\nproduced.\n\nTo prove this, Mr. _Freke_ has brought, two very simple, common, but\ngood experiments--First, if you slide a wax thread, or small rope,\nthrough your fingers, it will burn them; so likewise fire is produced,\nby rubbing two hard bodies together, or two sticks; or, as is very\noften the case, a cart or coach wheel will take fire, for want of\ngrease.\n\nAnother no small proof of this, is what Mr. _Freke_ has mentioned,\nviz. that in the year 1703, in the night of the great hurricane and\nhigh wind, in the strongest part of the tempest, great quantities of\nfire were seen passing swiftly over the hills in the neighbourhood of\n_Warham_ in _Dorsetshire_. The cause of which fire seems very easily\naccounted for, according to the above theory, which might otherwise\nperhaps, elude the searches of our greatest philosophers: for in this\nph\u00e6nomenon it is plain, that the attrition of the particles of the air\nwas so great by the motion of the wind, as to produce fire or light.\nMr. _Freke_ has some other observations, which much strengthen the\nabove theory, viz. that in tempestuous weather, at sea, great flakes\nof fire are frequently seen passing, not only in the air, but on the\nwater. The like is also observed, in the night time, when the surface\nof the water is disturbed with the feathering of oars, or by a vessel\nor boat passing swiftly through it. This light or fire _in storms_ is\nno new observation; for Mr. _Boyle_ says, it is common in storms for\nthe fire called _Helena_, _Castor_, and _Pollux_, to hover about the\nmasts of ships. And, indeed,\n\nTo shew that fire or heat are produced in any place, or thing, where\nthere is a sufficient motion, seems not to be very difficult; for water\nis the opposite to fire; and yet, by mixing water and spirit of wine\n_suddenly_ together, a heat ensues; and this will happen if they have\nbeen separated ever so often; but this heat vanishes again after they\nare mixed, or as soon as the _motion_ of their parts ceases. The like\nwill happen by mixing salt of tartar and water. This ph\u00e6nomenon seems\nto proceed from the disposition and texture of the salt; whose pores\nare made of such a proper size, that, on receiving the water by the\npressure of the atmosphere into them, the texture of the salt may be\nthereby broken, and its parts put _into motion_; which _motion_ causes\nan _attrition_ of the air, and so produces a sensible heat.\n\n_Boerhaave_ has another observation, which seems to prove to a\ndemonstration, that fire or heat is caused by an _attrition_ of the\nair; which observation I shall give in his own words. \u201cA cannon ball,\nshot in the winter time, will fly 600 feet in a minute through the cold\nair, which makes a greater resistance than any wind, the most rapid\nof which only moves 22-1/2 feet; hence it appears how much _friction_\nthe ball must have undergone in its passage, which by the way did\nnot proceed in a right line, but by its whirling motion continually\ndescribes a cycloid with every point of its body. When it falls,\nit is found quite hot; notwithstanding in its whole passage, it had\ncontinually met with cold air. This heat could not have arisen from\nthe flaming gunpowder, whereby it was exploded, since it only remained\nin that flame, an incredible small space of time, in which it is by no\nmeans credible so solid a body should have acquired such a heat; which\nis much more naturally accounted for from the great attrition of the\nball, driven with such a velocity through the air, and repelled by a\nwind, which is above 27 times swifter than the strongest wind hitherto\nobserved.\u201d _Boerhaave_\u2019s Chym. by _Shaw_, Vol. 1. pag. 244.\n\nI shall mention one more experiment from Mr. _Boyle_, which proves that\n_air_ is not only convertible into _light_; but that it may afterwards\nbe forced through glass, and thereby the same _vacuum_ be made that\nis by an air pump. \u201cLiquid phosphorus being put into a vial, when\nit was disposed to shine in the dark, the cavity of the vial above\nthe liquor seemed to be full of whitish fumes, though at other times\ntransparent. The vial, when close stopped, was not luminous in the\ndark, but the light or flame appeared as soon as it was exposed to the\nair, and the vial was unstopped; and that the occasion and propagation\nof this flame depended on the contact of the air, appeared, since\nagitation would not kindle it, but when the bottle was unstopped, the\nkindled flame would gradually be propagated downwards; the flame always\nappeared most vivid the nearer the air, and when it was extinguished,\nit first disappeared in the bottom, and then expired at the top. When\nthe Vial was unstopped for some time, when it was stopped again, the\nair that had leisurely insinuated itself would cherish the flame for\nan hour or two. It was observable, that when the air had been long\npent up with this shining liquor, its resistance would be so weakened,\nthat when the vial was unstopped, the external air would presently\nrush in with violence, from whence appears the interest of the air in\npropagating the shining of this liquor. The agitation before the vial\nwas unstopped would not kindle the light; yet when it was opened, it\nwould be increased by it, and even when it was in its dull state, if\nI poured a little of it upon my hand, and rubbed it with my finger,\nit would presently become vivid, and emit store of luminous rays, as\nwell as fumes very offensive to the nostrils; and when I ceased to\nrub, and the luminous quality was lost, it would be renewed again by\na repeated attrition; but in a little time its lucid virtue would\ndecay,\u201d _Boulton_\u2019s Epitome of _Boyle_\u2019s works, vol. 2. pag. 246. From\nthese experiments it may be observed, that this liquid phosphorus could\nnot be made to emit light, without a communication with the air, not\neven by the utmost agitation; though when it had a free communication\nwith the air, a small agitation greatly increased the quantity and\nstrength of the light; that, whenever the air was admitted to join it,\na violent intestine motion came on, by which motion or attrition, light\nwas not only produced, but also a great deal of the liquid was carried\noff by it; which might be perceived either by the sight, or smell.