Part 13

In a letter written to Collinson on October 19, 1752, Franklin says he had heard of the success in France of the experiment he had suggested for drawing the lightning from clouds by means of an elevated metal rod; but in the mean time he had contrived another method for accomplishing the same result without the aid of a steeple or lofty iron rod. This was the kite experiment of which we have heard so much, and he goes on to describe it:

"Make a small cross of two light strips of cedar, the arms so long as to reach to the four corners of a large thin silk handkerchief when extended; tie the corners of the handkerchief to the extremities of the cross, so you have the body of a kite; which being properly accommodated with a tail, loop, and string, will rise in the air, like those made of paper; but this being of silk is fitter to bear the wet and wind of a thunder gust without tearing. To the top of the upright stick of the cross is to be fixed a very sharp pointed wire, rising a foot or more above the wood. To the end of the twine, next the hand, is to be tied a silk ribbon, and where the silk and twine join, a key may be fastened. This kite is to be raised when a thunder-gust appears to be coming on, and the person who holds the string must stand within a door or window, or under some cover, so that the silk ribbon may not be wet; and care must be taken that the twine does not touch the frame of the door or window. As soon as any of the thunder clouds come over the kite, the pointed wire will draw the electric fire from them, and the kite, with all the twine, will be electrified, and the loose filaments of the twine, will stand out every way, and be attracted by an approaching finger. And when the rain has wetted the kite and twine, so that it can conduct the electric fire freely, you will find it stream out plentifully from the key on the approach of your knuckle. At this key the phial may be charged: and from electric fire thus obtained, spirits may be kindled, and all the other electric experiments be performed, which are usually done by the help of a rubbed glass globe or tube, and thereby the sameness of the electric matter with that of lightning completely demonstrated."

This is the only description by Franklin of the experiment which added so much to his reputation. Franklin and the kite became a story for school-books; innumerable pictures of him and his son drawing the lightning down the string were made and reproduced for a century or more in every conceivable form, and even engraved on some of our national currency.

The experiment was made in June, 1752; in the following October the above letter was written, and the news it contained appears to have rushed over the world without any effort on his part to spread it. He never wrote anything more concerning this experiment than the very simple and unaffected letter to Mr. Collinson. But people, of course, asked him about it, and from the details which they professed to have obtained grand statements have been built up describing his conduct and emotions on that memorable June afternoon on the outskirts of Philadelphia, probably somewhere in the neighborhood of the present Vine Street, near Fourth; how his heart stood still with anxiety lest the trial should fail; how with trembling hand he applied his knuckles to the key, and the wild exultation with which he saw success crown his efforts.

But it is safe to say that there were none of these theatrical exhibitions, and that he made the experiment in that matter-of-fact and probably half-humorous way in which he did everything. Nothing important depended on it, for he had already proved conclusively, not only by reasoning but by his suggested experiments which had been tried in Europe, that thunder and lightning were phenomena of electricity. The kite was used because there were in Philadelphia no high steeples on which he could try the experiment that had proved his discovery in France.

But it was Franklin's good fortune on a number of occasions to be placed in picturesque and striking situations, which greatly increased his fame. He did not foresee that kite-flying would be one of these, and as it was not essential to his discovery of the nature of lightning, he was disinclined at first to think much of it, and did not even report it to Mr. Collinson until after several months had elapsed. But the world fixed upon it instantly as something easy to remember. To this day it is the popular way of illustrating Franklin's discovery, and is all that most people know of his contributions to science.

He went on steadily reporting his experiments to Collinson, and in 1753 was at work on the mistaken hypothesis of the sea being the grand source of lightning, but at the same time making the discovery of the negative and sometimes positive electricity of the clouds. He had a rod erected on his house to draw down into it the mystical fire of any passing clouds, with bells arranged to warn him when his apparatus was working; and it was about this time that he was struck senseless and almost killed while trying the effect of an electrical shock on a turkey.

Collinson kept his letters, and in May, 1751, had them published in a pamphlet called "New Experiments and Observations in Electricity made at Philadelphia in America." It had immediately, like all of Franklin's writings, a vast success, at first in France, and afterwards in England and other countries. Franklin was, strange to say, always more popular in France than in either America or England. In England his experiments in electricity were at first laughed at, and the Royal Society refused to publish his letters in their proceedings. But after Collinson had secured their publication in a pamphlet, they were translated into German, Italian, and Latin, as well as into French, and were greatly admired not only for the discoveries and knowledge they revealed, but for their fascinating style and noble candor tinged occasionally with the most telling and homely humor.

