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I suspect some mistake creeps in by the au- 1 is the same thing as giving it 1 f; (i. e. if thor's not distinguishing between a great force force applied to matter at rest, can put it in applied at once, or a small one continually ap. motion, and give it equal force) where then plied to a mass of matter, in order to move it. I is vis inertiæ ? If it existed at all in matter, think it is generally allowed by the philoso- should we not find the quantity of its resistphers, and, for aught we know, is certainly ance subtracted from the force given ? true, that there is no mass of matter, how great In No. 4. our author goes on and says, “the soever, but may be moved by any force how body a requires a certain force to be impressed small soever, (taking friction out of the ques- on it to be moved with a celerity as c, or such tion) and this small force continued, will in a force is necessary; and therefore makes a time bring the mass to move with any veloci- certain resistance, &c. A body as 2 a rety whatsoever.-Our author himself seems to quires twice that force to be moved with the allow this towards the end of the same No. 2, same celerity, or it makes twice that resistwhen he is subdividing his celerities and ance; and so on. This I think is not true; forces; for as in continuing the division to but that the body 2 a moved by the force 1 eternity by his method of 3 c, } c, c, &c. (though the eye may judge otherwise of it) &c. you can never come to a fraction of ve- does really move with the same celerity as it locity that is equal to c, or no celerity at all; did when impelled by the same force; for 2 so dividing the force in the same manner, a is compounded of 1 axla: and if each of you can never come to a fraction of force the 1 a's or each part of the compound were that will not produce an equal fraction of ce- made to move with 1 c (as they might be by lerity.—Where then is the mighty vis iner- 2f) then the whole would move with 2 c, and tiæ, and what is its strength; when the not with 1 c, as our author supposes. But 1 greatest assignable mass of matter will give f applied to 2 a, makes each a move with tc; to, or be moved by the least assignable force ? and so the whole moves with 1c; exactly the Suppose two globes, equal to the sun and to same as 1 a was made to do by 1 f before. one another, exactly equipoised in Jove's ba- What is equal celerity but a measuring the lance; suppose no friction in the centre of mo- same space by moving bodies in the same tion, in the beam or elsewhere; if a moscheto time?–Now if 1 a impelled by 1.f measures then were to light on one of them, would he 100 yards in a minute; and in 2 a impelled by not give motion to them both, causing one to 1 f, each a measures 50 yards in a minute, descend and the other to rise ? If it is objected, which added make 100; are not the celerithat the force of gravity helps one globe to de- ties as the forces equal ? and since force and scend, I answer, the same force opposes the celerity in the same quantity of matter are other's rising: here is an equality that leåves always in proportion to each other, why the whole motion to be produced by the mos- should we, when the quantity of matter is cheto: without whom those globes would not doubled, allow the force to continue unimbe moved at all. What then does vis inertia paired, and yet suppose one half of the celedo in this case ? and what other effect could rity to be lost? I wonder the more at our we expect if there were no such thing? Sure- author's mistake in this point, since in the ly if it were any thing more than a phantom, same number I find him observing : “We there might be enough of it in such vast bo- may easily conceive that a body as 3 a, 4 c, dies, to annihilate so trifling a force by its op- &c., would make 3 or 4 bodies equal to once position to motion ?
