Nor was the attention given by Franklin to ventilation by any means confined to chimneys. Air vitiated by human respiration also came in for a share of it. Describing an experiment by which he demonstrated the manner in which air affected in this way is purified, Alexander Small said:
The Doctor confirmed this by the following experiment.
He breathed gently through a tube into a deep gla.s.s mug, so as to impregnate all the air in the mug with this quality. He then put a lighted bougie into the mug; and upon touching the air therein the flame was instantly extinguished; by frequently repeating the operation, the bougie gradually preserved its light longer in the mug, so as in a short time to retain it to the bottom of it; the air having totally lost the bad quality it had contracted from the breath blown into it.
Franklin became deeply interested in the brilliant course of investigation pursued by Priestley with respect to gases, and several penetrating glances of his into the relations of carbonic acid gas to vegetation have come down to us. Observing on a visit to Priestley the luxuriance of some mint growing in noxious air, he suggested to Priestley that "the air is mended by taking something from it, and not by adding to it." He hoped, he said in a letter to Priestley, that the nutriment derived by vegetation from carbonic acid gas would give some check to the rage of destroying trees that grew near houses, which had accompanied recent improvements in gardening from an opinion of their being unwholesome.
Just as he was consulted about the best methods of protecting St. Paul"s Cathedral and the a.r.s.enals at Purfleet from lightning, so he was also consulted by the British Government as to the best method for ventilating the House of Commons. "The personal atmosphere surrounding the members," he thought, "might be carried off by making outlets in perpendicular parts of the seats, through which the air might be drawn off by ventilators, so placed, as to accomplish this without admitting any by the same channels."
The experiment might be tried upon some of our City Councilmen. Principles of ventilation, expounded by Franklin, were also utilized by the Messrs.
Adam of the Adelphi, in the construction of the large room built by them for the meetings of the Society for the Encouragement of Arts. We also find him suggesting openings, close to the ceilings of rooms, and communicating with flues, constructed alongside of chimney flues, as effective means for ventilating rooms.
With all his primary and secondary gifts for scientific research, it is difficult to believe that, if Franklin had not been diverted from it by engrossing political cares, he would have added both to his special reputation as a student of electricity and to his general reputation as a man of science. As it was, his civic activity and popular leadership in Pennsylvania, his several agencies abroad, his partic.i.p.ation in the American Revolution, his career as Minister to France, and his official duties, after his return, made such imperious demands upon his time that he had little or no leisure left for scientific pursuits. This picture of his situation which he presented in a letter to Ingenhousz, when he was in France, was more or less true of almost every part of his life after he became famous:
Besides being hara.s.s"d with too much Business, I am expos"d to numberless Visits, some of Kindness and Civility, many of mere idle Curiosity, from Strangers of America & of different Parts of Europe, as well as the Inhabitants of the Provinces who come to Paris.
These devour my Hours, and break my Attention, and at Night I often find myself fatigu"d without having done anything. Celebrity may for a while flatter one"s Vanity, but its Effects are troublesome. I have begun to write two or three Things, which I wish to finish before I die; but I sometimes doubt the possibility.
Some of the reflections of Franklin on scientific subjects, such as his early letters to Cadwallader Colden with regard to "perspirants and absorbents" are, to use his own expression in one of them, too plainly _ultra crepidam_ to have any value. Of others, we might fairly say that his knowledge of the topics which he handled in them was hardly deep enough to deserve any praise more confident than that which he allowed himself when writing to Cadwallader Colden in 1751 of the Philadelphia Experiments.
"So," he said to Colden in this letter, "we are got beyond the skill of _Rabelais"s_ devils of two years old, who, he humorously says, had only learnt to thunder and lighten a little round the head of a cabbage." All the same, even aside from his electrical experiments, Franklin acquired no little fame as a philosopher, made more than one fruitful suggestion to fellow-workers of his in the domain of science and contributed many useful observations to the general fund of scientific thought.
Apparently his views on medical topics were held in very considerable respect. In 1777, he was elected a member of the Royal Medical Society of Paris, and in 1787 an honorary member of the Medical Society of London.
