this wire to the coating, and the other at the same time to the prime conductor, the phial will be discharged; and if the balls are not electrified before the discharge, neither will they appear to be so after the discharge, for they will not repel each other.

If the phial really exploded at both ends, and discharged fire from both coating and wire, the balls would be more electrified, and recede farther; for none of the fire can escape, the wax handle preventing.

But if the fire with which the inside surface is surcharged be so much precisely as is wanted by the outside surface, it will pass round through the wire fixed to the wax handle, restore the equilibrium in the glass, and make no alteration in the state of the prime conductor.

Accordingly we find, that if the prime conductor be electrified, and the cork balls in a state of repellency before the bottle is discharged, they continue so afterwards. If not, they are not electrified by that discharge.

To Peter Collinson, London. Accumulation of the electrical Fire proved to be in the electrified Glass.-Effect of Lightning on the Needle of Compasses, explained.-Gunpowder fired by the electric Flame.

PHILADELPHIA, July 27, 1750.

MR. WATSON, I believe, wrote his Observations on my last paper in haste, without having first well considered the experiments related 17, which still appear to me decisive in the question,- Whether the accumulation of the electrical fire be in the electrical glass, or in the non-electric matter connected with the glass? and to demonstrate that it is really in the glass.

As to the experiment that ingenious gentleman mentions, and which he thinks conclusive on the other side, I persuade myself he will change his opinion of it, when he considers, that as one person applying the wire of the charged bottle to warm spirits, in a spoon held by another person, both standing on the floor, will fire the spirits, and yet such firing will not determine whether the accumulation was in the glass or the non-electric; so the placing another person between them, standing on wax, with a bason in his hand, into which the water from the phial is poured, while he at the instant of pouring presents a finger of his other hand to the spirits, does not at all alter the case; the stream from the phial, the side of the bason, with the arms and body of the person on the wax, being all together but as one long wire, reaching from the internal surface of the phial to the spirits.

June 29, 1751. In capt. Waddell's account of the effects of lightning on his ship, I could * See the paper entitled, Farther Experiments, &c.

not but take notice of the large comazants (as he calls them) that settled on the spintles at the top-mast heads, and burnt like very large torches (before the stroke.) According to my opinion, the electrical fire was then drawing off, as by points, from the cloud; the largeness of the flame betokening the great quantity of electricity in the cloud: and had there been a good wire communication from the spintle heads to the sea, that could have conducted more freely than tarred ropes, or mats of turpentine wood, I imagine there would either have been no stroke, or, if a stroke, the wire would have conducted it all into the sea without damage to the ship.

His compasses lost the virtue of the loadstone, or the poles were reversed; the north point turning to the south.- By electricity we have (here at Philadelphia) frequently given polarity to needles, and reversed it at pleasure. Mr. Wilson, at London, tried it on too large masses, and with too small force.

A shock from four large glass jars, sent through a fine sewing-needle, gives it polarity, and it will traverse when laid on water.

If the needle, when struck, lies east and west, the end entered by the electric blast points north.-If it lies north and south, the end that lay towards the north will continue to fire entered at that end, or at the contrary end, point north when placed on water, whether the

needle is struck lying north and south, weakThe polarity given is strongest when the the force was still greater, the south end, enest when lying east and west; perhaps if tered by the fire (when the needle lies north and south) might become the north, otherwise it puzzles us to account for the inverting must always be found in that situation, and of compasses by lightning; since their needles entered the north and went out at the south by our little experiments, whether the blast end of the needle, or the contrary, still the end that lay to the north should continue to point north.

dles are sometimes finely blued like a watchIn these experiments the ends of the neespring by the electric flame.-This colour given by the flash from two jars only, will wipe off, but four jars fix it, and frequenthave had their heads and points melted off by ly melt the needles. I send you some that point melted off, and some part of its head and our mimic lightning; and a pin that had its

neck run.

Sometimes the surface on the body of the needle is also run, and appears blistered when examined by a magnifying glass: the jars I make use of hold seven or eight gallons, and are coated and lined with tin-foil; each of them takes a thousand turns* of a globe nine inches diameter to charge it.

* The cushion being afterwards covered with a long flap of buckskin, which might cling to the globe; and

I send you two specimens of tin-foil melted | may seem to many a little extravagant to between glass, by the force of two jars only. suppose. So we are not got beyond the skill I have not heard that any of your European of Rabelais's devils of two years old, who, he electricians have ever been able to fire gun- humourously says, had only learnt to thunder powder by the electric flame. We do it and lighten a little round the head of a cabhere in this manner:-A small cartridge is bage. B. FRANKLIN. filled with dry powder, hard rammed, so as to bruise some of the grains; two pointed wires are then thrust in, one at each end, the Queries and Answers referred to in the forepoints approaching each other in the middle of the cartridge, till within the distance of half an inch; then, the cartridge being placed in circuit, when the four jars are discharged, the electric flame leaping from the point of one wire to the point of the other, within the cartridge amongst the powder, fires it, and the explosion of the powder is at the same instant with the crack of the discharge.

