Experiments and observations on electricity, made at Philadelphia in America
Franklin, Benjamin, 1706-1790 | Cave, Edward, 1691-1754, printer | Jefferys, Thomas, -1771, engraver | Franklin, Benjamin, 1706-1790, former owner. MB | Livingston, Edward, 1764-1836, former owner. MB | Barton, Thomas Pennant, 1803-1869, former owner. MB
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' l y/i r t trrt ri, /j ysi ^y/ly fJ r '* n^s — X <^ /X 1 if Ct) t< n AX A As LTAtSy i Ae^±* EXPERIMENTS AND OBSERVATIONS O N ELECTRICITY, MADE AT Philadelphia in America, B Y Mr. BENJAMIN FRANKLIN, AND Communicated in feveral Letters to Mr. P. Collinson, of London , F. R. S. LONDON: Printed and fold by E. Cave, at St. Johns Gate . 1751. (Price 2s. 6d.) tVtlJXH f f 7T- # ■ ? - A r r 4 A ij ■ 1 ¥. 0 Cx . il o .’At.) ' .«* ''.S'- ■ ' ‘ ' The PREFACE. Tfftj tfC i * . / ^ Y /& , \ sA* 0/7 ^ IT may be necejjary to acquaint the reader , that the fol- lowing obfervations and experiments were not drawn up with a view to their being made publick, but were communicated at different times , and mofi of them in letters wrote on various topicks , as matters only of private amufement. But fome perfons to whom they were redd , and who had themfelves been converfant in eleCirical difquifitions , were of opinion , they contain d fo many curious and inter e fling parti- culars relative to this affair , that it would be doing a kind of injujlice to the publick , to confine them folely to the limits of a private acquaintance. The Editor was therefore prevailed upon to commit fuch ex - traCis of letter s, and other detach'd pieces as were in his hands to the prefs , without waiting for the ingenious au- thor's permiffion fo to do ; and this was done with the lefs hefi~ tation , as it was apprehended the author s engagements in other affairs , would fcarce afford him leifure to give the publick his reflections and experiments on the fubjeCt , finijhd with that care and precifion , of which the treatife before us Jhews he is alike fiudious and capable . He was only apprized of the fiep that had been thus taken , while the firfi fleets were in the prefs, and time enough for him to tranfmit fome far- ther remarks , together with a few corrections and additions y which are placed at the end, and may be confuted in theperufaL The experiments which our author relates are mofi of them peculiar to himfelf they are conducted with judgment , and the inferences from them plain and conclufive > though fome-* times propofed under the terms of fuppofitions and conjectures. And indeed the fcene he opens , firikes us with a pleafi'ng afionifhment , whilfi he conducts us by a train of faCts and judicious reflections, to a probable caufe of thofe phenomena, which are at once the mofi awful \ and , hitherto , accounted for with the leaft verifimilitude. He PREFACE. He exhibits to our confederation, an invifeble , fubtile mat- ter, difjeminated through all nature in various proportions , equally unobferved, and , whilfi all thofe bodies to which it pecu- liarly adheres are alike charged with it, inoffenfeve. He Jhews , however , /to tf an unequal diferibution is by any means brought about ; if there is a coacervation in one part of fpace , tf lefs proportion , vacuity , or want , tftftf- Zto ; the near approach of a body capable of conduct- ing the coacervated paj't to the emptier fpace , it becomes perhaps the mofe formidable and irrefifeible agent in the uni- verfe . Animals are in an Infant ft ruck breathlefs , bodies almofi impervious by any force yet known , tf/Y perforated, and metals fufed by it, in a moment. From the femilar effects of lightening and electricity our author has been led to make feme protable conjectures on the caufe of the former j tfW tf/ the fame tune, to propofe feme rational experiments in order to fecure ourfelves , and thofe things on which its force is often directed, from its perni- cious effeCts j a circumfeance of no fmall importance to the publick , and therefore worthy of the utmoft attention. It has, indeed, been of late the fajhion to aferibe every grand or unufual operation of nature, fuch as lightening and earthquakes, to electricity, not, as one would imagine, from the manner of reafening on thefe occafeons, that the authors of thefe fchemes have difeovered any connection betwixt the caufe and eff 'eCt , or faw in what manner they were related ; but, as it would feem, merely becaufe they were unacquainted with any other agent, of which it could not pofetively be faid the con- nection was impofeible. But of thefe, and many other interefeing circumfeances, the reader will be more fatisfaClorily informed in the following letters, to which he is therefore referred by The EDITOR, LETTER FROM l* // ?s/ - / a >* /? T • ; „ ^ « Mr Benj. Franklin, in Philadelphia. t o Mr Peter Collinson, F.R. S. London. S /i?, 28> *747* HE neceffary trouble of copying long letters, which perhaps when they come to your hands may contain nothing new, or worth your reading (fo quick is the progrefs made with you in E- ledlricity) half difcourages me from writing any more on that fubjeft. Yet I cannot forbear adding a few obfervations on M. Mufchenbroek s won- derful bottle. B i. The 2 Mr B. FRANKLIN’s 1. The non-eledlric contain’d in the bottle differs when eledtrifed from a non-eledtric eledtrifed out of the bottle, in this : that the eledtrical fire of the latter is accumulated on its furface , and forms an eledtrical atmofphere round it of confiderable extent : but the eledtrical fire is crouded into the fuhjlance of the former, the glafs confining it. 2. At the fame time that the wire and top of the bot- tle, &c. is eledtrifed pojitively or plus , the bottom of the bottle is eledtrifed negatively or minus , in exadt propor- tion : i. e . whatever quantity of eledtrical fire is thrown in at top, an equal quantity goes out of the bottom. To underftand this, fuppofe the common quantity of Eledtri- city in each part of the bottle, before the operation begins, is equal to 20 5 and at every ftroke of the tube, fuppofe a quantity equal to 1 is thrown in 5 then, after the firft ftroke, the quantity contain’d in the wire and upper part of the bottle will be 21, in the bottom 19. After the fecond, the upper part will have 22, the lower 18, and fo on ’till after 20 ftrokes, the upper part will have a quan- tity of eledtrical fire equal to 40, the lower part none : and then the operation ends : for no more can be thrown into the upper part, when no more can be driven out of the lower part. If you attempt to throw more in, it is fpued back thro’ the wire, or flies out in loud cracks thro’ the fides of the bottle. 3 . The equilibrium cannot be reftored in the bottle by inward communication or contadt of the parts ; but it muft be done by a communication form’d without the bot- tle, Letters on Electricity. 3 tie, between the top and bottom, by fome non-eledtric, touching both at the fame time ; in which cafe it is re- ftored with a violence and quicknefs inexpreffible : or, touching each alternately, in which cafe the equilibrium is reftored by degrees. 4. As no more eledtrical fire can be thrown into the top of the bottle, when all is driven out of the bottom, fo in a bottle not yet eledtrifed, none can be thrown into the top, when none can get out at the bottom ; which happens either when the bottom is too thick, or when the bottle is placed on an eledtric per fe. Again, when the bottle is eledtrifed, but little of the eledtrical fire can be drawn out from the top, by touching the wire, unlefs an equal quantity can at the fame time get in at the bot- tom. Thus, place an eledtrifed bottle on clean glafs or dry wax, and you will not, by touching the wire, get out the fire from the top. Place it on a non-eledtric, and touch the wire, you will get it out in a fhort time ; but fooneft when you form a diredt communication as above. So wonderfully are thefe two ftates of Eledtricity, the plus and minus , combined and balanced in this miraculous bottle ! fituated and related to each other in a manner that I can by no means comprehend ! If it were poffible that a bottle fhould in one part contain a quantity of air ftrongly compreft, and in another part a perfedt vacuum, we know the equilibrium would be inftantly reftored within . But here we have a bottle containing at the fame time a plenum of eledtrical fire, and a vacuum of the fame fire $ and yet B 2 the 4 Mr B. FRANKLIN’s the equilibrium cannot be reftored between them but by a communication without ! though the plenum preiTes vio- lently to expand, and the hungry vacuum feems to attraft as violently in order to be filled. 5. The fhock to the nerves (or convulfion rather) is oc- cafion’d by the fudden pafling of the fire through the body in its way from the top to the bottom of the bottle. The fire takes the fhorteft courfe, as Mr JVatfon juftly obferves : But it does not appear, from experiment, that, in order for a perfon to be fhocked, a communication with the floor is neceflary ; for he that holds the bottle with one hand, and touches the wire with the other, will be fhock’d as much, though his fhoes be dry, or even ftanding on wax, as otherwife. And on the touch of the wire (or of the gun-barrel, which is the fame thing) the fire does not proceed from the touching finger to the wire, as is fuppofed, but from the wire to the finger, and pafles through the body to the other hand, and fo into the bottom of the bottle. Experiments confirming the above. EXPERIMENT I. Place an eledtrifed phial on wax; a fmall cork-ball fufpended by a dry filk-thread held in your hand, and brought near to the wire, will fir ft be attracted, and then repelled : when in this ftate of repellency, fink your hand, that the ball may be brought towards the bottom of the Letters on Electricity. 