F PREFACE TO THE (1623) TO THE GREAT Variety of READERS ROM the most able, to him that can but spell: There you are number'd. We had rather you were weighd. Especially, when the fate of all Bookes depends vpon your capacities: and not of your heads alone, but of your purses. Well! it is now publique, & you wil stand for your priuiledges wee know: to read, and censure. Do so, but buy it first. That doth best commend a Booke, the Stationer saies. Then, how odde soeuer your braines be, or your wisedomes, make your licence the same, and spare not. Iudge your sixe-pen'orth, your shillings worth, your fiue shillings worth at a time, or higher, so you rise to the iust rates, and welcome. But, what euer you do, Buy. Censure will not driue a Trade, or make the lacke go. And though you be a Magistrate of wit, and sit on the Stage at Black-Friers, or the Cock-pit, to arraigne Playes dailie, know, these Playes haue had their triall alreadie, and stood out all Appeals; and do now come forth quitted rather by a Decree of Court, then any purchas'd Letters of commendation. It had bene a thing, we confesse, worthie to haue bene wished, that the Author himselfe had liu'd to haue set forth, and ouerseen his owne writings; But since it hath bin ordain'd otherwise, and he by Little more than half of Shakespeare's plays were published during his lifetime; and in the publication of these there is no evidence that the author had any hand. Seven years after his death, John Heminge and Henry Condell, two of his fellow-actors, collected the unpublished plays, and, in 1623, issued them along with the others in a single volume, usually known as the First Folio. When one considers what would have been lost had it not been for the enterprise of these men, it seems safe to say that the volume they introduced by this quaint and not too accurate preface, is the most important single book in the imaginative literature of the world. death departed from that right, we pray you do not envie his Friends, the office of their care, and paine, to haue collected & publish'd them; and so to haue publish'd them, as where (before) you were abus'd with diuerse stolne, and surreptitious copies, maimed, and deformed by the frauds and stealthes of iniurious imposters, that expos'd them: euen those, are now offer'd to your view cur'd, and perfect of their limbes; and all the rest, absolute in their numbers, as he conceiued them. Who, as he was a happie imitator of Nature, was a most gentle expresser of it. His mind and hand went together: And what he thought, he vttered with that easinesse, that wee haue scarse receiued from him a blot in his papers. But it is not our prouince, who onely gather his works, and giue them you, to praise him. It is that reade him. And there we hope, to your diuers capacities, you will finde enough, both to draw, and hold you: for his wit can no more lie hid, then it could be lost. Reade him, therefore; and againe, and againe: And if then you doe not like him, surely you are in some manifest danger, not to vnderstand him. And so we leaue you to other of his Friends, whom if you need, can bee your guides: if you neede them not, you can leade your selues, and others. And such Readers we wish him. JOHN HEMINGE. yours PREFACE TO THE PHILOSOPHIAE NATURALIS PRINCIPIA MATHEMATICA BY SIR ISAAC NEWTON. (1686) INCE the ancients (as we are told by Pappus) made great account of the science of mechanics in the investigation of natural things; and the moderns, laying aside substantial forms and occult qualities, have endeavored to subject the phenomena of nature to the laws of mathematics, I have in this treatise cultivated mathematics so far as it regards philosophy. The ancients considered mechanics in a twofold respect; as rational, which proceeds accurately by demonstration, and practical. To practical mechanics all the manual arts belong, from which mechanics took its name. But as artificers do not work with perfect accuracy, it comes to pass that mechanics is so distinguished from geometry, that what is perfectly accurate is called geometrical; what is less so is called mechanical. But the errors are not in the art, but in the artificers. He that works with less accuracy is an imperfect mechanic: and if any could work with perfect accuracy, he would be the most perfect mechanic of all; for the description of right lines and circles, upon which geometry is founded, belongs to mechanics. Geometry does not teach us to draw these lines, but requires them to be drawn; for it requires that the learner should first be taught to describe these accurately, before he enters upon geometry; then it shows how by these operations problems may be solved. To describe Sir Isaac Newton, the great English mathematician and physicist, was born at Woolsthorpe in 1642, and died at Kensington in 1727. He held a professorship at Cambridge, represented the University in Parliament, as master of the mint reformed the English coinage, and for twenty-five years was president of the Royal Society. His theory of the law of universal gravitation, the most important of his many discoveries, is expounded in his "Philosophiae Naturalis Principia Mathematica," usually known merely as the "Principia," from which this Preface is translated. 