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 anch.o.r.ed 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 alt.i.tude of a mile, to see far below them a vast stretch of the terrestrial surface. Already, said Franklin, one philosopher, M. Pilatre 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 c.o.c.k, who except the c.o.c.k 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 f.a.ggots 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 compet.i.tion. 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 princ.i.p.al 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. Pilatre de Rozier, whom we have already mentioned, and who was no less a person than the Professor of Chemistry, at the Athenee Royale, of which he was the founder, fell with a companion, from an alt.i.tude 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 const.i.tute 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 a.s.sent, 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 circ.u.mstance 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 gla.s.s 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 quant.i.ty 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 sh.o.r.e, an instant calmness diffused itself over a s.p.a.ce 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-gla.s.s. 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 bl.u.s.tering, unpleasant day, he attempted, with the co-operation of Sir Joseph Banks and other friends, to still the surf on a sh.o.r.e 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 ill.u.s.trations 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 sh.o.r.e 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 sh.o.r.e 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 Derwent.w.a.ter 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 Abbe 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 Abbe 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 _a la Franklin_."
Struck, when travelling on a ca.n.a.l 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 ca.n.a.l 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 r.e.t.a.r.ding 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 acc.u.mulation 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 a.s.signed 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 gla.s.ses, 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 gla.s.ses, 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 pa.s.sing 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 gla.s.ses, 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 Gla.s.ses cut, and half of each kind a.s.sociated 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 Gla.s.ses being always ready. This I find more particularly convenient since my being in France, the Gla.s.ses 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
magick circle, consisting of 8 concentric circles, and 8 radial rows, filled with a series of numbers, from 12 to 75, inclusive, so disposed as that the numbers of each circle or each radial row, being added to the central number 12, they made exactly 360, the number of degrees in a circle; and this circle had, moreover, all the properties of the square of 8.
Both of these conceits were duly forwarded to Collinson and, with regard to the square of 16, Franklin wrote to him playfully that he made no question but that he would readily allow that it was the most magically magical of any magic square ever made by any magician. From the terms of this letter, it is plain that the practical intellect of Franklin was a little ashamed of these feats as but _difficiles nugae_, but his misgivings were somewhat soothed by the suggestion of Logan that they might not be altogether useless if they produced by practice an habitual readiness and exactness in mathematical disquisitions.
Hardly more profitable than the magic squares but indicative, too, of the same mental initiative, was the scheme formed by Franklin for a new alphabet and a reformed mode of spelling. In the new alphabet, the first effort was to arrange the letters in what was supposed to be a more natural order than that of the old alphabet by beginning with the simple sounds framed by the breath with no or very little help from the tongue, teeth and lips, and proceeding gradually forward from sounds, produced at the back of the mouth, to the sound produced by closing the lips, that is _m_.
The _c_ of the old alphabet was omitted, _k_ being left to supply its hard sound, and _s_ its soft, and _k_ being also left to supply the place of _q_, and with an _s_ added, the place of _x_. _W_ as well as _q_ and _x_ was also dismissed from service, the vowel _u_, sounded as _oo_, being relied upon to perform its function. _Y_ also went by the board, _i_ taking its place, where used singly, and two vowels, where used as a diphthong.
_J_ was superseded by an entirely new symbol, shaped something like a small _h_, and sounded as _ish_, when used singly, but subserving various other offices, when conjoined with _d_, _t_ and _z_. As a whole, the new alphabet was so systematized that the sound of any letter, vowel or consonant was always the same, wherever it occurred, or whatever its alphabetical collocation. Nor did the new alphabet contain any silent letters, or fail to provide a letter for every distinct sound in the language. The difference between short and long vowels was compa.s.sed by a single vowel where short, and a double one, where long. For ill.u.s.tration, "mend"
remained "mend" and "did," "did," but "remained" reappeared as "remeened,"
and "deed" as "diid." Typographical obstacles prevent us from bringing to the eye of the reader a specimen of the reformed alphabet and spelling as they looked on a printed page. They, of course, issued from the mind of Franklin as stillborn as his reformed Episcopal Prayer Book. His only proselytes appear to have been Polly, who even wrote a letter to him in the strange forms, and his loving sister, Jane, who was delighted to have another language with which to express her affection for him. Our world is one in which some things are made but others make themselves, and, however arbitrary their character, will not allow themselves to be made over, even at the behest of such merciless rationalism as that of Franklin.
