Volume Ii Part 19 (1/2)
If the picture were highly charged [he said], the consequence might perhaps be as fatal as that of high treason.
The operator [he continues], who holds the picture by the upper end, where the inside of the frame is not gilt, to prevent its falling, feels nothing of the shock, and may touch the face of the picture without danger, which he pretends is a test of his loyalty. If a ring of persons take the shock among them, the experiment is called _The Conspirators_.
Another far more significant exploit was the application of electrical energy in such a way as to set an electrical Jack revolving with such force and swiftness as to carry a spitted fowl around before a fire with a motion fit for roasting.
This wheel was driven by an electrical battery, but Franklin also devised what he called a self-moving wheel that was, by a different electrical method, revolved with so much force and rapidity that he thought that it might be used for the ringing of chimes and the movement of light-made orreries. And after observing that a thin gla.s.s bubble, about an inch in diameter, weighing only six grains, being half filled with water, partly gilt on the outside, and furnished with a wire hook, gave, when electrified, as great a shock as a man can well bear, Franklin exclaims, ”How great must be the quant.i.ty (of electrical fire) in this small portion of gla.s.s! It seems as if it were of its very substance and essence. Perhaps if that due quant.i.ty of electrical fire so obstinately retained by gla.s.s, could be separated from it, it would no longer be gla.s.s; it might lose its transparency, or its brittleness, or its elasticity.”
This letter also reaches the conclusion that bodies, having less than the common quant.i.ty of electricity, repel each other, as well as those that have none.
It concludes with a lively paragraph:
Chagrined a little that we have been hitherto able to produce nothing in this way of use to mankind; and the hot weather coming on, when electrical experiments are not so agreeable, it is proposed to put an end to them for this season, somewhat humorously, in a party of pleasure on the banks of _Skuylkil_. Spirits, at the same time, are to be fired by a spark sent from side to side through the river, without any other conductor than the water; an experiment which we some time since performed, to the amazement of many. A turkey is to be killed for our dinner by the _electrical shock_, and roasted by the _electrical jack_, before a fire kindled by the _electrified bottle_; when the healths of all the famous electricians in _England_, _Holland_, _France_ and _Germany_ are to be drank in _electrified b.u.mpers_, under the discharge of guns from the _electrical_ battery.
An electrified b.u.mper, a note to the letter explained, was a small thin gla.s.s tumbler, nearly filled with wine, and charged, which, when brought to the lips of a person, gave him a shock, if he was close-shaved, and did not breathe on the liquor. Another note states that the biggest animal that the experimenters had yet killed was a hen.
A later letter to Collinson on the phenomena of thunder-gusts takes Franklin away from the Leyden Jar of the laboratory to the stupendous batteries of the outer universe--from the point of a bodkin to the lofty natural or artificial objects, upon which lightning descends from the illimitable sky. ”As electrified clouds pa.s.s over a country,” he remarks, ”high hills and high trees, lofty towers, spires, masts of s.h.i.+ps, chimneys, &c., as so many prominencies and points, draw the electrical fire, and the whole cloud discharges there.” From this observation to the lightning rod was but a short step.
Another letter to Collinson in the succeeding year brings us to the lightning rod in principle if not in name. Speaking of what a sea captain had said of luminous objects, which had settled on the spintles at the topmast heads of his s.h.i.+p before an electrical shock, and burned like very large torches, he says:
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 quant.i.ty 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 masts 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 s.h.i.+p.
In the same letter, there is an adumbration of his grandest experiment, when he speaks of the flash from two of his jars as ”our mimic lightning.”
This letter also shows that with electricity Franklin had frequently imparted polarity to needles and reversed it at pleasure. Wilson, at London, he said, had failed to produce these results because he had tried it on too large ma.s.ses and with too small force. The letter also evidences the fact that he had employed the electric spark for the practical purpose of firing gunpowder.
Another letter to Collinson dated July 29, 1750, is accompanied by an additional paper on the properties and effects of the Electrical Matter. It acknowledges the debt that Franklin owed to Collinson for the gla.s.s tube and the instructions which attended it, and to the Proprietary for the generous present of a complete electrical apparatus which ”that bountiful benefactor to our library,” as he calls him, had made to it. The telegraph, the Marconi tower, the telephone, the electric bulb, the electric automobile and the trolley car rise up before us when we read this observation in the paper that accompanied the letter: ”The beneficial uses of this electric fluid in the creation, we are not yet well acquainted with, though doubtless such there are, and those very considerable.” The paper is the most important that Franklin ever wrote on electricity; containing as it does the two suggestions which, when carried into execution, made his name famous throughout the world, that is to say, his suggestion, already quoted by us at length, that houses, churches and s.h.i.+ps might be protected by upright rods of iron, and his suggestion, already quoted by us, too, as to how the ident.i.ty of lightning and electricity could be established. The point of the bodkin and the electrified shot and ball, and the mimic brightness, agility and fury of the lurking fire in the wonderful bottle had led, step by step, to two of the most splendid conceptions in the early history of electrical science.[54]
With the discovery that electricity and lightning were the same thing, the real achievements of Franklin in the province of electricity came to an end. But he still continued his electrical experiments with undiminished ardor. We find him on one occasion prostrating with a single shock six persons who were so obliging as to lend themselves to the pursuit of scientific truth. Twice he was the victim of his own inadvertence. Speaking of one of these occasions, in a letter to a friend in Boston, he said:
The flash was very great, and the crack as loud as a pistol; yet, my senses being instantly gone, I neither saw the one nor heard the other; nor did I feel the stroke on my hand, though I afterwards found it raised a round swelling where the fire entered, as big as half a pistol-bullet; by which you may judge of the quickness of the electrical fire, which by this instance seems to be greater than that of sound, light, or animal sensation.... I then felt what I know not how well to describe; a universal blow throughout my whole body from head to foot, which seemed within as well as without; after which the first thing I took notice of was a violent quick shaking of my body, which gradually remitting, my sense as gradually returned, and then I thought the bottles must be discharged, but could not conceive how, till at last I perceived the chain in my hand, and recollected what I had been about to do. That part of my hand and fingers, which held the chain, was left white, as though the blood had been driven out, and remained so eight or ten minutes after, feeling like dead flesh; and I had a numbness in my arms and the back of my neck, which continued till the next morning, but wore off. Nothing remains now of this shock, but a soreness in my breast-bone, which feels as if it had been bruised. I did not fall, but suppose I should have been knocked down, if I had received the stroke in my head. The whole was over in less than a minute.
