Benjamin Franklin Papers

To Benjamin Franklin from Giambatista Beccaria, 24 December 1757

From Giambatista Beccaria6

I. MS translation and MS Latin original: The Royal Society. II. MS “Note”: The Royal Society7

Father Beccaria, the strongest and most active supporter of Franklin’s electrical theories on the Continent, addressed this letter to him in Latin soon after learning of his arrival in England. Dr. James Parsons8 made an English translation which, after some delay, was read at the Royal Society, Feb. 7, 1760. Because Beccaria’s terminology differed in some particulars from that which had become familiar to English scientists (in large part through Franklin’s writings), Franklin undertook to clear up points of possible misunderstanding in a brief “Note” read at the next meeting of the Society, February 14.9

Parsons’ translation is printed here, rather than the Latin original, both in order to make it available to a larger number of present-day readers, and because this was the version actually read to the members of the Royal Society. Parsons, however, was more distinguished as an antiquary than as an “electrician.” His translation of Beccaria’s Latin (obviously difficult in some places) is stiff and far too literal; in some instances he clearly misses the sense, and in others he seems to give up and simply transliterates a technical term into what looks like, but is not, an English equivalent. The editors have therefore undertaken to substitute their own rendering of certain words and phrases, identifying them either in footnotes, by the use of brackets surrounding their substitutions, by adding the Latin original in italics after their rendering, or by a combination of these devices as seems most appropriate in each instance. In two particularly troublesome passages Parsons’ translation is given unchanged in the text but Beccaria’s Latin and the editors’ suggested freer translation appear in footnotes. Readers interested in the Latin original are referred to that version as printed in the Philosophical Transactions.


[Turin, December 24, 1757]

John Baptist Beccaria [of the sacred schools, sends greetings] to Benjamin Franklin Esqr. the first in Electrical Knowledge &c.

1. Learned Sir, I am glad you are safe arriv’d in London from America; and send you an hypothesis which I struck out from experiments concerning electrical motions: This I divide into two parts, as the very difference [between] these kind of motions seems to require; In the first part I treat of attractions, and in the second of repulsions;1

2. And I now Comprehend the whole of my consideration of attraction in a few words as follows: “when the Electrical Fire, being in greater quantity in One body, throws it self by the power of Expansion into another; towards an Equilibrium, it removes the greater part of the Interjected, or Interstitial air2 from its place, according to its own greater [mass (copia)]. Whence it follows, that the air which is near the bodies,3 for want of the resistance of the intermediate air, rushes, towards that middle place: but not by passing round the bodies, which is a longer way, and more interrupted from the flowing out of the fire, but by rushing in, from nearby. It is by this [displacing (trusione)] of the air, that bodies unequally electrify’d approach [each other]; and while they approach they are accelerated, because the more fire flows in, the greater quantity of intermediate air is thrown out, and therefore the greater the attraction; and thus the momentum of the air [displaced] from nearby will be increased.

Experiment 1.

3. That the air is [expelled] by the Electrical fire flowing in, is demonstrated by the experiment of the spark which is excited in the middle of the Tube, hermetically seald at one end, and stop’d with [some liquid] at the Other; for while the spark throws out the [liquid], it is [proved (testatur)] the air is thrown out also.

4. Nor indeed can the fire, when it flows in, supply the [support (fulcrum)] of the intermediate air now driven out, whereby the air adjacent to bodies may be sustain’d; for it flows out again very freely, and passes into the Other body, wherfore as it is not itself sustaind or resisted, neither can it act as a [support].

Experim: 2.

