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Your explication of the crooked direction of be repelled from the then generally electrilightning appears to me both ingenious and solid. When we can account as satisfactorily for the electrification of clouds, I think that branch of natural philosophy will be nearly complete.

fied surface of the sea, and fly away with them into the air. I thought too, that possibly the great mixture of particles electric per se, in the ocean water, might, in some degree, impede the swift motion and dissipaThe air, undoubtedly, obstructs the motion tion of the electric fluid through it to the of the electric fluid. Dry air prevents the shores, &c.—But having since found, that salt dissipation of an electric atmosphere, the den- in the water of an electric phial does not ser the more, as in cold weather. I question lessen the shock; and having endeavoured whether such an atmosphere can be retained in vain to produce that luminous appearance by a body in vacuo. A common electrical from a mixture of salt and water agitated; phial requires a non-electric communication and observed, that even the sea-water will from the wire to every part of the charged not produce it after some hours standing in a glass; otherwise, being dry and clean, and bottle; I suspect it to proceed from some filled with air only, it charges slowly, and principle yet unknown to us (which I would discharges gradually, by sparks, without a gladly make some experiments to discover, if shock: but exhausted of air, the communica- I lived near the sea) and I grow more doubttion is so open and free between the inserted ful of my former supposition, and more ready wire and surface of the glass, that it charges to allow weight to that objection (drawn from as readily, and shocks as smartly as if filled the activity of the electric fluid, and the reawith water and I doubt not, but that in the diness of water to conduct) which you have experiment you propose, the sparks would not indeed stated with great strength and clearonly be near strait in vacuo, but strike at a ness. greater distance than in the open air, though perhaps there would not be a loud explosion. As soon as I have a little leisure, I will make the experiment, and send you the result.

In the mean time, before we part with this hypothesis, let us think what to substitute in its place. I have sometimes queried whether the friction of the air, an electric per se, in violent winds, among trees, and against the surface of the earth, might not pump up, as so many glass globes, quantities of the electric fluid, which the rising vapours might receive from the air, and retain in the clouds they form? on which I should be glad to have your sentiments. An ingenious friend of mine supposes the land-clouds more likely to be electrified than the sea-clouds. I send his letter for your perusal, which please to return me.

My supposition, that the sea might possibly be the grand source of lightning, arose from the common observation of its luminous appearance in the night, on the least motion; an appearance never observed in fresh water. Then I knew that the electric fluid may be pumped up out of the earth, by the friction of a glass globe, on a non-electric cushion; and that notwithstanding the surprising activity and swiftness of that fluid, and the nonelectric communication between all the parts I have wrote nothing lately on electricity, of the cushion and the earth, yet quantities nor observed any thing new that is material, would be snatched up by the revolving sur-my time being much taken up with other afface of the globe, thrown on the prime con- fairs. Yesterday I discharged four jars ductor, and dissipated in air. How this was through a fine wire, tied up between two done, and why that subtle active spirit did not strips of glass: the wire was in part melted, immediately return again from the globe, into and the rest broke into small pieces from half some part or other of the cushion, and so into an inch long, to half a quarter of an inch. My the earth, was difficult to conceive; but whe-globe raises the electric fire with greater ease, ther from its being opposed by a current set- in much greater quantities, by the means of ting upwards to the cushion, or from what- a wire extended from the cushion, to the iron ever other cause, that it did not so return pin of a pump handle behind my house, which was an evident fact. Then I considered the communicates by the pump spear with the separate particles of water as so many hard water in the well. spherules, capable of touching the salt only in points, and imagined a particle of salt could therefore no more be wet by a particle of water, than a globe by a cushion; that there might therefore be such a friction between these originally constituent particles of salt and water, as in a sea of globes and cushions; that each particle of water on the surface might obtain from the common mass, some particles of the universally diffused much finer, and more subtle electric fluid, and forming to itself an atmosphere of those particles,

By this post I send to ****, who is curious in that way, some meteorological observations and conjectures, and desire him to communicate them to you, as they may afford you some amusement, and I know you will look over them with a candid eye. By throwing our occasional thoughts on paper, we more readily discover the defects of our opinions, or we digest them better and find new arguments to support them. This I sometimes practise: but such pieces are fit only to be seen by friends. B. FRANKLIN.

