PROGRESS OF MODERN ASTRONOMY 



mass which gave birth to our solar system was divided 

 into several planetary bodies instead of remaining a 

 single mass ? Were the planets struck from the sun by 

 the chance impact of comets, as Buff on has suggested ? 

 or thrown out by explosive volcanic action, in accord- 

 ance with the theory of Dr. Darwin? or do they owe 

 their origin to some unknown law ? In any event, how 

 chanced it that all were projected in nearly the same 

 plane as we now find them ? 



LAPLACE AND THE NEBULAR HYPOTHESIS 



It remained for a mathematical astronomer to solve 

 these puzzles. The man of all others competent to 

 take the subject in hand was the French astronomer 

 Laplace. For a quarter of a century he had devoted 

 his transcendent mathematical abilities to the solu- 

 tion of problems of motion of the heavenly bodies. 

 Working in friendly rivalry with his countryman La- 

 grange, his only peer among the mathematicians of the 

 age, he had taken up and solved one by one the prob- 

 lems that Newton left obscure. Largely through the 

 efforts of these two men the last lingering doubts as to 

 the solidarity of the Newtonian hypothesis of universal 

 gravitation had been removed. The share of Lagrange 

 was hardly less than that of his co-worker ; but Laplace 

 will longer be remembered, because he ultimately 

 brought his completed labors into a system, and, in- 

 corporating with them the labors of his contemporaries, 

 produced in the Mt-canique Ctleste the undisputed 

 mathematical monument of the century, a fitting com- 

 plement to the Principia of Newton, which it supple- 

 its and in a sense completes. 



