Volume 2 — CHAPTER IV

Franklin as a Man of Science

Franklin, as we have said, was primarily a man of action. If we do not always think of him as deeply involved in what Goethe calls "being's ocean, action's storm," it is only because he moved from appointed task to appointed task with such frictionless self-command and ease. But, throughout his life, his mind was quick to make excursions into the domain of philosophical speculation and experiment, whenever business cares or political responsibilities allowed it to do so. Poor Richard would seem to have little in common with Prometheus, but Prometheus, if Condorcet is to be believed, as well as Poor Richard, Franklin was; to say nothing of other transmigrations. That his interest in natural phenomena began at a very early age, is disclosed by his Journal of a Voyage from London to Philadelphia in 1726, when he was in his twenty-first year. Throughout the course of this voyage, his faculties were intently concentrated upon all the marvels of the sea and its setting. With sedulous minuteness, he registers the state of the winds each day, and records the impression made on him by every object with a secret at its heart, to be plucked out by an inquisitive mind. A lunar rainbow, an eclipse of the sun, which darkened ten twelfths of his disk, an eclipse of the moon, which spread over six digits of her surface, dolphins in their bright mail of mixed green, silver and gold, a shark moving around the ship in a slow, majestic manner, and attended by an obsequious retinue of pilot fish, schools of harried flying fish, groups of young crabs, clinging to seaweeds, with indented leaves about three quarters of an inch long, and small yellow berries filled with nothing but wind, a white, tropical bird, said never to be seen further north than latitude 40, and marked by short wings and a single tail feather, other birds, too near the western continent not to be Americans, are among the things that the open-eyed and thoughtful youth jotted down in his Journal in terms that plainly enough indicated not only the eager curiosity but the exactitude of a future man of science. As almost always, the child was but the father of the man. Upon each of his subsequent six voyages across the Atlantic, Franklin exhibited the same, though severer, and more practised, vigilance in observing everything that the ocean, including the instruments of commerce afloat on it, have for a penetrating and suggestive intelligence. How essentially he was a man of science, is demonstrated by the fact that, whenever he was on the element, where alone he could hope for exemption from the political demands of his countrymen, his intellect turned at once with ardor to the study of Nature. Old and feeble as he was, he wrote no less than three valuable dissertations on his last voyage across the Atlantic, one on the causes and cure of smoky chimneys, one on his smoke-consuming stove, and a third, distinguished by an extraordinary wealth of knowledge and observation, on the construction, equipment and provisioning of ships, and the winds, currents and temperature of the sea; which was accompanied by valuable thermometric tables, based upon observations made by him during three of his transatlantic voyages. The maritime essay was written with the closest regard to detail, and contains such a mass of information and luminous comment as has rarely been condensed into the same space. It makes up some thirty-four quarto pages of Smyth's edition of Franklin's works, exclusive of the thermometric notes. The other two essays occupy some forty-nine pages more. All three are elucidated by numerous explanatory charts and illustrations, and are marked by the mastery of scientific principles, which no mere artificer or artisan could have displayed in discussing such topics; but, at the same time, they could not have been more intensely practical, as respects minutiæ of construction, if Franklin had been a professional sailor, mason or stove-maker. The maritime observations range from the Chinese method of dividing the hulls of vessels into separate compartments, which is now regarded as one of the most efficient devices for securing the safety of ocean greyhounds, to an inquiry into the reason why fowls served up at sea are usually too tough to be readily masticated and the best means of dishing soup on a rolling and pitching vessel.

After his return in his youth from London to Philadelphia, Franklin was for a long time too much immersed in business and civic projects to give much attention to natural phenomena. "Why does the flame of a candle tend upward in a spire?", "whence comes the dew, that stands on the outside of a tankard that has cold water in it in the summer time?", are among the few questions of a scientific nature that he appears to have framed for the discussions of the Junto; and they are elementary enough. But with the coming of pecuniary ease, the natural bent of his mind soon asserted itself. While in Boston in 1746, he happened to see some electrical experiments performed by a Dr. Spence, who had recently arrived from Scotland. They were clumsily conducted, but crude as they were, they filled his mind with mixed sensations of surprise and delight; so much so that, when, shortly after his return to Philadelphia from Boston, the Library Company found itself the owner of a glass tube, for the production of electricity by friction, given to it by Peter Collinson, then a Fellow of the Royal Society of London, with instructions for its use, he eagerly availed himself of Collinson's generosity to repeat the experiments that he had witnessed at Boston, and, by continuous practice, became very expert in making them as well as others. Indeed, his house was soon overrun to such an extent with eager visitors that he was compelled in self-defence to relieve it of its congestion by supplying some of his friends with similar tubes blown at the Philadelphia glass-house. One of these friends was his ingenious neighbor, Kinnersley, who chanced at the time to be out of business. Franklin advised him to exhibit the experiments for profit, and followed up the advice by preparing two lectures for him, in which the details of the experiments were clearly set forth. Kinnersley himself employed skilled workmen to make the necessary electrical apparatus for him, modelled upon the rough agencies designed by Franklin for himself, and used in his own exhibitions. The lectures, when delivered by him in Philadelphia, were so well attended that he made a tour of all the chief towns of the Colonies with a considerable degree of pecuniary success. Some years later, similar instructions given by Franklin to Domien, a Greek priest, proved so useful to him on a long tramp that he wrote to his benefactor that he had lived eight hundred miles upon electricity, and that it had been meat, drink and clothing to him. When Franklin last heard from him, he was contemplating a journey from Havana to Vera Cruz, thence through Mexico to Acapulco, on its western coast, and from Acapulco to Manila, and from Manila through China, India, Persia and Turkey to his home in Transylvania; all with electricity as his main viaticum.