\nAnd when the vial had been long without a cork, by which means it was\nfilled to the utmost with air, the light would continue a considerable\ntime after the vial was stopped. We likewise find, that, after the vial\nhas been stopped some time, and the liquor has acted upon the air as\nmuch as it possibly can, there is not only a less quantity of gross\nair than there was when the vial was first stopped, but that there is\nthe same _vacuum_ as is made by the air pump; for as soon as ever it\nis unstopped, the air presseth in with violence, the fluid above the\nphosphorus (within the vial) being of a more subtle nature than the air\nwithout.\n\nThis experiment seems sufficiently to prove, that air and light are\nof the same essence or substance; for we are certain that gross air\nentered the vial, and, when it was first stopped, the quantity of\ngross air was of an uniformity with the air without the vial; but at\nits being opened, we are assured, there was a less quantity than when\nit was first stopped; for the air without presseth in with the same\nviolence it does into the exhausted receiver of an air-pump; by which\nwe may be assured, that some parts of the air have passed the vial in\nform of _light_; and, as the pores of the glass are not big enough to\nadmit gross air to return, the consequence must be, that there is a\nless quantity of gross air in the vial at the opening, than there was,\nwhen it was first stopped.\n\nFire and light are easily proved to be dispersed through the whole air,\nfrom the immediate action of _speculums_; and that air itself is of the\nsame substance with fire seems very plain; for as fire cannot subsist\nwithout air, (and in proportion to the quantity of air forced into the\nfire, in such proportion will be the force of the fire;) so, neither\ncan fire act but on the outside of bodies next the air; for even the\nmost inflammable bodies can only catch fire on their outermost surface\ncontiguous to the air; and fire in action, if immerged in a body of\nthe most inflammable matter, so as to leave no lighted part above such\nsurface in the air, will be so far from kindling the inflammable body,\nthat itself will be extinguished. Thus \u201cif a flaming brimstone match\nbe plunged into the highest rectified spirit of wine, the spirit of\nwine will extinguish it as intirely, as if dipped in cold water; it\nwill also extinguish a live burning sparkling coal; but in the former\nexperiment, if the least bit of the burning match remains above the\nspirit of wine, it will then catch fire, and the flame will presently\nspread over the whole surface.\u201d This is an experiment of the great\n_Boerhaave_, in the first vol. of his chymistry, by _Shaw_, pag. 316.\n\nAll these experiments, I think, prove to a certainty, that air is\nconvertible into light. I shall now bring one experiment, from\n_Boerhaave_, Vol. 1. p. 998. which proves, that fire or light may be\nchanged into air.\n\n\u201cIf a spherical glass vial be kept in a glass-house furnace, till ready\nto melt, and then be hermetically sealed in that heat, and suffered to\ncool; if now, it be held inverted, under cold water, and the end of the\nneck be carefully broken off, the water will be violently forced into\nit, and fill the glass, but so as to leave a bubble of true elastic\nair at the bottom.\u201d\n\nThe above experiments prove, that, whenever air is sufficiently divided\nor broken to pieces, light is produced; so that the light or heat in\nelectricity, is no other than, we find, may be produced several other\nways. For the air being violently rubbed or ground to pieces between\nyour hand and the glass globe, whirled briskly about, the air between\nyour hand and the globe is ground so small as to be in the form of\n_light_, which is expanded or sent off from the glass globe in the same\nmanner as _light_ from a candle, or other luminous body; which emission\nis continually supplied by the common air pressing in between the rays\nof _light_, emitted from the glass ball. That this is the method, by\nwhich it acts, seems very clear: for you may not only hear the hissing\nnoise of the air pressing towards the globe, but also plainly feel the\nair with your hand, near the globe or tube.\n\nThe chief reason (and what has been our great misfortune) that we\nhave not been able to discover the cause of electricity, seems to\nbe the leaving that philosophy, which has been _revealed_ to us,\nand putting in its stead _theories_ of _our own invention_. For, if\nwe had considered (from the _revealed_ account that is given us of\nthe formation of light) the _method_ of its _first_ production, we\nshould not be at such a loss to account for that light in electricity,\nas we hitherto seem to have been; for we are _there_ told, that\nthe _heavens_, or airs, were created in a state of _darkness_, or\ninactivity; and that the first thing God did, was to cause a _motion_,\nor _wind_ amongst the airs; which _motion_ was to _continue_, and\n_encrease_, till it produced _light_; and, after this _light_ was\nproduced, God called it _Day_, or as it is expressed in the original,\n_tumultuousness_; it being produced from the impetuous or violent\nmotion of the airs: and the _darkness_ he called _night_, or, as it\nis likewise expressed, the time when this _languishes_ or _decays_;\nfor the _congealing_ or _thickning_ of the air, by which _darkness_ is\nproduced, is in proportion as the _force_ of the _light_ abates.