5. The matter is confirm’d by the following [very] clear experiment: I roll’d up a slip of Gilt paper of about eight inches long and four lines broad, so as to form a little solid cillinder D.4 I suspend this by a silk thread D.G. under [an opening (fornice)] of an air pump I.H.K. thro’ the top of which, H. the mettal rod BC. passes, [descending into (desinens in)] the mettal ball C. I fix the mettal rod LE. arm’d with [a similar] ball [on top], to the plate IK. [Now] the spheres C and E. are in the same plane with the cillinder D. and at equal distances from it; then fixing the Chain A. B. which belongs to the electrical Machine [to] the rod B.C. and consequently the electrical fire being sent into the rod B.C. I observe: 1st. that before the air is remov’d, the paper cillinder D. is agitated with the most violent vibrations between the two spheres E.C. 2dly. that while the air is remov’d the agitation is plainly diminished in proportion to the quantity of air removed. 3dly. [when as much air as possible is removed]5 the cillinder D. hardly stirs. When I have observ’d these things, I restore the air again by degrees, and observe that the vibrations increase again in proportion to the restored air, and at length become as violent as before. Which circumstances when I contemplate in particular, and consider them also together, I understand that the quantity or greatness of electrical motions is owing6 to the air, either intire or in part.

Experiment. III.

6. Because light bodies such as gold leafe, Dust &c. are agitated in rarifyed air with a motion sufficiently sensible, was the reason why I thought, with other [physicists (physicis)], from the beginning, that electrical motions, receiv’d in the air, ought not to be attributed to the action of electrical fire. But because, [having now considered the matter more carefully,]7 I see that motions in the residual air bear not a greater proportion to the first motions that are made in the intire atmospherical air, than that which passes between the residual and the first air, I am inclined to acknowledge this error in my self and others, and adopt the contrary Opinion; which experience verifies.

7. I must not omit a part of my Observation, which is very [opportune] towards confirming this matter: Sometimes I used to bring my Experiment from the last [stage] into a dark room; and then I observed that the fire vibrating the pendulum, before the air was remov’d, shined here and there with crackling, light but short sparks near each ball: afterwards this fire in proportion to the removed air, and also the minuteness of the vibrations of the pendulum, flow’d out in a more ample, gentle, Continual, tho’ not so shining a Radius.

8. And this truely demonstrates a reaction of the air, compelling the electrical fire in a certain density; which [corresponds to] the proportion of its Own density; and this reaction of the air [cannot avoid responding] to the action of the electrical fire,8 endeavoring to throw out the air; and clearly throwing it out, where it can prevail against the fire with a necessary [force (vi)].

9. To these I shall add no more towards explaining the attractions of bodies unequally electrify’d, I have brought some arguments in my letters to [Beccari]9 in which however I treated of the mechanical cause of attractions but doubtfully; but a more accurate consideration of the experiments, occasions my discoursing of the cause of attractions with more confidence.

10. Bodies equally electrified repel each other; The cause of which I now proceed to explain:

11. The electrical fire which is in bodies, by what means soever, [sparks in order to balance] the electrical fire1 which is in the air. (Give me leave to call the one the proper, and the Other the aerial fire.) If both have an equal proportion to the native capacity of the bodies and of the air, the bodies are attracted, or are at rest in their [original position (nativa directione)]; Otherwise if either the proper or aerial fire is excess, it equally [sets free (explicat)] the bodies and compells them to a repulsion.

This is the account:

Experiment IV.

12. As often as I proceed to electrifie a Chain several times [for a longer period (diutius)], in my Chamber which is a very large One [but closed],2 I find, that part of its electrical fire is diffus’d into the ambient air; and renders [that air, however much there is in the Chamber,] electrical to excess,3 whilst it is in a dry State either from the weather or from fire. For I carry into any part of the room two flaxen threads which I suspend either between two fingers, or at the end of a stick, and they repel each other; and whether I keep them in the same place or move them to any Other part of the room, yet they continue to diverge for half an hour, an hour, and sometimes longer.

Experiment. V.

13. If the threads are seperated from the stick or reed, by the assistance of the glass, and in like manner from the ground, they first diverge, and then return to their [original position]. But these things happen after all the sparks are as much as possible drawn out from the Chain, after all the redundant fire4 is remov’d from it, after the Connexion of the Chain with the ground.

Experiment. VI

14. From a long continued electrification5 of the Machine I find the Phaenomena in all respects the same:6 But if the long electrification of the machine continually follows a long electrification of the Chain, or vice versa, the threads fix’d to the reed or stick, are constantly observ’d to diverge from the electrification of another body; in the begining I observe that they attract one another, at the begining electrification of another body; and then again to diverge as before.