Franklin's own experiments fortunately ended in something better than vagabondage, however respectable or profitable. Grateful to Collinson for his timely gifts, he wrote to him several letters, laying before him the results of the Philadelphia experiments. Collinson procured for these letters the privilege of being read before the Royal Society, where they did not excite enough notice to be printed among its Transactions. Another letter, one to Kinnersley, in which Franklin propounded the identity of lightning and electricity, he sent to Dr. Mitchell, an acquaintance of his, and also a member of the Royal Society, who replied by telling him that it had been read before the Society, but had been laughed at by the connoisseurs. Then it was that the happy obstetric suggestion of Dr. Fothergill that the letters were of too much value to be stifled led Collinson to gather them together for publication by Cave in the Gentleman's Magazine. They were not published in this magazine, but Cave did bring them out in pamphlet form with a preface by Dr. Fothergill. The event showed that he and the general public had more acumen than the sages of the Royal Society, for the letters, when subsequently published in a quarto volume, with additions by Franklin, ran through five editions, without the cost of a penny to Cave for copyright. It was from France, however, that they first received the full meed of prompt approbation that they deserved. A copy of them happened to fall into the hands of Buffon, who prevailed upon D'Alibard to translate them into French. Their publication in that language provoked an attack upon them by the Abbé Nollet, Preceptor in Natural Philosophy to the Royal Family, and the author of a popular theory of Electricity. At first, the Abbé could not believe that America was capable of producing such letters, and insisted that they must have been fabricated at Paris for the purpose of discrediting his system. In fact, he even doubted whether there was such a person as Franklin, but, afterwards, being convinced upon that point, he published a volume of letters, mainly addressed to Franklin, in which he defended his own theory, and denied the accuracy of Franklin's experiments and conclusions. Le Roy, of the Royal Academy of Sciences, rejoined on behalf of Franklin, who had decided to let the truth be its own champion, and easily refuted the Abbé. The papers could not have asked for a better advertisement than this controversy. They were further translated into the Italian, German and Latin languages, and Franklin's theory of electricity was so generally adopted by the learned men of Europe, in preference to that of the Abbé, that the latter lived, Franklin tells us, to see himself the last of his sect, except Monsieur B. of Paris, his élève and immediate disciple. It is surprising that even the solitary élève should have been left clinging to his master; for, in the meantime, the most momentous experiment, suggested by Franklin in his letters, had been performed, substantially in the manner outlined by him, with brilliant success, by D'Alibard, on a hill at Marly-la-Ville, where a pointed rod of iron, forty feet high, and planted on an electric stand, had been erected for the purpose of carrying it into execution. When a thundercloud passed over the rod on May 10, 1752, between 2 and 3 o'clock in the afternoon, the persons, set by D'Alibard to watch it, had drawn near "and attracted from it sparks of fire, perceiving the same kind of commotions as in the common electrical experiments." A week later, the fire and crackling sound, elicited by M. de Lor from a rod, erected at his house in Paris on a cake of resin, and electrified by a cloud between 4 and 5 o'clock in the afternoon, told the same story. He had previously performed what he called the "Philadelphia experiments" in the presence of Louis XV., who seems to have been as much delighted with them as if they had been a new mistress. In a short time, they became so popular that we are told by Franklin that "all the curious of Paris flocked to see them." One of the results of the fame acquired by him in France was a letter written by Dr. Wright, an English physician, then in Paris, to a member of the Royal Society, apprising the latter of the excitement that the experiments had created in France, and expressing his astonishment that Franklin's papers had been so little noticed in England. Quickened by Dr. Wright's words, the Society reconsidered the letters which had been read before them, and caused an abstract of them and the other letters on electricity, sent to England by Franklin, to be printed among its Transactions. Afterwards, when several members of the Society had themselves drawn down lightning from the clouds, it elected Franklin a member, and, in view of the fact that the honor had not been sought by him, voted that he "was not to pay anything"; which meant that he was to be liable for neither admission fee nor annual dues, and was even to receive his copy of the Transactions of the Society free of charge. Nor did it stop here. It also awarded to Franklin, for the year 1753, the Copley gold medal, accompanied by an address, in which Lord Macclesfield, its President, endeavored to make full amends to him for its belated recognition of the value of his discoveries.

The suggestion by Franklin, which led to the experiments of D'Alibard and De Lor, is as matter-of-fact as a cooking recipe.

To determine the question [he said in a letter to Peter Collinson] whether the clouds that contain lightning are electrified or not, I would propose an experiment to be try'd where it may be done conveniently. On the top of some high tower or steeple, place a kind of centry box,... big enough to contain a man and an electrical stand. From the middle of the stand let an iron rod rise and pass bending out of the door, and then upright 20 or 30 feet, pointed very sharp at the end. If the electrical stand be kept clean and dry, a man standing on it when such clouds are passing low, might be electrified and afford sparks, the rod drawing fire to him from a cloud. If any danger to the man should be apprehended (though I think there would be none), let him stand on the floor of his box, and now and then bring near to the rod the loop of a wire that has one end fastened to the leads, he holding it by a wax handle; so the sparks, if the rod is electrified, will strike from the rod to the wire, and not affect him.

Before the news of the success achieved by D'Alibard and De Lor reached Franklin, he himself had conducted a similar experiment "though made in a different and more easy manner." This experiment has become one of the veriest commonplaces of physical science. It was performed, when a thunder gust was coming on, in a field near Philadelphia, with such simple materials as a silk kite, topped off with a foot or more of sharp pointed wire, and controlled by a twine string, equipped with a key for casting off the electric sparks, and ending in a silk ribbon to secure the safety of the hand that held it. The whole construction is set out in a letter written to Collinson by Franklin shortly after the incident, in which, with his usual modesty, the latter describes the kite as if he had had nothing to do with it. Something like the feelings of Sir Isaac Newton, when the falling apple brought to his ear the real music of the spheres, must have been those of Franklin, when the loose filaments of twine bristled up stiffly, as if stirred by some violated instinct of wild freedom, and the stream of sparks from the key told him that he was right in supposing that the mysterious and appalling agency, which had for centuries been associated in the human mind with the resistless wrath of Omnipotence, was but the same subtle fluid that had so often lit up his electrical apparatus with its playful corruscations.

The letters to Collinson contained another suggestion almost equally pregnant. Speaking of the power of pointed conductors to draw off electricity noiselessly and harmlessly, Franklin asked,

May not the knowledge of this power of points be of use to mankind, in preserving houses, churches, ships, &c. from the stroke of lightning, by directing us to fix on the highest parts of those edifices, upright rods of iron made sharp as a needle, and gilt to prevent rusting, and from the foot of those rods a wire down the outside of the building into the ground, or down round one of the shrouds of a ship, and down her side till it reaches the water? Would not these pointed rods probably draw the electrical fire silently out of a cloud before it came nigh enough to strike, and thereby secure us from that most sudden and terrible mischief?

The suggestion was but slowly adopted, not in Europe, indeed, at all, until the efficacy of the lightning rod in protecting buildings had been generally recognized in America. In time, however, the device came into use both in Great Britain and on the Continent; Voltaire being one of the first persons in Geneva to erect one, and, wherever it was erected, it helped to confirm the fame of Franklin by its silent effect upon the human imagination. In recent years, the lightning rod, once in almost universal use in America, has fallen into neglect, but the explanation of this fact is to be found not in any just doubts about its utility, when properly constructed, affixed and grounded, but in the growth of fire insurance, and the inutility, or danger, of such rods, if carelessly set in place.[51]

The domestication of lightning and the invention of the lightning rod were the two things to which Franklin was principally indebted for his brilliant reputation as a philosopher. At this day, the application of electricity to common uses is so familiar to us that it is hard, without a little reflection, to realize how well calculated his electrical achievements were to send a thrill of astonishment and awe through the human mind. Of all the manifestations of the physical world, lightning with its inscrutable, swift, and all but irresistible, stroke, followed by the sublime detonations of thunder, is the one most suggestive of supernatural influence exerted by an all-powerful deity. The mythological dreams of the Greeks, the visions of the Old Testament, the simple emotions of the savage had all paid their homage of dread to the fearful force—like a madman pitilessly destructive, and yet like a madman diverted from its rage by the barest trifle—which had clothed Jove with the greater part of his grandeur, licked up even the water that was in the trench about the altar, built by Elijah in the name of the Lord, and filled the breast of the Indian with superstitious terror. Discovery, that laid bare the real nature and destructive limits of this force, could not fail to excite an extraordinary degree of attention everywhere. It was the singular fortune of Franklin, though a practical, sober-minded denizen of the earth, if ever man was, to have enjoyed in his day a reputation not unlike that of a divinity of the upper ether.[52] It so happens that the atmosphere was, in one way or another, the home of all the scientific problems which engaged his interest most deeply. His philosophical Pegasus, so little akin to the humble brute bestrid by Poor Richard, was "a beast for Perseus—pure air and fire"; and especially, it is needless to say, was this true of his relations to the lightning. When the fact became known throughout the civilized world that human ingenuity had succeeded in even snaring it, Franklin was exalted for a time to a seat on Olympus. All the literature of the period, as well as that of a much later period, bears out the statement that rarely has any single, peaceful incident ever so fired the human imagination.[53] For many years, the natural background for a portrait of Franklin might have been a bank of cloud lit up by the incessant play of summer lightning. Eripuit coelo fulmen sceptrumque tyrannis, was but the mightiest of the electrical discharges that flattery poured upon him. Turn where we may to the poetry of the latter half of the eighteenth century, and of the earlier part of the nineteenth, whether epigram or otherwise, we are likely to come upon some imprint left upon the thought of those periods by the subjugation of lightning.