Many works on medical subjects were dedicated to him by their authors. He was one of the commission which exposed the imposture of Mesmer. There are few things that give us a better idea of the extraordinary celebrity enjoyed by him than the wide currency obtained by a spurious opinion of his, ascribing great merit to tobacco ashes as a remedy for dropsy. It won such an extensive circulation, and brought down on his head such a flood of questions from physicians and others, that he was compelled to deny flatly the truth of the story. One person, Lord Cadross, afterwards the Earl of Buchan, firmly believed that he would have perished at the hands of a professional physician, who wished to blister him, when he was afflicted with a fever, if Franklin had not dissented from the treatment. Franklin probably deserved no higher credit for his dissent on this occasion than that of sharing the opinion of Sir John Pringle, who was convinced that, out of every one hundred fevers, ninety-two cured themselves. So far as we can see, there is nothing in the works of Franklin to warrant the belief that he possessed any uncommon degree of medical knowledge, though he was full of curiosity with regard to medicine as with regard to every other branch of human learning. In one of his letters to Colden, written in his fortieth year, he expressed the hope that future experiment would confirm the idea that the yaws could be cured by tar-water. In a later letter to Colden, he expressed his pleasure at hearing more instances of the success of the poke-weed "in the Cure of that horrible Evil to the human Body, a Cancer." At his suggestion, a young physician, with the aid of Sanctorius"
balance, tested alternately each hour, for eight hours, the amount of the perspiration from his body, when naked, and when warmly clad, and found that it was almost as great during the hours when he was naked. By his investigations into the malady known in his time popularly as "the dry bellyache," and learnedly as the "_colica Pictonum_," he conferred a real benefit upon medical science. His views upon the subject received the honor of being incorporated with due acknowledgments into Dr. John Hunter"s essay on the _Dry Bellyache of the Tropics_. Summarily speaking they were that the complaint was a form of lead poisoning.
I have long been of opinion [he wrote to Dr.
Cadwallader Evans in 1768] that that distemper proceeds always from a metallic cause only; observing that it affects, among tradesmen, those that use lead, however different their trades,--as glaziers, letter-founders, plumbers, potters, white-lead makers, and painters;...
although the worms of stills ought to be of pure tin, they are often made of pewter, which has a great mixture in it of lead.
The year before this letter was written, Franklin had found on reading a pamphlet, containing the names and vocations of the persons, who had been cured of the colic at Charite, a Parisian hospital, that all of them had followed trades, which handle lead in some form or other. On going over the vocations, he was at first puzzled to understand why there should be any stonecutters or soldiers among the sufferers, but his perplexity was cleared up by a physician at the hospital, who informed him that stonecutters frequently used melted lead for fixing the ends of iron bal.u.s.trades in stone, and that the soldiers had been employed as laborers by painters, when grinding colors. These facts were long afterwards communicated by Franklin to Benjamin Vaughan in a letter, in which he cited other incidents, interesting partly because they corroborated his theory, and partly because they are additional proofs of his vigilance and patience in collecting facts, before advancing an hypothesis, as well as of a memory, which retained every instructive circ.u.mstance imparted to it by eye or ear as imperishably as hardening cement retains the impression of a dog"s foot. When he was a boy at Boston, Franklin said, it was discovered that New England rum, which had produced the dry bellyache and paralyzed the limbs in North Carolina, had been made by distilleries with leaden still-heads and worms. Later, when he was in London, he had been warned by an old workman at Palmer"s printing-house, as well as by an obscure pain in his own hands, that it was a dangerous practice to handle a heated case of types. About the same time, a letter-founder in the same close at Palmer"s, in a conversation with him, ascribed the existence of the ailment among his workmen to the fact that some of them were slovenly enough to go to their meals with unwashed hands that had come into contact with molten lead. He had also observed in Derbyshire that the smoke from lead furnaces was pernicious to gra.s.s and other vegetables, and in America had often observed that streaks on shingle roofs, made by white lead, washed from bal.u.s.ters or dormer window frames, were always entirely free from moss. He had also been told of a case where this colic had afflicted a whole family, and was supposed to be due to the corrosive effect of the acid in leaves, shed upon the roof, from which the family derived the supply of rain water, upon which it relied for drink.
More important still than the insight that Franklin obtained into the Painter"s Colic was the insight which he obtained into the salutary effect of the custom which is now almost universal, except in the homes of the ignorant and squalid, of sleeping at night in rooms with the windows up.
