The atmosphere of Boston was completely theological. There was no room, no opportunity, for science, and no inducement or even suggestion that would lead to it, still less to original research in it. We find Franklin in a state of rebellion against the prevailing tone of thought, writing against it in his brother's newspaper at the risk of imprisonment, and in a manner more bitter and violent than anything he afterwards composed. If he had remained in Boston it is not likely that he would ever have taken seriously to science, for all his energies would have been absorbed in fighting those intolerant conditions which smothered all scientific inquiries.

In Pennsylvania he found the conditions reversed. The Quakers and the German sects which made up the majority of the people of that province in colonial times had more advanced ideas of liberty and free thought than any of the other religious bodies in America, and in consequence science flourished in Pennsylvania long before it gained entrance into the other colonies. The first American medical college, the first hospital, and the first separate dispensary were established there.

Several citizens of Philadelphia who were contemporaries of Franklin achieved sufficient reputation in science to make their names well known in Europe.

David Rittenhouse invented the metallic thermometer, developed the construction of the compensation pendulum, and made valuable experiments on the compressibility of water. He became a famous astronomer, constructed an orrery to show the movements of the stars which was an improvement on all its predecessors, and conducted the observations of the transit of Venus in 1769. Pennsylvania was the only one of the colonies that took these observations, which in that year were taken by all the European governments in various parts of the world. The Legislature and public inst.i.tutions, together with a large number of individuals, a.s.sisted in the undertaking, showing what very favorable conditions for science prevailed in the province.[18]

These were the conditions which seem to have aroused Franklin. Without them his mind tended more naturally to literature, politics, and schemes of philanthropy and reform; but when his strong intellect was once directed towards science, he easily excelled in it. Some of the early questions discussed by the Junto, such as "Is sound an ent.i.ty or body?"

and "How may the phenomena of vapors be explained?" show an inclination towards scientific research; and it is very likely that he studied such subjects more or less during the ten years which followed his beginning business for himself.

In his _Gazette_ for December 15, 1737, there is an essay on the causes of earthquakes, summarizing the various explanations which had been given by learned men, and this essay is supposed to have been written by him. Six years afterwards he made what has been usually considered his first discovery,--namely, that the northeast storms of the Atlantic coast move against the wind; or, in other words, that instead of these storms coming from the northeast, whence the wind blows, they come from the southwest. He was led to this discovery by attempting to observe an eclipse of the moon which occurred on the evening of October 21, 1743; but he was prevented by a heavy northeaster which did great damage on the coast. He was surprised to find that it had not prevented the people of Boston from seeing the eclipse. The storm, though coming from the northeast, swept over Philadelphia before it reached Boston. For several years he carefully collected information about these storms, and found in every instance that they began to leeward and were often more violent there than farther to windward.

He seems to have been the first person to observe these facts, but he took no pains to make his observations public, except in conversation or in letters to prominent men like Jared Eliot, of Connecticut, and these letters were not published until long afterwards. This was his method in all his investigations. He never wrote a book on science; he merely reported his investigations and experiments by letter, usually to learned people in England or France. There were no scientific periodicals in those days. The men who were interested in such things kept in touch with one another by means of correspondence and an occasional pamphlet or book.

During the same period in which he was making observations on northeast storms he invented the "Pennsylvania Fireplace," as he called it, a new sort of stove which was a great improvement over the old methods of heating rooms. He published a complete description of this stove in 1745, and it is one of the most interesting essays he ever wrote. It is astonishing with what pleasure one can still read the first half of this essay written one hundred and fifty years ago on the driest of dry subjects. The language is so clear and beautiful, and the homely personality of the writer so manifest, that one is inclined to lay down the principle that the test of literary genius is the ability to be fascinating about stoves.

He explained the laws of hot air and its movements; the Holland stove, which afforded but little ventilation; the German stove, which was simply an iron box fed from outside, with no ventilating properties; and the great open fireplace fed with huge logs, which required such a draft to prevent the smoke from coming back into the room that the outer door had to be left open,--and if the door was shut the draft would draw the outer air whistling and howling through the crevices of the windows.

His "Pennsylvania Fireplace" was what we would now call an open-fireplace stove. It was intended to be less wasteful of fuel than the ordinary fireplace and to give ventilation, while combining the heating power of the German and Holland stoves. It continued in common use for nearly a century, and modified forms of it are still called the Franklin stoves.

One of its greatest advantages was that it saved wood, which, for some time prior to the introduction of coal, had to be brought such a long distance that it was becoming very expensive. Franklin refused to take out a patent for his invention; for he was on principle opposed to patents, and said that as we enjoyed great advantages from the inventions of others, we should be willing to serve them by inventions of our own. He afterwards learned that a London ironmonger made a few changes in the "Pennsylvania Fireplace" and sold it as his own, gaining a small fortune.