four glass jars had upon a fine wire, tied be

J. Bowdoin to Benjamin Franklin. Effect of Lightning on Captain Waddel's Com-tween two strips of glass, puts me in mind of a pass, and the Dutch Church at New York. Read at the Royal Society, June 3, 1752. BOSTON, March 2, 1752.

very similar one of lightning, that I observed at New York, October, 1750, a few days after I left Philadelphia. In company with a of the city from the Dutch church steeple, in number of gentlemen, I went to take a view which is a clock about twenty or twenty-five feet below the bell. From the clock went a wire through two floors, to the clock-hammer

I HAVE received your favour of the 24th of January past, enclosing an extract from your letter to Mr. Collinson, and ****'s letter to yourself, which I have read with a great deal of pleasure, and am much obliged to you for. Your extract confirms a correction Mr. Kinnersley made a few days ago, of a mistake I was under respecting the polarity given to needles by electrical fire," that the end which receives the fire always points north;" and "that the needle being situated east and west will not have a polar direction." You find, however, the polarity strongest when the needle is shocked lying north and south; weakest when lying east and west; which makes it probable that the communicated magnetism is less, as the needle varies from a north and south situation. As to the needle of captain Waddel's compass, if its polarity was reversed by the lightning, the effect of lightning and electricity, in regard of that, seems dissimilar; for a magnetic needle in a north and south situation (as the compass needle was) instead of having its power reversed, or even diminished, would have it confirmed or increased by the electric fire. But perYour information about your globe's raising haps the lightning communicated to some the electric fire in greater quantities, by means nails in the binnacle (where the compass is of a wire extended from the cushion to the placed) the magnetic virtue, which might dis-earth, will enable me, I hope, to remedy a

turb the compass.

This I have heard was the case; if so, the seeming dissimilarity vanishes: but this remarkable circumstance (if it took place). I should think would not be omitted in captain

Waddel's account.

I am very much pleased that the explication I sent you, of the crooked direction of lightning, meets with your approbation.

As to your supposition about the source of lightning, the luminous appearance of the sea in the night, and the similitude between the friction of the particles of salt and water, as you considered them in their original separate state, and the friction of the globe and cushion, very naturally led you to the ocean, as the grand source of lightning: but the activity of lightning, or the electric element, and the fitness of water to conduct it, together with the experiments you mention of salt and water, seem to make against it, and to prepare the way for some other hypothesis. Accordingly you propose a new one, which is very curious, and not so liable, I think, to objections as the former. But there is not, as yet, I believe, a sufficient variety of experiments to establish any theory, though this seems the most hopeful of any I have heard of. The effect which the discharge of your

near the bell, the holes in the floor for the wire being perhaps about a quarter of an inch diameter. We were told, that in the spring of 1750, the lightning struck the clock hammer, and descended along the wire to the clock, melting in its way several spots of the wire, from three to nine inches long, through one third of its substance, till coming within a few feet of the lower end, it melted the wire quite through, in several places, so that it fell down in several pieces; which spots and pieces we saw. When it got to the end of the wire, it flew off to the hinge of a door, shattered the door, and dissipated. In its passage through the holes of the floors it did not do the least damage, which evidences that wire is a good conductor of lightning (as it is of electricity) provided it be substantial enough, and might, in this case, had it been continued to the earth, have conducted it without damaging the building.*

lect the fire with the electrifying glass I use,
inconvenience I have been under, to col-
great
which is fixed in a very dry room, three stories
from the ground. When you send your me-
teorological observations to ****, I hope I shall
have the pleasure of seeing them.

J. BOWDOIN.

Proposal of an experiment to measure the time taken up by an Electric Spark in moving through any given space. By James Alexander, of New York.-Read at the Royal Society, Dec. 26, 1756.

IF I remember right, the Royal Society made one experiment to discover the velocity

*The wire mentioned in this account was replaced by a small brass chain. In the summer of 1763, the lightning again struck that steeple, and from the clockhammer near the bell, it pursued the chain as it had be fore done the wire, went off to the same hinge, and again shattered the same door. In its passage through the same holes of the same floors, it did no damage to the floors, nor to the building during the whole extent of the chain. But the chain itself was destroyed, being partly scattered about in fragments of two or three links melted and stuck together, and partly blown up or reduced to smoke, and dissipated. [See an account of the same effect of lightning on a wire at Newbury, p. 296.] The steeple, when repaired, was guarded by an iron conductor, or rod, extending from the foot of the vanespindle down the outside of the building, into the earth.

