Franklin and Lightning
A LONGER and more comprehensive caption would be ‘What did Benjamin Franklin know about thunderstorms, and what do we know to-day?’ A flash of lightning, like any other flash, holds the eye and compels attention. But, as in case of the spurt of light when a gun is fired, we listen for the report; and later give some thought to the size and make of the gun, and perhaps to its deadliness as a weapon. So, then, we can best study lightning in connection with its source, the thundercloud; and to understand that better we must go back to the storm of which cloud, flash, and report are but incidents.
Briefly, lightning is an equalization of electric strain along a given atmospheric path. It has been defined by our leading American authority on lightning, Dr. F. W. Peek, as an electrical explosion. He should know, for, like Jove, he is keeper of the thunderbolts, what we may call ‘near lightning.’ In the high-voltage laboratory of the General Electric Company at Pittsfield, Massachusetts, one can see the outcome of years of work with various ten-foot-long lowbrow streaks of lightning, deadly enough to suit the most carping critic. These are summoned, measured for the work in hand, and then sent forth to do it.
Truly this gives a categorical answer to one of the questions that stumped poor old sore-troubled Job: ‘Canst thou send lightnings, that they may go, and say unto thee, Here we are?’ At Pittsfield and also at Schenectady the answer is: ‘Yes! We can send them with voltage of a million and current of ten thousand amperes giving for short periods a power of several million kilowatts. And a kilowatt is considerably more (33 per cent) than a horse power. These flashes are warranted to split large wooden posts, puncture metal, break down air and water gaps, give such snappy reports that the listener jumps, and in brief do all the things that a not entirely grownup flash of lightning can do!' And it is not conducive to long life to stand near them.
While we may accept the definition given above, —the electrical explosion, — which does define the flash itself, perhaps a better conception is given by antedating the flash a little and picturing a state of strain in the dielectric, the air, followed by a break or rupture and a quick readjustment. Indeed a lightning flash may be said to resemble an earthquake, for the latter is only a slip along an earth fault-line or path of previous fracture. So, in a way, a Hash is to the air what the sudden break is in the earth crust. Furthermore, just as the seismograph picks up the feeble tremors or waves of earth motion, so the break in the air causes electromagnetic waves in the ether (if there be one) and these are picked up in places far distant by radio receivers. Thus a severe thunderstorm in the heart of Africa may cause stutter and splutter in the Sundayafternoon sermon broadcast from Brooklyn or elsewhere. If on the golden sands of Africa’s sunny fountains the heathen could turn on thunderstorms at pleasure (and enough of them), they could (and perhaps would) muffle, muddle, and muzzle all the missionary sermons of the wide, wide world.
But Franklin knew naught of this, He invented, discovered, and suggested much in science, particularly in the field of electricity; but even his most admiring followers — and we are in that class — cannot claim that he heard the first radio-message. And yet, in some of his experiments with Leyden jars, we of to-day can see operating the same etheric wave-transmission which makes radio possible.
And what is a Leyden jar?
Ten years before Braddock was defeated and a young volunteer officer named Washington saved the retreating column from total destruction, someone in Pomerania made a glass jar with a cork pierced by a long nail. When the jar was half-filled with water and held in the hand, it could be brought near the pole of an electrostatic machine and charged. Removing the hand and touching the head of the nail produced a little spark and a feeble shock. Later, metallic coatings inside and outside were used instead of water.
Writing from Philadelphia to Peter Collinson, Esq., F. R. S., London, on March 28, 1747, Benjamin Franklin, Esq., says: —
Your kind present of an electric tube with directions for using it, has put several of us [meaning the Library Company started by Franklin in 1730, when he was twenty-four years old] on making electrical experiments in which we have observed some particular phenomena that we look upon to be new.