5 the bottle j it will there be inftantly and ftrongly attracted, ’till it has parted with its fire. If the bottle had an eledtrical atmofphere, as well as the wire, an eledtrified cork would be repelled from one as well as from the other. EXPERIMENT II. Fig. 1. From a bent wire [a) flicking inthetable,letafmall linen thread ( b ) hang down within half an inch of the elec- trifed phial (c). Touch the wire of the phial repeatedly with your finger, and at every touch you will fee the thread in- ftantly attracted by the bottle. (This is beft done by a vinegar cruet, or fome fuch belly’d bottle). As foon as you draw any fire out from the upper part by touching the wire, the lower part of the bottle draws an equal quantity in by the thread. EXPERIMENT III. Fig. 2. Fix a wire in the lead, with which the bottom of the bottle is armed, (d) fo as that bending upwards, its ring- end may be level with the top or ring-end of the wire in the cork (e), and at three or four inches diftance. Then elec- tricife the bottle, and place it on wax. If a cork fufpended by a filk threa d.(f) hang between thefe two wires, it will play inceflantly from one to the other, ’till the bottle is no longer eledtrifed ; that is, it fetches and carries fire from the top to the bottom of the bottle, ’till the equilibrium is reftored. 6 Mr B. FRANKLIN’s EXPERIMENT IV. Fig. 3. Place an eledlricifed phial on wax ; take a wire (g) in form of a C, the ends at fuch a diftance when bent, as that the upper may touch the wire of the bottle, when the lower touches the bottom : flick the outer part on a flick of fealing wax (h) which will ferve as a handle. Then ap- ply the lower end to the bottom of the bottle, and gradu- ally bring the upper-end near the wire in the cork. The confequence is, fpark follows fpark till the equilibrium is reflored. Touch the top firft, and on approaching the bot- tom with the other end, you have a conflant fir earn of fire, from the wire entering the bottle. Touch the top and bot- tom together, and the equilibrium will foon be reflored, but filently and imperceptibly 5 the crooked wire forming the communication. EXPERIMENT V. Fig. 4. Let a ring of thin lead or paper furround a bottle (i ), even at fome diflance from or above the bottom. From that ring let a wire proceed up, ’till it touch the wire of the cork ( k) . A bottle fo fixt cannot by any means be eledtrifed : the equilibrium is never deflroyed : for *• while the communication between the upper and lower pasjtaof the bottle is continued by the outfide wire, the fire only circulates : what is driven out at bottom, is con- flantly fupply’d from the top. Hence a bottle cannot be eledtrifed that is foul or moifl on the outfide. EX- Letters on Electricity. 7 EXPERIMENT VI. Place a man on a cake of wax, and prefent him the wire of the eleCtrified phial to touch, you Handing on the floor, and holding it in your hand. As often as he touches it, he will be electrified plus ; and any one Handing on the floor may draw a fpark from him. The fire in this experi- ment paflfes out of the wire into him • and at the fame time out of your hand into the bottom of the bottle. EXPERIMENT VII. Give him the eleCtrified phial to hold ; and do you touch the wire ; as often you touch it he will be eleCtrified minus , and may draw a fpark from any one Handing on the floor. The fire now paffes from the wire to you, and from him into the bottom of the bottle. EXPERIMENT VIII. Lay two books on two glaffes, back towards back, two or three Inches diflant. Set the eleCtrified phial on one, and then touch the wire ; that book will be eleCtrified minus ; the eleCtrical fire being drawn out of it by the bottom of the bottle. Take off the bottle, and holding it in your hand, touch the other with the wire ; that book will be eleCtrifed plus ; the fire pafiing into it from the wire, and the bottle at the fame time fupply’d from your hand. A fufpended fmall cork-ball will play between thefe books ’till the equilibrium is reflored. EX- 8 Mr B. FRANKLIN’s EXPERIMENT IX. When a body is eledlrifed plus it will repel an eledlrified feather or fmall cork-ball. When minus (or when in the common {late) it will attradl them, but ftronger when minus than when in the common Hate, the difference being greater. EXPERIMENT X. Tho’, as in EX PER. VI. a man {landing on wax may be eledtrifed a number of times, by repeatedly touching the wire of an eledlrifed bottle (held in the hand of