Abbildungen der Seite


second experiment, must be in a much more and imbibed by the balls to supply the defidense part of the atmosphere of the tube, be- ciency; and that more plentifully at the apfore they will repel each other. At the ap- proach of excited glass; or a body positively proach of an excited stick of wax to the balls, electrified, than before; whence the distance in the first experiment, the electrical fire is between the balls will be increased, as the supposed to come through the threads into the fluid surrounding them is augmented. And balls, and be condensed there, in its passage in general, whether by the approach or recess towards the wax; for, according to Mr. of any body; if the difference between the Franklin, excited glass emits the electrical density of the internal and external fluid be fluid, but excited wax receives it.

increased or diminished; the repulsion of the

balls will be increased or diminished accordEXPERIMENT III.

ingly. Let a tin tube, of four or five feet in length, and about two inches in diameter, be insulated by silk; and from one end of it let the

When the insulated tin tube is not electricork-balls be suspended by linen threads. fied, bring the excited glass tube towards the Electrify it, by bringing the excited glass middle of it, so as to be nearly at right angles tube near the other end, so as that the balls with it, and the balls at the end will repel may stand an inch and a half, or two inches each other; and the more so, as the excited apart: then, at the approach of the excited tube is brought nearer. When it has been held tube, they will by degrees, lose their repelling

a few seconds, at the distance of about six power, and come into contact; and as the tube inches, withdraw it, and the balls will apis brought still nearer, they will separate proach each other till they touch; and then again to as great a distance as before : in the separating again, as the tube is moved farther return of the tube they will approach 'each off, will continue to repel when it is taken other till they touch, and then repel as at quite away. And this repulsion between the first. If the tin tube be electrified by wax, balls will be increased by the approach of exor the wire of a charged phial, the balls will cited glass, but diminished by excited wax; be affected in the same manner at the ap- just as if the apparatus had been electrified proach of excited wax, or the wire of the by wax, after the manner described in the phial.

third experiment.



Electrify the cork-balls as in the last ex Insulate two tin tubes, distinguished by A periment by glass, and at the approach of an and B, so as to be in a line with each other, excited stick of wax their repulsion will be and about half an inch apart; and at the reincreased. The effect will be the same, if mote end of each, let a pair of cork balls be the excited glass be brought towards them, suspended. Towards the middle of A, bring when they have been electrified by wax. the excited glass tube, and holding it a short

The bringing the excited glass to the end, time, at the distance of a few inches, each or edge of the tin tube, in the third experi- pair of balls will be observed to separate: withment, is supposed to electrify it positively, or draw the tube, and the balls of A will come to add to the electrical fire it before contained; together, and then repel each other again; and therefore some will be running off through but those of B will hardly be affected. By the the balls, and they will repel each other. But approach of the excited glass tube, held under at the approach of excited glass, which like- the balls of A, their repulsion will be increaswise emits the electrical fluid, the discharge ed: but if the tube be brought, in the same of it from the balls will be diminished; or manner, towards the balls of B, their repulpart will be driven back, by a force acting in sion will be diminished. à contrary direction: and they will come In the fifth experiment, the common stock nearer together. If the tube be held at such of electrical matter in the tin tube is supposa distance from the balls, that the excess of ed to be attenuated about the middle, and to be the density of the fluid round about them, condensed at the ends, by the repelling power above the common quantity in air, be equal to of the atmosphere of the excited glass tube, the excess of the density of that within them, when held near it. And perhaps the tin tube above the common quantity contained in cork; may lose some of its natural quantity of the their repulsion will be quite destroyed. But electrical fluid, before it receives any from the if the tube be brought nearer; the fluid with glass; as that fluid will more readily run off out being more dense than within the balls, it froin the ends and edges of it, than enter at will be attracted by them, and they will re- the middle: and accordingly, when the glass cede from each other again.

tube is withdrawn, and the fluid is again equalWhen the apparatus has lost part of its na- ly diffused through the apparatus, it is found tural share of this fluid, by the approach of to be electrified negatively: for excited glass excited wax to one end of it, or is electrified brought under the balls will increase their renegatively; the electrical fire is attracted pulsion.