The interest of Franklin in electrical science was but another sequel of the world-wide avidity with which learned men had recently turned to the study of that subject. One of them, Grey, had pursued a series of experiments for the purpose of determining the relative conductivity of various substances, another, Du Fay, had erroneously classified electricity as resinous and vitreous, and the perfected Leyden Jar particularly had given a new momentum to the progress of electrical investigation. Into this movement, after witnessing Dr. Spence's awkward experiments at Boston, Franklin threw himself with the utmost enthusiasm, and his discovery of the identity of lightning and electricity and his lightning-rod conception were but the chief fruits of this enthusiasm. Between the Autobiography and his letters, we are at no loss to follow closely the steps by which he reached all the results which have given him such a high position as an electrical investigator. "I purchased all Dr. Spence's apparatus ..." he tells us in the Autobiography, "and I proceeded in my electrical experiments with great alacrity." How keen this alacrity became, after he had been rubbing for a time the glass tube, sent over to Philadelphia by Collinson, may be seen in what he wrote to Collinson himself on March 28, 1747:

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 Acquaintance, who, from the novelty of the thing, come continually in crouds to see them, I have, during some months past, had little leisure for anything else.

The result of this experimentation was the various letters to Collinson and others that constitute Franklin's highest claim to distinction as a man of science. By following them in their chronological order, the reader can trace with little difficulty the genesis of each of his more valuable conclusions touching electricity. They are distinguished by remarkable simplicity and force of reasoning and by a clearness of statement as transparent as crystal. Moreover, they are even enlivened at times by gleams of fancy or humor. In a word they indisputably merit the judgment that Sir Humphry Davy, no mean judge of style as well as scientific truth, passes upon them:

The style and manner of his publication on electricity are almost as worthy of admiration as the doctrine it contains. He has endeavoured to remove all mystery and obscurity from the subject. He has written equally for the uninitiated and the philosopher; and he has rendered his details amusing as well as perspicuous, elegant as well as simple. Science appears in his language in a dress wonderfully decorous, the best adapted to display her native loveliness. He has in no instance exhibited that false dignity, by which philosophy is kept aloof from common applications; and he has sought rather to make her a useful inmate and servant in the common habitations of man, than to preserve her merely as an object of admiration in temples and palaces.

While recalling these words, it is not amiss to recall, too, what Lord Brougham had to say about the agencies with which Franklin conducted his experiments.

He could make an experiment [said Brougham] with less apparatus and conduct his experimental inquiry to a discovery with more ordinary materials than any other philosopher we ever saw. With an old key, a silk thread, some sealing wax and a sheet of paper he discovered the identity of lightning and electricity.

The truth of these observations is strikingly instanced in a story told of Franklin in Pettigrew's Life of Lettsom. When Henry Smeathman was insisting that the flight of birds is on inclined planes, and that they could not fly at all, but would simply float with the wind, if they were not heavier than the air, Franklin launched half a sheet of paper obliquely into the air, observing, as he watched its course, that that was an evident proof of the propriety of Smeathman's doctrines.

In a letter to Collinson, dated July 11, 1747, Franklin communicated to him the earliest results of his experimental use of the glass tube that Collinson had sent over to Philadelphia. The first phenomenon, which fixed his attention, was the wonderful effect of pointed bodies in drawing off the electrical fire. This was the lightning rod in its protoplasmal stage. The manner in which he described the experiment, by which this particular truth was demonstrated, is a good specimen of his remarkable faculty for simple and clear statement:

Place an iron shot of three or four inches diameter on the mouth of a clean dry glass bottle. By a fine silken thread from the ceiling, right over the mouth of the bottle, suspend a small cork ball, about the bigness of a marble; the thread of such a length, as that the cork ball may rest against the side of the shot. Electrify the shot, and the ball will be repelled to the distance of four or five inches, more or less, according to the quantity of Electricity. When in this state, if you present to the shot the point of a long slender sharp bodkin, at six or eight inches distance, the repellency is instantly destroy'd, and the cork flies to the shot. A blunt body must be brought within an inch, and draw a spark, to produce the same effect. To prove that the electrical fire is drawn off by the point, if you take the blade of the bodkin out of the wooden handle, and fix it in a stick of sealing wax, and then present it at the distance aforesaid, or if you bring it very near, no such effect follows; but sliding one finger along the wax till you touch the blade, and the ball flies to the shot immediately. If you present the point in the dark, you will see, sometimes at a foot distance, and more, a light gather upon it, like that of a firefly, or glowworm; the less sharp the point, the nearer you must bring it to observe the light; and, at whatever distance you see the light, you may draw off the electrical fire, and destroy the repellency. If a cork ball so suspended be repelled by the tube, and a point be presented quick to it, tho' at a considerable distance, 'tis surprizing to see how suddenly it flies back to the tube. Points of wood will do near as well as those of iron, provided the wood is not dry; but perfectly dry wood will no more conduct electricity than sealing-wax.

The repellency between the ball and the shot was likewise destroyed, Franklin stated, 1, by sifting fine sand on it; this did it gradually, 2, by breathing on it, 3, by making a smoke about it from burning wood, and 4, by candlelight, even though the candle was at a foot distance; these did it suddenly.

The same result was also produced, he found, by the light of a bright coal from a wood fire, or the light of red-hot iron; but not at so great a distance. Such was not the effect, however, he said, of smoke from dry resin dropped on hot iron. It was merely attracted by both shot and cork ball, forming proportionable atmospheres round them, making them look beautifully, somewhat like some of the figures in Burnet's or Whiston's Theory of the Earth.

Franklin also noted the fact that, unlike fire-light, sunlight, when thrown on both cork and shot, did not impair the repellency between them in the least.

In the same letter, guided by the belief that he had formed that electricity is not created by friction but, except when accumulated or depleted by special causes, is equally diffused through material substances generally, he also reached the conclusion that electrical discharges are due to circuits set up by substances that offer little resistance to the transit of the electrical current between bodies charged with more than the ordinary quantity of electrical energy and bodies not in that condition. In other words, electricity is always alert to restore its equilibrium when lost, and, if accumulated beyond its normal measure in one body, seeks with violent eagerness, as soon as a favorable medium of transmission is presented to it, to pass on its surplus of electrical energy to another body less amply supplied.

These conceptions, too, which lie at the very foundations of modern electrical science, are illustrated by Franklin with extraordinary simplicity and clearness as follows:

1. A person standing on wax, and rubbing the tube, and another person on wax drawing the fire, they will both of them, (provided they do not stand so as to touch one another) appear to be electrised, to a person standing on the floor; that is, he will perceive a spark on approaching each of them with his knuckle.

2. But, if the persons on wax touch one another during the exciting of the tube, neither of them will appear to be electrised.

3. If they touch one another after exciting the tube, and drawing the fire as aforesaid, there will be a stronger spark between them, than was between either of them and the person on the floor.

4. After such strong spark, neither of them discover any electricity.

These appearances we attempt to account for thus: We suppose, as aforesaid, that electrical fire is a common element, of which every one of the three persons above mentioned has his equal share, before any operation is begun with the tube. A, who stands on wax and rubs the tube, collects the electrical fire from himself into the glass; and his communication with the common stock being cut off by the wax, his body is not again immediately supply'd. B, (who stands on wax likewise) passing his knuckle along near the tube, receives the fire which was collected by the glass from A; and his communication with the common stock being likewise cut off, he retains the additional quantity received. To C, standing on the floor, both appear to be electrised: for he having only the middle quantity of electrical fire, receives a spark upon approaching B, who has an over quantity; but gives one to A, who has an under quantity. If A and B approach to touch each other, the spark is stronger, because the difference between them is greater: After such touch there is no spark between either of them and C, because the electrical fire in all is reduced to the original equality. If they touch while electrising, the equality is never destroy'd, the fire only circulating. Hence have arisen some new terms among us: We say, B, (and bodies like circumstanced) is electrised positively; A, negatively. Or rather, B is electrised plus; A, minus. And we daily in our experiments electrise bodies plus or minus, as we think proper. To electrise plus or minus, no more needs to be known than this, that the parts of the tube or sphere that are rubbed, do, in the instant of the friction, attract the electrical fire, and therefore take it from the thing rubbing: The same parts immediately, as the friction upon them ceases, are disposed to give the fire they have received, to anybody that has less. Thus you may circulate it, as Mr. Watson has shown; you may also accumulate or subtract it upon, or from anybody, as you connect that body with the rubber or with the receiver, the communication with the common stock being cut off.