It has been repeatedly charged that Franklin was indebted to his fellow-worker, Kinnersley, for his discoveries in electricity. The charge is so vaguely made that it is impossible to ascertain which of them are supposed to have been stolen. In Franklin's letters on electricity there are frequent footnotes giving credit to Hopkinson and Syng for their original work, and there are also in his published works letters to and from Kinnersley. He and Kinnersley seem to have been always fast friends, and, so far as I can discover, the latter never accused Franklin of stealing from him.

After he had proved in such a brilliant manner that lightning was merely one of the forms or phenomena of that mysterious fire which appears when we rub a glass tube with buckskin, Franklin made no more discoveries in science; but his interest and patience of research were unabated. He cannot be ranked among the great men of science, the Newtons and Keplers, or the Humboldts, Huxleys, or Darwins. He belongs rather in the second class, among the minor discoverers. But his discovery of the nature of lightning was so striking and so capable of arousing the wonder of the masses of mankind, and his invention of the lightning-rod was regarded as so universally valuable, that he has received more popular applause than men whose achievements were greater and more important.

During the rest of his life his work in science was principally in the way of encouraging its study. He was always observing, collecting facts, and writing out his conclusions. The public business in which he was soon constantly employed, and the long years of his diplomatic service in England and France, were serious interruptions, and during the last part of his life it was not often that he could steal time for that loving investigation of nature which after his thirtieth year became the great passion of his life.

His command of language had seldom been put to better use than in explaining the rather subtle ideas and conceptions in the early development of electricity. Even now after the lapse of one hundred and fifty years we seem to gain a fresher understanding of that subject by reading his homely and beautiful explanations; and modern students would have an easier time if Franklin were still here to write their text-books. His subsequent letters and essays were many of them even more happily expressed than the famous letters on electricity.

In old editions of his works all his writings on science were collected in one place, so that they could be read consecutively, which was rather better than the modern strictly chronological plan by which they are scattered throughout eight or ten large volumes. As we look over one of the old editions we feel almost compelled to begin original research at once,--it seems so easy and pretty. There are long investigations about water-spouts and whirlwinds,--whether a water-spout ever actually touches the surface of the sea, and whether its action is downward from the sky or upward from the water. He interviewed sea-captains and received letters from people in the West Indies to help him, and those who had once come within the circle of his fascination were never weary of giving aid.

He investigated what he called the light in sea-water, now called phosphorescence. The cause of the saltness of the sea and the existence of masses of salt or salt-mines in the earth he explained by the theory that all the water of the world had once been salt, for sea-shells and the bones of fishes were found, he said, on high land; upheavals had isolated parts of the original water, which on evaporation had left the salt, and this being covered with earth, became a salt-mine. This explanation was given in a letter to his brother Peter, and is really a little essay on geology, which was then not known by that or any other name, but consisted merely of a few scattered observations.

Many of his most interesting explanations of phenomena appear in letters to the young women with whom he was on such friendly terms. Indeed, it has been said that he was never at his best except when writing to women. People believe, he tells Miss Stevenson, that all rivers run into the sea, and he goes on to show in his most clever way that some rivers do not. The waters of the Delaware, for example, and the waters of the rivers that flow into Chesapeake Bay, probably never reach the ocean. The salt water backing up against them twice a day acts as a dam, and their fresh water is dissipated by evaporation. Only a few, like the Amazon and the Orinoco, are known to force their fresh water far out on the surface of the sea. In this same letter he describes the experiments he made to prove that dark colors absorb more of the sun's rays, and are therefore warmer than white.

While representing Pennsylvania in England, and living with Mrs. Stevenson, in Craven Street, London, he made an experiment to prove that vessels move faster in deep than in shallow water. This was generally believed by seafaring men; but Franklin had a wooden trough made with a false bottom by which he could regulate the depth of water, and he put in it a little boat drawn by a string which ran over a pulley at the end of the trough, with a shilling attached for a weight. In this way he succeeded in demonstrating a natural law which, though known to practical men, had never been described in books of science.