On the second occasion, while making ready to give a healing shock to a paralytic, he received a charge through his own head. He did not see the flash, hear the report or feel the stroke.
When my Senses returned [he told Jan Ingenhousz], I found myself on the Floor. I got up, not knowing how that had happened. I then again attempted to discharge the Jars; but one of the Company told me they were already discharg'd, which I could not at first believe, but on Trial found it true. They told me they had not felt it, but they saw I was knock'd down by it, which had greatly surprised them. On recollecting myself, and examining my Situation, I found the Case clear. A small swelling rose on the Top of my Head, which continued sore for some Days; but I do not remember any other Effect good or bad.
One of Franklin's contemporaries, Professor Richmann, of St. Petersburg, did not fare so well; for a stroke of the lightning that he had allured from the clouds brought his life to an end. Priestley, however, seems to have regarded such a death as a form of euthanasia. At any rate, in speaking of this martyr of science in his _History of Electricity_ he terms him ”the justly envied Richmann.”
After Franklin learned how to impound lightning, his intercourse with electricity was more familiar than ever.
In September, 1752 [he wrote to Collinson], I erected an iron rod to draw the lightning down into my house, in order to make some experiments on it, with two bells to give notice when the rod should be electrify'd: a contrivance obvious to every electrician.
I found the bells rang sometimes when there was no lightning or thunder, but only a dark cloud over the rod; that sometimes, after a flash of lightning, they would suddenly stop; and, at other times, when they had not rang before, they would, after a flash, suddenly begin to ring; that the electricity was sometimes very faint, so that, when a small spark was obtain'd, another could not be got for some time after; at other times the sparks would follow extremely quick, and once I had a continual stream from bell to bell, the size of a crow quill: Even during the same gust there were considerable variations.
In the winter following I conceived an experiment, to try whether the clouds were electrify'd _positively_ or _negatively_.
The result of these experiments, conducted with Franklin's usual painstaking completeness, was the conclusion on his part that thunder-clouds are, as a rule, in a negatively electrical state, and that, therefore, generally speaking, they do not discharge electricity upon the earth, but receive it from the earth. For the most part, he said, ”_tis the earth that strikes into the clouds, and not the clouds that strike into the earth_.”
The thoroughness with which he addressed himself to the study of electricity was very marked. His investigation was as searching and minute as that of an anatomist engaged in the dissection of nervous tissue. Under his hands, the bare Leyden Jar became a teeming storehouse of instruction and amus.e.m.e.nt. He collected electricity from common objects by friction, he brought it down from the sky, he sought its properties in amber, in the tourmaline stone, in the body of the torpedo; he thought that he discerned it in the radiance of the Aurora Borealis. He put it through all its vagaries, juggled with it, teased it, cowed it until it confessed its kins.h.i.+p with the tempestuous heavens. He tested its destructive effects upon hens and turkeys, its therapeutic value to paralytic patients, its efficacy as a corrective of tough meat. He even, it is said, charged the railing under his windows with it to repel loafers standing about his front door. And, in his relations to electricity, as to everything else, his purposes were always those of practical utility. In one of his papers, he admits that he cannot tell why points possess the power of drawing off the electrical fire;
nor is it of much importance to us [he adds] to know the manner in which nature executes her laws. 'Tis enough if we know the laws themselves. 'Tis of real use to know that china left in the air unsupported will fall and break; but _how_ it comes to fall, and _why_ it breaks, are matters of speculation. 'Tis a pleasure indeed to know them, but we can preserve our china without it.
He antic.i.p.ated, or, in some instances, all but antic.i.p.ated, several of the more important discoveries of modern electrical science. He knew that, when a number of Leyden jars are connected up under certain conditions, the extent, to which each jar can be charged from a given source, varies inversely as the number of jars. For a time, he was puzzled by the fact that the light of a candle, or of a fire-coal, or of red-hot iron, would destroy the repellency between his electrified ball and shot, but that the light of the sun would not. But it was not long before he hit upon this ingenious explanation:
This different Effect probably did not arise from any difference in the light, but rather from the particles separated from the candle, being first attracted and then repelled, carrying off the electric matter with them; and from the rarefying the air, between the glowing coal or red-hot iron, and the electrised shot, through which rarefied air the electric fluid could more readily pa.s.s.