15. By these experiments, I say, we are in my Opinion taught: I. that while we accumulate several successive fires in the Chain, several successive parts of it passes widely into the ambient air, and adheres to it; and so all the air containd in the chamber becomes electrified to excess.7 In like manner while we draw out of the machine several successive fires, the machine draws in several successive parts of the fire from the ambient air, and so all the air contain’d in the Chamber becomes deficient of electricity, or electrifyd in Defect.8 II. The threads carry’d in either the fingers or at the end of the stick, repel each other in the air by the electrical excess from the chain, or the electrical defect from the machine,9 or by the force of the proper native fire overcoming the aerial if they [come together in] the electrical air from the machine; or by the power of the aerial fire overcoming the native proper fire of the threads, if they [come together] in the electrical air from the Chain. III. That these kind of threads diverging by the electrification of the chain, from the consequent electrification of the machine, or the contrary,1 first attract; because the machine first takes in from the air the excess it had from the chain; or the chain restores to the air, the fire taken from the machine; and so the fire in the air restored to its Native quantity ought to equilibrate with the native fire remaining in the threads. IV. But furthermore from a longer electrification of the machine consequent to the electrification of the chain, or the contrary, the threads diverge again; because either the machine goes on to take in part of the native fire, or the chain goes on to add more fire to the air than the native quantity. V. that the same threads, when seperated by the glass, diverge in the begining, because they, which have only their Own Native fire, come together in the air which is electric by excess or defect; and then when they are seperated by the glass they at length come to their [original position] because either part of the aerial fire, if the air is electric in excess from the chain, at last pours itself into the threads towards an equilibrium, and also flows by the compelling power of the glass, or part of the native fire, or of the proper fire of the threads pours itself into the air, if the air is electric by defect, [because] it may be supply’d from elsewhere by the compulsion of the glass.

16. From hence the following things seem universally to hold: I. that the air contains in itself, its own Native fire. II. that to the native fire of the air, another fire may be added, that part of the native fire may be subtracted from the air, but slowly, and as it were by force. III. that the air lets go the [excess], and takes in the deficient fire, but that in a very slow manner. IV. If the air has, like other bodies, its own native fire, then these are in a native state, if the air, while their native fire remains in bodies, has a greater or less quantity of fire than its native quantity, the bodies repel each other; but every one of these theorems can be illustrated in a surprising manner by other experiments; and be more fully demonstrated.

Experiment 7.

17. Two threads, fastened to the chain, after a few turns of the globe, diverge very much: afterwards from a longer-lasting electrification in the chain they begin to diverge less; and this diverging is diminish’d to a certain degree; so that sometimes the angle of the diverging, after a [longer] continuation of the friction of the globe, becomes double2 that of the diverging which happen’d from the same electrification when first excited. When I percieve this diverging of the threads diminish enough, then I cease the friction of the globe, but gently apply a very sharp stilus to the chain, wherby I slowly draw forth all the redundant fire from it; while this is doing the threads approach each other slowly, then gently again diverge to an angle indeed less than the first, tho’ great enough, which sometimes scarce amounts to forty five degrees; but then they proceed to diverge for a longer time.

18. That is, the greatest angle from the Electrification first excited, because then a very great quantity of fire is sent in to the chain, and in the threads connected with it, but little or none into the air. Afterwards the angle becomes less, as the fire increases and is consequently sent into the air, the same excess of the fire remaining in the chain. While the fire sent into the chain is slowly diminished by the application of the Stilus, the angle is still diminished in proportion as the residual fire in the chain, and the fire, sent in and Joind to the air, approach to an equilibrium; and where both the fires come to an equality the threads resume their [original] direction: when again the fire, yet redundant in the chain, if further diminshd, and the redundant fire in the air not so (for it is Joind to the air, and as we observe is slowly diminished by it,) the threads again repel each other because of the excess of the aerial fire over that in the chain, which aerial fire, in fine, because it is most slowly discharg’d, the threads proceed to diverge [for a very long time (diutissime)].

Experiment VIII.

19. If the threads are connected with the Machine, all the same Phaenomena happen in them from a long electrification of the machine, that they had from a long electrification of the chain when connected with it.