In the sixth experiment, part of the fluid | tively. And it is probable, that all bodies driven out of one tin tube enters the other; whatsoever may have the quantity they conwhich is found to be electrified positively, by tain of the electrical fluid increased or dimithe decreasing of the repulsion of its balls, at nished. The clouds, I have observed, by a the approach of excited glass.

great number of experiments, to be some in a positive, and others in a negative state of

electricity. For the cork balls, electrified Let the tin tube, with a pair of balls at by them, will sometimes close at the approach one end, be placed three feet at least from of excited glass; and at other times be sepaany part of the room, and the air rendered rated to a greater distance. And this change very dry by means of a fire: electrify the ap- I have known to happen five or six times in paratus to a considerable degree; then touch less than half an hour; the balls coming togethe tin tube with a finger, or any other con- ther each time, and remaining in contact a few ductor, and the balls will, notwithstanding, seconds, before they repel each other again. continue to repel each other; though not at It may likewise easily be discovered, by a so great a distance as before.

charged phial, whether the electrical fire be The air surrrounding the apparatus to the drawn out of the apparatus by the negative distance of two or three feet, is supposed to cloud, or forced into it by a positive one: and contain more or less of the electrical fire, by which soever it be electrified, should that than its common share, as the tin tube is cloud either part with its overplus, or have its electrified positively, or negatively: and when deficiency supplied suddenly, the apparatus very dry, may not part with its overplus, or will lose its electricity : which is frequently have its deficiency supplied so suddenly, as observed to be the case, immediately after a the tin; but may continue to be electrified, af- flash of lightning. Yet when the air is very ter that has been touched for a considerable dry," the apparatus will continue to be electritime.

fied for ten minutes, or a quarter of an hour,

after the clouds have passed the zenith; and Having made the Torricellian vacuum about towards the horizon. Rain, especially when

sometimes till they appear more than half-way five feet long, after the manner described in the drops are large, generally brings down the Philosophical Transactions, vol. xlvii. p. the electrical fire; and hail, in summer, I be 370, if the excited tube be brought within a lieve never fails. When the apparatus was small distance of it, a light will be seen through last electrified, it was by the fall of thawing more than half its length; which soon vanishes, if the tube be not brought nearer; but will snow, which happened so lately, as on the appear again, as that is moved farther off. - 12th of November; that being the twentyThis may be repeated several times, without electrified, since it was first set up; which

sixth day, and sixty-first time it has been exciting the tube afresh. This experiment may be considered as a renheit's thermometer was but seven degrees

was about the middle of May. And as Fahkind of ocular demonstration of the truth of above freezing, it is supposed the winter will Mr. Franklin's hypothesis; that when the electrical fluid is condensed on one side of thin not entirely put a stop to observations of this glass, it will be repelled from the other, if it sort. At London no more than two thunder meets with no resistance. According to

storms have happened during the whole sum- . which, at the approach of the excited tube, the mer; and the apparatus was sometimes so fire is supposed to be repelled from the inside strongly electrified in one of them, that the of the glass surrounding the vacuum, and to be the clouds, so loud as to be heard in every

bells, which have been frequently rung by carried through the columns of mercury; but as the tube is withdrawn, the fire is supposed room of the house (the doors being open)

were silenced by the almost constant stream to return.

of dense electrical fire, between each bell and

the brass ball, which would not suffer it to Let an excited stick of wax, of two feet strike. and a half in length, and about an inch in I shall conclude this paper, already too long, diamater, be held near its middle. Excite with the following queries: the glass tube, and draw it over one half of 1. May not air, suddenly rarified, give elecit; then, turning a little about its axis, let the trical fire to, and air suddenly condensed, retube be excited again, and drawn over the same ceive electrical fire from, clouds and yapours half; and let this operation be repeated seve- passing through it? ral times; then will that half destroy the re 2. Is not the aurora borealis, the flashing pelling power of balls electrified by glass, and of electrical fire from positive, towards negathe other half will increase it.

tive clouds at a great distance, through the By this experiment it appears, that wax upper part of the atmosphere, where the re also may be electrified positively and nega- sistance is least?