The same letter recounts some of the tricks that Franklin and his fellow-experimenters were in the habit of making their new plaything perform. They fired spirits, lit candles just blown out, mimicked lightning, produced sparks with the touch of the finger, on the human hand or face, and gave electrical kisses. Other feats consisted in animating an artificial spider in such a way as to keep him oscillating in a very lifelike and entertaining manner between two wires, and lighting up the gilding on the covers of a book with a brilliant flash. This letter also shows that the provincial philosophers had already made improvements in the usual electrical methods. They had found that it was better to fill the phial with granulated lead than with water because of the superior facility with which the former could be warmed, and kept warm and dry in a damp place. They rubbed their tubes with buckskin, and, by observing certain precautions, such as never sullying the tubes by handling them, and keeping them in tight, close-fitting cases of pasteboard, lined with flannel, increased their efficiency. Their spheres for charging phials with electricity were mounted on iron axes with a small handle on one end, with which they could be set revolving like a common grindstone. It was in this same letter that Franklin with his usual generosity was careful to state that the power of pointed bodies to throw off as well as draw off the electrical fire was a discovery of his friend Hopkinson, and that the revolving sphere used by them was the invention of his friend Syng. About a month later, Franklin wrote to Collinson that, in the course of further experiments, he had observed several phenomena which made him distrust some of his former conclusions. "If there is no other use discover'd of Electricity," he said, "this however is something considerable, that it may help to make a vain man humble."

Another letter from Franklin to Collinson, written about two weeks later, communicated to him some valuable observations upon "M. Muschenbroeck's wonderful bottle"—the Leyden Jar. This bottle was a mere ordinary bottle, with a common cork in its neck, into which a common wire had been inserted. He wrote that, at the same time that the wire and the top of the bottle were electrised positively or plus, the bottom of the bottle was electrised negatively or minus, in exact proportion; the consequence was that, whatever quantity of electrical fire was thrown in at the top, an equal quantity went out at the bottom until, if the process was kept up long enough, the point was reached in the operation, when no more could be thrown into the upper part of the bottle, because no more could be drawn out of the lower part. If the attempt was made to throw more in, the fire was spewed back through the wire, or flew out in loud cracks through the sides of the bottle.

He also noted that an equilibrium could not be restored in the bottle by inward communication or contact of the parts, but only by a communication, formed without the bottle between its top and bottom.

He also noted that no electrical fire could be thrown into the top of the bottle, when none could get out at its bottom, either because the bottom was too thick, or because it stood on some non-conducting material, and likewise that, when the bottle was electrified, but little of the electrical fire could be drawn from the top by touching the wire, unless an equal quantity could at the same time get in at the bottom.

So wonderfully [he adds] are these two states of electricity, the plus and minus, combined and balanced in this miraculous bottle! situated and related to each in a manner that I can by no means comprehend! If it were possible that a bottle should in one part contain a quantity of air strongly comprest, and in another part a perfect vacuum, we know the equilibrium would be instantly restored within. But here we have a bottle containing at the same time a plenum of electrical fire, and a vacuum of the same fire; and yet the equilibrium cannot be restored between them but by a communication without! though the plenum presses violently to expand, and the hungry vacuum seems to attract as violently in order to be filled.

The letter concludes with an elaborate statement of the experiments by which the correctness of its conclusions could be established.

Franklin's next discovery communicated to Collinson in a letter dated the succeeding year was that, when the bottle was electrified, the electric fluid resided in the glass itself of the bottle. The manner in which he proved this fact is a good example of his inductive thoroughness.

Purposing [he said] to analyze the electrified bottle, in order to find wherein its strength lay, we placed it on glass, and drew out the cork and wire, which for that purpose had been loosely put in. Then taking the bottle in one hand, and bringing a finger of the other near its mouth, a strong spark came from the water, and the shock was as violent as if the wire had remained in it, which shewed that the force did not lie in the wire. Then, to find if it resided in the water, being crouded into and condensed in it, as confin'd by the glass, which had been our former opinion, we electrified the bottle again, and, placing it on glass, drew out the wire and cork as before; then, taking up the bottle, we decanted all its water into an empty bottle, which likewise stood on glass; and taking up that other bottle, we expected, if the force resided in the water, to find a shock from it; but there was none. We judged then, that it must either be lost in decanting, or remain in the first bottle. The latter we found to be true; for that bottle on trial gave the shock, though filled up as it stood with fresh unelectrified water from a teapot.

By a similar course of experimentation with sash glass and lead plates, he also demonstrated that the form of the glass in the bottle was immaterial, that the power resided in the glass as glass, and that the non-electrics in contact served only like the armature of a loadstone to unite the force of the several parts, and to bring them at once to any point desired; it being the property of a non-electric that the whole body instantly receives or gives what electric fire is given to, or taken from, anyone of its parts. These experiments suggested the idea of intensifying the application of electrical forces by grouping numerous electrical centres.

We made [he said] what we called an electrical battery, consisting of eleven panes of large sash-glass, arm'd with thin leaden plates, pasted on each side, placed vertically, and supported at two inches distance on silk cords, with thick hooks of leaden wire, one from each side, standing upright, distant from each other, and convenient communications of wire and chain, from the giving side of one pane, to the receiving side of the other; that so the whole might be charged together, and with the same labour as one single pane; and another contrivance to bring the giving sides, after charging, in contact with one long wire, and the receivers with another, which two long wires would give the force of all the plates of glass at once through the body of any animal forming the circle with them. The plates may also be discharged separately, or any number together that is required.

When the idea of the electrical battery was formed by him, Franklin was not aware that Smeaton and Bains had previously assembled panes of glass for the purpose of giving an electrical shock.

At the time that this letter was written, Franklin had added to his electrical exploits that of electrifying a mezzotint of the King in such a manner that, if anyone attempted to take the crown off his head, he would receive a "terrible blow."

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 glass 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 quantity (of electrical fire) in this small portion of glass! It seems as if it were of its very substance and essence. Perhaps if that due quantity of electrical fire so obstinately retained by glass, could be separated from it, it would no longer be glass; it might lose its transparency, or its brittleness, or its elasticity."

This letter also reaches the conclusion that bodies, having less than the common quantity 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 bumpers, under the discharge of guns from the electrical battery.

An electrified bumper, a note to the letter explained, was a small thin glass 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 pass over a country," he remarks, "high hills and high trees, lofty towers, spires, masts of ships, 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 ship 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 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 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 ship.

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 masses 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 glass 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 ships might be protected by upright rods of iron, and his suggestion, already quoted by us, too, as to how the identity 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 amusement. 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 kinship 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 anticipated, or, in some instances, all but anticipated, 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 pass.

Referring to what Franklin had to say about the action of sunlight in this connection, Arthur Schuster, in his Some Remarkable Passages in the Writings of Benjamin Franklin, observes: "Had Franklin used a clean piece of zinc instead of iron shot he might have anticipated Hertz's discovery of the action of strong light on the discharge of gases."