He took much pains to collect information about the Gulf Stream. This wonderful river in the ocean has been long known, but the first people to observe it closely were the Nantucket whalemen, who found that their game was numerous on the edges of it, but was never seen within its warm waters. In consequence of their more exact knowledge they were able to make faster voyages than other seamen. Franklin learned about it from them, and on his numerous voyages made many observations, which he carefully recorded. He obtained a map of it from one of the whalemen, which he caused to be engraved for the general benefit of navigation on the old London chart then universally used by sailors. But the British captains slighted it, and this, like his other efforts in science, was first appreciated in France.

He has been called the discoverer of the temperature of the Gulf Stream; but this statement is somewhat misleading. That the stream was warmer than the surrounding ocean seems to have been long known; but Franklin was the first to take its temperature at different points with a thermometer. He did this most systematically on several of his voyages, even when suffering severely from sea-sickness, and thus suggested the use of the thermometer in investigating ocean currents. He first took these temperatures in 1775, and the next year Dr. Charles Blagden, of the British army, took them while on the voyage to America with troops to suppress the Revolution. He and Franklin are ranked together as the first to show the value of an instrument which is now universally used in ocean experiments as well as in the practical navigation of ships.[19]

In the same careful manner he collected all that was known of the effect of oil in stilling waves by making the surface so smooth and slippery that the wind cannot act on it. So fascinated was he with this investigation that he had a cane made with a little receptacle for oil in the head of it, and when walking in the country in England experimented on every pond he passed. But it would be long to tell of all he wrote on light and heat, the _vis inertiæ_ of matter, magnetism, rainfall, evaporation, and the aurora borealis.

One of the discomforts of colonial times, when large open fireplaces were so common, was a smoky chimney. Franklin's attention was drawn to this question about the time that he invented the Pennsylvania fireplaces, and he made an exhaustive study of the nature of smoke and heated air. He became very skilful in correcting defects in the chimneys of his friends' houses, and while he was in England noblemen and distinguished people often sought his aid. It was not, however, until 1785, near the close of his life, that he put his knowledge in writing in a letter to Dr. Ingenhausz, physician to the Emperor of Austria. The letter was published and extensively circulated as the best summary of all that was known on this important question. It is as fresh and interesting to-day as when it was written, and well worth reading, because it explains so charmingly the philosophy of some phenomena of common occurrence which modern books of science are not at much pains to make clear.

His enemies, of course, ridiculed him as a chimney doctor, and his friends have gone to the other extreme in implying that he was the only man in the world who understood the action of heat and smoke, and that, alone and unaided, he delivered mankind from a great destroyer of their domestic comfort. But his letter shows that most of his knowledge and remedies were drawn from the French and Germans. In this, as in many other similar services, he was merely an excellent collector of scattered material, which he summarized so well that it was more available than before. He was by no means the only person in the world who could doctor a chimney; but there were few, if any, who could describe in such beautiful language the way in which it was done.

He invented a stove that would consume its own smoke, taking the principle from a Frenchman who had shown how the flame of a burning substance could be made to draw downward through the fuel, so that the smoke was burnt with the fuel. But the way in which this invention is usually described would lead one to suppose that it was entirely original with Franklin.

He was much interested in agriculture, and was an earnest advocate of mineral manures, encouraged grape culture, and helped to introduce the basket willow and broom-corn into the United States. He at one time owned a farm of three hundred acres near Burlington, New Jersey, where he tried agricultural experiments. He dabbled in medicine, as has been shown, and also wasted time over that ancient delusion, phonetic spelling.

Knowing, as we do, Franklin's versatility, it is nevertheless somewhat of a surprise to find him venturing into the sphere of music. He is said to have been able to play on the harp, the guitar, and the violin, but probably only in a philosopher's way and not well on any of them. Some people in England had succeeded in constructing a musical instrument made of glasses, the idea being taken from the pleasant sound produced by passing a wet finger round the brim of a drinking-glass. When in England Franklin was so delighted with these instruments that he set about improving them. He had glasses specially moulded of a bell-like shape and ground with great care until each had its proper note. They were placed in a frame in such a way that they could all be set revolving at once by means of a treadle worked by the foot, and as they revolved they were played by the wet fingers pressed on their brims. He gave the name "Armonica" to his instrument, and describes its tones as "incomparably sweet beyond those of any other." It is said to have been used in public concerts, and it was one of the curiosities at his famous Craven Street lodging-house in London, where he also had a fine electrical apparatus, and took pleasure in showing his English friends the American experiments of which they had heard so much.

