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de cet événement dans toutes les occasions. | by wetting the apparatus, the electricity was Coiffier a été le premier qui a fait l'expéri- dissipated too soon to be perceived upon ence et l'a répétée plusieurs fois; ce n'est qu'à l'occasion de ce qu'il a vu qu'il m'a envoyé prier de venir. S'il étoit besoin d'autres temoins que de lui et de moi, vous les trouveriez. Coiffier presse pour partir.

Je suis avec une respectueuse consideration, Monsieur, votre, et. signè RAULET, Prieur de Marly. 10 Mai, 1752.

"On voit, par le détail de cette lettre, que le fait est assez bien constaté pour ne laisser aucun doute à ce sujet. Le porteur m'a ascuré de vive voix qu'il avoit tiré pendant près d'un quart-d'heure avant que M. le Prieur arrivât, en présence de cinq ou six personnes, des étincelles plus fortes et plus bruyantes que celles dont il est parlé dans la lettre. Čes premieres personnes arrivant successivement, n'osient approcher qu'à 10 ou 12 pas de la machine; et à cette distance, malgré le plein soleil, ils voyoient les étincelles et entendoient le bruit.

"Il résulte de toutes les expériences et observations que j'ai rapportées dans ce mémoire, et surtout de la derniere expérience faite à Marly-la-ville, que la matière du tonnerre est incontestablement la même que celle de l'électricité. L'idée qu'en a eue M. Franklin cesse d'être une conjecture: la voilà devenue une réalité, et j'ose croire que plus on approfondira tout ce qu'il a publié sur l'électricité, plus on reconnoîtra combien la physique lui est redevable pour cette partie."

Letter of Mr. W. Watson, F. R. S. to the Royal Society, concerning the Electrical Experiments in England upon ThunderClouds.-Read Dec. 1752. Trans. Vol. xlvii.

AFTER the communications, which we have received from several of our correspondents in different parts of the continent, acquainting us with the success of their experiments last summer, in endeavouring to extract the electricity from the atmosphere during a thunderstorm, in consequence of Mr. Franklin's hypothesis, it may be thought extraordinary, that no accounts have been yet laid before you of our success here from the same experiments. That no want of attention, therefore, may be attributed to those here, who have been hitherto conversant in these inquiries, I thought proper to apprize you, that, though several members of the Royal Society, as well as myself, did, upon the first advices from France, prepare and set up the necessary apparatus for this purpose, we were defeated in our expectations, from the uncommon coolness and dampness of the air here, during the whole summer. We had only at London one thunder-storm; viz. on July 20; and then the thunder was accompanied with rain; so that,

touching those parts of the apparatus, which served to conduct it. This, I say, in general prevented our verifying Mr. Franklin's hypothesis: but our worthy brother, Mr. Canton, was more fortunate, I take the liberty, therefore, of laying before you an extract of a letter, which I received from that gentleman, dated from Spital-square, July 21, 1752.

"I had yesterday, about five in the afternoon, an opportunity of trying Mr. Franklin's experiment of extracting the electrical fire from the clouds; and succeeded, by means of a tin tube, between three and four feet in length, fixed to the top of a glass, one of about eighteen inches. To the upper end of the tin tube, which was not so high as a stack of chimnies on the same house, I fastened three needles with some wire; and to the lower end was soldered a tin cover, to keep the rain from the glass tube, which was set upright in a block of wood. I attended this apparatus as soon after the thunder began as possible, but did not find it in the least electrified, till between the third and fourth clap; when applying my knuckle to the edge of the cover, I felt and heard an electrical spark; and approaching it a second time, I received the spark at the distance of about half an inch, and saw it distinctly. This I repeated four or five times in the space of a minute, but the sparks grew weaker and weaker; and in less than two minutes the tin tube did not appear to be electrified at all. The rain continued during the thunder, but was considerably abated at the time of making the experiment." Thus far Mr. Canton.

Mr. Wilson likewise of the Society, to whom we are much obliged for the trouble he has taken in these pursuits, had an opportunity of verifying Mr. Franklin's hypothesis. He informed me, by a letter from near Chelmsford, in Essex, dated August 12, 1752, that, on that day about noon, he perceived several electrical snaps, during, or rather at the end of a thunder-storm, from no other apparatus than an iron curtain rod, one end of which he put into the neck of a glass phial, and held this phial in his hand. To the other end of the iron he fastened three needles with some silk. This phial, supporting the rod, he held in one hand, and drew snap from the rod with a finger of his other. This experiment was not made upon any eminence, but in the garden of a gentleman, at whose house he then was.