Society, Dec. 25, 1756. SUPPOSE a tube of any length open at both ends, and containing a moveable wire of just the same length, that fills its bore. If I attempt to introduce the end of another wire into the same tube, it must be done by pushing forward the wire it already contains; and the instant I press and move one end of that wire, the other end is also moved, and introducing one inch of the same wire, I extrude, at the same time, an inch of the first, from the other end of the tube.

of the electric fire, by a wire of about four | Answer to the foregoing.-Read at the Royal miles in length, supported by silk, and by turning it forwards and backwards in a field, so that the beginning and end of the wire were at only the distance of two people, the one holding the Leyden bottle and the beginning of the wire, and the other holding the end of the wire and touching the ring of the bottle; but by this experiment no discovery was made, except that the velocity was extremely quick. As water is a conductor as well as metals, it is to be considered whether the velocity of the electric fire might not be discovered by means of water; whether a river, or lake, or sea, may not be made part of the circuit through which the electric fire passes? instead of the circuit all of wire, as in the above experiment.

Whether in a river, lake, or sea, the electric fire will not dissipate and not return to the bottle? or, will it proceed in strait lines through the water the shortest courses possible back to the bottle?

If the last, then suppose one brook that falls into Delaware doth head very near to a brook that falls into Schuylkill, and let a wire be stretched and supported as before, from the head of the one brook to the head of the other, and let the one end communicate with the water, and let one person stand in the other brook, holding the Leyden bottle, and let another person hold that end of the wire not in the water, and touch the ring of the bottle. If the electric fire will go as in the last question, then will it go down the one brook to Delaware or Schuylkill, and down one of them to their meeting, and up the other brook; the time of its doing this may possibly be observable, and the further upwards the brooks are chosen, the more observable it would be.

If the tube be filled with water, and I inject an additional inch of water at one end, I force out an equal quantity at the other in the very same instant.

And the water forced out at one end of the tube is not the very same water that was forced in at the other end at the same time, it was only in motion at the same time.

The long wire, made use of in the experiment to discover the velocity of the electric fluid, is itself filled with what we call its natural quantity of that fluid, before the hook of the Leyden bottle is applied to one end of it.

The outside of the bottle being at the time of such application in contact with the other end of the wire, the whole quantity of electric fluid contained in the wire is, probably, put in motion at once.

For at the instant the hook, connected with the inside of the bottle, gives out; the coating or outside of the bottle, draws in a portion of that fluid.

If such long wire contains precisely the quantity that the outside of the bottle demands, the whole will move out of the wire to the outside of the bottle, and the over quantity which the inside of the bottle contained, being exactly equal, will flow into the wire, and remain there, in the place of the quantity the wire had just parted with to the outside of the bottle.

Should this be not observable, then suppose the two brooks falling into Susquehanna and Delaware, and proceeding as before, the electric fire may, by that means, make a circuit round the North Cape of Virginia, and go But if the wire be so long as that one tenth many hundred miles, and in doing that, it (suppose) of its natural quantity is sufficient would seem it must take some observable time. to supply what the outside of the bottle deIf still no observable time is found in that mands, in such a case the outside will only reexperiment, then suppose the brooks falling ceive what is contained in one tenth of the the one into the Ohio, and the other into Sus-wire's length, from the end next to it; though quehanna, or Potowmac, in that the electric fire would have a circuit of some thousands of miles to go down the Ohio to Mississippi, to the Bay of Mexico, round Florida, and round the South Cape of Virginia; which, I think, would give some observable time, and discover exactly the velocity.

But if the electric fire dissipates, or weakens in the water, as I fear it does, these experiments will not answer.

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the whole will move so as to make room at the other end for an equal quantity issuing, at the same time, from the inside of the bottle.

So that this experiment only shows the extreme facility with which the electric fluid moves in metal; it can never determine the velocity.

And, therefore, the proposed experiment (though well imagined, and very ingenious) of sending the spark round through a vast length of space, by the waters of Susquehanna, or Potowmac, and Ohio, would not afford the satisfaction desired, though we could be sure that the motion of the electric fluid would be

in that tract, and not under ground in the wet stand. Then electrising the stand, I had the earth by the shortest way.