20. Wherefore as I have shew’d in general from the begining, if the proper fire of bodies, whatsoever it’s quantity be, is in equilibrium with the fire of the ambient air, bodies either remain in their native state or return to it; if one fire exceeds the other bodies repel each other by the power of the fire in excess.

21. And hence if I mistake not learn’d Sir you see the reason why those bodies electrify’d as well from the chain as the Machine repel each other: the proper fire in bodies electrified by the chain3 overcomes the aerial, and the aerial in like manner overcomes the proper fire in bodies electrified by the Machine.

Experiment IX.

22. As often as the threads mutually repel each Other, and diverge from either the increased or diminishd native fire in them, they are attracted to my finger when advanced to them; as often as they repel each other and diverge preserving their native fire, from the native fire of the air either increased or diminish’d, they fly from my finger.

23. And this indeed is very agreable to the Known laws of electrical attraction, and repulsion; for when the native fire in the threads is either increased or diminished, they become as unequally electrified as my finger, which has its own native fire; but when the native fire stands firm in the threads, and they repel each other from the increased or diminished fire in the air; then as they diverge from one another, so they must be repelled by my finger, having also its native fire, by the power of the air, in which the native fire is increasd or diminished. But besides, this very repulsion of the threads from my finger also proves the cause of repulsions which I assert; for both the finger and threads communicate with the ground, and therefore they have not in them any Other fire but the native, by which because they do not repel each other, it remains that they repel by the native fire, either increased or diminish’d, in the air.

24. When I first fell upon this theory of electrical repulsions, I was doubtful whether the aerial fire could not make repulsions in the machine, equal in velocity and greatness to those which the proper fire makes in the chain; thence I again suspected that the quantity of the fire in the machine and chain (universally conveying to all bodies) might be quickly changed; but that the measure of the fire in the ambient air is but slowly increased or diminished: besides another consideration increased my suspicion: that I could never draw as much fire from the air as from the machine, nor could I ever add as much to the air as to the chain; for I could never come to be able to sustain the whole diverging of the threads by the electricity of the air alone, as much as existed from the intire electricity of the machine or chain.

However hence it came to pass, that I communicated these same experiments, and also Others, by Letters to the most learned president of the Bononian Institute,4 wherin I establish’d this theory of repulsions at large.

But upon considering the matter more maturely I found that the velocity of the repulsions, caused by the aerial fire, ought not to answer to the velocity whereby its quantity is either increased or diminsh’d; but to that velocity whereby its inherent quantity acts; and that the greatness of the repulsions, which come from the same fire, ought not to answer to its absolute, but to its comparative greatness; I have observ’d both these to happen upon occasion.

Experiment X.

25. If in the Sixth experiment, after the diverging of the threads is diminished from a longer electrification of the chain, I draw all the redundant fire, not slowly but immediatly, from the chain (my hand being apply’d to it) the threads indeed begin to come together [as fast as possible] but they suddenly return with equal velocity before they arrive at their [original position]. But this other repulsion, because it happens from the aerial fire overcoming the proper residual fire in the threads, I perceive nevertheless that the very aerial fire (altho’ its quantity is slowly changed) causes repulsions of equal velocity with those that are made without the proper fire.

Experiment XI.

26. And that these equally great repulsions happen from the aerial fire I thus understand. After the fire receiv’d into the air, as much as may be, that is round the chain, (all the redundant fire being taken away from the chain, and so the threads now diverging from the aerial fire), I substitute a globe of Sulphur instead of glass, and from the friction of this I observe, the angle of divergence to increase in the begining, which the aerial fire effected, and then continually to diminish.

27. And this is certain that the first frictions of the Sulphureous globe takes away part of the native fire from the chain, and does not in like manner take away the excess of fire of the ambient air (for the air, as we observd before, slowly receives the fire of another body and as slowly parts with it) wherefore the greatness of the divergence is increased which is causd by the aerial fire, not changed by the absolute greatness of the aerial fire, but only by its comparative greatness, the proper fire being therefore diminished, and the proportion of the aerial to the proper [fire] being increased. Therefore because as much of the fire as is collected in the chain, so much is drawn from the machine; the proportion of the aerial fire about the machine, to the residual fire in the machine, will be the same as the proportion of the redundant fire in the chain, to the aerial fire about the chain: wherefore the aerial fire about the machine will make repulsions, not only equally swift, but equally great with those made by the proper fire in the chain.

