Volume Ii Part 21 (2/2)
But as this is Heresy here, and perhaps may be so with you, I only whisper it, and expect you will keep my Secret. Our Physicians have begun to discover that fresh Air is good for People in the Small-pox & other Fevers. I hope in time they will find out that it does no harm to People in Health.
At times his language on what he called _aerophobia_ grew highly animated.
What Caution against Air [he said in a letter to Thomas Percival], what stopping of Crevices, what wrapping up in warm Clothes, what shutting of Doors and Windows!
even in the midst of Summer! Many London Families go out once a day to take the Air; three or four Persons in a Coach, one perhaps Sick; these go three or four Miles, or as many Turns in Hide Park, with the Gla.s.ses both up close, all breathing over & over again the same Air they brought out of Town with them in the Coach with the least change possible, and render'd worse and worse every moment. And this they call _taking the Air_.
Indeed, there is at times something just a little ludicrous in the uncompromising fervor with which Franklin insisted upon his proposition. It seemed strange he said, in the letter from which we have just quoted, that a man whose body was composed in great part of moist fluids, whose blood and juices were so watery, and who could swallow quant.i.ties of water and small beer daily without inconvenience, should fancy that a little more or less moisture in the air should be of such importance; but we abound in absurdity and inconsistency.
It is a delightful account that John Adams gives us of a night which he spent in the same bed with Franklin at New Brunswick, on their way to the conference with Lord Howe:
The chamber [Adams tells us] was little larger than the bed, without a chimney, and with only one small window.
The window was open, and I, who was an invalid, and afraid of the air in the night, shut it close. ”Oh!”
says Franklin, ”don't shut the window, we shall be suffocated.” I answered I was afraid of the evening air. Dr. Franklin replied, ”The air within this chamber will soon be, and indeed is now, worse than that without doors. Come, open the window and come to bed, and I will convince you. I believe you are not acquainted with my theory of colds.” Opening the window and leaping into bed, I said I had read his letters to Dr. Cooper, in which he had advanced that n.o.body ever got cold by going into a cold church or any other cold air, but the theory was so little consistent with my experience, that I thought it a paradox. However, I had so much curiosity to hear his reasons, that I would run the risk of a cold. The Doctor then began a harangue upon air and cold, and respiration and perspiration, with which I was so much amused that I soon fell asleep, and left him and his philosophy together; but I believe they were equally sound and insensible within a few minutes after me, for the last words I heard were p.r.o.nounced as if he was more than half asleep. I remember little of the lecture, except that the human body, by respiration and perspiration, destroys a gallon of air in a minute; that two such persons as we were now in that chamber would consume all the air in it in an hour or two; that by breathing over again the matter thrown off by the lungs and the skin, we should imbibe the real cause of colds, not from abroad, but from within.
At times Franklin merely gave hints to brother philosophers and left them to run the hints down. For instance, he suggested to M. De Saussure, of Geneva, who succeeded in ascending Mont Blanc, the idea of ascertaining the lateral attraction of the Jura Mountains for the purpose of discovering the mean density of the earth upon the Newtonian theory of gravitation.
This was subsequently done with complete success by Nevil Maskelyne on Mt.
Schehallion in Perths.h.i.+re. To Ingenhousz he suggested the idea of ”hanging a weight on a spiral spring, to discover if bodies gravitated differently to the earth during the conjunctions of the sun and moon, compared with other times.”
He gave very close study to the philosophy of waterspouts and whirlwinds and came to the conclusion that they were generated by the same causes, and were of the same nature, ”the only Difference between them being, that the one pa.s.ses over Land, the other over Water.” He was the first person to discover that northeast storms did not begin in the northeast at all. The manner in which he did it is another good ill.u.s.tration of his quickness in noting the significance of every fact by which his attention was challenged. He desired to observe a lunar eclipse at nine o'clock in the evening at Philadelphia, but his efforts were frustrated by a northeast storm, which lasted for a night and a day, and did much damage all along the Atlantic coast. To his surprise he afterwards learnt from the Boston newspapers that the eclipse had been visible there, and, upon writing to his brother for particulars, was informed by him that it had been over for an hour when the storm set in at Boston; though it was apparently fair to a.s.sume that the storm began sooner at Boston than at Philadelphia. This information and further inquiry satisfied him that northeast storms commence southward and work their way to the northeast at the rate of a hundred miles an hour. When we read the words in which he stated his theory of such storms, we begin to understand what Sir Humphry Davy meant in saying that science appeared in Franklin's language in a dress wonderfully decorous, and best adapted to display her native loveliness.