To Cadwallader Colden,* at New York, com- trics per se, alone contained electric matter in municated to Mr. Collinson.

This proposition is since found to be too general; This gentleman was afterwards lieutenant-go. Mr. Wilson having discovered that melted wax and vernor of New York. rosin will also conduct.

(by the way) shows a new relation between we concluded that the air's elasticity was not metals and water heretofore unknown. affected thereby.

To illustrate this by a comparison, which, however, can only give a faint resemblance. An experiment towards discovering more of Electric matter passes through conductors as water passes through a porous stone, or spreads on their surfaces as water spreads on a wet stone; but when applied to non-conductors, it is like water dropt on a greasy stone, it neither penetrates, passes through, nor spreads on the surface, but remains in drops where it falls. See farther on this head, in my last printed piece, entitled, Opinions and Conjectures, &c. 1749.

Query. What are the effects of air in electrical experiments?

are

the qualities of the electrical fluid. FROM the prime conductor, hang a bullet by a wire hook; under the bullet, at half an inch distance, place a bright piece of silver to receive the sparks; then let the wheel be turned, and in a few minutes, (if the repeated sparks continually strike in the same spot) the silver will receive a blue stain, nearly the colour of a watch-spring.

A bright piece of iron will also be spotted, but not with that colour; it rather seems corroded.

On gold, brass, or tin, I have not perceived it makes any impression. But the spots on the silver or iron will be the same, whether the bullet be lead, brass, gold, or silver.

On a silver bullet there will also appear a small spot, as well as on the plate below it.

Cadwallader Colden, New York.

Mistake, that only Metals and Waters were conductors, rectified.-Supposition of a region of electric fire above our atmosphere.-Theorem concerning Light.-Poke-weed a cure for Can-Read at the Royal Society, of London, Nov. 11, 1756.

cers.

PHILADELPHIA, April 23, 1752. In considering your favour of the 16th past, I recollected my having wrote you answers to some queries concerning the difference be tween electrics per se, and non-electrics, and the effects of air in electrical experiments, which, I apprehend, you may not have received. The date I have forgotten.

Answer. All I have hitherto observed these. Moist air receives and conducts the electrical matter in proportion to its moisture, quite dry air not at all: air is therefore to be classed with the non-conductors. Dry air as sists in confining the electrical atmosphere to the body it surrounds, and prevents its dissipating; for in vacuo it quits easily, and points operate stronger, i. e. they throw off or attract the electrical matter more freely, and at greater distances; so that air intervening obstructs its passage from body to body in some degree. A clean electrical phial and wire, containing air instead of water, will not be charged nor give a shock, any more than if it was filled with powder of glass; but exhausted of air, it operates as well as if filled with water. Yet an electric atmosphere and air do not seem to exclude each other, for we breathe freely in such an atmosphere, and dry air will blow through it without displacing or driving it away. I question whether the strongest dry north-wester would dissipate it. I once electrified a large cork-ball at the end of a silk thread three feet long, the other We have been used to call those bodies end of which I held in my fingers, and whirl'd electrics per se, which would not conduct the it round, like a sling one hundred times in electric fluid; we once imagined that only the air, with the swiftest motion I could such bodies contained that fluid; afterwards sibly give it, yet it retained its electric atmos- that they had none of it, and only educed it phere, though it must have passed through from other bodies: but further experiments eight hundred yards of air, allowing my arm showed our mistake. It is to be found in all in giving the motion to add a foot to the semi-matter we know of; and the distinctions of diamater of the circle.-By quite dry air, I electrics per se, and non-electrics, should now mean the dryest we have: for perhaps we be dropt as improper, and that of conductors never have any perfectly free from moisture. and non-conductors assumed in its place, as I An electrical atmosphere raised round a thick mentioned in those answers. wire, inserted in a phial of air, drives out none of the air, nor on withdrawing that atmosphere will any rush in, as I have found by a curious experiment accurately made, whence

The cold dry wind of North America.

pos

The experiment here mentioned was thus made. An empty phial was stopped with a cork. Through the cork passed a thick wire, as usual in the Leyden experiment, which wire almost reached the bottom. Through another part of the cork passed one leg of a small glass syphon, the other leg on the outside came down almost to the bottom of the phial. This phial was first held a short time in the hand, which, warming, and of course ratifying the air within, drove a

red ink in a tea-spoon was applied to the opening of small part of it out through the syphon. Then a little the outer leg of the syphon; so that as the air within cooled, a little of the ink might rise in that leg. When the air within the bottle came to be of the same temperature of that without, the drop of red ink would rest in a certain part of the leg. But the warmth of a finger applied to the phial would cause that drop to descend, as the least outward coolness applied would make it ascend. When it had found its situation, and was at rest, the wire was electrified by a communica. tion from the prime conductor. This was supposed to give an electric atmosphere to the wire within the bottle, which might likewise rarify the included air, and of course depress the drop of ink in the syphon. But no such effect followed.

