392 HISTORY OF PHYSICAL ASTRONOMY. 



who first came into the presence of Truth herself, were those who never 

 entered this imagined antechamber, and those who were in the ante- 

 chamber first, were the last in penetrating further. In partly the same 

 spirit, Playfair has noted it as a service which Newton perhaps owed 

 to Descartes, that " he had exhausted one of the most tempting forms 

 of error." We shall see soon that this temptation had no attraction 

 for those who looked at the problem in its true light, as the Italian 

 and English philosophers already did. Voltaire has observed, far more 

 truly, that Newton's edifice rested on no stone of Descartes' foundations. 

 He illustrates this by relating that Newton only once read the work 

 of Descartes, and, in doing so, wrote the word " error" repeatedly, on 

 the first seven or eight pages ; after which he read no more. This 

 volume, Voltaire adds, was for some time in the possession of Newton's 

 nephew. 13 



(Gassendi?) Even in his own country, the system of Descartes was 

 by no means universally adopted. We have seen that though Gassendi 

 was coupled with Descartes as one of the leaders of the new philoso- 

 phy, he was far from admiring his work. Gassendi's own views of the 

 causes of the motions of the heavenly bodies are not very clear, nor 

 even very clearly referrible to the laws of mechanics ; although he was 

 one of those who had most share in showing that those laws apply to 

 astronomical motions. In a chapter, headed 14 " Qua? sit motrix siderum 

 causa," he reviews several opinions ; but the one which he seems to 

 adopt, is that which ascribes the motion of the celestial globes to certain 

 fibres, of which the action is similar to that of the muscles of animals. 

 It does not appear, therefore, that he had distinctly apprehended, either 

 the continuation of the movements of the planets by the First Law of 

 Motion, or their deflection by the Second Law ; — the two main steps 

 on the road to the discovery of the true forces by which they are made 

 to describe their orbits. 



(Leibnitz, dx.) Nor does it appear that in Germany mathematicians 

 had attained this point of view. Leibnitz, as we have seen, did not 

 assent to the opinions of Descartes, as containing the complete truth ; 

 and yet his own views of the physics of the universe do not seem to 

 have any great advantage over these. In 1671 he published A new 

 physical hypothesis, by which the causes of most phenomena are deduced 

 from a certain single universal motion supposed in our globe ; — not to 

 be despised either by the Tychonians or the Copernicans. He supposes 



13 Cartesianism, Enc. Phil. u Gassendi, Opera, vol. i. p. G39. 