Dr. Bevis observed, at Mr. Cave's, at St. John's Gate, nearly the same phenomena as Mr. Canton, of which an account has been already laid before the public.

Trifling as the effects here mentioned are, when compared with those which we have received from Paris and Berlin, they are the

only ones, that the last summer here has | ger to it, a spark will issue from it to your finproduced; and as they were made by persons ger: now when a phial, prepared for the worthy of credit, they tend to establish the Leyden experiment, is hung to the gun-barauthenticity of those transmitted from our rel or prime conductor, and you turn the correspondents. globe in order to charge it; as soon as the electric matter is excited, you can observe a spark to issue from the external surface of the phial to your finger, which, Mr. Franklin says, is the natural electric matter of the glass driven out by that received by the inner sur

I flatter myself, that this short account of these matters will not be disagreeable to you; and am, W. WATSON.*

Remarks on the Abbé Nollet's Letters to Ben-face from the conductor. If it be only drawn jamin Franklin, of Philadelphia, on elec-out by sparks, a vast number of them may tricity: by David Colden, of New York.

COLDENHAM, in New York, Dec. 4, 1753.

be drawn; but if you take hold of the external surface with your hand, the phial will soon receive all the electric matter it is capaIN considering the Abbé Nollet's Letters ble of, and the outside will then be entirely to Mr. Franklin, I am obliged to pass by all destitute of its electric matter, and no spark the experiments which are made with, or in, can be drawn from it by the finger: here then bottles hermetically sealed, or exhausted of is a want of that effect, which all bodies chargair; because, not being able to repeat the ex-ed with electricity have. Some of the effects periments, I could not second any thing which of an electric body, which I suppose the Abbe occurs to me thereon, by experimental proof. has observed in the exterior surface of a Wherefore, the first point wherein I can dare charged phial, are, that all light bodies are atto give my opinion, is in the Abbé's 4th tracted by it. This is an effect which I have letter, where he undertakes to prove, that constantly observed, but do not think that it the electric matter passes from one surface to proceeds from an attractive quality in the exanother through the entire thickness of the terior surface of the phial, but in those light glass: he takes Mr. Franklin's experiment of bodies themselves, which seem to be attractthe magical picture, and writes thus of it: ed by the phial. It is a constant observation, "When you electrise a pane of glass coated that when one body has a greater charge of on both sides with metal, it is evident that electric matter in it than another (that is in whatever is placed on the side opposite to proportion to the quantity they will hold) this that which receives the electricity from the body will attract that which has less: now, I conductor, receives also an evident electrical suppose, and it is a part of Mr. Franklin's virtue." Which Mr. Franklin says, is that system, that all those light bodies which apequal quantity of electric matter, driven out pear to be attracted, have more electric matof this side, by what is received from the con- ter in them than the external surface of the ductor on the other side; and which will con- phial has, wherefore they endeavour to attinue to give an electrical virtue to any thing tract the phial to them, which is too heavy to in contact with it, till it is entirely discharg- be moved by the small degree of force they ed of its electrical fire. To which the Abbé exert, and yet being greater than their own thus objects: "Tell me (says he,) I pray you, weight, moves them to the phial. The folhow much time is necessary for this pretend-lowing experiment will help the imagination ed discharge? I can assure you, that after in conceiving this. Suspend a cork ball, or having maintained the electrisation for hours, a feather, by a silk thread, and electrise it; this surface, which ought, as it seems to me, to be entirely discharged of its electrical matter, considering either the vast number of sparks that were drawn from it, or the time that this matter had been exposed to the action of the expulsive cause; this surface, I say, appeared rather better electrised thereby, and more proper to produce all the effects of an actual electric body."