This custom, as well as the outdoor regimen, which has proved of such signal value in the treatment of tuberculosis, originated in hygienic conceptions identical with those steadfastly inculcated by him. His opinions with regard to colds and the benefits of pure air were expressed at many different times, and in many different forms, but nowhere so conveniently for the purposes of quotation as in a letter which he wrote to Dr. Benjamin Rush in 1773.
I hope [he said in this letter] that after having discovered the benefit of fresh and cool air applied to the sick, people will begin to suspect that possibly it may do no harm to the well. I have not seen Dr.
Cullen"s book, but am glad to hear that he speaks of catarrhs or colds by contagion. I have long been satisfied from observation, that besides the general colds now termed _influenzas_ (which may possibly spread by contagion, as well as by a particular quality of the air), people often catch cold from one another when shut up together in close rooms, coaches, &c., and when sitting near and conversing so as to breathe in each other"s transpiration; the disorder being in a certain state. I think, too, that it is the frouzy, corrupt air from animal substances, and the perspired matter from our bodies, which being long confined in beds not lately used, and clothes not lately worn, and books long shut up in close rooms, obtains that kind of putridity, which occasions the colds observed upon sleeping in, wearing, and turning over such bedclothes, or books, and not their coldness or dampness. From these causes, but more from too full living, with too little exercise, proceed in my opinion most of the disorders, which for about one hundred and fifty years past the English have called _colds_.
As to Dr. Cullen"s cold or catarrh _a frigore_, I question whether such an one ever existed. Travelling in our severe winters, I have suffered cold sometimes to an extremity only short of freezing, but this did not make me _catch cold_. And, for moisture, I have been in the river every evening two or three hours for a fortnight together, when one could suppose I might imbibe enough of it to _take cold_ if humidity could give it; but no such effect ever followed. Boys never get cold by swimming. Nor are people at sea, or who live at Bermudas, or St. Helena, small islands, where the air must be ever moist from the dashing and breaking of waves against their rocks on all sides, more subject to colds than those who inhabit part of a continent where the air is driest. Dampness may indeed a.s.sist in producing putridity and those miasmata which infect us with the disorder we call a cold; but of itself can never by a little addition of moisture hurt a body filled with watery fluids from head to foot.
Franklin"s belief that colds and overeating often went hand in hand also found expression in one of his letters to Polly Stevenson. When sending her an account of some seamen, who had experienced considerable relief from thirst by wearing clothes kept constantly wet with salt water, he said, "I need not point out to you an Observation in favour of our Doctrine, that you will make on reading this Paper, that, _having little to eat_, these poor People in wet Clothes Day and Night _caught no cold_." In every, or in practically every, case, he seems to have referred colds to what he rather vaguely calls a siziness and thickness of the blood, resulting from checked perspiration, produced by different agencies, including a gross diet.
Thus [he says in his _Notes and Hints for Writing a Paper Concerning what is called Catching Cold_], People in Rooms heated by a Mult.i.tude of People, find their own Bodies heated; thence the quant.i.ty of perspirable Matter is increased that should be discharged, but the Air, not being changed, grows so full of the same Matter, that it will receive no more. So the Body must retain it. The Consequence is, the next Day, perhaps sooner, a slight putrid Fever comes on, with all the Marks of what we call a Cold, and the Disorder is suppos"d to be got by coming out of a warm Room, whereas it was really taken while in that Room.
He did not shrink from any of the consequences of his reasoning about colds however extreme.
Be so kind as to tell me at your leisure [he wrote to Barbeu Dubourg], whether in France, you have a general Belief that moist Air, and cold Air, and damp Shirts or Sheets, and wet Floors, and Beds that have not lately been used, and Clothes that have not been lately worn, and going out of a warm Room into the Air, and leaving off a long-worn Wastecoat, and wearing leaky Shoes, and sitting near an Open Window, or Door, or in a Coach with both Gla.s.ses down, are all or any of them capable of giving the Distemper we call _a Cold_, and you _a Rheum, or Catarrh_? Or are these merely _English_ ideas?
His views on the wholesomeness of fresh air were far in advance of the general intelligence of his time, and were expressed in spirited terms.
After stating in a letter to Jean Baptiste Le Roy that he had become convinced that the idea that perspiration is checked by cold was an error as well as the idea that rheum is occasioned by cold, he added:
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 Perthshire. 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, shine 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.