In the course of one of his experiments with an electrified can, Franklin reached the conclusion that a cork, which he had lowered into the can, was not attracted to its internal surface, as it would have been to its external, because the mutual repulsion of the two inner opposite sides of the can might prevent the accumulation of an electrical atmosphere upon them. From the same experiment, the genius of Henry Cavendish deduced his law that electrical repulsion varies inversely as the square of the distance between the charges.

Instead of declining, it can truly be said that the reputation of Franklin as an electrical investigator and writer has increased with the progress of electrical science. "We shall, I am sure," remarks Professor J. J. Thomson in his Electricity and Matter, "be struck by the similarity between some of the views which we are led to take by the results of the most recent researches, with those enunciated by Franklin in the very infancy of the subject." Nor should we omit a tribute of Dr. William Garnett, in his Heroes of Science, in regard to the statements in Franklin's first letters to Collinson. "They are," he says, "perfectly consistent with the views held by Cavendish and by Clerk Maxwell, and, though the phraseology is not that of modern text-books, the statements themselves can hardly be improved upon to-day."

If Franklin achieved a higher degree of success in the electrical than in any other scientific field, it was partly, at any rate, because he never again had the opportunity to give such continuous attention to scientific pursuits. To him this was at times a source of very great disappointment. In one of his letters to Beccaria, dated Sept. 21, 1768, he tells the latter that, preoccupied as he was, he had constantly cherished the hope of returning home, where he could find leisure to resume the philosophical studies that he had shamefully put off from time to time. In a letter, some eleven years later, from Paris, to the same correspondent, he said that he was then prevented by similar distractions from pursuing those studies in which he always found the highest satisfaction, and that he was grown so old as hardly to hope for a return of the leisure and tranquillity, so necessary for philosophical disquisitions. To Sir Joseph Banks he was inspired some years later, by recent astronomical discoveries, made under the patronage of the Royal Society, to write: "I begin to be almost sorry I was born so soon, since I cannot have the happiness of knowing what will be known 100 years hence," Indeed, to him, leisure, whether only the seclusion of a thirty-day voyage across the Atlantic, or the final cessation of public life, was but another term for recurrence to his scientific predilections. When he received his leave from Congress to return home from Paris, he wrote joyously to Ingenhousz: "I shall now be free of Politicks for the Rest of my Life. Welcome again my dear Philosophical Amusements." There was, to use his own expression, still too much flesh on his bones for his countrymen to allow him any time except for political experiments; but, for proof of the eager interest that he felt in science, and of the prominent position, that he occupied in the scientific world of America, until the last, we need go no further than the fact that, when he died, the meetings of the American Philosophical Society had, for some time, been held at his home in Philadelphia.

How far Franklin might have added to his reputation as a man of science, if he had not become engrossed by political duties and cares, is mere matter of surmise. But there can be no doubt that he was eminently fitted in many respects for scientific inquiry. The scientific temperament he possessed in the very highest degree. He loved the truth too much to allow the workings of human weakness in himself or others to deface its fair features. In reporting to Collinson the electrical achievements, which crowned him with such just renown, he almost invariably spoke of them as if they were the joint achievements of a group of collaborators, of whom he was but one. The generous alacrity, with which he credits to his friends Hopkinson, Kinnersley, or Syng exclusively special discoveries or inventions, made by them, shows conclusively enough how little this was true. There is no reason to believe that his letters to Collinson on electricity would ever have been published but for the unsolicited initiative of Dr. Fothergill and Collinson; or that they would ever have been translated into French but for the spontaneous persuasion that Buffon brought to bear upon D'Alibard. In a letter to Collinson, after expressing distrust of an hypothesis, advanced by him in former letters to the same correspondent, he declares that he is ashamed to have expressed himself in so positive a manner. Indeed, he said, he must request Collinson not to expose those letters, or, if he communicated them to any of his friends, at least to conceal the name of the author. His attitude towards his scientific triumphs was, when not that of entire self-effacement, always that of unaffected humility.

I am indebted for your preceding letter [he wrote in his forty-seventh year to John Perkins] but 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; which ought always to give place, when careful observation militates against them. I own I have too strong a penchant to the building of hypotheses; they indulge my natural indolence: I wish I had more of your patience and accuracy in making observations, on which, alone, true philosophy can be founded.

Equally candid and noble are other observations in a subsequent letter to the same correspondent. Referring to certain objections, made by Perkins to his theory of water spouts, he observed:

Nothing certainly can be more improving to a Searcher into Nature, than Objections judiciously made to his Opinions, taken up perhaps too hastily: For such Objections oblige him to re-study the Point, consider every Circumstance carefully, compare Facts, make Experiments, weigh Arguments, and be slow in drawing Conclusions. And hence a sure Advantage results; for he either confirms a Truth, before too lightly supported; or discovers an Error, and receives Instruction from the Objector.

In this View I consider the Objections and Remarks you sent me, and thank you for them sincerely.

When he found that he was in error, it cost him no struggle to recant. For a while he believed the sea to be the grand source of lightning, and built up an imposing fabric of conclusions upon the belief; but he did not hesitate afterwards to admit that he had embraced this opinion too hastily. The same thing is true of the opinion that he held for a time, that the progress of a ship westward, across the Atlantic, is retarded by the diurnal motion of the earth. He supposed that the melting brought about by the action of lightning was a cold fusion until holes burnt in a floor by portions of a molten bell wire convinced him that this was not so.

I was too easily led into that error [he said] by accounts given even in philosophical books, and from remote ages downwards, of melting money in purses, swords in scabbards, etc. without burning the inflammable matters that were so near those melted metals. But men are, in general, such careless observers, that a philosopher can not be too much on his guard in crediting their relations of things extraordinary, and should never build an hypothesis on anything but clear facts and experiments, or it will be in danger of soon falling, as this does, like a house of cards.

In one of his letters to Collinson, he declared that, even though future discoveries should prove that certain conjectures of his were not wholly right, yet they ought in the meantime to be of some use by stirring up the curious to make more experiments and occasion more exact disquisitions. Following out the same thought in another letter to Collinson he concluded: "You are at liberty to communicate this paper to whom you please; it being of more importance that knowledge should increase, than that your friend should be thought an accurate philosopher." In a letter to John Lining, in which he described the experiment from which Cavendish deduced the law of which we have spoken, he observed:

I find a frank acknowledgement of one's ignorance is not only the easiest way to get rid of a dificulty, but the likeliest way to obtain information, and therefore I practise it: I think it an honest policy. Those who affect to be thought to know everything, and so undertake to explain everything often remain long ignorant of many things that others could and would instruct them in, if they appeared less conceited.

The fact is that Franklin had such a keen sense of the dignity and invincibility of truth that he could not be induced to enter into any personal controversy about it. His feelings with regard to such controversies are pointedly expressed in the Autobiography in connection with the attack made by the Abbé Nollet upon his electrical experiments.

I once purpos'd [he said] answering the abbé, and actually began the answer; but, on consideration that my writings contain'd a description of experiments which anyone might repeat and verify, and if not to be verifi'd, could not be defended; or of observations offer'd as conjectures, and not delivered dogmatically, therefore not laying me under any obligation to defend them; and reflecting that a dispute between two persons, writing in different languages, might be lengthened greatly by mistranslations, and thence misconceptions of one another's meaning, much of one of the abbé's letters being founded on an error in the translation, I concluded to let my papers shift for themselves, believing it was better to spend what time I could spare from public business in making new experiments, than in disputing about those already made.