28. Therefore that I may comprehend in a few words all that seem most likely to explain universally all electrical motions, (for you may easily observe that all suspensions, adhesions, vibrations and an infinite number of Other compositions as so many electrical Ludi [games, demonstrations] are comprehended in the repulsions and attractions). This at length is the Sum of my hypothesis: that the attractions of bodies, unequally electrified, are affected by the electric fire of one body, in which it is more abundant, flowing out into another, thro’ the [intermediate] air, and even throwing off that. But that repulsions are caused by the proper fire of bodies expanding it self against the aerial [fire], or by the aerial expanding it self more strongly against the proper fire; which expansion however, of the fire of one body overcoming another, seems to happen without the mutual admixtion of one with the other. For the air contains its own fire whatsoever its quantity be, nor can it discede from it, and drives away the proper fire of conducting bodies that it may not adhere to it.5

29. I have I say Learnd Sir, Laid before you this hypothesis, and you will thereby improve it; and if you think it worthy of being laid before the Royal Society, It will be very agreable to me, who, [since] I am not able to add any Ornament, hope my dilligence will be acceptable to it. Be careful of your Health, for it is fit you should be long preserv’d for the improvement of Science, and the amplification of what you have so certainly established.

Endorsed: Translation of a latin Letter from Professor Beccaria of Turin to Mr. Franklin concerning some Electrical experiments. by Dr. Parsons Read at R S. 7 February 1760

A Note6

December 24, 1757

For the better understanding this Paper, it is necessary to know, that Father Beccaria uses a large Chain, suspended by Silk Lines, for the Purpose of a Prime Conductor; and that his Machine for turning the Glass Globe, is so contriv’d, as that he can on occasion readily isolate it, (i.e. place it on Glass or Wax) together with the Person that works it. When the Communication is thus cut off, between the Earth and the Chain, and also between the Earth and the Machine, he observes, that the Globe being turn’d, both the Chain and the Machine show Signs of Electricity; and as these Signs, when examined, appear to be different in the Chain and in the Machine; and the Globe having, as he supposes, drawn from the Machine Part of its natural or common Quantity of Electricity, and given it to the Chain; he calls the Electricity appearing in the Chain, Electricity by Excess; and the Electricity appearing in the Machine, Electricity by Defect; which answer to our Terms, of positive and negative Electricity, or Electricity plus and minus. And thus his Expressions, Electrifying by the Chain, and Electrifying by the Machine, are to be understood, Electrifying positively, and Electrifying negatively.

Endorsed: 14 Feb. 1760. No. 1 Phil. Trans. Vol. LI. part II. p. 525.

[Note numbering follows the Franklin Papers source.]

6On Beccaria, of the teaching order of Piarists and professor of experimental philosophy at Turin, see above, V, 395 n.

7The Latin letter sent to BF appears to be in the hand of a trained scribe, perhaps a fellow member of Beccaria’s religious order; it does not bear the author’s personal signature. The translation is in Parsons’ hand, and BF’s explanatory note is an unsigned autograph. The Latin original and BF’s note were printed in Phil. Trans., LI, Part II (1760), 514–26.

8On Parsons, see above, VI, 85 n. He was one of the sponsors of BF’s election to the Royal Society (above, VI, 376).

9The dates as here given are those endorsed on the translation and the Latin original and on the MS of BF’s note, respectively, and as recorded in the Society’s Journal Book, but the Latin text printed in Phil. Trans. is incorrectly noted as “Read Feb. 14, 1760.” The Journal Book, in turn, errs in stating that the letter itself was dated “Turin 24th December 1759,” although the original reads “1757,” as do Parson’s translation and the printed Latin text in Phil. Trans.

1Here and elsewhere when Beccaria wrote some form of the words accedo (or accessio) and discedo (or discessio), Parsons used “accede” and “discede” or corresponding nouns such as “accessions” and “discessions.” In each instance the present editors have silently substituted the appropriate form of “attract” or “approach” and “repel,” or some similar words.

2Beccaria: partem interjecti aeris.