\n\nBy all which, I think, we may be assured, that the _light_, and all the\n_ph\u00e6nomena_ produced in electricity, are caused by a violent _friction_\nor _grinding_ of the grains of air between the glass globe and the hand.\n\nTo illustrate and prove, that this is the method by which the\nelectrical _light_ is produced, I shall bring some experiments, from\nMr. _Hauksbee_, which, I imagine, will make it indisputable. In his\nfirst and second experiments, he shews us, that by dropping mercury\non a glass in an exhausted receiver, the _action_ of the mercury\non that subtil fluid gives the mercury the appearance of fire; but\nobserves, that in all these experiments on mercury, no _light_ is to\nbe obtained without _motion_, and that the same motion which produced\nthis light in _vacuo_, did not produce it, when given to mercurial\nglobules in _open air_. This experiment shews us, that there was a\nlarger quantity of _light_ in the exhausted receiver than when it was\nfilled with common air; nay farther, that the _subtil fluid_ contained\nin the exhausted receiver, was _light_; but, for want of _motion_, was\nnot perceptible by our senses; but by so small a motion as that of\nthe descending mercury, it was pushed forward in the same manner, as\n_light_ from a candle, or other luminous bodies. We also find, that\nthe same experiments performed in an _unexhausted_ receiver, would not\nproduce the _ph\u00e6nomenon_ of _light_; which one might easily suppose to\nbe the case. For in the _exhausted_ receiver, any the least _motion_,\nthat is sufficient to _push_ this subtil fluid (_light_) from one\nplace to another must give us the perception of _light_; but in the\n_unexhausted_ receiver the _motion_ or _friction_ must be great enough,\nnot only to _push_ the air from place to place, but also to _break\nit_ so small, as to be in form of _light_: which he shews us by his\nthird, fourth, and fifth experiments to be the case; for by these\nexperiments he produced _light_ in an _unexhausted_ receiver; but then\nthe _motion_ or _agitation_ was required to be much _greater_ than that\nwhich produced _light_ in _vacuo_. The difference of these two _lights\nwas very considerable_, and consisted particularly in this, that the\nluminous particles are _distinct_ and _separate_ in the experiment\nperformed in the _open air_; and _united_ and _blended_ into one\ncontinued body of _light_, in the other experiments in _vacuo_; which\ndifference proves to a demonstration, that the exhausted receiver was\nfull of nothing but _light_; for, on shaking the mercury therein, the\nwhole body of the receiver seemed to be _one continued body of light_;\nbut on shaking the mercury with ever so great a violence in the common\nair, it seemed full only of _little_, _bright_, _twinkling sparks_;\nand not one continued body, as in _vacuo_. For, as the appearance of\n_light_ is produced in the common air, by the _friction_ of the mercury\nagainst the glass receiver, _breaking_ or _grinding_ the air to pieces\n(which small particles put on the form of _light_) so, when the common\nair _presses_ in between these small particles, the appearance must be,\nand cannot be otherwise than is shewn by these experiments.\n\nThese many and various experiments abundantly prove, that _light_ is\nproduced as above described; and not, as the generality of people have\nimagined (from that mistaken notion of _action_ being performed by\n_solids_ and not by _fluids_) that this electrical _light_ proceeded\nfrom the glass globe, emitting, what they call, _electrical effluvia_,\nwhich has been shewn before to be impossible; because if any quantity\nof matter sends off part of its own body, there must be less of that\nbody remaining, than before the above matter was sent off, which we\nfind is not the case of the glass globe; and to prove that it does not,\nI shall bring one experiment more from Mr. _Hauksbee_ which will put it\nbeyond doubt.\n\nPag. 27. he shews us, that by a violent _attrition_ of _woollen_\nagainst _woollen_ in _vacuo_, he produced _light_, as well as from\nany _hard_ or _electrical_ body; but not so vivid, nor in so large a\nquantity. Now, as woollen is reckoned by all to be a _non-electrical_\nbody, it shews us that the _light_ must proceed from the _attrition_\nof the air, and not from the _electrical body_, as has been falsely\nimagined.\n\nAs _light_ may be produced by other methods than have been yet\ndescribed, as from _rotten wood_, _fish_, _meat_ &c. I shall endeavour\nto give an account, how, and in what manner, that _light_ is produced.