one {land- ing on the floor) he receiving the fire from the wire each time : yet holding it in his own hand, and touching the wire, tho’ he draws a llrong fpark, and is violently {hock’d, no Eledlricity remains in him ; the fire only pafiing thro* him from the upper to the lower part of the bottle. Ob- ferve, before the fhock, to let fome one on the floor touch him to rellore the equilibrium in his body for in taking hold of the bottom of the bottle, he fometimes becomes a little eledlrifed minus , which will continue after the fhock ; as would alfo any plus Eledlricity, which he might have given him before the fhock. For, reftoring the equilibrium in the bottle does not at all affedl the Eledlricity in the man thro’ whom the fire palfes ; that Eledlricity is neither in- creafed nor diminifh’d. EXPERIMENT XI. The paffing of the eledlrical fire from the upper to the lower part of the bottle, to rellore the equilibrium is render’d llrongly vifible by the following pretty experi- ment. Letters on Electricity. 9 ment. Take a book whofe cover is filletted with gold ; bend a wire of eight or ten inches long in the form of (m) Fig. 5> flip it on the end of the cover of the book over the gold line, fo as that the fhoulder of it may prefs upon one end of the gold line, the ring up, but leaning towards the other end of the book. Lay the book on a glafs or wax ; and on the other end of the gold lines, fet the bottle elec- trifed : then bend the fpringing wire, by prefling it with a flick of wax till its ring approaches the ring of the bottle wire ; inftantly there is a ftrong fpark and ftroke, and the whole line of gold, which completes the communication between the top and bottom of the bottle, will appear a vi- vid flame, like the fharpeft lightning. The clofer the con- tad: between the fhoulder of the wire, and the gold at one end of the line, and between the bottom of the bottle and the gold at the other end, the better the experiment fuc- ceeds. The room fhould be darkened. If you would have the whole filletting round the cover appear in fire at once, let the bottle and wire touch the gold in the diagonally oppofite corners. I am> &c. B. FRANKLIN. C LET- 10 Mr B. FRANKLIN’s LETTER II. FROM Mr Benj. Franklin, in Philadelphia , t o 4 Mr Peter Collinson, F. R. S. London. SIR, SepUj., 1747. IN my laft I informed you that, in purfuing our electrical enquiries, we had obferved fome particular Phenomena, which we looked upon to be new, and of which I pro- mifed to give you fome account, tho’ I apprehended they might poffibly not be new to you, as fo many hands are daily employ’d in eledtrical experiments on your fide the water, fome or other of which would probably hit on the fame obfervations. The ftrlt is the wonderful effeCt of pointed bodies, both in drawing off and throwing off the electrical fire. For example : Place an iron fhot of three or four inches diameter, on the mouth of a clean dry glafs bottle. By a fine filken thread from the cieling, right over the mouth of the bottle, fuf- pend a fmall cork-ball, about the bignefs of a marble ; the thread Letters on Electricity. ii thread of fuch a length, as that the cork-ball may reft a- gainft the fide of the fliot. Eledtrify the fhot, and the ball will be repelled to the diftance of four or five inches, more or lefs, according to the quantity of Electricity. — When in this ftate, if you prefent to the fliot the point of a long flender fliarp bodkin, at fix or eight inches diftance, the repellency is inftantly deftroy’d, and the cork flies to the fliot. A blunt body muft be brought within an inch, and draw a fpark, to produce the fame effedt. To prove that the eledtrical fire is drawn off by the point, if you take the blade of the bodkin out of the wooden handle, and fix it in a flick of fealing wax, and then prefent it at the diftance aforefaid, or if you bring it very near, no fuch efifedt fol- lows ^ but Aiding one finger along the wax till you touch the blade, and the ball flies to the fhot immediately. — If you prefent the point in the dark, you will fee, fometimes at a foot diftance, and more, a light gather upon it like that of a fire-fly or glow-worm ; the lefs fliarp the point, the nearer you muft bring it to obferve the light ; and at what- ever diftance you fee the light, you may draw off the eledtrical fire, and deftroy the repellency. — If a cork-ball fo fufpended be repelled by the tube, and a point be pre- fented quick to it, tho’ at a confiderable diftance, ’tis fur- prizing to fee how fuddenly it flies back to the tube. Points of wood will do as well as thofe of iron, provided the wood is not dry ; for perfectly dry wood will no more condudt Eledtricity than fealing wax. C 2 To 12 Mr B. FRANKLINs To fhew that points will throw off as well as draw off the eledtrical fire ; lay a long fharp needle upon the fhot, and you cannot eleftrife the fhot, fo as to make it repel the cork-ball. — Or fix a needle to the end of a fufpended gun- barrel, or iron rod, fo as to point beyond it like a little ba- yonet ; and while it remains there, the gun-barrel, or rod, cannot by applying the tube to the other end be eledtrifed fo as to give a fpark, the fire continually running out filently at the point. In the dark you may fee it make the fame appearance as it does in the cafe beforementioned. The repellency between the cork-ball and the fhot is likewife deftroy’d ; i. By fifting fine fand on it ; this does it gradually. 