He promises to communicate details in a later letter, saying that probably someone on that side of the water has hit on the observations. He ends with a sentence in which we read a forecast of much that did come to pass: —
For my own part I never was before engaged in any study that so totally engrossed my attention and my time, as this has lately done; for what with making experiments when I can be alone, and repeating them to my Friends and Acquaintances, who from the novelty of the thing, come continually in crowds to see them, I have during some months past had little leisure for any thing else.
Oh, rare old Ben! Even then a public character, disseminating knowledge.
April, May, and June passed without the promised letter; but during the second week in July Franklin found time to write, and almost in the opening sentence says: —
The first is the wonderful effects of pointed bodies both in drawing off and throwing off the electrical fire.
This discovery, if such it can be called, long dominated Franklin’s views on the nature of electricity. Strangely enough he did not himself devise the experiment demonstrating the ‘throwing off’ effect. His esteemed and ingenious friend, Mr. Thomas Hopkinson, discovered this by chance and communicated it to Franklin. There were also certain experiments with pinwheels (Yes! Newton played with soap bubbles and Franklin played with pinwheels; both to some purpose) which seemed to show an afflux and an efflux of electricity. These did not originate with Franklin, but were made and communicated by another of his ‘worthy and ingenious friends,’ Mr. Philip Syng. Evidently the Library Company had an open season, that spring, hunting this new electrical fire, coaxing it from glass globes rubbed on leather cushions, bottling it in coated jars, chasing it away from insulated shot, always sparking, tickling, shocking themselves or admiring friends.
With all their astuteness and originality they failed, however, to detect the discharging power of a certain kind of light, — the ultra-violet rays,— though they did reflect sunlight from a mirror and found that it produced no result. They also tried light from an open fire and found that it did rob the charged cork ball; but later concluded that, as with smoke from a candle, it was the current of smoky air which facilitated the discharge. But the greatest entertainment was in ‘electrising’ — Franklin’s word for our electrifying — themselves and others. One person stood on wax and rubbed the tube, which was of green glass, about twenty-seven or thirty inches long. Another person on wax drew the fire. Both were thus electrified; and a third person standing on the floor could present his knuckle and get a spark from each. And so they tried to puzzle out the problem which has required one hundred and seventy-eight years to answer, and still is not entirely solved: ‘What is electricity? ‘
Small wonder these Colonial physicists could not give a satisfactory answer. It is only within the past five years that an acceptable explanation of electric force has been obtained. The underlying conceptions are entirely at variance with those held for a century. Only now is man beginning to understand the true nature of electricity. What is known as the quantum theory provides the clue, and the structure of matter is as an open book to those who can follow the processes of radiation and energy-transfer in the orbits of electrons.
The luminiferous ether and the Newtonian law of attraction wave us a farewell greeting with classical dynamics and physics as they all depart from the heights they Held so long and so well. Sic transit gloria mentis; the greatest generalizations of the human mind give way to modern requirement.
But back to our Colonial experimenters.
‘As the vessel is just upon sailing,’ writes Franklin, ‘I can not give you so large an account of American Electricity as I intended.’ Note the word ‘American.’
In a brilliant lecture (Sixteenth Kelvin, February 5, 1925, Institute of Electrical Engineers, London) Jeans notes the difference between the engineering type of mind of Britain and the more metaphysical Continental mind. It was something more than a coincidence that Newton, Kelvin, Maxwell, and Faraday were all British, while Boscovich, Einstein, Bohr, and Weyl are not. One wonders who best represent the American type. Franklin, Edison, Thomson, Steinmetz!
Our earliest investigators had a certain humor of gallantry. They developed the electric kiss. Thus, let a gentleman and lady stand on wax, one holding the electric phial. Let them kiss. When their lips approach, ‘they will be struck and shocked.’ They made counterfeit spiders of burnt cork and linnen (sic) thread; and these wriggled their legs ‘in a very entertaining manner.’ And finally the ‘ worthy and ingenious ‘ Mr. Syng made a simple and effective electrical machine, because the Europeans used a heavy, clumsy affair which made rubbing the tube a fatiguing exercise.