\nMr. _Boyle_ (in vol. 2. p. 233. of the epitome by _Boulton_) tells us,\nthat by putting _rotten wood_, _fish_, _flesh_ &c. in the receiver\nof an air-pump, and then extracting the gross air, they all, in a\nlittle time, lost their _shining_ or _luminous_ quality; but, upon\na re-admission of air, this _luminous_ quality returned. From which\nwe may learn, that the air is essentially necessary to continue\nthis _light_; and, of consequence, that this _light_ is produced by\nthe _action_ and _re-action_ of the air on the body, which cause an\n_intestine motion_ of its parts; and thereby the emission of the said\nlight; for when any thing begins to ferment and _putrify_ (which cannot\nbe performed in any place, but where the gross air is present) the\n_intestine motion_ of its parts is thereby _increased_; which _motion_\nacting upon the air pressed into it, the air is thereby _ground_ very\nsmall, and by the continual pressure of the atmosphere is sent out so\nsmall, as to be in form of _light_.--In the common _fermentation_ of\nliquids, when it rises to any height, those particles of _light_ being\n_stopped_, and _entangled_ by the _watry parts_ of the fermenting mass,\nthereby produce _heat_; and some mixtures will produce _light_, _heat_\nand _flame_ on fermentation; as _steel_, _water_, and _sulphur_.\n\nBy these experiments we have a clear idea of the means and method by\nwhich _fermentation_ is performed, which operation has been hitherto\nunintelligible. From hence we may likewise see the reason why, in an\nair either _too hot_ or _too cold_, _fermentation_ cannot be performed;\nfor in an air _too cold_, the pressure is _too great_, and also the\ngrains of air _too large_ to _enter_ and _divide_ the thing to be\n_fermented_; by which means the _motion_ of its parts requisite to\n_fermentation_ is prevented; but in air that is _too hot_, there must\nbe just the contrary effect, for there the parts of the thing to be\n_fermented_ are so far _expanded_, and the air so _rarified_, as to\npass through the body with little or no obstruction, and of consequence\nto produce little or no _intestine motion_ of its parts; and that\nthere is in _fermentations an intestine motion_ of the parts of a\n_fermenting_ liquid, is easily discernible by the naked eye. This also\ngives us the reason, why the _glow-worm_ shines only in the summer\nmonths, when the air is greatly _rarified_, or _divided_, and then\nrequires but a small _motion_ to give it the form of _light_.\n\nThe _light_ proceeding from _diamonds_ &c. seems to be easily accounted\nfor from the _motion_ of the _airs_; that there is a _perpetual motion_\nof the _airs_, may be proved by the following experiment. In a still\nplace, suppose a close darkened room, illuminated only by one small\nhole in the window shutter; where, if a person at rest views the\nenlightened current of air sideways, as it extends along the room,\nhe will perceive a _surprising motion_ of the dusty atoms therein,\n_perpetually rolling and tossing_ about _with great rapidity_. This\n_motion_ must be very _considerable_, as it is _perpetual_, and pushed\non with the power of _gravity_ in the air equal to a column of water\n33 feet high. By this _action_ on _diamonds_, whose _pores_ are very\n_small_, and the bodies themselves of such a _make_ and _hardness_, as\nthat, when the air is pressed on them with so great a _force_ as that\nof the _incumbent atmosphere_, the air is _broke exceedingly small_,\nand, by the continuance of the _pressure_, is sent off from the body\nin form of _light_. We likewise find from experiments, that where\n_diamonds_, or other bodies of that kind, have not their outward parts\nof a proper _make_, or their _substance_ of a _sufficient hardness_ or\n_closeness of parts_, to emit _light_ with no greater _force_, than the\npressure of the _atmosphere_ only, then this deficiency may be supplied\nby _rubbing_; by which means the air is _ground_ to pieces, and emitted\nin form of _light_, as is shewn in all electrical experiments.\n\nOne great property of _light_, or, as it is commonly called the\n_electrical effluvia_, is (as Mr. _Hauksbee_ has proved from many\nexperiments,) that it passes _through glass_, as water does through a\nsieve, or as if no body of matter interposed. This _light_ of itself,\nwhen _pure_, or _simple_, hurts or destroys no material bodies;\nbut when _pushed_ on by the following air with _great violence_,\nand _meeting_ with a _great resistance_ from an impeding body, the\n_conflict_ is so great, that if the following air _presses_ on with\n_sufficient violence_, it _dissolves_ or _destroys_ the _solidity_\nof any material body. As all bodies become _solid_ according to the\n_temperature_ of the surrounding air; some retaining their _solidity_\nin such a degree of _heat_, as _metals_ of most kinds; whilst others\nrequire a particular degree of _cold_ before they become _solid_,\nas _water_ &c. which when froze is as much a _solid_ as any thing\nelse--this proves that the _solidity_ of bodies depends on the\n_temperature_ of the air, as will be more fully proved hereafter.\n\nThe glass globe, with the electrical experiments, seems to give\na very clear idea in what manner the _sun_ is _supported_, how\nthis _terraqueous globe_ and the rest of the _planets_ are made to\n_move_, and _continued in motion_; and also, what is the cause of\nthe _attraction_ of the _sun_, _earth_, _moon_ and the rest of the\n_planets_.\n\nThat the _sun_ is the chief, material, ruling agent, is very clearly\nrevealed; as are some of its chiefest actions on the planets and the\nrest of the universe. For, in the sun we find a power of melting,\ndividing and (with the assistance of the air) expanding and sending out\nthe air, first in form of _fire_, and afterwards in that of _light_;\nwhich power seems to be so regulated, as to be able to reach the\nextremities of the universe, where it is _congealed_, _condensed_, and\n_returned_ back again to the _sun_, to be again _melted_, _divided_,\nand sent out as before. This action seems to be represented by water\nin a _still_, for there the fire, forcing its way through the water\ncontained in the _still_, carries off some of the watry particles with\nit; and when it has reached the head of the _still_, if it has no\npassage into the outward air, and the _action_ of the fire is not great\nenough to break the _still_, it is by the coldness of the surrounding\nair (or as is commonly the case by the coldness of water placed thereon\nfor that purpose) _condensed_ and _returned_ into the water contained\nin the body of the _still_, there to be _rarified_, _expanded_, and\nsent off in _steam_, as before.