The Abbé does not tell us what those effects were, all the effects I could never observe, and those that are to be observed can easily be accounted for, by supposing that side to be entirely destitute of electric matter. The most sensible effect of a body charged with electricity is, that when you present your fin

* This is the sometime celebrated Watson, bishop of

Landaff,

then bring this ball nigh to any fixed body, and it will appear to be attracted by that body, for it will fly to it: now, by the consent of electricians, the attractive cause is in the ball itself, and not in the fixed body to which it flies: this is a similar case with the apparent attraction of light bodies, to the external surface of a charged phial.

The Abbé says, "that he can electrise a hundred men, standing on wax, if they hold hands, and if one of them touch one of these surfaces (the exterior) with the end of his finger:" this I know he can, while the phial is charging, but after the phial is charged I am as certain he cannot: that is, hang a phial, prepared for the Leyden experiment, to the conductor, and let a man, standing on the floor, touch the coating with his finger, while the globe is turned, till the electric matter

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spews out of the hook of the phial, or some give; neither can it give as much to the part of the conductor, which I take to be the coating of the other phial as it is ready to take certainest sign that the phial has received all when one is only applied to me: but when the electric matter it can: after this appears, both are applied, the coating takes from me let the man, who before stood on the floor, what the hook gives: thus I receive the fire step on a cake of wax, where he may stand from the first phial at B, the exterior surface for hours, and the globe all that time turned, of which is supplied from the hand at A; I and yet have no appearance of being elec- give the fire to the second phial at C, whose trised. After the electric matter was spewed interior surface is discharged by the hand at out as above from the hook of the phial pre- D. This discharge at D may be made evipared for the Leyden experiment, I hung ano-dent by receiving that fire into the hook of a ther phial, in like manner prepared, to a hook third phial, which is done thus: in place of fixed in the coating of the first, and held this other phial in my hand; now if there was any electric matter transmitted through the glass of the first phial, the second one would certainly receive and collect it; but having kept the phials in this situation for a considerable time, during which the globe was continually turned, I could not perceive that the second phial was in the least charged, for when I touched the hook with my finger, as in the Leyden experiment, I did not feel the least commotion, nor perceive any spark to issue from the hook.

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I likewise made the following experiment: having charged two phials (prepared for the Leyden experiment) through their hooks; two persons took each one of these phials in his hand; one held his phial by the coating, the other by the hook, which he could do by removing the communication from the bottom before he took hold of the hook. These persons placed themselves one on each side of me, while I stood on a cake of wax, and took hold of the hook of that phial which was held by its coating (upon which a spark issued, When this experiment is considered, I but the phial was not discharged, as I stood think, it must fully prove that the exterior on wax) keeping hold of the hook, I touched surface of a charged phial wants electric matthe coating of the phial that was held by its ter, while the inner surface has an excess of hook with my other hand, upon which there it. One thing more worthy of notice in this was a large spark to be seen between my experiment is, that I feel no commotion or finger and the coating, and both phials were shock in my arms, though so great a quantity instantly discharged. If the Abbé's opinion of electric matter passes them instantaneously. be right, that the exterior surface, communi- I only feel a pricking in the ends of my fingers. cating with the coating, is charged, as well as This makes me think the Abbé has mistook, the interior, communicating with the hook; when he says, that there is no difference behow can I, who stand on wax, discharge both tween the shock felt in performing the Leythese phials, when it is well known I could den experiment, and the pricking felt on drawnot discharge one of them singly? Nay, sup- ing simple sparks, except that of greater to pose I have drawn the electric matter from less. In the last experiment, as much elecboth of them, what becomes of it? For I ap-tric matter went through my arms, as would pear to have no additional quantity in me have given me a very sensible shock, had when the experiment is over, and I have not there been an immediate communication, by stirred off the wax: wherefore this experiment my arms, from the hook to the coating of the fully convinces me, that the exterior surface is not charged; and not only so, but that it wants as much electric matter as the inner has of excess: for by this supposition, which is a part of Mr. Franklin's system, the above experiment is easily accounted for, as follows: When I stand on wax, my body is not capable of receiving all the electric matter from the hook of one phial, which it is ready to

same phial; because when it was taken into a third phial, and that phial discharged singly through my arms, it gave me a sensible shock. If these experiments prove that the electric matter does not pass through the entire thickness of the glass, it is a necessary consequence that it must always come out where it entered.

The next thing I meet with is in the Abbe's fifth letter, where he differs from Mr.