He seems to have studied music with great care as a science, just as he studied the whirlwinds, the smoke, and the lightning; but he was unalterably opposed to the so-called modern music then becoming fashionable, and which is still to a great extent the music of our time. The pleasure derived from it was, he said, not the natural pleasure caused by harmony of sounds, but rather that felt on seeing the surprising feats of tumblers and rope-dancers.

"Many pieces of it are mere compositions of tricks. I have sometimes, at a concert, attended by a common audience, placed myself so as to see all their faces, and observed no signs of pleasure in them during the performance of a great part that was admired by the performers themselves; while a plain old Scotch tune, which they disdained, and could scarcely be prevailed upon to play, gave manifest and general delight."

In a letter to Lord Kames which has been often quoted he explained at length, and for the most part in very technical language, the reasons for the superiority of the Scotch tunes.

"Farther, when we consider by whom these ancient tunes were composed and how they were first performed we shall see that such harmonical successions of sounds were natural and even necessary in their construction. They were composed by the minstrels of those days to be played on the harp accompanied by the voice. The harp was strung with wire, which gives a sound of long continuance and had no contrivance like that in the modern harpsichord, by which the sound of the preceding could be stopped the moment a succeeding note began. To avoid actual discord, it was therefore necessary that the succeeding emphatic note should be a chord with the preceding, as their sounds must exist at the same time. Hence arose that beauty in those tunes that has so long pleased, and will please forever, though men scarce know why."

Franklin's numerous voyages naturally turned his mind to problems of the sea. He pondered much on the question whether the daily motion of the earth from west to east would increase the speed of a ship sailing eastward and retard it on a westward passage. He was not quite sure that the earth's motion would have such an effect, but he thought it possible.

"I wish I had mathematics enough to satisfy myself whether the much shorter voyages made by ships bound hence to England, than by those from England hither, are not in some degree owing to the diurnal motion of the earth, and if so in what degree. It is a notion that has lately entered my mind; I know not if ever any other's." (Bigelow's Works of Franklin, vol. ii. p. 14.)

He referred to the subject again soon after, and finally a few years before his death,[20] but always as an unsettled question. The idea seems never to have got beyond the stage of investigation with him, but Parton has built up out of it a wonderful discovery.

"He conceived an idea still more practically useful, which has since given rise to a little library of nautical works, and conferred unmerited honor upon a naval charlatan--Maury. This idea was that by studying the form and motions of the earth and directing a ship's course so that it shall partake of the earth's diurnal motion a voyage may be materially shortened." (Parton's "Life of Franklin," vol. ii. p. 72.)

This is certainly a most extraordinary statement to be made by a writer like Parton, who has given the main facts of Franklin's life with considerable fidelity. He refers to it again in another passage, in which he says that this method of navigation is now used by all intelligent seamen. But there is no evidence that it was ever so used. He may have confused it with great circle sailing. The theory is an exploded one. There is no library of nautical works on the subject, and I think that the officers of the United States navy, the captains of the great ocean liners, and thousands of sailors all over the world would be very much surprised to hear Maury called a charlatan.

Maury's wonderful investigations were not in the line of sailing a ship so as to take advantage of the earth's diurnal motion, and could not have been suggested by such an idea. He explored the physical geography of the sea, and particularly the currents, trade-winds, and zones of calm. It was he who first worked out the shortest routes from place to place, which are still used. Although he never made a picturesque and brilliant discovery about lightning, and had not Franklin's exquisite power of expression, he was a much more remarkable man of science.

In a long letter to Alphonsus Le Roy, of Paris, written in 1785, on his voyage home from France with Captain Truxton, Franklin summed up all his maritime observations, including what he knew of the Gulf Stream. This letter is full of most curious suggestions for the navigation of ships, and was accompanied by a plate of carefully drawn figures, which has been reproduced in most editions of his works.