\n\nWe must suppose the streams of _light_ to be always acting on one\nside of this terraqueous globe, and there _dividing_, _expanding_\nand _rarifying_ the air; the consequence of which must be a kind of\n_vacuum_, which is immediately filled by the _pressing in_ of the\n_congealed air_ from the extremities; and as the earth is placed in\nthis fluid of airs, we may as easily conceive that the air pressing\nin as above, must, with it, turn round the earth, in the same manner,\nand with as much ease, as water does a common mill-wheel, or the air a\nwind-mill. By these powers also the terraqueous globe is kept _solid_\nand _entire_; for, was this force once taken off, it would soon drop\nto _atoms_, notwithstanding the pretended _attracting_ power of its\nmaterials.\n\nTo confirm what is here advanced, I shall bring an experiment (which\nMr. _Boyle_ has laid down as a paradox) which proves that this\nterraqueous globe has no _attraction_, nor any _solid_, falling towards\nit, any _gravitation_; but that all bodies _are forced_ to it by the\n_incumbent atmosphere_, as much as water is _forced_ up a pump by it\n(the atmosphere) which, till the time of the great Mr. _Boyle_, was\nimagined to be performed by, what they called, the _suction_ of the\npump. But this is no more than has often happened in philosophy, where\nwhen we cannot well account for any thing, we put the _effect for the\ncause_.\n\nMr. _Boyle_ found that a _solid body_, as _ponderous_ as any yet known,\nthough near the top of the water it would sink by _its own weight_,\nyet if it be placed at a greater depth than twenty times its own\nthickness, it will _not sink_, if its descent be not assisted by the\n_weight_ of the _incumbent water_. To prove this, he gives us a curious\nexperiment, viz. by keeping off the _pressure_ of the water, from\nthe _top_ of the _sinking body_, and _sinking_ it to a proper depth,\nhe found, that the _most ponderous_ body would be _buoyed up_, and\n_supported_ by the water only. See the 2d vol. of _Boulton_\u2019s epitome,\npag. 305. This experiment shews us beyond all contradiction, that the\n_earth_ has no power of _attraction_, nor a _descending body_ any power\nof _gravitation_; for if it had, the farther it was sunk in the water,\nthe nearer it must be to the centre of the earth, and of consequence\nthe _attraction_ must be the greater; but this, we find, is contrary\nto experience; so that the whole power of descending is impressed upon\nit by the _air_, or by other bodies forced upon it by the _incumbent\nair_. This experiment alone is more than sufficient to destroy the fine\ntheories of _attraction_ and _gravitation_; it also shews us how, and\nby what means, two marble slabs, finely polished, are what they call\n_attracted_ to each other, and require a great force to separate them;\na force in proportion to the breadth of the slabs; but this has been\nshewn by other experiments to be nothing but the _pressure_ of the\n_air_, or _atmosphere_; for put them into an air pump, and extract the\n_gross air_, and they will immediately separate from each other.\n\nOne reason, which seems to have led us into the mistake that the\n_solidity_, or _firmness_ of bodies is not caused by the _air_, has\nbeen, that, for the generality, we consider the _air_, or _atmosphere_\nas _pressing_ only _downwards_; for if we had considered that it\n_presseth_ equally _every way_, as well as _downwards_, (as _Boerhaave_\nin his chym. by _Shaw_, vol. 1. p. 389. has shew by the following\nexperiment) I believe we should not have overlooked that force, or have\nthought it insufficient for this operation. \u201cFill three glass vessels,\nthe one of a cylindrical figure, the other conical, the third bellied\nwith a cylindrical neck; let these be filled to the brim with fair\nwater, and covered with a single piece of paper, so as to touch the\nsurface of the water, and by pressing it down with the hand, prevent\nthe external air insinuating between the paper and the water; if the\nglasses be now inverted, whilst the paper remains close with the palm\nof the hand, and the hand be afterwards gently withdrawn, the water\nwill still remain in the glasses. The same holds true, though the\nglasses be held horizontal, or in any other position.\u201d As the cause of\nthe _solidity_ or _firmness_ of bodies is the _pressure_ of the _air_\nor _atmosphere_, so likewise it must depend on the _make_ and _size_ of\nthe _pores_ of such bodies; for bodies whose _pores_ are _smallest_,\nmust be acted upon with a greater power than those whose _pores_\nare _largest_, or whose _pores_ are so _large_ as not only to admit\n_light_, but also _common air_ into them. This Mr. _Hauksbee_ proves by\na curious experiment, for having placed two brass hemispheres, of 3-1/2\ninches diameter, upon each other, and then extracting the gross air out\nof them by the air pump, and by these means taking off the _resistance_\nof the _common air_ that was _within_ the two brass hemispheres, he\nsays, it required 140 pound weight to separate them; this experiment\nwith that of the two marble slabs before mentioned, is a demonstration\nof the _power_ that keeps _solid bodies_ from _falling_ to _pieces_.