2. By breathing on it. 3. By making a fmoke about it from burning wood.* 4. By candle light, even tho’ the candle is at a foot diftance : thefe do it fud- denly. — The light of a bright coal from a wood fire ; and the light of red-hot iron do it likewife ; but not at fo great a diftance. Smoke from dry rofin dropt on hot iron, does not deftroy the repellency ; but is attracted by both fhot and cork-ball, forming proportionable atmofpheres round them, making them look beautifully, fomewhat like fome of the figures in Burnet s or Whijlons theory of the earth. * We fuppofe every particle of fand, moifture, or fmcke, being firft at- tracted and then repelled, carries off with it a portion of the electrical fire j but that the fame ftrll fubfifts in thofe particles, till they communicate it to fomething elfe ; and that it is never realiy deftroyed. --- So when water is thrown on common fire, we do not imagine the element is thereby deftroyed or annihilated, but only difperfed, each particle of water carrying off in vapour its portion of the fire, which it had attra&ed and attached to itfelf. N.B. This Letters on Electricity. *3 N. B. This experiment fhould be made in a clofet where the air is very ftill. The light of the fun thrown {Irongly on both cork and {hot by a looking-glafs for a long time together, does not impair the repellency in the lead. This difference be- tween fire-light and fun-light, is another thing that feems new and extraordinary to us. We had for fometime been of opinion, that the electri- cal fire was not created by friction, but collected, being re- ally an element diffus’d among, and attrated by other matter, particularly by water and metals. We had even difcovered and demonflrated its afflux to the eletrical fphere, as well as its efflux, by means of little light wind- mill wheels made of fliff paper vanes, fixed obliquely and turning freely on fine wire axes. Alfo by little wheels of the fame matter, but formed like water wheels. Of the difpofition and application of which wheels, and the various phenomena refulting, I could, if I had time, fill you a flieet. The impoffibility of eletrifing one’s felf (tho’ {landing on wax) by rubbing the tube and drawing the fire from it and the manner of doing it by paffing the tube near a per- fon or thing {landing on the floor, &c. had alfo occurred to us fome months before Mr Watforis ingenious Sequel came to hand, and thefe were fome of the new things I intended to have communicated to you. — But now I need only mention fome particulars not hinted in that piece* with our reafonings thereupon 5 though perhaps the latter might well enough be fpared. 2* A 1+ Mr B. FRANKLI N’s 1. A perfon {landing on wax, and rubbing the tube, and another perfon on wax drawing the fire ; they will both of them, (provided they do not {land fo as to touch one ano- ther) appear to be eledtrifed, to a perfon {landing on the floor y that is, he will perceive a fpark on approaching each of them with his knuckle. 2. But if the perfons on wax touch one another during the exciting of the tube, neither of them will appear to be eledtrifed. 3. If they touch one another after exciting the tube, and drawing the Are as aforefaid, there will be a flronger fpark between them, than was between either of them and the perfon on the floor. 4. After fuch flrong fpark, neither of them difcover any eledlricity. Thefe appearances we attempt to account for thus. We fuppofe as aforefaid, that eledtrical fire is a common element, of which every one of the three perfons abovementionedhas his equal {hare, before any operation is begun with the Tube. Ay who {lands on wax and rubs the tube colledls the eledtrical fire from himfelf into the glafs ; and his com- munication with the common flock being cut off by the wax, his body is not again immediately fupply’d. By (who Hands on wax likewile) pafling his knuckle along near the tube, receives the fire which was colledled by the glafs from A y and his communication with the common flock being likewife cut off, he retains the additional quantity received. — To C, {landing on the floor, both appear to be Letters on Electricity. 