150 right lines and circles are problems, but not geometrical problems. The solution of these problems is required from mechanics; and by geometry the use of them, when so solved, is shown; and it is the glory of geometry that from those few principles, fetched from without, it is able to produce so many things. Therefore geometry is founded in mechanical practice, and is nothing but that part of universal mechanics which accurately proposes and demonstrates the art of measuring. But since the manual arts are chiefly conversant in the moving of bodies, it comes to pass that geometry is commonly referred to their magnitudes, and mechanics to their motion. In this sense rational mechanics will be the science of motions resulting from any forces whatsoever, and of the forces required to produce any motions, accurately proposed and demonstrated. This part of mechanics was cultivated by the ancients in the five powers which relate to manual arts, who considered gravity (it not being a manual power) no otherwise than as it moved weights by those powers. Our design, not respecting arts, but philosophy, and our subject, not manual, but natural powers, we consider chiefly those things which relate to gravity, levity, elastic force, the resistance of fluids, and the like forces, whether attractive or impulsive; and therefore we offer this work as mathematical principles of philosophy; for all the difficulty of philosophy seems to consist in this-from the phenomena of motions to investigate the forces of nature, and then from these forces to demonstrate the other phenomena; and to this end the general propositions in the first and second book are directed. In the third book we give an example of this in the explication of the system of the World; for by the propositions mathematically demonstrated in the first book, we there derive from the celestial phenomena the forces of gravity with which bodies tend to the sun and the several planets. Then, from these forces, by other propositions which are also mathematical, we deduce the motions of the planets, the comets, the moon, and the sea. I wish we could derive the rest of the phenomena of nature by the same kind of reasoning from mechanical principles; for I am induced by many reasons to suspect that they may all depend upon certain forces by which the particles of bodies, by some causes hitherto unknown, are either mutually impelled towards each other, and cohere in regular figures, or are repelled and recede from each other; which forces being unknown, philosophers have hitherto attempted the search of nature in vain; but I hope the principles here laid down will afford some light either to that or some truer method of philosophy. In the publication of this work, the most acute and universally learned Mr. Edmund Halley not only assisted me with his pains in correcting the press and taking care of the schemes, but it was to his solicitations that its becoming public is owing; for when he had obtained of me my demonstrations of the figure of the celestial orbits, he continually pressed me to communicate the same to the Royal Society, who afterwards, by their kind encouragement and entreaties, engaged me to think of publishing them. But after I had begun to consider the inequalities of the lunar motions, and had entered upon some other things relating to the laws and measures of gravity, and other forces; and the figures that would be described by bodies. attracted according to given laws; and the motion of several bodies moving among themselves; the motion of bodies in resisting mediums; the forces, densities, and motions of mediums; the orbits of the comets, and such like; I put off that publication till I had made a search into those matters, and could put out the whole together. What relates to the lunar motions (being imperfect) I have put all together in the corollaries of proposition 66, to avoid being obliged to propose and distinctly demonstrate the several things there contained in a method more prolix than the subject deserved, and interrupt the series of the several propositions. Some things, found out after the rest, I chose to insert in places less suitable, rather than change the number of the propositions and the citations. I heartily beg that what I have here done may be read with candor; and that the defects I have been guilty of upon this difficult subject may be not so much reprehended as kindly supplied, and investigated by new endeavors of my readers. Cambridge, Trinity College, May 8, 1686. ISAAC NEWTON. |