\nAnd even, if these slabs are not so _perfectly smooth_, yet the weting\nthem with water, which prevents the gross air from _entering_, will\nproduce the like effect. That solids _expand_ themselves by _heat_ or\n_fire_, is proved by heating an iron rod in the fire: in which case,\nit is always found to be _bigger_ and _longer_ when _hot_ than _cold_;\nand it was the opinion of _Boerhaave_, that cold _consolidates_ all\nthose that are called firm bodies; that is, brings that part, which\nwe call _body_ in them, into a _less compass_ than before, and thus\n_unites_ the matter thereof more closely together: by which means the\n_cohesion_ of the whole mass is usually increased; which makes what we\ncall, _strength_ and _firmness_ in bodies.\n\nHaving shewn that _solid bodies_ have no power either of _attraction_\nor _gravitation_, and that their _firmness_ or _solidity_ depends on\nthe _pressure_ of the _atmosphere_; I shall now endeavour to shew, from\nelectrical experiments, how, and by what means they _descend_ towards\nthe earth.\n\nWhat is called the _attraction_ of the _earth_ seems to be performed\nin the same manner as that of the _glass globe_ in electricity; the\nexplaining of which will give us a clear idea, by what means _heavy\nbodies_ are _forced_ towards the terraqueous globe. In accounting for\nthis electrical _attraction_, Mr. _Hauksbee_ seems to be very clear;\nfor, says he, \u201cif by the heat and rarefaction, consequent upon the\nattrition, the medium contiguous to the glass be made specifically\nlighter; then of course, to keep up the ballance, the remoter air,\nwhich is denser, must press in towards the tube, and so carry away (in\nthe torrent) the little bodies lying in its way, thither also. The\nvarious irregularities in the excitation, or the emission and discharge\nof the electrical matter or light from the tube (which will be followed\nwith proportional irregularities, in the motion and tendency of the\ndenser air, towards the glass globe, by the hydrostatical laws) may\nbe sufficient to account for the various uncertain motions of the\nlittle bodies carried towards the glass globe.\u201d This account of Mr.\n_Hauksbee_\u2019s being so very clear, it is a little surprising that he\nshould allow the power of _attraction_ to matter, as in some places he\ndoes; for this is no more than in other words, telling us, that the\nair round the ball is _divided_ and _rubbed_ or _ground_ to pieces by\nthe _friction_ between the glass globe and your hand, and thereby made\nto _expand_ itself; so the air pressing in to make up that deficiency,\nforces every thing towards the glass globe, that by its number of\nparticles is not able to withstand the _current_ of _air_, pressing\ntowards the globe. So in like manner near the surface of the earth, the\nsun-beams being _reflected_ by the terraqueous globe, must by these\nmeans be in a greater quantity near the surface of the earth, than at a\ndistance from it; and so _divide_, _expand_ and _rarify_ the air near\nits surface, which _rarified_ or _divided_ air is forced off from the\nearth on all sides, by the _pressing_ in of the air from above, which\nmust of consequence _drive_ every thing before it, towards the earth.\nBy which we find, that the cause of bodies _descending_ towards the\nearth, is not from any _property_ either of the _earth_ or of the\n_descending bodies_; but that these are _forced_ towards that, by the\nsurrounding _air_, in its said _motion_.\n\nTo prove that this is the method by which, in electricity, bodies are\nforced towards the glass globe, I shall bring an experiment or two from\nMr. _Hauksbee_; and as these experiments prove to a certainty, that\nthis is the manner of the _attraction_ in _electricity_, it will give\nus little room to doubt, but that the _attraction_ of the _earth_ is\nperformed in the same manner.\n\nMr. _Hauksbee_ observed, that the _electrical effluvia_ were not only\nperceiveable by sight; but also, if the hand was held near the tube,\nseemed to make such sort of strokes upon the skin, as a number of fine\nlimber hairs pushing against it might be supposed to do: and in order\nto find whether the electrical _attraction_ was regular and uniform,\nhe made the following curious experiment, shewing that all bodies, not\ntoo heavy, are _forced_ (or, as is commonly supposed, _attracted_) to\na cylindrical glass, equally all round, if these bodies are, as _they\nterm it_, within the sphere of its activity.\n\nThis experiment seemed to affect Mr. _Hauksbee_ so much, that (speaking\nof electricity) he says, \u201cit affords us a sort of _representation_ of\nthe _great ph\u00e6nomena_ of the _universe_.\u201d Page 53.\n\n[Illustration]\n\n\u201cFor, says he, having observed (in electricity) that light bodies,\nplaced near any part of the rubbed cylinder, seemed to be equally\nattracted, I contrived a semicircle of wire, which I could fasten at\na constant distance, making it encompass the upper semi-cylindrical\nsurface of the glass, at 4 or 5 inches distance. This wire had\nseveral pieces of woollen threads fastened to it at pretty near equal\ndistances. The length of them was such, that being extended in a\ndirection towards the center of that imaginary circle, on the surface\nof the glass, in the plane of which the wire was placed; they would\nthen reach within an inch of the circumference of that circle: but\nif left to their own liberty, they hung in that parallel portion\nrepresented, fig.