a, each of which would require once the first Our author would have reasoned more force to be moved with the celerity c.” If clearly, I think, if, as he has used the letter then in 3 a, each a requires once the first a for a certain quantity of matter, and c for a force f to be moved with the celerity, c, would certain quantity of celerity, he had employed not each move with the force f and celerity one letter more, and put f perhaps, for a cerc; and consequently the whole be 3 a movtain quantity of force. This let us suppose to ing with 3 f and 3 c? After so distinct an ob be done; and then as it is a maxim that the servation, how could he miss of the conseforce of bodies in motion is equal to the quan- quences, and imagine that I cand 3 c were the tity of matter multiplied by the celerity, (or same? Thus as our author's abatement of cef=cx a ;) and as the force received by and lerity in the case of 2 a moved by 1 f is imasubsisting in matter, when it is put in mo- ginary, so must be his additional resistance.tion, can never exceed the force given; so if And here again, I am at a loss to discover any f moves a with c, there must needs be re-effect of the vis inertiæ. quired 2 f to move a with 2 o; for a moving In No. 6, he tells us, that all this is likewith 2 c would have a force equal to 2 f, which wise certain when taken the contrary way, it could not receive from 1s; and this, not viz. from motion to rest ; for the body a movbecause there is such a thing as vis inertiæ, ing with a certain velocity, as c, requires a cerfor the case would be the same if that had no tain degree of force or resistance to stop that existence; but because nothing can give more motion, &c." that is, in other words, equal than it has, if 1 f can to 1 a give 1 c, which I force is necessary to destroy force. It may
But how does this discover a vis iner-panies it, have reconciled me to those convultiæ ? Would not the effect be the
same if there sions which all naturalists agree this globe has were no such thing? A force 1 f strikes a suffered. Had the different strata of clay, body 1 a, and moves it with the celerity 1 c, gravel, marble, coals, lime-stone, sand, minei. e. with the force 1f: it requires, even ac- rals, &c. continued to lie level, one under the cording to our author, only an opposing 1 f other, as they may be supposed to have done to stop it. But ought it not (if there were a before those convulsions, we should have had vis inertia) to have not only the force 1 f, but the use only of a few of the uppermost of the an additional force equal to the force of vis in- strata, the others lying too deep and too diffiertiæ, that obstinate power by which a body cult to be come at; but the shell of the earth endeavours with all its might to continue in being broke, and the fragments thrown into its present state, whether of motion or rest ? this oblique position, the disjointed ends of a I
say, ought there not to be an opposing force great number of strata of different kinds are equal to the sum of these ?- The truth how- brought up to-day, and a great variety of useever is, that there is no body, how large ful materials put into our power, which would soever, moving with any velocity, how great otherwise have remained eternally concealed soever, but may be stopped by any opposing from us. So that what has been usually lookforce, how small soever, continually applied. ed upon as a ruin suffered by this part of the At least all our modern philosophers agree to universe, was, in reality, only a preparation, tell us so.
or means of rendering the earth more fit for Let me turn the thing in what light I please, use, more capable of being to mankind a conI cannot discover the vis inertiæ, nor any ef- venient and comfortable habitation. fect of it. It is allowed by all, that a body 1
B. FRANKLIN. a moving with a velocity 1 c, and a force 1 f striking another body i a at rest, they will
To the Abbé Soulavie.* afterwards move on together, each with JC and 1 f; which, as I said before, is equal in Theory of the Earth.-Read in the American the whole to 1 c and 1 f. If vis inertiæ, as
Philosophical Society, November 21, 1788. in this case, neither abates the force nor the
Passy, September 22, 1782. velocity of bodies, what does it, or how does it I RETURN the papers with some corrections. discover itself?
I did not find coal mines under the calcareous I imagine I may venture to conclude my rock in Derbyshire. ! only remarked, that observations on this piece, almost in the at the lowest part of that rocky mountain words of the author; that if the doctrines of which was in sight, they were oyster shells the immateriality of the soul and the existence mixed in the stone; and part of the high of God and of divine providence are demon- county of Derby being probably as much above strable from no plainer principles, the deist the level of the sea, as the coal mines of [i. e. theist] has a desperate cause in hand. Whitehaven were below it, it seemed a proof, I oppose my theist to his atheist, because I that there had been a great boulversement think they are diametrically opposite; and not in the surface of that island, some part of it near of kin, as Mr. Whitfield seems to sup having been depressed under the sea, and other pose; where (in his journal) he tells us, Mr. parts, which had been under it, being raised B. was a deist, I had almost said an atheist;" above it. Such changes in the superficial that is chalk, I had almost said charcoal. parts of the globe, seemed to me unlikely to
The din of the market* increases upon me; happen, if the earth were solid to the centre. and that, with frequent interruptions, has, í I therefore imagined, that the internal parts find, made me say some things twice over; might be a fluid more dense, and of greater and, I suppose, forget some others I intended specific gravity than any of the solids we are
It has, however, one good effect, as acquainted with, which therefore might swim it obliges me to come to the relief of your pa- in or upon that fluid. Thus the surface of tience with B. FRANKLIN. the globe would be a shell, capable of being
broken and disorded by the violent move
ments of the fluid on which it rested. And To Dr. John Pringle.