Experiments made in pursuance of those the atmosphere of the glass tube not having made by Mr. Canton, dated December 6, mixed with the atmosphere of the prime con1753; with explanations, by Benjamin ductor, is withdrawn entire, having made no Franklin.-Read at the Royal Society, addition to, or diminution from it. Dec 18, 1755. PHILADELPHIA, March 14, 1755.

Bring the excited tube under the tuft of

threads, and they will close a little. I. ELECTRIC atmospheres, that flow round They close, because the atmosphere of the non-electric bodies, being brought near each glass tube repels their atmosphere, and drives other, do not readily mix and unite into one part of them back on the prime conductor. atmosphere, but remain separate, and repel Withdraw it, and they will diverge as much. each other.

This is plainly seen in suspended cork-balls, For the portion of atmosphere which they and other bodies eleetrified.

had lost returns to them again. II. An electric atmosphere not only repels another electric atmosphere, but will also repel the electric matter contained in the sub- Excite the glass tube, and approach the prime stance of a body approaching it; and without

conductor with it, holding it across, near joining or mixing with it, force it to other the end opposite to that on which the parts of the body that contained it.

threads hang, at the distance of five or six This is shown by some of the following ex

inches. Keep it there a few seconds, and periments.

the threads of the tassels will diverge. III. Bodies electrified negatively, or de

Withdraw it, and they will close. prived of their natural quantity of electricity, They diverge, because they have received repel each other, (or at least appear to do so, electric atmospheres from the electric matter by a mutual receding) as well as those elec- before contained in the substance of the prime trified positively, or which have electric at- conductor ; but which is now repelled and mospheres.

driven away, by the atmosphere of the glass This is shown by applying the negatively tube, from the parts of the prime conductor charged wire of a phial to two cork-balls, sus- opposite and nearest to that atmosphere, and pended by silk threads, and many other expe- forced out upon the surface of the prime conriments.

ductor at its other end, and upon the threads

hanging thereto. Were it any part of the atFix a tassel of fifteen or twenty threads, mosphere of the glass tube that flowed over three inches long, at one end of a tin prime and along the prime conductor to the threads, conductor (mine is about five feet long, and and gave them atmospheres (as is the case when four inches diameter) supported by silk lines. a spark is given to the prime conductor from Let the threads be a little damp, but not wet. the glass tube) such part of the tube's atmo

sphere would have remained, and the threads

continue to diverge; but they close on withPass an excited glass tube near the other end drawing the tube, because the tube takes

of the prime conductor, so as to give it with it all its own atmosphere, and the elecsome sparks, and the threads will diverge. tric matter, which had been driven out of the

Because each thread, as well as the prime substance of the prime conductor, and formed conductor, has acquired an electric atmo- atmospheres round the threads, is thereby sphere, which repels and is repelled by the at- permitted to return to its place. mospheres of the other threads : if those several atmospheres would readily mix, the threads Take a spark from the prime conductor near might unite and hang in the middle of one at the threads when they are diverged as bemosphere, common to them all.

fore, and they will close. Rub the tube afresh, and approach the prime For by so doing you take away their atconductor therewith, crossways, near that mospheres, composed of the electric matter end, but not nigh enough to give sparks; driven out of the substance of the prime conand the threads will diverge a little more. ductor, as aforesaid, by the repellency of the Because the atmosphere of the prime con

atmosphere of the glass tube. By taking ductor is pressed by the atmosphere of the ex- this spark you rob the prime conductor of cited tube, and driven towards the end where part of its natural quantity of the electric the threads are, by which each thread ac- matter, which part so taken is not supplied quires more atmosphere.

by the glass tube, for when that is aferwards

withdrawn, it takes with it its whole atmoWithdraw the tube, and they will close as sphere, and leaves the prime conductor elecmuch.

trised negatively, as appears by the next opeThey close as much, and no more; because ration.