Franklin, who thinks that the whole power retained by the glass. If after the spark is of giving a shock is in the glass itself, and not drawn from the conductor, you touch the in the non-electrics in contact with it. The coating of the phial (which all this while is experiments which Mr. Franklin gave to prove supposed to hang in the air, free from any this opinion, in his Observations on the Ley- non-electric body) the threads on the conductden Bottle, convinced me that he was in the or will instantly start up, and show that the right; and what the Abbé has asserted, in con- conductor is electrised. It receives this electradiction thereto, has not made me think trisation from the inner surface of the phial, otherwise. The Abbé, perceiving as I sup- which, when the outer surface can receive pose, that the experiments, as Mr. Franklin what it wants from the hand applied to it, had performed them, must prove his assertion, will give as much as the bodies in contact with alters them without giving any reason for it, it can receive, or if they be large enough, all and makes them in a manner that proves no- that it has of excess. It is diverting to see thing. Why will he have the phial, into how the threads will rise and fall by touching which the water is to be decanted from a the coating and conductor of the phial altercharged phial, held in a man's hand? If the nately. May it not be that the difference bepower of giving a shock is in the water con- tween the charged side of the glass, and the tained in the phial, it should remain there outer or emptied side, being lessened by though decanted into another phial, since no touching the hook or the conductor; the outer non-electric body touched it to take that power side can receive from the hand which touchoff. The phial being placed on wax is no ob-ed it, and by its receiving, the inner side canjection, for it cannot take the power from the not retain so much; and for that reason so water, if it had any, but it is a necessary much as it cannot contain electrises the wameans to try the fact; whereas, that phial's ter, or filings and conductor; for it seems to being charged when held in a man's hand, be a rule, that the one side must be emptied only proves that water will conduct the elec- in the same proportion that the other is filled: tric matter. The Abbé owns, that he had though this from experiment appears eviheard this remarked, but says, why is not a dent, yet it is still a mystery not to be acconductor of electricity an electric subject? counted for. This is not the question; Mr. Franklin never I am in many places of the Abbé's book sursaid that water was not an electric subject; prised to find that experiments have succeeded he said, that the power of giving a shock was so differently at Paris, from what they did in the glass, and not in the water; and this, with Mr. Franklin, and as I have always obhis experiments fully prove; so fully, that it served them to do. The Abbé, in making exmay appear impertinent to offer any more; periments to find the difference between the yet as I do not know that the following has two surfaces of a charged glass, will not have been taken notice of by any body before, my the phial placed on wax: for, says he, dont inserting of it in this place may be excused. you know that being placed on a body origiIt is this: hang a phial, prepared for the Ley-nally electric, it quickly loses its virtue? I den experiment, to the conductor, by its cannot imagine what should have made the hook, and charge it; which done, remove the Abbé think so: it certainly is contradictory communication from the bottom of the phial: to the notions commonly received of electrics now the conductor shows evident signs of be- per se; and by experiment I find it entirely ́ing electrised; for if a thread be tied round otherwise: for having several times left a it, and its ends left about two inches long, charged phial, for that purpose, standing on they will extend themselves out like a pair of wax for hours, I found it to retain as much of horns; but if you touch the conductor, a its charge as another that stood at the same spark will issue from it, and the threads will time on a table. I left one standing on wax fall, nor does the conductor show the least from ten o'clock at night till eight the next sign of being electrised after this is done. I morning, when I found it retain a sufficient think that by this touch, I have taken out all quantity of its charge, to give me a sensible the charge of electric matter that was in the commotion in my arms, though the room in conductor, the hook of the phial, and water or which the phial stood had been swept in that filings of iron contained in it; which is no time, which must have raised much dust to more than we see all non-electric bodies will facilitate the discharge of the phial. receive: yet, the glass of the phial retains its power of giving a shock, as any one will find that pleases to try. This experiment fully evinces, that the water in the phial contains no more electric matter than it would do in an open bason, and has not any of that great quantity which produces the shock, and is only

* See pages 246 to 249, of this volume.

I find that a cork-ball suspended between two bottles, the one fully and the other but little charged, will not play between them, but is driven into a situation that makes a triangle with the hook of the phials: though the Abbé has asserted the contrary of this, in order to account for the playing of a corkball between the wire thrust into the phial, and one that rises up from its coating.