Suppose [he said to Jared Eliot] a great tract of country, land and sea, to wit, Florida and the Bay of Mexico, to have clear weather for several days, and to be heated by the sun, and its air thereby exceedingly rarefied. Suppose the country northeastward, as Pennsylvania, New England, Nova Scotia, and Newfoundland, to be at the same time covered with clouds, and its air chilled and condensed. The rarefied air being lighter must rise, and the denser air next to it will press into its place; that will be followed by the next denser air, that by the next, and so on. Thus, when I have a fire in my chimney, there is a current of air constantly flowing from the door to the chimney; but the beginning of the motion was at the chimney, where the air being rarefied by the fire rising, its place was supplied by the cooler air that was next to it, and the place of that by the next, and so on to the door. So the water in a long sluice or mill-race, being stopped by a gate, is at rest like the air in a calm; but as soon as you open the gate at one end to let it out, the water next the gate begins first to move, that which is next to it follows; and so, though the water proceeds forward to the gate, the motion which began there runs backward, if one may so speak, to the upper end of the race, where the water is last in motion.
It may be truly said of every province of scientific research into which Franklin ventured that he brought to it a bold and original spirit of speculation which gave it new interest and meaning. Even when he was not the first to kindle a light, he had a happy and effective way of tr.i.m.m.i.n.g it anew and freshening its radiance. To Collinson he wrote on one occasion, ”But I must own I am much in the _Dark_ about _Light_.” But noonday is not more luminous than what he had to say on the subject in this letter.
May not all the Phaenomena of Light [he asked] be more conveniently solved, by supposing universal s.p.a.ce filled with a subtle elastic Fluid, which, when at rest, is not visible, but whose Vibrations affect that fine Sense the Eye, as those of Air do the grosser Organs of the Ear? We do not, in the Case of Sound, imagine that any sonorous Particles are thrown off from a Bell, for Instance, and fly in strait Lines to the Ear; why must we believe that luminous Particles leave the Sun and proceed to the Eye? Some Diamonds, if rubbed, s.h.i.+ne in the Dark, without losing any Part of their Matter. I can make an Electrical Spark as big as the Flame of a Candle, much brighter, and, therefore, visible farther, yet this is without Fuel; and, I am persuaded no part of the Electric Fluid flies off in such Case to distant Places, but all goes directly, and is to be found in the Place to which I destine it. May not different Degrees of Vibration of the above-mentioned Universal Medium occasion the Appearances of different Colours? I think the Electric Fluid is always the same; yet I find that weaker and stronger Sparks differ in apparent Colour; some white, blue, purple, red; the strongest, White; weak ones, red. Thus different Degrees of Vibration given to the Air produce the 7 different Sounds in Music, a.n.a.lagous to the 7 Colours, yet the Medium, Air, is the same.
”Universal s.p.a.ce, as far as we know of it,” he declared in his _Loose Thoughts on a Universal Fluid_, ”seems to be filled with a subtil Fluid, whose Motion, or Vibration is called Light.” And he then proceeds to found on this statement a series of speculations marked by too high a degree of temerity to have much scientific value. One sentiment in the paper, however, is well worth recalling as showing how clearly its author had grasped the conservation of matter. ”The Power of Man relative to Matter,”
he observed, ”seems limited to the dividing it, or mixing the various kinds of it, or changing its Form and Appearance by different Compositions of it; but does not extend to the making or creating of new Matter, or annihilating the old.”
The Science of Palaeontology was in its infancy during the lifetime of Franklin. Many years before Cuvier gave the name of mastodon to the prehistoric beast, whose fossil remains had been brought to sight from time to time in different parts of the world, George Croghan, the Indian trader, sent to Franklin a box of tusks and grinders, which had been found near the Ohio, and which he supposed to be parts of a dismembered elephant. In his reply of thanks, Franklin observed that the tusks were nearly of the same form and texture as those of the African and Asiatic elephant. ”But the grinders differ,” he added, ”being full of k.n.o.bs, like the grinders of a carnivorous animal; when those of the elephant, who eats only vegetables, are almost smooth. But then we know of no other animal with tusks like an elephant, to whom such grinders might belong.” The fact that, while elephants inhabited hot countries only, fragments such as those sent to him by Croghan were found in climates like those of the Ohio Territory and Siberia, looked, Franklin concluded, ”as if the earth had anciently been in another position, and the climates differently placed from what they are at present.” Contrasting the observations of this letter with the paper read long afterwards by Thomas Jefferson before the American Philosophical Society on the bones of a large prehistoric quadruped resembling the sloth, William B. Scott, the American palaeontologist, remarks:
Franklin's opinions are nearer to our present beliefs than were Jefferson's, written nearly forty years later. Of course, we now know that Franklin was mistaken in supposing that such bones were found only in what is now Kentucky and in Peru, and his comparison of the teeth of the mastodon with the ”grinders of a carnivorous animal” is not very happy, but the inferences are remarkably sound, when we consider the state of geological knowledge in 1767.