3Beccaria: aer a tergo corporibus adjacens. Here and elsewhere Parsons, apparently puzzled, included an untranslated a Tergo somewhere in his sentence. The present editors have silently substituted “near” or “nearby” where necessary, or omitted the Latin entirely.

4Phil. Trans. inserts at this point “[Vide Tab. IXX],” referring to the plate inserted there on the facing page and reproduced here opposite. Beccaria’s original drawing does not survive, probably because it was turned over to the engraver of the plate, James Mynde.

5Beccaria: Omni, quantus potest, aere subducto; Parsons: “that all the air being as much as can be taken away.”

6Beccaria’s words here are: intelligo magnitudinem motuum electricorum aeri, vel toti, vel residuo proportione respondere. Parsons keyed a footnote to “owing,” which reads: “Answers to the air: which can mean no more than that the quantity of Electrical motions is as the quantity of air removed.”

7Beccaria: quod, re nunc accuratius collata; Parsons: “But because, upon more mature consideration.”

8Beccaria: haec autem aeris reactio non potest actioni non respondere ignis electrici. Parsons: “this reaction of the air must answer to the action of the electrical fire.”

9Perhaps understandably, Parsons mistranslated ad Beccarion as “to Beccaria” thereby confusing the author of this letter, Giambatista Beccaria (1716–1781) of Turin, with Giacomo Bartolomeo Beccari (1682–1766), president of the Institute of Sciences and Arts of Bologna, to whom the former addressed his Dell’ Elettricismo: lettere, which was in the press when this letter was written. See the next document.

1Beccaria: nititur, ut libretur cum igne electrico. Parsons: “endeavours to be in equilibrio with the electrical fire.”

2Parsons overlooked Beccaria’s “at clauso.”

3Beccaria: ipsumque etiam, quantuscumque in cubiculo est … facere excessu electricum; Parsons: “and renders it electrical to excess, for so much as there is in the Chamber.” As BF explains in his “Remarks,” printed with this letter, Beccaria’s facere excessu electricum would appear in BF’s terminology as “electrified positively.”

4In BF’s terminology: “all the positive electricity.”

5Here and repeated hereafter Parsons translated Beccaria’s electricitas as “electricity,” even where the sense clearly calls for “electrification”; the correction is made silently wherever necessary.

6The remainder of this paragraph in the original reads: At, si diuturna electricitas machinae continuo consequitur diuturnam electricitatem catenae, aut contra, fila, quae arundine suspensa constanter divergere videbam ex alterius electricitate, video principio accedere mutuo incipiente electricitate alterius, tum iterum divergere quemadmodum antea. Parsons’ translation is printed above (except for silent corrections as specified in previous notes), but, in the light of BF’s “Note” and of later passages in the letter, the sentence might be freely rendered as follows: “But if a long-continued negative electrification follows a long positive electrification, or vice versa, I see that the threads fixed to the stick, which I saw constantly diverging as a result of the first electrification, now attract one another at the start of the second electrification and then again diverge as before.”

7In BF’s terminology: “electrified positively.”

8In BF’s terminology: “electrified negatively.”

9That is, repel each other by their positive or negative charge.

1That is, diverging by the initial positive electrification, from the following negative electrification, or vice versa.

2Beccaria: subduplus, more correctly rendered as “a little less than double,” but leaving Beccaria’s actual intent somewhat doubtful.

3That is, those bodies electrified positively as well as those electrified negatively.

4Giacomo Bartolomeo Beccari of Bologna. See above, p. 306 n.

5Beccaria: Aer enim ignem continet suum quantuncumque, ne discedat, arcet proprium deferentium corporum ignem, ne adhaerescat sibi. Parsons’ translation is as printed above, but the editors suggest that this passage might better be somewhat freely rendered as: “For the air retains its own fire sufficiently to keep it from dispersing; it holds off the fire of the conducting bodies so that fire does not cling to the air itself.”

6So captioned by BF in his autograph MS. The Royal Society’s clerk struck the words through and substituted: “Remark on the preceeding paper by Benjamin Franklin LL.D.” In the adjoining margin he noted: “Read at R.S. 7 Febr. 1760.”

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