15 be eledtrifed : for he having oniy the middle quantity of eledtrical fire, receives a fpark upon approaching B , who has an over quantity ; but gives one to A , who has an un- der quantity. If A and B approach to touch each other, the fpark is ftronger, becaufe the difference between them is greater ; after fuch touch there is no fpark between ei- ther of them and C, becaufe the eledtrical fire in all is re- duced to the original equality. If they touch while elec- trifing, the equality is never deftroy’d, the fire only circu- lating. Hence have arifen fome new terms among us : we fay, 5, (and bodies like circumstanced) is eledtrifed pofoively ; A, negatively . Or rather, B is eledtrifed plus ; A , minus . And we daily in our experiments electrife bodies plus k or minus as we think proper. — To eledtrife phis or minus , no more needs to be known than this, that the parts of the tube or fphere that are rubbed, do, in the inftant of the fridiion attradl the eledtrical fire, and there- fore take it from the thing rubbing : the fame parts imme- diately, as the fridiion upon them ceafes, are difpofed to give the fire they have received, to any body that has lefs. Thus you may circulate it, as Mr Watfon has fhewn ; you may alfo accumulate or fubftradt it upon or from any body, as you connedt that body with the rubber or with the re- ceiver, the communication with the common flock being cut off We think that ingenious gentleman was deceived, when he imagined (in his Sequel) that the eledtrical fire came down the wire from the* deling to the gun- barrel, thence to the fphere, and fo eledtrifed the machine and ‘Mr B. FRANKLIN’s 16 and the man turning the wheel, &c. We fuppofe it was driven off, and not brought on thro’ that wire ; and that the machine and man, &c. were eleCtrifed minus \ i. e . had j lefs electrical fire in them than things in common. As the vefiel is juft upon failing, I cannot give you fo large an account of American Electricity as I intended : I {hall only mention a few particulars more. — We find gra- nulated lead better to fill the phial with, than water, being eafily warmed, and keeping warm and dry in damp air. — We fire fpirits with the wire of the phial. We light candles, juft blown out, by drawing a fpark among the fmoke between the wire and fnuffers. — We reprefent lightning, by pafling the wire in the dark over a china plate that has gilt flowers, or applying it to gilt frames of looking-glafles, &c. — We eledtrife a perfon twenty or more times running, with a touch of the finger on the wire, thus : He ftands on wax. Give him the eledtrifed bottle in his hand. Touch the wire with your finger, and then touch his hand or face ; there are fparks every time. — We encreafe the force of the eleCtrical kifs vaftly, thus : Let A and B ftand on wax ; give one of them the eleftrifed phial in hand ; let the other take hold of the wire 3 there will be a fmall fpark ; but when their lips ap- proach, they will be ft ruck and {hock’d. The fame if another gentleman and lady, C and D, {landing alfo on wax, and joining hands with A and B, falute, or fhake hands. — We fufpend by fine fiik thread a counterfeit fpi- der, made of a fmall piece of burnt cork, with legs of lin- nen Letters on Electricity. 17 nen thread, and a grain or two of lead (luck in him to give him more weight. Upon the table, over which he hangs, we Hick a wire upright as high as the phial and wire, two or three inches from the fpider ; then we animate him by fetting the eledtrified phial at the fame diftance on the other fide of him ; he will immediately fly to the wire of the phial, bend his legs in touching it, then fpring off, and fly to the wire in the table ; thence again to the wire of the phial, playing with his legs againft both in a very entertaining manner, appearing perfectly alive to per- fons unacquainted. D axis Mr B. FRANKLIN’s 18 axis there is a fmall handle, with which we turn the fphere like a common grindftone. This we find very commodious, as the machine takes up but little room, is portable, and may be enclofed in a tight box, when not in ufe. *Tis true, the fphere does not turn fo fwift, as when the great wheel is ufed : but fwiftnefs we think of little importance, fince a few turns will charge the phial, &c. fufficiently. I am, &c. B. FRANKLIN, LET- Letters on Electricity. 