as air has been compressed by art so as to be On the different Strata of the Earth. twice as dense as water, in which case, if such
CRAVEN-STREET, Jan. 6, 1758. air and water could be contained in a strong I RETURN you Mr. Mitchell's paper on the glass vessel, the air would be seen to take the strata of the eartht with thanks. The read-Nowest place, and the water to float above and ing of it, and perusal of the draft that accom- upon it; and as we know not yet the degree * Dr. Franklin lived in Market-street, on the North
of density to which air may be compressed, side, between 4th & 5th streets, on the east corner of an alley, where the first metal conductor still remains. * Occasioned by his sending me some notes be had
The paper of Mr. Mitchell, here referred to, was pub- taken of what I had said to him in conversation on the Jished afterwards in the Philosophical Transactions of Theory of the Earth. I wrote it to set him right in some
poixt i wherein be had mistaken my meaning. B. F. VOL. II. ...3C
and M. Amontons calculated, that its density star, he migh govern his course by the comincreasing as it approached the centre, in the pass ; that it was by the power of this genesame proportion as above the surface, it would ral inagnetism this globe became a particular at the depth of -leagues, be heavier than magnet. In soft or hot iron the fluid of maggold; possibly the dense fluid occupying the netism is naturally diffused equally; when internal parts of the globe might be air com- within the influence of the magnet it is drawn pressed. And as the force of expansion in dense to one end of the iron, made denser there and air when heated, is in proportion to its density, rarer at the other. While the iron continues this central air might afford another agent to soft and hot, it is only a temporary magnet; move the surface, as well as be of use in keep- if it cools or grows hard in that situation, it ing alive the subterraneous fires; though, as becomes a permanent one, the magnetic fluid you observe, the sudden rarefaction of water not easily resuming its equilibrium. Perhaps coming into contact without those fires, may it may be owing to the permanent magnetism also be an agent sufficiently strong for that of this globe, which it had not at first, that its purpose, when acting between the incumbent axis is at present kept parallel to itself, and earth and the fluid on which it rests. not liable to the changes it formerly suffered,
If one might indulge imagination in sup- which occasioned the rupture of its shell, the posing how such a globe was formed, I should submersions and emersions of its lands, and conceive, that all the elements in separate the confusion of its seasons.
The present poparticles being originally mixed in confusion, lar and equatorial diameters differing from each and occupying a great space, they would (as other near ten leagues, it is easy to conceive, soon as the almighty fiat ordained gravity, or in case some power should shift the axis grathe mutual attraction of certain parts, and the dually, and place it in the present equator, mutual repulsion of others, to exist) all move and make the new equator pass through the to their common centre : that the air being a present poles, what a sinking of the waters fluid whose parts repel each other, though would happen in the present equatorial redrawn to the common centre by their gravity gions, and what a rising in the present polar would be densest towards the centre, and regions; so that vast tracts would be disco rarer as more remote; consequently all mat-vered, that now are under water, and others ters lighter than the central parts of that air covered, that are now dry, the water rising and immersed in it, would recede from the and sinking in the different extremes near centre, and rise till they arrived at that region five leagues. Such an operation as this posof the air which was of the same specific gra- sibly occasioned much of Europe, and among vity with themselves, where they would rest; the rest this mountain of Passy on which I while other matter, mixed with the lighter live, and which is composed of limestone, air, would descend, and the two meeting rock and sea-shells, to be abandoned by the would form the shell of the first earth, leav- sea, and to change its ancient climate, which ing the upper atmosphere nearly clear. The seems to have been a hot one. The globe beoriginal movement of the parts towards their ing now become a perfect magnet, we are, common centre would naturally form a whirl perhaps, safe from any change of its axis.there; which would continue upon the turn- But we are still subject to the accidents on ing of the new-formed globe upon its axis, and the surface, which are occasioned by a wave the greatest diameter of the shell would be in the internal ponderous fluid; and such a in its equator. If by any accident afterwards wave is producible by the sudden violent exthe axis should be changed, the dense internal plosion you mention, happening from the juncfluid, by altering its form, must burst the shell |tion of water and fire under the earth, which and throw all its substance into the confusion not only lifts the incumbent earth that is over in which we find it. I will not trouble you the explosion, but impressing with the same at present with my fancies concerning the force the fluid under it, creates a wave, that manner of forming the rest of our system.— may run a thousand leagues, lifting, and thereSuperior beings smile at our theories, and at by shaking, successively, all the countries unour presumption in making them. I will just der which it passes. I know not, whether I mention, that your observations on the ferrugi- have expressed myself so clearly, as not to nous nature of the lava which is thrown out get out of your sight in these reveries. If from the depths of our volcanoes, gave me they occasion any new inquiries, and produce great pleasure. It has long been a supposition a better hypothesis, they will not be quite of mine, that the iron contained in the surface useless. You see I have given a loose to of the globe has made it capable of becoming imagination; but I approve
much more your as it is, a great magnet ; that the fluid of mag- method of philosophising, which proceeds upnetism perhaps exists in all space ; so that on actual observation, makes a collection of there is a magnetical north and south of the facts, and concludes no farther than those universe, as well as of this globe, and that if facts will warrant. In my present circuniit were possible for a man to fly from star to stances, that mode of studying the nature of
che globe is out of my power, and therefore I but does not extend to the making or creating have permitted myself to wander a little in new matter, or annihilating the old. Thus, the wilds of fancy. With great esteem, if fire be an original element or kind of mat
B. FRANKLIN. ter, its quantity is fixed and permanent in the P. S. I have heard, that chemists can by universe. We cannot destroy any part of it, their art decompose stone and wood, extract- or make addition to it; we can only separaté ing a considerable quantity of water from the it from that which confines it, and so set it at one, and air from the other. It seems natural liberty; as when we put wood in a situation to conclude from this, that water and air were to be burnt, or transfer it from one solid to aningredients in their original composition; for other, as when we make lime by burning men cannot make new matter of any kind.