Then on September 1, 1747, Franklin could not forbear writing another letter to Collinson about M. Muschenbroek’s wonderful bottle. He finds that the electrical fire is ‘crowded into the substance,’ that is, the glass; and he begins to talk about positive and negative electricity.
Now appears upon the scene another experimenter, the ‘ingenious’ Mr. Kinnersley. Why Franklin dropped the ‘worthy,’ we know not, for they were good friends; and Kinnersley loaned him a large electrical machine. They made magical pictures. ‘Having a large metzotinto with a frame and glass, suppose of the KING (God preserve him) take out the print.’ Then follow minute directions about pasting gold leaf. We wonder what he really meant when he adds, ‘ Hold the picture horizontally by the top and place a little moveable gilt crown on the king’s head.’ (This time king is in lower case.) Evidently kings arc not different from other people when it comes to electrical shocks. The picture being electrified, if a person touched the inside gilding with one finger and with his free hand tried to take off the crown, he would ‘receive a terrible blow and fail in the attempt.’ Surely a satisfactory result to all good royalists. If the picture was big enough and highly charged the consequence might perhaps be as fatal as that of high treason. Oh, rare old Ben! But at any event they were able, in 1750, to kill a hen. (Whether the hen remained killed, our philosopher fails to mention. In all likelihood the bird got up after being stunned and indulged in choice hen profanity regarding the experiment.)
Then, hot weather coming on, it is proposed to put an end to the experiments for this season ‘somewhat humourously in a party of pleasure on the banks of the Skuylkil. ... 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 bumpers under the discharge of guns from the electrical battery
Oh, rare old Ben! Where were the Prohibition agents? Notice that the bottle and bumpers were electrified while all the rest of the outfit was only electrical.
And now we come to thundergusts. There is no date to the long letter, written perhaps in 1749, but there is one sentence which is characteristic. Franklin was ever awake to natural phenomena. He set forth the view that after a thunderclap the concussion or jerk given to the air shook down the rain, not only from the two clouds, but from others near them. This makes Franklin the Father of Rainmakers. It does seem as if rain-gushes were caused by thunder. Such seeming relationships die hard; and there are still many who believe that concussion produces rain. We know, however, that it has no such effect.
In the long letter of July 1750 he draws the conclusion that ‘ the fire of electricity and that of lightning are the same.’ And he proposes an experiment. On the top of some high tower, place a sentry-box big enough to hold a man and an electric stand. An iron rod passes up thirty feet, pointed very sharp at the end. The rod is to draw the fire from the cloud and the sparks are to electrify the man. There is much more — many, many pages — and he concludes: —
But I shall never have done if I tell you all my conjectures, thoughts and imaginations on the nature and operations of this electric fluid.
There are some strange entries in the letters of 1750. One, dated July 1750, contains matters which were reported to Franklin only in June 1751. Probably a letter was begun one year and not finished until the following year.
It is evident, however, that in 1751 Franklin had clear-cut ideas of the power of lightning, for he wrote to C. C. Esq. at New York (Colden?), though he was exceedingly busy. He thinks the greatest known effects of common lightning may be exceeded. Who but rare old Ben would have dared to say that? But as yet this has not been done.
So we are got beyond the skill of Rabelais’s devils of two years old, who he humorously says had only learned to thunder and lighten a little round the head of a cabbage.
In the spring of 1752, Franklin at Philadelphia and Kinnersley at Boston were busy discussing certain experiments with the latter’s sulphur-globe machine, which he loaned in February to Franklin.