\u00a01. The cylinder was placed with its axis parallel to\nthe horizon; and in this posture, it was turned swiftly round; and\nthen by the rapid motion and agitation of the surrounding air, the\nthreads were placed into such portions, as are expressed fig. 2. viz.\nthey were all lifted up and bent upwards from the axis of the cylinder.\n\n\u201cAll this while, there was only the swift motion of the cylinder\nround its axis, without any attrition, but now when I came to apply\nmy hand to the lower part of the glass (so swiftly whirled about)\nand consequently to add attrition to the former motion; the threads\npresently began to change their direction, and all harmoniously pointed\nto the center of the circle, in whose plane the wire was placed, as\nin fig.\u00a03. neither were they at all disordered or flung out of that\nposition, by the wind occasioned by that violent motion (but as if\nthere had been no such hurry of air about them) they still persisted\nin their central direction; I found I could by shifting the place of\nthe attrition hither or thither, draw the threads towards this or that\nend of the cylinder; but yet they all still went uniformly converging\ntowards some center in the axis of it; so that they formed themselves\ninto a sort of conical surface.\n\n\u201cFarther, if the wire with its loose threads was reverted, so as to\nencompass the lower part of the cylinder (as before it did the upper\npart) yet the effect still answered with the same exactness. For the\nthreads were all erected into so many strait lines, still directing\nthemselves towards a center in the axis of the glass.\n\n\u201cHitherto the axis of the cylinder was placed horizontally; in the next\nplace I set it in a vertical position, so that it stood perpendicular\nto the plane of the horizon; in which case I made use of a wire hoop,\nwhich was necessary to be placed parallel to the horizon, that it might\nencompass the cylinder, in the same manner as the semicircular wire did\nbefore: only one small part of this wire was left open, to make way\nfor the touch of the hand, which was to give the attrition. And the\nwire being thus placed, it was evident that the threads (without some\nexternal force to support them) must all flag and hang perpendicularly\ndownwards. Yet, as soon as the motion and attrition were given, the\nthreads presently began to be extended; and as if they were become\nstiff and hard, formed themselves into an horizontal plane; their loose\nends pointing to a center in the axis of the glass, as before.\n\n\u201cAnd thus (in all sorts of positions whatsoever, both of the wire and\nof the glass too) were the threads acted upon by a sort of centripetal\nforce; to the laws of which they were always conformable.\u201d See\n_Hauksbee_\u2019s experiments, page 53 &c.\n\nIt may be observed in this experiment, that the _attractive_ power of\nbodies does not lie in _solids_, as has been falsly imagined, neither\nhave such bodies any _centripetal_ or _centrifugal_ force; but that\nthis _power_ and _force_ are given them from _without_. For, on placing\nthe wire with the threads round the cylinder, they were all _forced_\n(or as it is often called, _attracted_) towards the _earth_; but, on\ngiving a _violent motion_ to the cylinder, they were drove from the\ncylinder, as if forced by a strong wind; but, by applying the hand to\nthe glass cylinder, they were recalled, and all pointed to a center\nin the axis of the cylinder: and this _central_ direction might be\naltered at any time, by only moving the hand to different parts of\nthe cylinder; the threads always pointing to the place where the\n_attrition_ was made: by which we find, that the _central_ force, both\nof the cylinder and the threads, are caused by the _attrition_ of the\n_air_ between your hand and the cylinder; whereas, at any other time,\nthey are quite inactive: so we are assured that these _central_ forces\nwhich have been imagined to be _within_ the _solid_, are not there, but\nin the _air without it_.\n\nOn putting something between any of the threads and the cylinder; then,\nthose threads would return to their first and _natural position_, viz.\npoint towards the center of the earth. So, as Mr. _Hauksbee_ observes,\n\u201cin these small orbs of matter we have some little resemblances of the\n_grand ph\u00e6nomena_ of the _universe_.\u201d\n\nAnother thing observable was, \u201cthat by putting these threads within a\nglass, when they became extended, this position of the threads would be\naltered at any time on the approach of one\u2019s hand, finger, or any other\nbody, to the surface of the glass.\u201d This is sufficient proof that the\n_light_, or as it is generally called, the _electrical effluvia pass_\nthrough the _glass_, with as much ease as water does through a sieve.\n\nOne thing which seemed a little surprising to Mr. _Hauksbee_ was, that\nupon exhausting the _gross air_ out of the tube or globe made use of\nin electricity, what he called the power of _attraction_, would cease;\nbut upon suffering the air again to enter, it returned as vigorous as\nbefore. This must be the case; for (as was before observed) whenever\nthe gross air is extracted by an air pump, the fluid remaining is\nnothing but _light_. So, whenever this attrition is performed on an\nexhausted globe (for want of the resistance of the gross air within, to\nforce off the particles of air ground so small as _light_, and thereby\nto make an _expansion_ or _rarefaction_ round the glass globe, which\nhas been shewn to be the cause of light bodies being _forced_ towards\nthe globe) these particles of _light_ do immediately enter the globe on\none side, and _force_ out the same quantity on the other; in the same\nmanner as water through a sieve, without ever making any _expansion_ or\n_rarefaction_.