I do not remember any experiment by sun's surface, with a swiftness so prodigious! which it appeared that high rectified spirit Must not the smallest particle conceivable will not conduct; perhaps you have made have, with such a motion, a force exceeding such. This I know, that wax, rosin, brim- that of a twenty-four pounder, discharged stone, and even glass, commonly reputed elec- from a cannon? Must not the sun diminish trics, per se will, when in a fluid state, con- exceedingly by such a waste of matter; and duct pretty well. Glass will do it when only the planets, instead of drawing nearer to red hot. So that my former position, that him, as some have feared, recede to greater only metals and waters were conductors, and distances through the lessened attraction. other bodies more or less such as they par- Yet these particles, with this amazing motook of metal or moisture, was too general. tion, will not drive before them, or remove, the least or lightest dust they meet with: and the sun, for aught we know, continues of his ancient dimensions, and his attendants move in their ancient orbits.

Your conception of the electric fluid, that it is incomparably more subtle than air, is undoubtedly just. It pervades dense matter with the greatest ease; but it does not seem to mix or incorporate willingly with mere May not all the phenomena of light be air, as it does with other matter. It will not more conveniently solved, by supposing uniquit common matter to join with air. Air ob- versal space filled with a subtle elastic fluid, structs, in some degree, its motion. An elec- which, when at rest, is not visible, but whose tric atmosphere cannot be communicated at vibrations affect that fine sense in the eye, as so great a distance, through intervening air, those of air do the grosser organs of the ear?" as through a vacuum. Who knows then, but We do not, in the case of sound, imagine that there may be as the ancients thought, a re- any sonorous particles are thrown off from a gion of this fire above our atmosphere, prevent- bell, for instance, and fly in strait lines to the ed by our air, and its own too great distance ear; why must we believe that luminous parfor attraction, from joining our earth? Per- ticles leave the sun and proceed to the eye? haps where the atmosphere is rarest, this fluid Some diamonds, if rubbed, shine in the dark, may be densest, and nearer the earth where without losing any part of their matter. I the atmosphere grows denser, this fluid can make an electrical spark as big as the may be rarer; yet some of it be low enough flame of a candle, much brighter, and, thereto attach itself to our highest clouds, and fore, visible further; yet this is without fuel; thence they becoming electrified, may be at- and I am persuaded, no part of the electric tracted by, and descend towards the earth, fluid flies off in such case to distant places, and discharge their watery contents, together but all goes directly, and is to be found in the with that ethereal fire. Perhaps the aurora place to which I destine it. May not difboreales are currents of this fluid in its own ferent degrees of the vibration of the above region, above our atmosphere, becoming from mentioned universal medium, occasion the aptheir motion visible. There is no end to con-pearance of different colours? I think the elecjectures. As yet we are but novices in this branch of natural knowledge.

tric fluid is always the same; yet I find that weaker and stronger sparks differ in apparent colour, some white, blue, purple, red; the strongest, white; weak ones, red. Thus different degrees of vibration given to the air produce the seven different sounds in music, analagous to the seven colours, yet the me

You mention several differences of salts in electrical experiments. Were they all equally dry? Salt is apt to acquire moisture from a moist air, and some sorts more than others. When perfectly dried by lying before a fire, or on a stove, none that I have tried will con-dium, air, is the same. duct any better than so much glass.

New flannel, if dry and warm, will draw the electric fluid from non-electrics, as well as that which has been worn.

I wish you had the convenience of trying the experiments you seem to have such expectations from, upon various kinds of spirits, salt, earth, &c. Frequently, in a variety of experiments, though we miss what we expected to find, yet something valuable turns out, something surprising, and instructing, though unthought of.

I thank you for communicating the illustration of the theorem concerning light. It is very curious. But I must own I am much in the dark about light. I am not satisfied with the doctrine that supposes particles of matter called light continually driven off from the

If the sun is not wasted by expenditure of light, I can easily conceive that he shall otherwise always retain the same quantity of matter; though we should suppose him made of sulphur constantly flaming. The action of fire only separates the particles of matter, it does not annihilate them. Water, by heat raised into vapour, returns to the earth in rain; and if we could collect all the particles of burning matter that go off in smoke, perhaps they might, with the ashes, weigh as much as the body before it was fired: and if we could put them into the same position with regard to each other, the mass would be the same as before, and might be burnt over again. The chymists have analysed sulphur, and find it composed, in certain proportions, of oil, salt, and earth; and having, by the analysis, disco