But in this instance, too, after all, he acted upon the principle, stated in one of his letters to Cadwallader Colden, that he who removes a prejudice, or an error from our minds contributes to their beauty, as he would do to that of our faces who should clear them of a wart or a wen. He went through his experiments again, and satisfied himself that the Abbé had not shaken his positions. At one time, when he was hesitating as to whether he should reply to him, he heard that D'Alibard was preparing to do so. "Perhaps," he wrote to his friend, James Bowdoin, "it may then appear unnecessary for me to do anything farther in it. And will not one's vanity be more gratified in seeing one's adversary confuted by a disciple, than even by one's self?" When Wilson published a pamphlet, contending that lightning rods should be blunt rather than pointed, he simply observed, "I have not answered it, being averse to Disputes."

Not only his temperament but his general mental attitude was instinctively scientific. As we have seen, while Whitefield's other auditors were standing mute and spellbound, he was carefully computing the distance that the words of the orator would carry. As we have also seen, when his soldiers were cutting down the giant pines at Gnadenhutten, he had his watch out, deep in his observation of the time that it took them to fell a tree. When his friend, Small, complained of deafness, he wrote to him that he had found by an experiment at midnight that, by putting his thumb and fingers behind his ear, and pressing it out and enlarging it as it were with the hollow of his hand, he could hear the tick of a watch at the distance of forty-five feet which was barely audible at a distance of twenty feet without these aids. Even in his relations to the simplest concerns of life, he had always the eye of a man of science to weight, measure, dimension and distance. If anyone wishes to see how easily he reduced everything to its scientific principles, let him read Franklin's letter to Oliver Neave, who thought that it was too late in life for him to learn to swim. With the confidence bred by a proper sense of the specific gravity of the human body as compared with that of water, Franklin said, there was no reason why a human being should not swim at the first trial. If Neave would only wade out into a body of water, until it came up to his breast and by a cast of his hand sink an egg to the bottom, between him and the shore, where it would be visible, but could not be reached except by diving, and then endeavor to recover it, he would be surprised to find what a buoyant thing water was.

Franklin also had all the inquisitiveness of a born philosopher. The winds, the birds, the fish, the celestial phenomena brought to his attention on his first voyage from England, the sluggish movement of his ship on his voyage to England in 1757, the temperature and movement of the Gulf Stream, the social and religious characteristics of the Moravians, Indian traits and habits, the still flies in their bath of Madeira wine—all excited his insatiable curiosity, and started him off on interesting trains of observation or reflection.

He was in the 78th year of his age, when, in the sight of fifty thousand people, one of the balloons recently invented by the Montgolfiers, and inflated with gas, produced by pouring oil of vitriol on iron filings, ascended from the Champs de Mars, shining brightly in the sun during the first stages of its ascent, then dwindling until it appeared scarcely larger than an orange, and then melting away in the clouds that had never before been invaded by such a visitant. But so fresh still was his interest in every triumph of human ingenuity, that it required a long letter to Sir Joseph Banks, the President of the Royal Society, supplemented by two postscripts, to disburthen his mind of the sensations and thoughts excited by the thrilling spectacle. Mingled in this letter with many precise details of size, weight and distance are the speculations of the Parisians with respect to the practical uses to which the toy might be put. Some believed that, now that men might be supported in the air, nothing was wanted but some light handy instruments to give and direct motion. Others believed that a running footman, or a horse, slung and suspended under such a globe, so as to diminish the weight of their feet on the ground to perhaps eight or ten pounds, might, with a fair wind, run in a straight line across country as fast as that wind, and over hedges, ditches and even waters. Still other fantasies were that in time such globes might be kept anchored in the air for the purpose of preserving game, or converting water into ice; or might be turned to pecuniary profit as a means of giving recreation-seekers a chance, at an altitude of a mile, to see far below them a vast stretch of the terrestrial surface. Already, said Franklin, one philosopher, M. Pilâtre de Rozier, had applied to the Academy for the privilege of ascending in a larger Montgolfier in order to make certain scientific experiments. The peasants at Gonesse, however, who had seen the balloon, cut adrift on the Champs de Mars, fall to the earth, had regarded it with very different feelings from the citizens of Paris. Frightened, and conceiving from its bounding a little, when it touched the ground, that there was some living animal in it, they had attacked it with stones and knives, so that it was much mangled.

With a subsequent letter to Dr. Price, Franklin enclosed a small balloon, which his grandson had filled with inflammable air the night before, and which, after mounting to the ceiling of Franklin's chamber, had remained rolling about there for some time. "If a Man," this letter suggestively asks, "should go up with one of the large ones, might there not be some mechanical Contrivance to compress the Globe at pleasure; and thereby incline it to descend, and let it expand when he inclines to rise again?" The same eager curiosity about the balloon was manifested by Franklin in many other later letters. Another great one, he informed Banks, had gone up from Versailles. It was supposed to have been inflated with air, heated by burning straw, and to have risen about two hundred toises; but did not continue long at that height, and, after being wafted in a horizontal direction by the wind, descended gently, as the air in it grew cooler. "So vast a Bulk," said Franklin, "when it began to rise so majestically in the Air, struck the Spectators with Surprise and Admiration. The Basket contain'd a Sheep, a Duck & a Cock, who except the Cock receiv'd no hurt by the fall." Another balloon of about five feet in diameter, the same letter stated, had been sent up about one o'clock in the morning with a large lanthorn under it by the Duke de Crillon at an entertainment, given by him, during the preceding week, in the Bois de Boulogne in honor of the birth of two Spanish princes. These were but a few of many recent ascensions. Most interesting of all, however, a new balloon, designed by Messieurs Charles and Robert, who were men of science and mechanical dexterity, was to carry up a man.

Another balloon, described by Franklin in one of his letters to Banks, was open at the bottom, and was fed with heated air from a grate, fixed in the middle of the opening, which was kept replenished with faggots and sheaves of straw by men, posted in a wicker gallery, attached to the outside of the lower part of the structure. By regulating the amount of fire in the grate, the balloon could be given an upward or downward direction at pleasure.

It was thought, Franklin said, that a balloon of this type, because of the rapidity and small expense, with which it could be inflated, might be made useful for military purposes.

Still another balloon described by Franklin in the same letter was one which was to be first filled with "permanently elastic inflammable air," and then closed. It was twenty-six feet in diameter, and made of gores of red and white silk, which presented a beautiful appearance. There was a very handsome triumphal car, to be suspended from it, in which two brothers, the Messrs. Robert, were to ascend with a table for convenience in jotting down their thermometric and other observations. There was no telling, Franklin declared, how far aeronautic improvements might be pushed. A few months before, the idea of witches riding through the air on a broomstick, and that of philosophers upon a bag of smoke would have appeared equally impossible and ridiculous. The machines, however, he believed, would always be subject to be driven by the winds, though perhaps mechanic art might find easy means of giving them progressive motion in a calm, and of slanting them a little in the wind. English philosophy was too bashful, and should be more emulous in this field of competition. If, in France, they did a foolish thing, they were the first to laugh at it themselves, and were almost as much pleased with a bon mot or a good chanson, that ridiculed well the disappointment of the project, as they might have been with its success.

The experiment might be attended with important consequences that no one could foresee.

Beings of a frank and—nature far superior to ours [the letter continued] have not disdained to amuse themselves with making and launching balloons, otherwise we should never have enjoyed the light of those glorious objects that rule our day and night, nor have had the pleasure of riding round the sun ourselves upon the balloon we now inhabit.

In due course, the Messrs. Robert, accompanied by M. Charles, a professor of experimental philosophy, and an enthusiastic student of aeronautics, made their perilous venture, which was likewise fully chronicled by Franklin. The spectators, he said, were infinite, crowding about the Tuileries, on the quays and bridges, in the fields and streets, and at the windows, and on the roofs, of houses. The device of stimulating flagging ascent by dropping sand bags from the car was one of the features of this incident, and so was the device of protecting the envelope of the balloon from rupture by covering it with a net, as well as that of lowering it by letting a part of its contents escape through a valve controlled by a cord.