B. FRANKLIN.

pleasure of seeing what I expected; the wooden needle turned round, carrying the pins with their heads foremost. I then electrised the stand negatively, expecting the needle to turn the contrary way, but was ex

Mr. Kinnersley to B. Franklin. Experiments on boiling Water, and glass heated by boiling water.--Doctrine of repulsion in elec-tremely disappointed, for it went still the trised bodies doubted.--Electricity of the atmosphere at different heights-Electrical Horserace.-Electrical thermometer.-In what cases the electrical fire produces heat.-Wire lengthened by Electricity-Good effect of a rod on the house of Mr. West, of Philadelphia.

PHILADELPHIA, March 12, 1761.

HAVING lately made the following experiments, I very cheerfully communicate them, in hopes of giving you some degree of pleasure, and exciting you to further explore your favourite, but not quite exhausted subject, electricity.

same way as before. When the stand was electrised positively, I suppose that the natural quantity of electricity in the air being increased on one side, by what issued from the points, the needle was attracted by the lesser quantity on the other side. When electrised negatively, I suppose that the natural quantity of electricity in the air was diminished near the points; in consequence whereof, the equilibrium being destroyed, the needle was attracted by the greater quantity on the opposite side.

The doctrine of repulsion, in electrised boI placed myself on an electric stand, and, dies, I begin to be somewhat doubtful of. I being well electrised, threw my hat to an think all the phenomena on which it is foundunelectrised person, at a considerable dis-ed, may be well enough accounted for withtance, on another stand, and found that the hat carried some of the electricity with it; for, upon going immediately to the person who received it, and holding a flaxen thread near him, I perceived he was electrised sufficiently to attract the thread.

I then suspended, by silk, a broad plate of metal, and electrised some boiling water under it at about four feet distance, expecting that the vapour, which ascended plentifully to the plate, would, upon the principle of the foregoing experiment, carry up some of the electricity with it; but was at length fully convinced, by several repeated trials, that it left all its share thereof behind. This I know not how to account for; but does it not seem to corroborate your hypothesis, that the vapours of which the clouds are formed, leave their share of electricity behind, in the common stock, and ascend in the negative state?

I put boiling water into a coated Florence flask, and found that the heat so enlarged the pores of the glass, that it could not be charged. The electricity passed through as readily, to all appearance, as through metal; the charge of a three-pint bottle went freely through, without injuring the flask in the least. When it became almost cold, I could charge it as usual. Would not this experiment convince the Abbé Nollet of his egregious mistake? For while the electricity went fairly through the glass, as he contends it always does, the glass could not be charged at all.

I took a slender piece of cedar, about eighteen inches long, fixed a brass cap in the middle, thrust a pin horizontally and at right angles, through each end (the points in contrary directions) and hung it, nicely balanced, like the needle of a compass, on a pin, about six inches long, fixed in the centre of an electric

out it. Will not cork balls, electrised negatively, separate as far as when electrised positively? And may not their separation in both cases be accounted for upon the same principle, namely, the mutual attraction of the natural quantity in the air, and that which is denser or rarer in the cork balls? it being one of the established laws of this fluid, that quantities of different densities shall mutually attract each other, in order to restore the equilibrium.

I can see no reason to conclude that the air has not its share of the common stock of electricity, as well as glass, and perhaps, all other electrics per se. For though the air will admit bodies to be electrised in it either positively or negatively, and will not readily carry off the redundancy in the one case, nor supply the deficiency in the other, yet let a person in the negative state, out of doors in the dark, when the air is dry, hold, with his arm extended, a long sharp needle, pointing upwards, and he will soon be convinced that electricity may be drawn out of the air; not very plentifully, for, being a bad conductor, it seems loth to part with it, but yet some will evidently be collected. The air near the person's body having less than its natural quantity, will have none to spare; but, his arm being extended, as above, some will be collected from the remoter air, and will appear luminous, as it converges to the point of the needle.