In a letter to Antoine Court de Gebelin, the author of the _Monde Primitif_, Franklin gave him a valuable caution, in relation to apparent linguistic variations. Strangers, who learnt the language of an Indian nation, he said, finding no orthography, formed each his own orthography according to the usual sounds given to the letters in his own language.
Thus the same words of the Mohawk language, written by an English, a French and a German interpreter, often differed very much in the spelling.
Franklin's letters to Herschel, Maskelyne, Rittenhouse, Humphrey Marshall and James Bowdoin reveal a keen interest in astronomy, but this is not one of the fields from which he came off _c.u.m laude_. Gratifying to the pride of an American, however, is an observation which he made to William Herschel, when the latter sent to him for the American Philosophical Society a catalogue of one thousand new nebulae and star-cl.u.s.ters and stated at the same time that he had discovered two satellites, which revolved about the Georgian planet. In congratulating him on the discovery, Franklin said:
You have wonderfully extended the Power of human Vision, and are daily making us Acquainted with Regions of the Universe totally unknown to mankind in former Ages. Had Fortune plac'd you in this part of America, your Progress in these Discoveries might have been still more rapid, as from the more frequent clearness of our Air, we have near one Third more in the year of good observing Days than there are in England.
The production of cold by evaporation was another subject which enlisted the eager interest of Franklin. In co-operation with Dr. Hadley, the Professor of Chemistry at Cambridge, England, he was so successful in covering a ball with ice by wetting it from time to time with ether, and blowing upon the ether with a bellows, that he could write to John Lining in these words: ”From this experiment one may see the possibility of freezing a man to death on a warm summer's day, if he were to stand in a pa.s.sage through which the wind blew briskly, and to be wet frequently with ether, a spirit that is more inflammable than brandy, or common spirits of wine.”
Geology was in its infancy during Franklin's time, but he hazarded some conjectures about the formation of the earth that are perhaps not less trustworthy than those advanced by riper geologists. In the letter, in which these conjectures were communicated to the Abbe Soulavie, he said:
Part of the high county of Derby being probably as much above the level of the sea, as the coal mines of Whitehaven were below it, seemed a proof that there had been a great _boulevers.e.m.e.nt_ in the surface of that Island (Great Britain), some part of it having been depressed under the sea, and other parts which had been under it being raised above it.... Such changes in the superficial parts of the globe [he continued] seemed to me unlikely to happen if the earth were solid to the centre. I therefore imagined that the internal parts might be a fluid more dense, and of greater specific gravity than any of the solids we are acquainted with; which therefore might swim in or upon that fluid. Thus the surface of the globe would be a sh.e.l.l, capable of being broken and disordered by the violent movements of the fluid on which it rested.
The letter contains other speculations equally bold:
It has long been a supposition of mine that the iron contained in the substance of this globe, has made it capable of becoming as it is a great magnet. That the fluid of magnetism exists perhaps in all s.p.a.ce; so that there is a magnetical North and South of the universe as well as of this globe, and that if it were possible for a man to fly from star to star, he might govern his course by the compa.s.s. That it was by the power of this general magnetism this globe became a particular magnet. In soft or hot iron the fluid of magnetism is naturally diffused equally; when within the influence of the magnet, it is drawn to one end of the Iron, made denser there, and rare at the other, while the iron continues soft and hot, it is only a temporary magnet: If it cools or grows hard in that situation, it becomes a permanent one, the magnetic fluid not easily resuming its equilibrium. Perhaps it may be owing to the permanent magnetism of this globe, which it had not at first, that its axis is at present kept parallel to itself, and not liable to the changes it formerly suffered, which occasioned the rupture of its sh.e.l.l, the submersions and emersions of its lands and the confusion of its seasons.
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