Then withdraw the tube, and they will open did from the finger; which demonstrates the . again.

finger to be negatively electrised, as well as For now the electric matter in the prime the lock of cotton so situated. conductor, returning to its equilibrium, or equal diffusion, in all parts of its substance, and the prime conductor having lost some of its natural quantity, the threads connected Turkey killed by Electricity.Effect of a with it lose part of theirs, and so are elec.

shock on the Operator in making the Extrised negatively, and therefore repel each

periment. other, by Pr. III.

As Mr. Franklin, in a former letter to Mr. Approach the prime conductor with the tube Collinson, mentioned his intending to try the near the same place as at first, and they power of a very strong electrical shock upon will close again.

a turkey, that gentleman accordingly has been Because the part of their natural quantity of so very obliging as to send an account of it, electric fluid, which they had lost, is now re

which is to the following purpose. stored to them again, by the repulsion of the fowls, and found, that two large thin glass

He made first several experiments on glass tube forcing that fluid to them from other parts of the prime conductor ; so they jars gilt, holding

each about six gallons, were are now again in their natural state.

sufficient, when fully charged, to kill common

hens outright; but the turkeys, though thrown Withdraw it, and they will open again. into violent convulsions, and then lying as

For what had been restored to them, is dead for some minutes, would recover in less now taken from them again, flowing back in than a quarter of an hour. However, having to the prime conductor and leaving them once added three other such to the former two, more electrised negatively.

though not fully charged, he killed a turkey

of about ten pounds weight, and believes that Bring the excited tube under the threads, they would have killed a much larger. He

and they will diverge more. conceited, as himself says, that the birds killed Because more of their natural quantity is in this manner eat uncommonly tender. driven from them into the prime conductor, In making these experiments, he found, that and thereby their negative electricity in- a man could, without great detriment, bear a creased.

much greater shock than he had imagined :

for he inadvertently received the stroke of The prime conductor not being electrified, when they were very near fully charged. It

two of these jars through his arms and body, bring the excited tube under the tassel, seemed to him an universal blow throughout and the threads will diverge.

the body, from head to foot, and was followed Part of their natural quantity is thereby by a violent quick trembling in the trunk, driven out of them into the prime conductor, which went off gradually, in a few seconds. and they become negatively electrised, and It was some minutes before he could recollect therefore repel each other.

his thoughts, so as to know what was the Keeping the tube in the same place with one matter; for he did not see the flash, though

hand, attempt 10 touch the threads with the his eye was on the spot of the prime conductor, finger of the other hand, and they will re- from whence it struck the back of his hand; cede from the finger.

nor did he hear the crack, though the byBecause the finger being plunged into the standers said it was a loud one; nor did he atmosphere of the glass tube, as well as the particularly feel the stroke on his hand, though threads, part of its natural quantity is driven he afterwards found it had raised a swelling back through the hand and body, by that at- His arms and the back of the neck felt some

there, of the bigness of half a pistol-bullet. mosphere, and the finger becomes, as well as what numbed the remainder of the evening, the threads, negatively electrised, and so repels, and is repelled by them. To confirm and his breast was sore for a week after, this, hold a slender light lock of cotton, two as if it had been bruised. From this experior three inches long, near a prime conductor, ment may be seen the danger, even under that is electrified by a glass globe, or tube. the greatest caution, to the operator, when You will see the cotton stretch itself out to making these experiments with large jars ; wards the prime conductor. Attempt to touch for it is not to be doubted, but several of these it with the finger of the other hand, and it will fully charged would as certainly, by increas be repelled by the finger. Approach it with ing them, in proportion to the size, kill a man,

as they before did a turkey. a positively charged wire of a bottle, and it will fly to the wire. Bring it near a nega N. B. The original of this letter, which tively charged wire of a bottle, it will recede was read at the Royal Society, has been misfrom that wire in the same manner that it laid.