stone, a part of the fire dislodged in the fuel In the same manner may we not suppose, that being left in the stone. May not this fluid, when we consume combustibles of all kinds, when at liberty, be capable of penetrating and and produce heat or light, we do not create entering into all bodies, organized or not, quitthat heat or light; but only decompose a sub- ting easily in totality those not organized, and stance, which received it originally as a part quitting easily in part those which are; the of its composition ? Heat may be thus consi- part assumed and fixed remaining till the body dered as originally in a fluid state ; but at- is dissolved? tracted by organized bodies in their growth,
Is it not this fluid ich keeps asunder the becomes a part of the solid. Besides this, I particles of air, permitting them to approach, can conceive, that in the first assemblage of or separating them more, in proportion as the particles of which this earth is composed,
its quantity is diminished or augmented ? each brought its portion of the loose heat that
Is it not the greater gravity of the particles had been connected with it, and the whole, of air, which forces the particles of this fluid to when pressed together, produced the internal mount with the matters to which it is attachfire that still subsists.
ed, as smoke or vapour?
Does it not seem to have a greater affinity
with water, since it will quit a solid to unite To David Rittenhouse.
with that Auid, and go off with it in vapour, New and curious Theory of Light and Heat. leaving the solid cold to the touch, and the
Read in the American Philosophical Society, degree measurable by the thermometer?
rises attached to this fluid, but UNIVERSAL space, as far as we know of it, at a certain height they separate, and the vaseems to be filled with a subtle fluid, whose pour descends in rain, retaining but little of motion, or vibration, is called light.
it, in snow or hail less. What becomes of This fluid may possibly be the same with that fluid ? Does it rise above our atmosphere, that, which being attracted by, and entering and mix with the universal mass of the same into other more solid matter, dilates the sub- kind? stance by separating the constituent particles, Or does a spherical stratum of it, denser, and so rendering some solids fluid, and main- as less mixed with air, attracted by this globe, taining the fluidity of others; of which fluid, and repelled or pushed up only to a certain when our bodies are totally deprived, they are height from its surface, by the greater weight said to be frozen; when they have a proper of air, remain there surrounding the globe, and quantity, they are in health, and fit to per proceeding with it round the sun ? form all their functions; it is then called na In such case, as there may be a continuity tural heat; when too much, it is called fever; or communication of this fluid through the air and when forced into the body in too great a quite down to the earth, is it not by the vibraquantity from without, it gives pain, by sepa- tions given to it, by the sun, that light aprating and destroying the flesh, and is then pears to us? And may it not be, that every called burning, and the fluid so entering and one of the infinitely small vibrations, striking acting is called fire.
common matter with a certain force, enters While organized bodies, animal or vegeta- its substance, is held there by attraction, and ble, are augmenting in growth, or are supply- augmented by succeeding vibrations, till the ing their continual waste, is not this done by matter has received as much as their force can attracting and consolidating this fluid called drive into it? fire, so as to form of it a part of their sub Is it not thus, that the surface of this globe stance? And is it not a separation of the is continually heated by such repeated vibraparts of such substance, which, dissolving its tions in the day, and cooled by the escape of solid state, sets that subtle fluid at liberty, the heat when those vibrations are discontiwhen it again makes its appearance as fire ? nued in the night, or intercepted and reflect
For the power of man relative to matter, ed by clouds ? seems limited to the separating or mixing the Is it not thus, that fire is amassed and various kinds of it, or changing its form and makes the greatest part of the substance of appearance by different compositions of it; combustible bodies ?