In the latter part of Franklin"s life, Noah Webster, the lexicographer, also formed a scheme for the reform of the alphabet, and Franklin had the pleasure of writing to him, "Our Ideas are so nearly similar, that I make no doubt of our easily agreeing on the Plan." Several years later, Webster, in his _Dissertations on the English Language_, stated that Franklin had compiled a dictionary, based upon his own reformatory system, and procured the types for printing it, but, finding himself too old to prosecute his design, had offered both ma.n.u.script and types to him. "Whether this project, so deeply interesting to this country," Webster said, "will ever be effected; or whether it will be defeated by insolence and prejudice, remains for my countrymen to determine."
Another thing upon which the ingenuity of Franklin was brought to bear, as the reader has already been told, was the Armonica. In his letter to Beccaria, extolling its merits, he describes it with a wealth of detail, not only thoroughly in keeping with his knack for mechanics, but showing that to music as to everything else, that won the favor of his intellect, he brought the ken of a man of science. The letter concludes with a dulcet compliment, which harmonizes well with its subject: "In honour of your musical language (the Italian), I have borrowed from it the name of this instrument, calling it the Armonica." In one of his papers, he drew up instructions for the proper use of the instrument which nothing but the most intimate familiarity with its operation could have rendered possible.
Admiration has often been expended upon the acuteness with which Franklin, in a letter to Lord Kames, accounted for the pleasure afforded by the old Scotch tunes, as compared with the pleasure afforded by the difficult music of his day, which, he said, was of the same nature as that awakened by the feats of tumblers and rope-dancers. The reason was this. The old Scotch melodies were composed by the minstrels of former 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 note 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 tones that had so long pleased, and would please forever, though men scarce knew why.
The most useful invention of Franklin was what came to be known as the Franklin stove. With modifications, it is still in use, and the essay written on it by Franklin, ent.i.tled _An Account of the New-invented Pennsylvanian Fireplaces_, is one of the best ill.u.s.trations of the capacity of his scientific genius to adapt itself to the hardest and barest offices that human comfort and convenience could impose upon it with a nicety and accuracy of trained insight and touch worthy of the cleverest journeyman, a command of scientific principles to be expected only of a professional student, and a gift of clear, lively expression which reminds us of the remark of Stella that Dean Swift could write agreeably even about a broomstick. The principle upon which the Franklin stove was constructed was that of making the heat from its open fireplace, after first ascending to its top, descend in such a manner at its back, before pa.s.sing off into the chimney, as to diffuse by radiation through the room, in which it stood, a large part of its warmth. The essay enumerates the different methods of heating rooms then in use: the great, open, smoky chimney-place, that the unremitting labor of one man could scarce keep supplied with fuel, and that gave out little more heat for human warmth than a fire outdoors; this chimney-place reduced to a smaller size with jambs, and free, to a great extent from the reproach of smokiness, yet, with its contraction setting up strong currents of whistling and howling air, which reminded Franklin of the Spanish proverb,
"If the Wind blows on you thro" a Hole, Make your Will, and take Care of your Soul";
the expensive and intricate French fireplaces with hollow backs, hearths and jambs of iron; the Holland stove, which shut off the sight of the fire, and could not conveniently be used for any purposes except those of warmth; the German stove which was subject to very much the same disadvantages as the Holland stove; and charcoal fires in pots which emitted disagreeable and dangerous fumes and were used chiefly in the shops of handicraftsmen.
From the shortcomings of all these methods of heating rooms, the Franklin stove, its inventor contended, was exempt. It diffused heat equally throughout a whole room; if you sat in an apartment warmed by it, you were not scorched before, while you were frozen behind; nor were you exposed to the drafts from which so many women, particularly, got colds in the head, rheums and defluxions that fell upon their jaws and gums, and destroyed early many a fine set of teeth in the northern colonies, and from which so many persons of both s.e.xes contracted coughs, catarrhs, toothaches, fevers, pleurisies and other diseases. It kept a sick room supplied with a fresh and yet properly tempered flow of pure air. It conserved heat. It economized fuel. With it, Franklin said, he could make his room twice as warm as it used to be with a quarter of the wood that he used to consume.
