482 POPULAR SCIENCE MONTHLY. 



liypothesis there are several fatal objections, as was subsequently dem- 

 onstrated by D'Alembert, of which it will be sufficient to mention 

 that the very existence of a spherical vortex is a mechanical impossi- 

 bility. And yet such was the weight of the authority of its author, and 

 the ingenuity with which it was defended by hunself and his followers, 

 that, as was mentioned above, it not only was received with general 

 favor but for more than half a century it was accepted by most men 

 of science without questioning and continued to be maintained by 

 some, even after Newton had announced and demonstrated the law of 

 gravitation. It is a notable illustration of the tenacity of error when 

 once it becomes firmly fixed and widespread, that for some years after 

 the publication of 'The Prineipia,' a Latin translation from the French 

 of 'The Physics of Eohault' — a work entirely Cartesian — continued 

 to be the text-book in Philosophy at the University of Cambridge — 

 jSTewton himself being at the time Lucasian Professor of Mathematics. 

 We have the authority of Play fair for the statement (which, indeed, 

 has been called in question by Sir David Brewster, in his 'Life of 

 Newton,' though so far as we have been able to see, without any suffi- 

 cient reason) that the doctrines of 'The Prineipia' were introduced 

 into the regular course of instruction at Cambridge by strategem. Dr. 

 Samuel Clarke, a zealous advocate of the Newtonian Philosophy, pre- 

 pared a new and more elegant translation of Eohault, with copious 

 notes, in which the doctrines of 'The Prineipia' were explained and 

 defended, and it was by this work, more directly than by the lectures 

 of Newton himself, that Cartesianism was finally driven from the 

 University. 



Whilst Kepler's speculations as to the cause of the motions of 

 heavenly bodies were soon supplanted by the hypothesis of Descartes, 

 his more just views in regard to terrestrial gravity commended them- 

 selves to the scientific world and speedily passed into universal and 

 abiding favor. In the memorable work of Galileo on the true system 

 of the universe — completed the very year after Kepler's death, and 

 published two years after; a work which, aside from its own merit, 

 'The Holy Inquisition,' by the persecution of its author, has made im- 

 mortal — we find the doctrine of Kepler, on the subject of gravity, 

 distinctly stated and elaborately defended. The Inquisition had power 

 to imprison Galileo and commit copies of his work to the flames, but 

 the truth it contained could not be burnt or bound. The earth 'still 

 moved,' and matter continued to attract matter, unawed by the terrors 

 of the Inquisition. The truth, once distinctly apprehended nnd an- 

 nounced, was never again to be lost, but was destined to grow in im- 

 portance and be extended in its application far beyond the conceptions 

 even of the great prophets of nature who were the first to proclaim it. 

 The doctrine of Kepler on the subject of gravity may be regarded as. 