The

phial which is least charged must have more | empty that the sides of the glass might proelectric matter given to it, in proportion to its tect the flame from the wind. There is nobulk, than the cork ball receives from the hook of the full phial.

The Abbé says, "That a piece of metal leaf hung to a silk thread and electrised, will be repelled by the bottom of a charged phial held by its hook in the air:" this I find constantly otherwise, it is with me always first attracted and then repelled: it is necessary, in charging the leaf, to be careful that it does not fly off to some non-electric body, and so discharge itself when you think it is charged; it is difficult to keep it from flying to your own wrist, or to some part of your body.

The Abbé says, "That it is not impossible, as Mr. Franklin says it is, to charge a phial while there is a communication formed between its coating and its hook." I have always found it impossible to charge such a phial so as to give a shock: indeed, if it hang on the conductor without a communication from it, you may draw a spark from it as you may from any body that hangs there, but this is very different from being charged in such a manner as to give a shock. The Abbé, in order to account for the little quantity of electric matter that is to be found in the phial, says, "that it rather follows the metal than the glass, and that it is spewed out into the air from the coating of the phial." I wonder how it comes not to do so too, when it sifts through the glass, and charges the exterior surface, according to the Abbe's system! The Abbé's objection against Mr. Franklin's two last experiments, I think, have little weight in them he seems, indeed, much at a loss what to say, wherefore he taxes Mr. Franklin with having concealed a material part of the experiment; a thing too mean for any gentleman to be charged with, who has not shown so great a partiality in relating experiments, as the Abbé has done.

To Dr. Pringle, London.

thing remarkable in all this; but what follows is particular. At supper, looking on the lamp, I remarked, that though the surface of the oil was perfectly tranquil, and duly preserved its position and distance with regard to the brim of the glass, the water under the oil was in great commotion, rising and falling in irregular waves, which continued during the whole evening. The lamp was kept burning as a watch light all night, till the oil was spent, and the water only remained. In the morning I observed, that though the motion of the ship continued the same, the water was now quiet, and its surface as tranquil as that of the oil had been the evening before. At night again, when oil was put upon it, the water resumed its irregular motions, rising in high waves almost to the surface of the oil, but without disturbing the smooth level of that surface. And this was repeated every day during the voyage.

Since my arrival in America, I have repeated the experiment frequently thus: I have put a packthread round a tumbler, with strings of the same, from each side meeting above it in a knot at about a foot distance from the top of the tumbler. Then putting in as much water as would fill about one third part of the tumbler, I lifted it up by the knot, and swung it to and fro in the air; when the water appeared to keep its place in the tumbler as steadily as if it had been ice. But pouring gently in upon the water about as much oil, and then again swinging it in the air as before, the tranquillity before possessed by the water, was transferred to the surface of the oil, and the water under it was agitated with the same commotions as at sea.

I have shown this experiment to a number of ingenious persons. Those who are but slightly acquainted with the principles of hydrostatics, &c. are apt to fancy immediately that they understand it, and readily attempt to explain it; but their explanations have been different, and to me not very intelligible.

Relating a curious Instance of the Effect of Oil Others, more deeply skilled in those princi

on Water.

PHILADELPHIA, Dec. 1, 1762.

ples, seem to wonder at it, and promise to consider it. And I think it is worth consider

ing; for a new appearance, if it cannot be explained by our old principles, may afford us new ones, of use perhaps in explaining some other obscure parts of natural knowledge.

B. FRANKLIN.

DURING our passage to Madeira, the weather being warm, and the cabin windows constantly open, for the benefit of the air, the candles at night flared and run very much, which was an inconvenience. At Madeira we got oil to burn, and with a common glass tumbler or breaker, slung in wire, and suspended to the ceiling of the cabin, and a little wire hoop for the wick, furnished with corks to float on the oil, I made an Italian lamp, that gave us very good light all over the table. The glass at bottom contained water to about one third of its height; another third was taken up with oil; the rest was left thy clergyman at Carlisle, whose great learn

Dr. Brownrigg to Dr. Franklin. Of the Stilling of Waves by means of Oil.Extracted from sundry letters accompanying. -Read at the Royal Society, June 2, 1774.

ORMATHWAITE, January 27, 1773. By the enclosed from an old friend, a wor

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