Volume Ii Part 20 (1/2)

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, s.h.i.+ning 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 vanis.h.i.+ng 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-s.h.i.+p, 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 s.h.i.+ps 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 s.h.i.+ps, 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 s.h.i.+ps 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 pus.h.i.+ng 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_.”