\n\nHaving thus shewn how and by what means the _fire_ and _light_ in\nelectricity are produced; our next inquiry must be, why some bodies\ncommunicate this _light_ to ever so great a distance, and that\ninstantaneously; whilst others will not; and also, why some bodies are\n_electrical_ and others _non-electrical_.\n\n_Electrical bodies_ are those, whose _pores_ are so _fine_, as to admit\nnothing through them but _light_, or air ground to a proper fitness;\nas _metalls_, _glass_, _amber_, _wax_ &c. Bodies _non-electrical_, are\nall those, which, by the _largeness_ of their _pores_, admit, not only\n_light_ but also _gross air_.\n\nWe see, when the air is _ground_ to pieces by an electrical machine,\nand _put_ into _sufficient motion_, by the _friction_ between the glass\nglobe and the hand, a wire being hung from the iron barrel, so as very\nnear to touch the ball, part of the _light_ issuing from the ball,\nas above described, _enters_ the wire, and is by it communicated to\nthe iron barrel, and from thence _carried_ by _another wire_ to any\ndistance, if not interrupted by some _non-electrical_ body: to the end\nof which, by a third wire is hung an egg; as soon as the globe is put\nin _motion_, and warm spirit of wine is placed so as to touch the egg,\nthe spirit of wine will immediately take fire from the contact of the\negg.\n\nIt has been already proved, that when the globe is put in _motion_, and\nyour hand is applied to it, it _grinds_ to pieces the air between the\nglobe and the hand, and so _rarefies_ and _expands_ it, and sends it\noff with great force, in the same manner, as _light_ is sent from any\nbody of _fire in action_; as may be seen, if the electrical machine is\nset at work in the dark; when the emission from the glass globe will\nappear lucid.\n\nThe wires which are hung over the glass globe, by the _smallness_ of\ntheir _pores_, admitting nothing through them but _light_, and light\nbeing a body so _subtil_, as to penetrate the _pores_ of all other\nbodies, even to the very center of the earth; the _interstices_ of the\n_wires_ are filled with it from one end to the other.\n\nAs the _light_ is one continued body, throughout the whole extent of\nthe wire, the _force_ it receives at the end next the glass globe, is\n_immediately_, and at the _same instant_ of time, communicated to the\nother end, let the _length_ or _extent_ of the wire be ever so great.\nAs, for example, a pipe of any length, being filled with any sort\nof fluid, as water; if you force in more water at one end, the same\nmoment, and in the same quantity, it will be forced out at the other.\n\nBy these experiments in electricity, we find that _fire_ and _light_\nare produced as has been before observed, only by _breaking_ the air\nto pieces, and putting it in _motion_; and that _fire_ and _light_ are\nin _all_ bodies, water and ice not excepted; for, if a piece of ice is\nhung at the end of the wire, it will set fire to spirit of wine, as\nwell as an egg.\n\nThe iron wire by the _closeness_ of its _pores_ prevents the\nsurrounding air from entering it, and by that means at the same time\nforms a kind of _canal_ for the _light_ to pass through.\n\nHaving thus as I conceive, given a tolerable clear account, and, I\nhope, a true one, how and by what means, the various _ph\u00e6nomena_ in\nelectricity are produced; I suppose, it will not be a very difficult\ntask, to form a judgment, what disorders electrical operations are\nlikely to be applied to, with hopes of service; as also in what others\nthey are likely to be detrimental.\n\nAs the _heat_ and _redness_ of the _blood_, may be easily proved, to\nbe in proportion to the _quantity_ and _motion_ of the _light_ it\ncontains; so, wherever the blood is _heated_ to a great degree, as in\n_fevers_, _Inflammations_ of all kinds &c. there we are to expect the\nworst and most pernicious consequences, from the use of electricity.\n\nBut, on the contrary, as the nerves have been proved to act by a\nsubtil fluid that passes through them, and that they, by the closeness\nof their pores, will not admit a fluid to pass through them, whose\nparticles are much larger than those of _light_; the consequences we\nmust often expect from such a make, must be obstructions; and as the\n_light_ in electricity is forced through our bodies and nerves, with\ngreat violence, it seems very reasonable to think, that where these\nobstructions are not too violent, there they may be broken through and\nremoved by its power, of which we have had many instances, especially\nin palsies.\n\nThis is also confirmed by the success of the present practice of\nphysick; for, the greatest relief, in these cases, is always found to\nproceed from _volatile_ and _penetrating_ medicines. But, care should\nbe taken, not to administer electricity, to a person of weak and\ndecayed nerves, instead of one whose nerves are obstructed.\n\n\n_FINIS._","title":"A Treatise on Electricity: Wherein its various ph\u00e6nomena are accounted for, and the cause of the attraction and gravitation of solids, assigned. To which is added, a short account, how the electrical effluvia act upon the animal frame, and in what disorders the same may probably be applied with success, and in what not.","tradition":"philosophy-ethics","translated_text":null,"word_count":8848}