CHAPTER I.
Prelude to Newton.
The Ancients.
EXPRESSIONS in ancient writers which may be interpreted as indicating a notion of gravitation in the Newtonian sense, no doubt occur. But such a notion, we may be sure, must have been in the highest degree obscure, wavering, and partial. I have mentioned (Book i. [Chap. 3]) an author who has fancied that he traces in the works of the ancients the origin of most of the vaunted discoveries of the moderns. But to ascribe much importance to such expressions would be to give a false representation of the real progress of science. Yet some of Newton’s followers put forward these passages as well deserving notice; and Newton himself appears to have had some pleasure in citing such expressions; probably with the feeling that they relieved him of some of the odium which, he seems to have apprehended, hung over new discoveries. The Preface to the Principia, begins by quoting[40] the authority of the ancients, as well as the moderns, in favor of applying the science of Mechanics to Natural Philosophy. In the Preface to David Gregory’s Astronomiæ Physicæ et Geometricæ Elementa, published in 1702, is a large array of names of ancient authors, and of quotations, to prove the early and wide diffusion of the doctrine of the gravity of the Heavenly Bodies. And it appears to be now made out, that this collection of ancient authorities [545] was supplied to Gregory by Newton himself. The late Professor Rigaud, in his Historical Essay on the First Publication of Sir Isaac Newton’s Principia, says (pp. 80 and 101) that having been allowed to examine Gregory’s papers, he found that the quotations given by him in his Preface are copied or abridged from notes which Newton had supplied to him in his own handwriting. Some of the most noticeable of the quotations are those taken from Plutarch’s Dialogue on the Face which appears in the Moon’s Disk: it is there said, for example, by one of the speakers, that the Moon is perhaps prevented from falling to the earth by the rapidity of her revolution round it; as a stone whirled in a sling keeps it stretched. Lucretius also is quoted, as teaching that all bodies would descend with an equal celerity in a vacuum:
Omnia quapropter debent per inane quietum
Æque ponderibus non æquis concita ferri.
Lib. ii. v. 238.
[40] Cum veteres Mechanicam (uti author est Pappus), in rerum Naturalium investigatione maximi fecerint, et recentiores, missis formis substantialibus et qualitatibus occultis, Phenonmena Naturæ ad leges mathematicas revocare aggressa sunt; visum est in hoc Tractatu Mathesin excolere quatenus ea ad Philosophiam spectat.
It is asserted in Gregory’s Preface that Pythagoras was not unacquainted with the important law of gravity, the inverse squares of the distances from the centre. For, it is argued, the seven strings of Apollo’s lyre mean the seven planets; and the proportions of the notes of strings are reciprocally as the inverse squares of the weights which stretch them.
I have attempted, throughout this work, to trace the progress of the discovery of the great truths which constitute real science, in a more precise manner than that which these interpretations of ancient authors exemplify.