Perhaps, when this globe was first formed, virtue of the masses of iron ore contained in and its original particles took their place at it, might not some ages pass before it had certain distances from the centre, in propor- magnetic polarity ? tion to their greater or less gravity, the fluid Since iron ore may exist without that pofire, attracted towards that centre, might in larity, and by being placed in certain circumgreat part be obliged, as lightest, to take place stances may obtain it, from an external cause, above the rest, and thus form the sphere of is it not possible that the earth received its fire above supposed, which would afterwards magnetism from some such cause? be continually diminishing by the substance, In short, may not a magnetic power exist it afforded to organized bodies, and the quan- throughout our system, perhaps through all tity restored to it again, by the burning or systems, so that if men could make a voyage other separating of the parts of those bodies. in the starry regions, a compass might be of
Is not the natural heat of animals thus pro- use ? And may not such universal magnetism, duced, by separating in digestion the parts of with its uniform direction, be serviceable in food, and setting their fire at liberty ? keeping the diurnal revolution of a planet more
Is it not this sphere of fire which kindles steady to the same axis ? the wandering globes that sometimes pass Lastly, as the poles of magnets may be through it in our course round the sun, have changed by the presence of stronger magnets
, their surface kindled by it, and burst when might not, in ancient times, the near passing their included air is greatly rarefied by the of some large comet of greater magnetic power heat on their burning surfaces ?
than this globe of ours have been a means of May it not have been from such consider changing its poles, and thereby wrecking and ations that the ancient philosophers supposed deranging its surface, placing in different rea sphere of fire to exist above the air of our gions the effect of centrifugal force, so as to atmosphere?
B. FRANKLIN. raise the waters of the sea in some, while they
were depressed in others ?
Let me add another question or two, not To Mr. Bowdoin.
relating indeed to magnetism, but, however, Queries and Conjectures relating to Magnetism to the theory of the earth.
and the Theory of the Earth.--Read in the Is not the finding of great quantities of American Philosophical Society, January 15, shells and bones of animals (natural to hot 1790.
climates) in the cold ones of our present world, I RECEIVED your favours by Messrs. Gore, some proof that its poles have been changed? Milliard, and Lee, with whose conversation I Is not the supposition that the poles have been was much pleased, and wished for more of it; changed, the easiest way of accounting for the but their stay with us was too short. When- deluge, by getting rid of the old difficulty how ever you recommend any of your friends to to dispose of its waters after it was over ? Since me, you oblige me.
if the poles were again to be changed, and I want to know whether your Philosophical placed in the present equator, the sea would Society received the second volume of our fall there about fifteen miles in height, and Transactions. I sent it, but never heard of rise as much in the present polar regions; and its arriving. If it miscarried, I will send the effect would be proportionable if the new another. Has your Society among its books poles were placed any where between the prethe French work Sur les Arts, et les Metiers ? sent and the equator. It is voluminous, well executed, and may Does not the apparent wreck of the surface useful in our country.. I have bequeathed it of this globe, thrown up into long ridges of them in my will; but if they have it already, mountains, with strata in various positions, I will substitute something else.
make it probable, that its internal mass is a Our ancient correspondence used to have fluid ; but a fluid so dense as to float the heasomething philosophical in it. As you are viest of our substances ? Do we know the limit now more free from public cares, and I ex- of condensation air is capable of? Supposing pect to be so in a few months, why may we it to grow denser within the surface, in the not resume that kind of correspondence ? Our same proportion nearly as it does without, at much regretted friend Winthrop once made what th may it be equal in density with me the compliment, that I was good at start- gold? ing game for philosophers, let me try if I can Can we easily conceive how the strata of start a little for you.
the earth could have been so deranged, if it Has the question, how came the earth by had not been a mere shell supported by a heaits magnetism, ever been considered? vier fluid ? Would not such a supposed inter
Is it likely that iron ore immediately ex- nal fluid globe be immediately sensible of a isted when this globe was first formed; or change in the situation of the earth's axis, may it not rather be supposed a gradual pro alter its form, and thereby burst the shell, and duction of time?
throw up parts of it above the rest ? As if we If the earth is at present magnetical, in I would alter the position of the fluid contained