author's abatement of celerity in the case of 20 moved by if is imaginary, so must be his additional resistance. And here again, I am at a loss to discover any effect of the vis inertia. In No. 6, he tells us, "that all this is likewise certain when taken the contrary way, viz. from motion to rest; for the body a, moving with a certain velocity, as c, requires a certain degree of force or resistance to stop that motion," &c. &c.; that is, in other words, equal force is necessary to destroy force. It may be so. But how does that discover a vis inertia? Would not the effect be the same, if there were no such thing? A force if strikes a body 1a, and moves it with the celerity Ic, that is, with the force if; it requires, even according to our author, only an opposing if to stop it. But ought it not (if there were a vis inertia) to have not only the force if, but an additional force equal to the force of vis inertiæ, that obstinate power by which a body endeavours with all its might to continue in its present state, whether of motion or rest? I say, ought there not to be an opposing force equal to the sum of these? The truth, however, is, that there is no body, how large soever, moving with any velocity, how great soever, but may be stopped by an opposing force, how small soever, continually applied. At least, all our modern philosophers agree to tell us so. Let me turn the thing in what light I please, I cannot discover the vis inertia, nor any effect of it. It is allowed by all, that a body 1a, moving with a velocity Ic, and a force If, striking another body 1a at rest, they will afterwards move on together, each with c and ƒ; which, as I said before, is equal in the whole to Ic and if. If vis inertia, as in this case, neither abates the force nor the velocity of bodies, what does it, or how does it discover itself? VOL. II-Y I imagine I may venture to conclude my observations on this piece, almost in the words of the author; that, if the doctrines of the immateriality of the soul and the existence of God, and of divine providence, are demonstrable from no plainer principles, the deist (that is, theist) has a desperate cause in hand. I oppose my theist to his atheist, because I think they are diametrically opposite; and not near of kin, as Mr. Whitefield seems to suppose, where (in his Journal) he tells us, "M. B. was a deist, I had almost said an atheist;" that is, chalk, I had almost said charcoal. The din of the Market' increases upon me; and that, with frequent interruptions, has, I find, made me say some things twice over; and, I suppose, forget some others I intended to say. It has, however, one good effect, as it obliges me to come to the relief of your patience with Your humble servant, B. FRANKLIN. SIR, 65. TO CADWALLADER COLDEN Philadelphia, August 6, 1747. The observations I sent you on Baxter's book were wrote on a sheet or two of paper in folio. He builds his whole argument on the vis inertia of matter. I boldly denied the being of such a property, and endeavoured to demonstrate the contrary. If I succeeded, all his edifice falls of course, unless some other way supported. I desired your sentiments of my argument. You left the book for me at New 1 Vaughan explains this as Hungerford Market, near Craven Street, London, where Franklin lived; but the letter was written in Philadelphia and obviously refers to the market in that city.—ED. York, with a few lines containing a short censure upon the author, and that your time had been much taken up in town with business, but you were now about to retire into the country, where you should have leisure to peruse my papers; since which I have heard nothing from you relating to them. I hope you will easily find them, because I have lost my rough draft; but do not give yourself much trouble about them; for if they are lost, it is really no great matter. I am glad to hear, that some gentlemen with you are inclined to go on with electrical experiments. I am satisfied we have workmen here, who can make the apparatus as well to the full as that from London; and they will do it reasonably. By the next post, I will send you their computation of the expense. If you shall conclude to have it done here, I will oversee the work, and take care that every part be done to perfection, as far as the nature of the thing admits. Instead of the remainder of my rough minutes on electricity, (which are indeed too rough for your view,) I send you enclosed copies of two letters I lately wrote to Mr. Collinson on that subject. When you have perused them, please to leave them with Mr. Nichols, whom I shall desire to forward them per next post to a friend in Connecticut. I am glad your Philosophical Treatise meets with so good reception in England. Mr. Collinson writes the same things to Mr. Logan; and Mr. Rose, of Virginia, writes me, that he had received accounts from his correspondents to the same purpose. I perceive by the papers, that they have also lately reprinted, in London, your "History of the Five Nations" in octavo. If it come to your hands, I should be glad to have a sight of it. Mr. Logan, on a second reading of your piece on Fluxions lately, is satisfied, that some of the faults he formerly objected to it were his own, and owing to his too little attention at that time. He desires me to tell you so, and that he asks your pardon. Upon what Mr. Collinson wrote, he again undertook to read and consider your Philosophical Treatise.' I have not seen him since, but shall soon, and will send you his sentiments. I am, Sir, I have lately written two long Letters to you on the Subject of Electricity, one by the Governor's Vessel, the other per Mesnard. On some further Experiments since I have observ'd a Phenomenon or two, that I cannot at present account for on the Principle laid down in those Letters, and am therefore become a little diffident of my Hypothesis, 1 The title of this treatise, as originally printed, was as follows; "Explication of the first Causes of Action in Matter; and of the Cause of Gravitation. London, 1746." A second edition enlarged was published five years afterwards with a different title, namely; "The Principles of Action in Matter, the Gravitation of Bodies and the Motion of the Planets explained from those Principles. By Cadwallader Colden, Esquire. London. Printed for Dodsley, 1751." The book was dedicated to the Earl of Macclesfield, then President of the Royal Society. Appended is a chapter entitled, "An Introduction to the Doctrine of Fluxions, or the Arithmetic of Infinities; in order to assist the Imagination in forming Conceptions of the Principles on which that Doctrine is founded." The volume contains eight chapters, besides the one on Fluxions, is printed in quarto, and extends to two hundred and fifteen pages. - S. 2 From the original in the collection of Mr. J. Pierpont Morgan. and asham'd that I have express'd myself in so positive a manner. In going on with these Experiments how many pretty Systems do we build which we soon find ourselves oblig'd to destroy! If there is no other Use discover'd of Electricity this however is something considerable, that it may help to make a vain man humble. I must now request that you would not Expose those Letters; or if you communicate them to any Friends you would at least conceal my Name. I have not Time to add but that I am, Sir, Your obliged and most hume Servt 67. TO PETER COLLINSON1 [Philadelphia,] Sept. 1, 1747. SIR, The necessary trouble of copying long letters, which perhaps, when they come to your hands, may contain nothing new, or worth your reading, (so quick is the progress made with you in Electricity,) half discourages me from writing any more on that subject. Yet I cannot forbear adding a few observations on M. Muschenbroek's wonderful bottle. 1. The non-electric contain'd in the bottle differs when electrised from a non-electric electrised out of the bottle, in this that the electrical fire of the latter is accumulated on its surface, and forms an electrical atmosphere round it of considerable extent; but the electrical fire is crowded into the substance of the former, the glass confining it." 1 From "Experiments and Observations on Electricity." London: 1769, P. 12. 2 See this opinion rectified in § 16 and 17 [of letter dated April 27, 1749]. The fire in the bottle was found by subsequent experiments not to be contained in the non-electric, but in the glass. 1748. |