Let a person electrised negatively present the point of a needle, horizontally, to a cork ball, suspended by silk, and the ball will be attracted towards the point, till it has parted with so much of its natural quantity of elcctricity as to be in the negative state, in the same degree with the person who holds the needle; then it will recede from the point, be

ing, as I suppose, attracted the contrary way | lowing description, you will readily apprehend by the electricity of greater density in the air the construction of it. (See the Plate.) behind it. But, as this opinion seems to deviate from electrical orthodoxy, I should be glad to see these phenomena better accounted for by your superior and more penetrating ge

nius.

Whether the electricity in the air, in clear dry weather, be of the same density at the height of two or three hundred yards, as near the surface of the earth, may be satisfactorily determined by your old experiment of the kite. The twine should have throughout a very small wire in it, and the ends of the wire, where the several lengths are united, ought to be tied down with a waxed thread, to prevent their acting in the manner of points. I have tried the experiment twice, when the air was as dry as we ever have it, and so clear that not a cloud could be seen, and found the twine each time in a small degree electrised positively. The kite had three metalline points fixed to it: one on the top, and one on each side. That the twine was electrised, appeared by the separating of two small cork balls, suspended on the twine by fine flaxen threads, just above where the silk was tied to it, and sheltered from the wind, That the twine was electrised positively, was proved, by applying it to the wire of a charged bottle, which caused the balls to separate further, without first coming nearer together. This experiment showed, that the electricity in the air, at those times, was denser above than below. But that cannot be always the case; for you know we have frequently found the thunder-clouds in the negative state, attracting electricity from the earth: which state, it is probable, they are always in when first formed, and till they have received a sufficient supply. How they come afterwards, towards the latter end of the gust, to be in the positive state, which is sometimes the case, is a subject for further inquiry.

After the above experiments with the wooden needle, I formed a cross, of two pieces of wood, of equal length, intersecting each other at right angles in the middle, hung it horizontally upon a central pin, and set a light horse with his rider, upon each extremity; whereupon, the whole being nicely balanced, and each courser urged on by an electrised point of a pair of spurs, I was entertained with an electrical horse-race.

I have contrived an electrical air thermometer, and made several experiments with it, that have afforded me much satisfaction and pleasure. It is extremely sensible of any alteration in the state of the included air, and fully determines that controverted point, Whether there be any heat in the electric fire? By the enclosed draught, and the fol

A B is a glass tube, about eleven inches long, and one inch diameter in the bore. It has a brass ferrule cemented on each end, with a top and bottom part, C and D, to be screwed on, air-tight, and taken off at pleasure. In the centre of the bottom part D, is a male screw, which goes into a brass nut, in the mahogany pedestal E. The wires F and G are for the electric fire to pass through, darting from one to the other. The wire G extends through the pedestal to H, and may be raised and lowered by means of a male screw on it. The wire F may be taken out, and the hook I be screwed into its place. K is a glass tube, with a small bore, open at both ends, cemented in the brass tube L, which screws into the top part C. The lower end of the tube K is immersed in water, coloured with cochineal, at the bottom of the tube A B. (I used, at first, coloured spirits of wine, but in one experiment I made, it took fire.) On the top of the tube K is cemented, for ornament, a brass ferrule, with a head screwed on it, which has a small air-hole through its side, at a. The wire b, is a small round spring, that embraces the tube K, so as to stay wherever it is placed. The weight M is to keep strait whatever may be suspended in the tube A B, on the hook I. Air must be blown through the tube K, into the tube A B, till enough is intruded to raise, by its elastic force, a column of the coloured water in the tube K, up to c, or thereabouts; and then, the gage-wire b, being slipt down to the top of the column, the thermometer is ready for use.

I set the thermometer on an electric stand, with the chain N fixed to the prime conductor, and kept it well electrised a considerable time; but this produced no sensible effect; which shows, that the electric fire, when in a state of rest, has no more heat than the air, and other matter wherein it resides.

When the wires F and G are in contact, a large charge of electricity sent through them, even that of my case of five and thirty bottles containing above thirty square feet of coated glass, will produce no rarification of the air included in the tube A B; which shows that the wires are not heated by the fire's passing through them.

When the wires are about two inches apart, the charge of a three pint bottle, darting from one to the other, rarifies the air very evidently; which shows, I think, that the electric fire must produce heat in itself, as well as in the air, by its rapid motion.

The charge of one of my glass jars (which will contain about five gallons and a half, wine measure) darting from wire to wire, will, by the disturbance it gives the air, re

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