Between one and two o'clock [Franklin's narrative states] all eyes were gratified with seeing it rise majestically from among the trees, and ascend gradually above the buildings, a most beautiful spectacle. When it was about two hundred feet high, the brave adventurers held out and waved a little white pennant, on both sides their car, to salute the spectators who returned loud claps of applause.

When Franklin last saw the vanishing form of this balloon, it appeared no bigger than a walnut. The experiment proved a most prosperous one. From first to last the aerial navigators retained perfect command of their air-ship, descending, when they pleased, by letting some of the air in it escape, and rising, when they pleased, by discharging sand; and at one time skimming over a field so low as to be able to talk to some laborers. Pleased as Franklin was with the experiment, he wrote to Henry Laurens that he yet feared that the machine would hardly become a common carriage in his time, though, being the easiest of all voitures, it would be extremely convenient to him, now that his malady forbade him the use of the old ones over a pavement. The idea, however, was such an agreeable one to him that, when he returned to Philadelphia, he wrote to his friend Jean Baptiste Le Roy that he sometimes wished that he had brought a balloon from France with him sufficiently large to raise him from the ground, and to permit him, without discomfort from his stone, to be led around in his novel conveyance by a string, attached to it, and held by an attendant on foot.

On the whole, it appeared to Franklin that the invention of the balloon was a thing of great importance.

Convincing sovereigns of the Folly of Wars [he wrote to Ingenhousz] may perhaps be one Effect of it; since it will be impracticable for the most potent of them to guard his Dominions. Five thousand Balloons, capable of raising two Men each could not cost more than Five Ships of the Line; and where is the Prince who can afford so to cover his Country with Troops for its Defence, as that Ten Thousand Men descending from the Clouds might not in many places do an infinite deal of mischief, before a Force could be brought together to repel them?

But nothing happened in Franklin's time, nor has happened since, to warrant the belief that human flying-devices of any sort will ever be free enough from danger to human life to be a really useful vehicle of transportation in times of peace. So far their principal value has been during war, when human safety has little to choose between the earth and the sky, but it is fair to say that Franklin would have loathed war even more deeply than he did, if he could have lived to see them in the form of aeroplane or dirigible, making their way through the air like winged monsters of the antediluvian past, and dropping devilish agencies of death and desolation upon helpless innocence, and the fairest monuments of human industry and art. Poor M. Pilâtre de Rozier, whom we have already mentioned, and who was no less a person than the Professor of Chemistry, at the Athenée Royale, of which he was the founder, fell with a companion, from an altitude of one thousand toises to the rocky coast near Boulogne-sur-Mer, and was, as well as his companion, dashed to pieces. Since his time the discharioted Phaetons, who have fallen from the upper levels of the atmosphere, even when not engaged in war, with the same fearful result, have been numerous enough to constitute a ghastly necrology. Nor, it would appear, was the peril under the conditions of aerial navigation in its earliest stages limited to the aeronaut himself. In dissuading Ingenhousz from attempting a balloon experiment, Franklin said that it was a serious thing to draw out from their affairs all the inhabitants of a great city and its environs, and that a disappointment made them angry. At Bordeaux lately, a person, who pretended to send up a balloon, and had received money from many people, not being able to make it rise, the populace were so exasperated that they pulled down his house, and had like to have killed him. Anyone, who has ever heard the execrations hurled at the head of a baseball umpire in the United States, when one of his decisions has failed to command general assent, will experience no difficulty, we are sure, in understanding the force of the impulse that provoked this outbreak of Gallic excitement.

The enthusiasm, aroused in Franklin by the balloon, is not more noticeable than his brooding desire to find some practical use for it. The visionary speculation, which seeks to take the moon in its teeth, was no part of his character. He grew no orchids in the air. To use his homely words in a letter to Charles Thomson, he made no shoes for feet that he had never measured. Every conclusion, every hypothesis had to be built upon a basis of patient observation and gradual induction; every invention or discovery had to have some useful application.

At an earlier period than that of the discovery of the balloon, his inquisitive spirit had led him to the study of marsh-gas and the pacifying effect of oil upon troubled waters. In 1764, he had reason to believe that a friend of his had succeeded in igniting the surface of a river in New Jersey, after stirring up the mud beneath it, but his scientific friends in England found it difficult to believe that he had not been imposed upon; and the Royal Society withheld from publication among its Transactions a paper on the experiment, written by Dr. Finley, the President of Princeton College, and read before it. Franklin twice tried it in England without success, and he prosecuted his investigation with such energy and persistency that he finally contracted an intermittent fever by bending over the stagnant water of a deep ditch, and inhaling its foul breath, or, as would now be said, by being bitten by a mosquito hovering about it.

In 1757, when on one of the ships, bound on Lord Loudon's fool's errand to Louisburg, he observed that the water in the wake of two of them was remarkably smooth, while that in the wake of the others was ruffled by the wind, which was blowing freshly, and, when he spoke of the circumstance to his captain, the latter answered somewhat contemptuously, as if to a person ignorant of what everybody else knew, "The cooks have, I suppose, been just emptying their greasy water through the scuppers, which has greased the sides of those ships a little." The incident, and what he had read in Pliny about the practice among the seamen of Pliny's time of calming rough seas with oil, made him resolve to test the matter by experiment at the first opportunity. This intention was afterwards strengthened, when he was again at sea in 1762, by the "wonderful quietness" of oil, resting on the surface of an agitated bed of water in the glass lamp swinging in his cabin, and by the supposition of an old sea captain that the phenomenon was in keeping with the practice, pursued by the Bermudians, of putting oil on water, when they would strike fish. By the same captain, he was told that he had heard that fishermen at Lisbon were in the habit of emptying a bottle or two of oil on the sea, when the breakers on the bar at that port were running too high for their boats to cross it in safety. From another person, he learnt that, when divers in the Mediterranean needed more light for their business, they spewed out from their mouths now and then a small quantity of oil, which, rising to the surface, smoothed out its refracting waves. This additional information supplied his curiosity with still further fuel. It all ended in his dropping a little oil from a cruet on a large pond at Clapham. The fluid spread with surprising swiftness over the surface, on which it had fallen; but he found that he had made the mistake of dropping it on the leeward, instead of the windward, side of the pond. When this mistake was repaired, and a teaspoonful of oil was poured on its windward side, where the waves were in an incipient state, and the oil could not be driven back on the shore, an instant calmness diffused itself over a space several yards square, which extended gradually until it reached the lee side of the pond, making all that quarter of it, perhaps half an acre, as smooth as a looking-glass. After this, he took with him, whenever he went into the country, a little oil, in the upper hollow joint of his bamboo cane for the purpose of repeating his experiment, whenever he had a chance to do so, and, when he did repeat it, it was usually with success.

Far from being so successful, however, was the experiment when, on a blustering, unpleasant day, he attempted, with the co-operation of Sir Joseph Banks and other friends, to still the surf on a shore at Portsmouth with oil poured continually on the sea, at some distance away, through a hole, somewhat bigger than a goose quill, in the cork of a large stone bottle, though the effusion did flatten out a considerable tract of the sea to such an extent that a wherry, making for Portsmouth, seemed to turn into that tract of choice, and to use it from end to end as a piece of turnpike road. All this is described by Franklin in a letter to William Brownrigg, dated November 7, 1773, in which he cited some other illustrations of the allaying effect of oil on waves besides those that we have mentioned, and developed the philosophy of the subject with that incomparable clarity of his, not unlike the action of oil itself in subduing refractions of light.

