INTRODUCTION 



PARAMOUNT ASTRONOMICAL PROBLEMS 



1. The Origin and Maintenance of Celestial Motions. 



2. The Law and Principle of Universal Gravita- 

 tion. 



3. The Tides. 



4. The Comets. 



5. The Source of the Sun's Heat. 



6. The Individual Characteristics of the Planets 

 and the Moon. 



7. Stellar Problems in General. 



8. The Genesis of the Solar System. 



9. The Destiny of the Universe. 



CELESTIAL MOTIONS 



Newton, in common with his backward age, believed 

 implicitly in the literal accuracy of the Mosaic cosmog- 

 ony, namely, that only six millenniums before him 

 Jehovah had created the heavens and the earth and, as 

 part of the creative plan, launched the moon in her orbit 

 around the earth and the planets in their orbits around 

 the sun. By thus directly invoking divine intervention 

 he evaded his obligation as a true scientist of assigning 

 physical causes for what obviously are purely physical 

 phenomena. Nor, as we shall later see, have his succes- 

 sors made good his delinquencies. The problem, how- 

 ever, was not simply that of getting the orbs into move- 

 ment any which way, but to get them moving exactly 

 tangentially, varying not by a single hairbreadth in a 

 mile from mathematical accuracy, and adjusted to the 

 strength of the central forces, in the matters of mass 

 and velocity, with absolute precision. That Newton 

 fully realized the demands he was thus making on 

 teleological causes appears plainly enough from the fol- 

 lowing statement in Newton 's own words as quoted by 

 his biographer, Sir David Brewster(Mewot*rs of Newton, 

 II. p. 81) : 



To make such a system with all its motions, required a cause 

 which understood and compared together the quantities of mat- 



