CONTENTS xiii 



CHAPTER XX 



NEWTON AND THE MOTOR FORCE OF THE 

 WORLD MACHINE 



PAGE 



The precise nature of his discovery Its history Just what it 



meant . . . . . ... 251 



CHAPTER XXI 



HALLEY AND THE MESSENGERS OF THE GODS 



The terror formerly inspired by the appearance of comets Its 

 powerful influence towards superstition Computation of the 

 first cometary orbit The first prediction and its realisation . 267 



CHAPTER XXII 



ROEMER AND THE PROOF OF THE EARTH'S MOTION 



How he came to his discovery Its general rejection Confirmed by 



Bradley's discovery of aberration . .. .-* ': . 279 



CHAPTER XXIII 



LAPLACE AND THE STABILITY OF THE SOLAR SYSTEM 



The work of Newton taken up by the French mathematicians 

 Laplace and Lagrange determine that the planets constitute a 

 stable system . . . . . . .291 



CHAPTER XXIV 



FIXING THE BOUNDARIES OF OUR SOLAR WORLD 



The ancient ideas of the world enlarged by the discovery of Uranus 

 and Neptune The triumph of the theory of gravitation through 

 the calculations of Adams and Leverrier . 303 