Now I imagine [he says] that the wind, blowing over water thus covered with a film of oil, can not easily catch upon it, so as to raise the first wrinkles, but slides over it, and leaves it smooth as it finds it. It moves a little the oil indeed, which being between it and the water, serves it to slide with, and prevents friction, as oil does between those parts of a machine that would otherwise rub hard together. Hence the oil dropped on the windward side of a pond proceeds gradually to leeward, as may be seen by the smoothness it carries with it, quite to the opposite side. For the wind being thus prevented from raising the first wrinkles, that I call the elements of waves, cannot produce waves, which are to be made by continually acting upon, and enlarging those elements, and thus the whole pond is calmed.

And the water in which the Bermudian struck his fish is not more limpid than these observations suggested by the Portsmouth experiment:

I conceive, that the operation of oil on water is, first, to prevent the raising of new waves by the wind; and, secondly, to prevent its pushing those before raised with such force, and consequently their continuance of the same repeated height, as they would have done, if their surface were not oiled. But oil will not prevent waves being raised by another power, by a stone, for instance, falling into a still pool; for they then rise by the mechanical impulse of the stone, which the greasiness on the surrounding water cannot lessen or prevent, as it can prevent the winds catching the surface and raising it into waves. Now waves once raised, whether by the wind or any other power, have the same mechanical operation, by which they continue to rise and fall, as a pendulum will continue to swing a long time after the force ceases to act by which the motion was first produced; that motion will, however, cease in time; but time is necessary. Therefore, though oil spread on an agitated sea may weaken the push of the wind on those waves whose surfaces are covered by it, and so, by receiving less fresh impulse, they may gradually subside; yet a considerable time, or a distance through which they will take time to move, may be necessary to make the effect sensible on any shore in a diminution of the surf; for we know, that, when wind ceases suddenly, the waves it has raised do not as suddenly subside, but settle gradually, and are not quite down till after the wind has ceased. So, though we should, by oiling them, take off the effect of wind on waves already raised, it is not to be expected that those waves should be instantly levelled. The motion they have received will, for some time, continue; and, if the shore is not far distant, they arrive there so soon, that their effect upon it will not be visibly diminished.

Nor was it on Clapham Pond and at Portsmouth alone that Franklin, when in England, tested the tranquillizing properties of oil. He performed the same experiment on Derwentwater and a small pond near the house of John Smeaton, the celebrated engineer, at Austhorpe Lodge; and also on a large sheet of water at the head of the Green Park. And the idea that there was something almost supernatural about his quick insight and fertility of conception, of which we find more than one trace in the utterances of his contemporaries, is suggested in an interesting manner in the account left to us by the Abbé Morellet of one of these experiments, which he witnessed when Colonel Barre, Dr. Hawkesworth, David Garrick, Franklin and himself happened to be guests of Lord Shelburne at Wycombe in 1772.

It is true [the Abbé says] it was not upon the waves of the sea but upon those of a little stream which flowed through the park at Wycombe. A fresh breeze was ruffling the water. Franklin ascended a couple of hundred paces from the place where we stood, and simulating the grimaces of a sorcerer, he shook three times upon the stream a cane which he carried in his hand. Directly the waves diminished and soon the surface was smooth as a mirror.

On one occasion, William Small wrote to him from Birmingham that Matthew Boulton had "astonished the rural philosophers exceedingly by calming the waves à la Franklin."

Struck, when travelling on a canal in Holland, with the statement of a boatman that their boat was going slow because the season had been a dry one, and the water in the canal was not as deep as usual, Franklin, by experiment with a trough and a little boat borrowed for the purpose, established the fact that the friction caused by the displacement by a moving boat of shallow water is measurably greater than that caused by the displacement by such a boat of deeper water. Under like conditions in other respects, the difference, he concluded, in a distance of four leagues, was the difference between five and four hours.

A conversation with Captain Folger, of Nantucket, produced far more important consequences. Influenced by what the captain told him of the knowledge that the Nantucket whalers had acquired of the retarding effect of the Gulf Stream upon navigation, Franklin induced him to plat for him the dimensions, course and swiftness of the stream, and to give him written directions as to how ships, bound from the Newfoundland Banks to New York, might avoid it, and at the same time keep clear of certain dangerous banks and shoals. The immediate object of Franklin was to procure information for the English Post Office that would enable the mail packets between England and America to shorten their voyages. At his instance, Captain Folger's drawing was engraved on the old chart of the Atlantic at Mount and Page's, Tower Hill, and copies of it were distributed among the captains of the Falmouth packets. Ever afterwards the Gulf Stream was a favorite field of investigation to him, when at sea, and its phenomena were mastered by him with remarkable thoroughness. It was generated, he conjectured, by the great accumulation of water on the eastern coast of America created by the trade winds which constantly blew there. He found that it was always warmer than the sea on each side of it, and that it did not sparkle at night; and he assigned to its influence the tornadoes, waterspouts and fogs by which its flow was attended.

Franklin also possessed to a striking degree the inventive capacity which is such a valuable qualification for experimental philosophy. We have already seen how ready his mechanical skill was in supplying printing deficiencies. Speaking of the pulse glasses, made by Nairne, in which water could be brought to the boiling point with the heat of the hand, he tells us:

I plac'd one of his glasses, with the elevated end against this hole (a hole that he had opened through the wainscot in the seat of his window for the access of outside air); and the bubbles from the other end, which was in a warmer situation, were continually passing day and night, to the no small surprize of even philosophical spectators.

As he sat in his library at Philadelphia, in his last years, he was surrounded by various objects conceived by his own ingenuity. The seat of his chair became a step-ladder, when reversed, and to its arm was fastened a fan that he could work with a slight motion of his foot. Against his bookcase rested "the long arm" with which he lifted down the books on its upper shelves. The hours, minutes and seconds were told for him by a clock, of his own invention, with only three wheels and two pinions, in which even James Ferguson, mathematician as he was, had to confess that he experienced difficulty in making improvements. The very bifocal glasses, now in such general use, that he wore were a triumph of his own quick wit. Describing this invention of his in a letter to George Whatley, he said:

I therefore had formerly two Pair of Spectacles, which I shifted occasionally, as in travelling I sometimes read, and often wanted to regard the Prospects. Finding this Change troublesome, and not always sufficiently ready, I had the Glasses cut, and half of each kind associated in the same Circle.... By this means, as I wear my Spectacles constantly, I have only to move my Eyes up or down, as I want to see distinctly far or near, the proper Glasses being always ready. This I find more particularly convenient since my being in France, the Glasses that serve me best at Table to see what I eat, not being the best to see the Faces of those on the other Side of the Table who speak to me; and when one's Ears are not well accustomed to the Sounds of a Language, a Sight of the Movements in the Features of him that speaks helps to explain; so that I understand French better by the help of my Spectacles.

The shrinking that a mahogany box, given to him in England, underwent, when subjected to the atmospheric conditions of America, suggested a hygrometer to him which Nairne afterwards constructed in accordance with his plans.[55]

His mind seems to have had no torpid moments, except, perhaps, when some Congressional orator was speaking. When, in early life, he had nothing else better to do, he would address himself to making magic squares and circles as intricate as Rosamond's walk. "He took it into his head," James Logan wrote to Collinson, "to think of magical squares, in which he outdid Frenicle himself, who published above eighty pages in folio on that subject alone." Not willing to be outdone even by Stifelius, Franklin drew a square of such extraordinary numerical properties that not only did the numbers on all the rows and diagonals on its face total 2056, but the sum of the numbers on every group of 16 smaller squares on its face, when revealed through a hole in a piece of paper, moved backwards and forwards over its face, equalled precisely 2056 too. He likewise drew a