If you burned candles near it, they did not flare and run off into tallow as in the case of ordinary fireplaces with their excessive drafts. It corrected most smoky chimneys. It prevented all kinds of chimneys from fouling, and if they fouled made them less likely to fire, and, if they fired, made the fire easier to repress. A flame could be speedily kindled in it with the help of the shutter or trap-bellows that went along with it. A fire could be readily extinguished in it, or could be so secured in it that not one spark could fly out of it to do any damage. A room once warmed remained warm all night. "With all these Conveniences," concludes Franklin, "you do not lose the pleasing Sight nor Use of the Fire, as in the Dutch Stoves, but may boil the Tea-Kettle, warm the Flat-Irons, heat Heaters, keep warm a Dish of Victuals by setting it on the Top, &c. &c."
Some years after the publication of this essay, Franklin devised an improvement in the open chimney-place which tended to abate drafts and check the escape of heat up the chimney by contracting the chimney opening, bringing its breast down to within three feet of the hearth, and placing an iron frame just under this breast, with grooves on each side of the frame, in which an iron plate could be slid backwards and forwards at pleasure, for the purpose of cutting off the mouth of the chimney entirely from the chimney itself, when there was no fire on the hearth, or of leaving a s.p.a.ce of not more than two inches for the escape of smoke between the further edge of the plate and the back of the chimney-mouth. This improved chimney-place was described by Franklin in letters to Alexander d.i.c.k and James Bowdoin. The letter to Bowdoin seems to leave little to be said on the subject of chimneys. It indicates that Franklin had subjected them to a scrutiny hardly less close than that which he had fixed upon the Leyden Jar. In connection with the currents and reverse currents, set up in them in summer by the relations of inequality, which the air in them sustains, at different hours of the day and night, to the outside temperature, he suggests that joints of meat might keep for a week or more during the hottest weather in chimney-openings, if well wrapt three or four fold in wet linen cloths, sprinkled once a day with water to prevent evaporation.
b.u.t.ter and milk in vessels and bottles covered with wet cloths might, he thought, be preserved in the same way. And he even thought, too, that the movements of air in chimneys might, with the aid of smoke-jack vanes, be applied to some mechanical purposes, where a small but pretty constant power only was needed. To appreciate how patiently and exhaustively Franklin was in the habit of pursuing every course of observation or reflection opened up by his scientific propensities, the whole of this letter, which had much more to say on the subject of chimneys than we have mentioned, should be read.
At a later period of his life, Franklin describes to Turgot what he called his new stove. The novel feature of this consisted of an aerial syphon by which the smoke from the fireplace of the stove was first drawn upwards through the longer leg of the syphon, and then downwards through its shorter leg, and over burning coals, by which it was kindled into flame and consumed.
The ingenuity of Franklin was also exerted very successfully in the rectification of smoky chimneys. In his essay on the causes and cure of such chimneys, written on his last ocean voyage, he resolved the causes into no less than nine heads, and stated with his accustomed perspicuity and precision the remedy for each cause. In his time, the art of properly carrying off smoke through chimneys was but imperfectly understood by ordinary builders and mechanics, and it was of too humble a nature to tempt discussion by such men of science as were capable of clearly expounding the physical principles upon which it rested. It was not strange, therefore, that Franklin, who deemed nothing, that was useful, to be beneath the dignity of philosophy, should have acquired in his time the reputation of being a kind of "universal smoke doctor" and should have been occasionally consulted by friends of his, such as Lord Kames, about refractory chimneys.
The only smoky chimney, that seems to have completely baffled his investigation, recalls in a way the philosopher, who thought that he had discovered a new planet, but afterwards found that what he saw was only a fly in the end of his telescope. After exhausting every scientific resource in an effort to ascertain why the chimney in the country-house of one of his English friends smoked, Franklin was obliged to own the impotence for once of his skill; but, subsequently, his friend, who made no pretensions to the character of a fumist, climbed to the top of the funnel of his chimney by a ladder, and, on peering down into it, found that it had been filled by nesting birds with twigs and straw, cemented with clay, and lined with feathers.