19 LETTER III. FROM Mr Benj. Franklin, in Philadelphia^ t o Mr Peter Col li ns on, F. R. S. London. Farther Experiments and Observations in ELECTRICITY. S I Ry I74-8. § 1. JTpHERE will be the fame explofion and fhock, A if the electrified phial is held in one hand by the hook, and the coating touch’d with the other, as when held by the coating, and touch’d at the hook. 2. To take the charg’d phial fafely by the hook, and not at the fame time diminifh its force, it muft firfi: be fet down on an eledtric per fe. 3. The phial will be electrified as ftrongly, if held by the hook, and the coating apply’d to the globe or tube ; as when held by the coating, and the hook apply d. D 2 4. But 20 Mr B. FRANKLINS 4. But the direction of the eledtrical fire being different in the charging, will alfo be different in the explofiorw The bottle charged/ thro’ the hook, will be difcharged thro’ the hook ; the bottle charged thro’ the coating, will be dif- charged thro’ the coating, and not other ways : for the file muff; come out the fame way it went in. 5. To prove this , take two bottles that were equally charged thro’ the hooks, one in each hand ; bring their hooks near each other, and no fpark or fhock will follow ; becaufe each hook is difpofed to give fire, and neither to receive it. Set one of the bottles down on glafs, take it up by the hook, and apply its coating to the hook of the other ; then there will be an expiofion and fhock, and both bot- tles will be difcharged. 6. Vary the experiment, by charging two phials equally, one thro’ the hook, the other thro’ the coating : hold that by the coating which was charged thro’ the hook ; and that by the hook which was charg’d thro’ the coating : ap- ply the hook of the firft to the coating of the other, and there will be no fhock or fpark. Set that down on glafs which you held by the hook, take it up by the coating, and bring the two hooks together : a fpark and fliock will follow, and both phials be difcharged. In this experiment the bottles are totally difcharged, or the equilibrium within them reftored. The abounding of fire in one of the hooks (or rather in the internal furface of one bottle) being exadtly equal to the wanting of the other : and therefore, as each bottle has in itfelf the abounding as well Letters on Electricity. 21 well as the wanting , the wanting and abounding muft be equal in each bottle. See §. 8, 9, 10, 11. But if a man holds in his hands two bottles, one fully eledtrify’d, the other not at all, and brings their hooks together, he has but half a fhock, and the bottles will both remain half eledtrified, the one being half difcharged, and the other half charged. 7. Place two phials equally charged on a table at five or fix inches diftance. Let a cork-ball, fufpended by a filk thread, hang between them. If the phials were both charged through their hooks, the cork, when it has been attra&ed and repell’d by the one, will not be attracted, but equally repelled by the other. But if the phials were charg- ed, the one through the hook, and the other * through the coating, the ball, when it is repelled from one hook, will be as ftrongly attracted by the other, and play vigoroufly between them, kill both phials are nearly difcharged. 8. When we ufe the terms of charging and dif chargin'? the phial, kis in compliance with cuftom, and for want of others more fuitable. Since we are of opinion, that there is really no more eledtrical fire in the phial after what is called its charging^thzn before, nor lefs after its difcharging ; excepting only the fmall fpark that might be given to, and taken from, the non-eledtric matter, if feparated from * To charge a bottle commodioufly through the coating, place it on a glafs Hand ; form acommunication from the prime conductor to the coating, and another from the hook to the wall or floor. When it is charged, re- move the latter communication before you take hold of the. bottle, other- wife great part of the fire will efcape by it. the 22 Mr B. FRANKLIN’s the bottle, which fpark may not be equal to a five hun- dredth part of what is called the explofion. For if, on the explofion, the eledtrical fire came out of the bottle by one part, and did not enter in again by ano- ther •, then, if a man ftanding on wax, and holding the bottle in one hand, takes the fpark by touching the wire hook with the other, the bottle being thereby difcharged \ the man would be charged or whatever fire was loft by one, would be found in the other, lince there is no way for its efcape : But the contrary is true. 9. Befides the phial will not fuffer what is called a char- ging, unlefs as much fire can go out of it one way, as is thrown in by another. A phial cannot be charged ftand- ding on wax or glafs, or hanging on the prime conductor, unlefs a communication be form’d between its coating and the floor. 