Dr. Lining at Charleston. to support himself chiefly by electricity. A Differences in the Qualities of the Glass.--Ac- strange project! But he was, as you observe, count of Domien, an Electrician and Travel- a very singular character. I was sorry the ler.-Conjectures respecting, the pores of tubes did not get to the Havanna in time for Glass.- Origin of the author's idea of draw- him. If they are still in being, please to ing down Lightning.No satisfactory Hypo send for them, and accept of them. What thesis respecting the manner in which Clouds became of him afterwards I have never become electrified.-Siz men knocked down at heard. He promised to write to me as often once by an electrical shock.-Reflections on the spirit of indention.

as he could on his journey, and as soon as he PHILADELPHIA, March 18, 1753.

should get home after finishing his tour. It I SEND you enclosed a paper containing is still in New Spain, as you imagine from

is now seven years since he was here. If he some new experiments I have made, in pur- that loose report, I suppose it must be that suance of those by Mr. Canton that are print. they confine him there, and prevent his writed with my last letters. I hope these, with ing: but I think it more likely that he may my explanation of them, will afford

you some

be dead. entertainment.*

The questions you ask about the pores of In answer to your several inquiries. The tubes and globes we use here, are chiefly glass, I cannot answer otherwise, than that I made here. The glass has a greenish cast,

know nothing of their nature; and supposibut is clear and hard, and, I think, better for tions, however ingenious, are often mere misclectrical experiments than the white glass near the middle of the glass, too small to ad

takes. My hypothesis, that they were smaller of London, which is not so hard. There are mit the passage of electricity, which could certainly great differences in glass. A white globe l'had made here some years since, middle, was certainly wrong; for soon after I

pass through the surface till it came near the would never, by any means, be excited. Two had written that letter, I did, in order to conof my friends tried it, as well as myself, without success. At length, putting it on an have done before I wrote it) make an experi

firm the hypothesis (which indeed I ought to electric stand, a chain from the prime conductor being in contact with it, I found it had ment. I ground away five sixths of the thick

ness of the glass, from the side of one of my the properties of a non-electric; for I could draw sparks from any part of it, though it was

phials, expecting that the supposed denser

part being so removed, the electric fluid very clean and dry. All I know of Domien, is, that by his own

might come through the remainder of the account he was a native of Transylvania, of glass, which I had imagined more open ; but Tartar descent, but a priest of the Greek ed as well after the grinding as before.

I found myself mistaken. The bottle chargchurch: he spoke and wrote Latin very readily and correctly. He set out from his own now, as much as ever, at a loss to know how country with an intention of going round the or where the quantity of electric fluid, on the world, as much as possible by land. He tra- positive side of the glass, is disposed of. velled through Germany, France, and Holland, is not only this, that some will conduct elec

As to the difference of conductors, there to England. Resided some time at Oxford. From England he came to Maryland ; thence tricity in small quantities, and yet do not con

duct it fast enough to produce the shock; but went to New England; returned by land to Philadelphia; and from hence travelled there are some that do it better than others,

even among those that will conduct a shock, through Maryland, Virginia, and North Caro- Mr. Kinnersley has found, by a very good exlina to you. He thought it might be of service to him in his travels to know something hath an opportunity of passing two ways, i. e.

periment, that when the charge of a bottle of electricity. I taught him the use of the straight through a trough of water ten feet

how to charge the Leyden phial, and some other experiments. He wrote to me

long, and six inches square; or round about from Charleston, that he had lived eight hun through twenty feet of wire, it passes through dred miles upon electricity, it had been meat, that is the shortest course; the wire being

the wire, and not through the water, though drink, and clothing to him. His last letter to the better conductor. When the wire is me was, I think, from Jamaica, desiring me

it to send the tubes you mention, to meet him at

passes through the water, as the Havanna, from whence he expected to but it cannot be felt in the water when the

be felt by a hand plunged in the water; get a passage to La Vera Cruz; designed wire is used at the same time. Thus, though travelling over land through Mexico to Acapulco; thence to get a passage to Manilla,

a small phial containing water will give and so through China, India, Persia, and smart shock, one containing the same quantity Turkey, home to his own country ; proposing mercury being the better conductor, while

of mercury will give one much stronger, the * See the preceding article, page 22, for the paper

one containing oil only, will scarce give any shock at all

I am

tube ;

taken away;

here referred to.

« ZurückWeiter »