In the meantime the Opinions and Conjectures had borne fruit. In Europe the suggestion of drawing sparks from the iron rod in the high sentry-box appealed to certain French investigators. At Marly on March 10, 1752, at 2.20 P.M., as a storm cloud passed overhead, the iron rod was touched by the finger of the insulated man. Sparks were seen. M. de Lor then erected a rod ninety-nine feet high, and on May 18 was able to get sparks. But the strongest sparks occurred without either thunder or lightning. Little did he suspect, when the sparks were seen during t he space of an Ave and a Pater, that he was receiving the first radiomessage. Far-distant flashes of lightning were broadcasting their signals, and this rough but effective antenna picked up the impulses. The sun soon shone out clear and the sparks ceased. The experimenters on radio transmission during the solar eclipse of January 24, 1925, will please note this earliest of experiments on fading.
London did not propose to lag behind Paris; and so W. Watson, F.R.S., tried to get sparks. There was, however, only one thunderstorm that summer and it contributed nothing, for the rain wet the apparatus and there were no sparks. But the worthy Mr. Canton had better luck. On the same July afternoon, with a tin tube and wires, he felt and heard sparks after the third or fourth thunderclap; but these grew weaker and ceased in two minutes. These reports wore published in due time in European newspapers. The printed accounts could hardly have reached Philadelphia in less than two months and it was after this that the famous kite-experiment was proposed. It is evident that the date June 1752, sometimes given (as in the Britannica), is of doubtful authenticity. Franklin made no mention in his own paper, the Pennsylvania Gazette, of any kind of kite-experiment until October 19, 1752, when the same letter addressed to Peter Collinson appears with minor alterations to suit home consumption. In this letter he does not explicitly say that he himself flew a kite, and the letter as a whole, particularly the latter sections, states only what may be done.
This is not to be regarded as unusual or in any way prejudicial to his fame as a scientist, for he generally followed this method. In August 1752, writing
to Dr. B—of Boston, in connection
with inoculation against smallpox, he said: —
Business sometimes obliges one to postpone philosophical amusements. Whatever I have wrote of that kind are really as they are entitled but Conjectures and Suppositions. . . .
And again, —
I own I have too strong a penchant to the building of hypotheses. They indulge my natural indolence. . . .
A concluding sentence in this smallpox correspondence has a direct appeal to some of us: —
I am sorry to hear that the number of your inhabitants decreases.
Well, he himself at the age of seventeen decreased the population of Boston by walking away from the city of his birth toward Philadelphia, the city of his adoption. In his will he remembered both cities generously.
Whether Franklin ever flew kites during thundergusts is uncertain, and it is greatly to be wished that some corroborative evidence by someone who saw these flights may yet be found in old journals and diaries. It is strange that Kinnersley, lecturing in various cities, made no mention of what would have been a capital experiment. Franklin himself apparently thought little of it, although in his autobiography he speaks of it as a capital experiment. It is hard to believe that emphasis would not have been placed upon both date and place at the time. Dr. Stuber’s story, which is the basis of the popular conception of the experiment, contains so many contradictions that it is charitable to regard it as the recollection of one old man concerning what another old man told him about something that happened a long time ago.
However, whether Ben did or did not fly kites during thunderstorms is not of much consequence; for his fame is secure and he well deserved the recognition accorded him for his work in electricity. There is an artistic element in the popular conception, mythical though it be. There is a suggestion of Prometheus stealing the fire of Heaven. Poor Prometheus paid the penalty for his temerity. So, for defying the lightning, did Ajax the Lesser — or the Greater, for Ajax seems to have been a big chief away from home, and a small person at home. But Benjamin in due time became the hero of the schoolbook. Rare old Ben, how he would be amused at being thus featured!
Contrary to popular belief and textbook statements, the identification of lightning as electricity was not determined by any kite-experiment. Franklin himself demonstrated this two years earlier than the date of doubtful authenticity given above, June 1752. It was this which led to the conception of the lightning rod in 1750. The function of the rod was to draw off the charge. The effect was illustrated by a pasteboard tube, an iron punch on the floor, a pair of scales, an electrical machine, a wire, and a needle. And rods had been placed upon the Academy and Statehouse spires previous to the experiments in France, and of course previous to the suggestion of using a kite.