10. But fufpend two or more phials on the prime con- ductor, one hanging to the tail of the other ; and a wire from the laft to the floor, an equal number of turns of the wheel fhall charge them all equally, and every one as much as one alone would have been. What is driven out at the tail of the firft, ferving to charge the fecond ; what is driven out of the fecond charging the third ; and fo on. By this means a great number of bottles might be charged with the fame labour, and equally high, with one alone, were it not that every bottle receives new fire, and lofes its old with fome reluCtance, or rather gives fome fmall re- fiftance to the charging, which in a number of bottles be- comes Letters on Electricity. 23 comes more equal to the charging power, and fo repels the fire back again on the globe, fooner than a Angle bottle would do. 1 1 . When a bottle is charged in the common way, its injide and outfide furfaces ftand ready, the one to give fire by the hook, the other to receive it by the coating ; the one is full, and ready to throw out, the other empty and extremely hungry ; yet as the firft will not give out , unlefs the other can at the fame inftant receive in ; fo neither will the latter receive in, unlefs the firft can at the fame inftant give out. When both can be done at once, ftis done with inconceivable quicknefs and violence. 12. So a ftrait fpring (tho’ the comparifon does not a- gree in every particular) when forcibly bent, muft, to reftore itfelf, contract that fide which in the bending was extended, and extend that which was contradled if either of thefe two operations be hindered, the other cannot be done. But the fpring is not faid to be charg'd with elafticity when bent, and difcharg’d when unbent its quantity of elafti- city is always the fame. 13. Glafs, in like manner, has, within its fubftance, always the fame quantity of eledlrical fire, and that a very great quantity in proportion to the mafs of glafs, as fhall.be fhewn hereafter. 14. This quantity, proportioned to the glafs, it ftrongly and obftinately retains, and will have neither more nor lefs, though it will fuffer a change to be made in its parts and fituation ; i, e. we may take away part of it from one of of the Tides, provided we throw an equal quantity into the other. 15. Yet when the fituation of the electrical fire is thus altered in the glafs ; when fome has been taken from one fide, and fome added to the other, it will not be at reft or in its natural ftate, till ’tis reftored to its original equality. — And this reftitution cannot be made through the fubftance of the glafs, but muft be done by a non-eleCtric communi- cation formed without, from furface to furface. 16. Thus, the whole force of the bottle, and power of giving a fhock, is in the glass itself ; the non-eleCtrics in contract with the two furfaces, ferving only to give and receive to and from the feveral parts of the glafs ; that is, to give on one fide, and take away from the other. 1 7. This was difcovered here in the following manner. Purpofing to analyfe the electrified bottle, in order to find wherein its ftrength lay, we placed it on glafs, and drew out the cork and wire which for that purpofe had been loofely put in. Then taking the bottle in one hand, and bringing a finger of the other near its mouth, a ftrong fpark came from the water, and the fhock was as violent as if the wire had remained in it, which fhewed that the force did not lie in the wire. Then to find if it refided in the water, being crouded into and condenfed in it, as connfi’d by the glafs, which had been our former opinion, we eleCtrify’d the bottle again, and placing it on glafs, drew out the wire and cork as before ; then taking up the bottle we decanted all its water into an empty bottle, which likewife ftood on glafs s Letters on Electricity. 25 glafs \ and taking up that other bottle, we expeCted if the force refided in the water, to find a fhock from it ; but there was none. We judged then, that it muft either be loft in decanting, or remain in the firft bottle. The latter we found to be true : for that bottle on trial gave the fhcck, though filled up as it ftood with frefh uneleCtrified water from a tea-pot. — To find then, whether glafs had this property merely as glafs, or whether the form contributed any thing to it ; we took a pane of fafh-glafs, and laying nd it on the ftand, placed a plate of lead on its upper furface ; then eleCtrify’d that plate, and bringing a finger to it, there was a fpark and fhock. We the$ took two plates of lead of equal dimenfions, but lefs than the glafs by two inches every way, and electrified the glafs between them, by electrifying the uppermoft lead ; then feparated the glafs from the lead, in doing which, what little fire might be in the lead was taken out and the glafs be- ing touched in the electrified parts with a finger, af- forded only very fmall pricking fparks, but a great number of them might be taken from different places. 