Franklin's invention was undoubtedly an improvement on the old methods of heating and ventilation; but he was not, as has been absurdly claimed, the founder of the "American stove system," for that system very soon departed from his lines and went back to the air-tight stoves of Germany and Holland.

It was not until 1746 or 1747, after he had been making original researches in science for about five years, that he took up the subject of electricity, and he was then forty-one years old. It appears that Mr.

Peter Collinson, of London, who was interested in botany and other sciences, and corresponded largely on such subjects, had presented to the Philadelphia Library one of the gla.s.s tubes which were used at that time for producing electricity by rubbing them with silk or skin.

Franklin began experimenting with this tube, and seems to have been fascinated by the new subject. On March 28, 1747, he wrote to Mr.

Collinson thanking him for the tube, and saying that they had observed with its aid some phenomena which they thought to be new.

"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 crowds to see them, I have, during some months past, had little leisure for anything else."

It will be observed that he speaks of crowds coming to see the experiments, and this confirms what I have already shown of the strong interest in science which prevailed at that time in Pennsylvania, and which had evidently first aroused Franklin. In fact, a renewed interest in science had been recently stirred up all over the world, and people who had never before thought much of such things became investigators.

Voltaire, who resembled Franklin in many ways, had turned aside from literature, and at forty-one, the same age at which Franklin began the study of electricity, had become a man of science, and for four years devoted himself to experiments.

Franklin was by no means alone in his studies. Besides the crowds who were interested from mere curiosity, there were three men--Ebenezer Kinnersley, Thomas Hopkinson, and Philip Syng--who experimented with him, and it was no mere amateurish work in which these men were engaged.

Franklin was their spokesman and reported the results of his and their labor by means of letters to Mr. Peter Collinson. Within six months Hopkinson had observed the power of points to throw off electricity, or electrical fire, as he called it, and Franklin had discovered and described what is now known as positive and negative electricity. Within the same time Syng had invented an electrical machine, consisting of a sphere revolved on an axis with a handle, which was better adapted for producing the electrical spark than the tube-rubbing practised in Europe.

The experiments and the letters to Collinson describing them continued, and about this time we find Franklin writing a long and apparently the first intelligent explanation of the action of the Leyden jar. Then followed attempts to explain thunder and lightning as phenomena of electricity, and on July 29, 1750, Franklin sent to Collinson a paper announcing the invention of the lightning-rod, together with an explanation of its action.

In these papers he also suggested an experiment which would prove positively that lightning was a form of electricity. The two phenomena were alike as regarded light, color, crooked direction, noise, swift motion, being conducted by metals, subsisting in water or ice, rending bodies, killing animals, melting metals, and setting fire to various substances. It remained to demonstrate with absolute certainty that lightning resembled electricity in being attracted by points; and for this purpose Franklin proposed that a man stand in a sort of sentry-box on the top of some high tower or steeple and with a pointed rod draw electricity from pa.s.sing thunder-clouds.

This suggestion was successfully carried out in France, in the presence of the king, at the county-seat of the Duke D'Ayen; and afterwards Buffon, D'Alibard, and Du Lor confirmed it by experiments of their own.

But they did not use steeples; they erected lofty iron rods, in one instance ninety-nine feet high. Nevertheless, it was in effect the same method that Franklin had suggested. The experiment was repeated in various forms in England, and the Philadelphia philosopher, postmaster, and author of "Poor Richard" became instantly famous as the discoverer of the ident.i.ty of lightning with electricity.

Two years before these experiments were inaugurated he had retired from business for various reasons, chief among which was his strong desire to devote more time to science. His letters continue to be filled with closely reasoned details of all sorts of experiments. So earnest were these Philadelphia investigators, that when Kinnersley wrote complaining that in travelling to Boston he found difficulty in keeping up his experiments, Franklin, in reply, suggested a portable electrical apparatus which would not break on a journey.

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 gla.s.s 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 ill.u.s.trating 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 pa.s.sing 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 n.o.ble 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 gla.s.s 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 cla.s.s, among the minor discoverers. But his discovery of the nature of lightning was so striking and so capable of arousing the wonder of the ma.s.ses 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 princ.i.p.ally 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 pa.s.sion 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 phosph.o.r.escence. The cause of the saltness of the sea and the existence of ma.s.ses 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-sh.e.l.ls 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 pa.s.sed. But it would be long to tell of all he wrote on light and heat, the _vis inertiae_ 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 n.o.blemen 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 gla.s.ses, the idea being taken from the pleasant sound produced by pa.s.sing a wet finger round the brim of a drinking-gla.s.s. When in England Franklin was so delighted with these instruments that he set about improving them. He had gla.s.ses 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."