Franklin speculated much on the nature of thunderclouds. He studied the effects of lightning and gave sensible advice. Indeed nearly all of his directions for behavior have stood the test of time. His speculations, however, have not, nor is it to be expected that they should. But through it all runs a vein of humor, as when he says: —
I must own I am much in the dark about light.
Someone may ask, ‘Is it possible to fly kites in a thunderstorm?’ The answer is: ‘It is exceedingly dangerous.’ It has been done and the experimenters have escaped. On the other hand, when kites could not be reeled in quickly enough with the approach of the storm, fatalities have resulted. One experience may be briefly given here. (A more detailed account can be found in the Popular Science Monthly, October 1897, p. 739.) August 9, 1892, at Blue Hill Observatory, a kite was sent up at 11 A.M. and kept in the air until after dark. A thunderstorm developed about sunset, but still far in the west. Whenever a finger was held near the insulated kite-wire, there was a perfect fusillade of sparks. As the storm drew near, the incessant sizzling and sparking threatened to burn out the large multiple quadrant electrometer used to measure the voltage. As the Observatory might be jeopardized, one of the four men present proposed to cut the kite string, which was wired, and let the kite go. To touch the string was to receive a severe shock. One of the party broke the connection between the electrometer and the Mascart insulators. As he did this, the others outside saw a flash in the west. The one inside saw only a brilliant flare-up in the electrometer and felt a severe blow across both arms. The kite wire was finally grounded. The flash which was nearest to the Observatory was, so far as could be ascertained, 4500 feet distant; and so the discharge which the observer felt must have been either an induced current or perhaps one of the many minor discharges which branch out from the main or trunk line discharge.
On other occasions steel kite-wire has been fused, men severely shocked, kite destroyed, and everybody thankful to have escaped alive.
Lightning is not an ordinary battery or dynamo current. It does not obey the usual law of ohmic resistance. The time curve of discharge has a very steep front; and consequently there are many peculiar effects, not like those of ordinary currents.
And there are all kinds of thunderstorms. Some pass quickly and do little damage. Some more slowly and do much damage. In London on July 9 and 10, 1923, a remarkable storm occurred, and during the six hours of its duration 6924 flashes were recorded. At the present price of ten cents per kilowatt hour, the bill for energy at two dollars per flash for this storm would have been $13,848.00.
The schoolboy’s definition of the difference between lightning and electricity is ‘You don’t have to pay for lightning.’
What, then, should one do or not do during thunderstorms? Remembering that the Law and Commandments were given on Sinai after a severe thunderstorm, we may paraphrase the Decalogue as follows: —
1. Thou shalt not be overanxious. There are a thousand flashes that do not strike mortals for one that does.
2. Thou shalt not fear horizontal flashes.
3. Thou shalt not stand out in the open (not attempt to fly kites). Nor remain on the beach, nor in an open field. Get hence.
4. Thou shalt not stand under a tree with thick foliage — more people are killed in this way than any other — nor in the doorway of a barn or at a window in proximity to a chimney.
5. Thou shalt not laugh at thy maiden aunt’s nervousness during a storm. It does not help.
6. Thou shalt not tie stock to wire fences.
7. Thou shalt not go to bed or try to stand on glass. There is not one chance in ten thousand of thy being injured in an ordinary residence.
8. If thou art near a person who has been struck, thou shalt make every effort to restore him to consciousness. Try artificial respiration. Don’t give up. Get a doctor as soon as possible.
9. Antennae of radio outfits should be grounded outside. Aerials are sometimes struck and wires melted, and fires may thus be started.
10. If thou art in a trolley car and fuses burn out, try to keep calm. The danger is over and, while it is unpleasant, thou art more frightened than hurt. Finally, if thou livest in the country, get good lightning-rods on thy house and barn. Dwellings in city blocks, however, are practically immune. When traveling in automobiles, do not. stop under trees, nor remain at rest on hilltops.