SCIENCE AT THE BEGINNING OF THE CENTURY 



has suggested ? or thrown out by explosive volcanic ac- 

 tion, in accordance 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 ? 



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 transcen- 

 dent mathematical abilities to the solution of problems 

 of motion of the heavenly bodies. Working in friendly 

 rivalry with his countryman Lagrange, his only peer 

 among the mathematicians of the age, he had taken up 

 and solved one by one the problems that Newton left 

 obscure. Largely through the efforts of these two men 

 the last lingering doubts as to the solidarity of the New- 

 tonian hypothesis of universal gravitation had been re- 

 moved. The share of Lagrange was hardly less than 

 that of his co-worker ; but Lagrange will longer be re- 

 membered, because he ultimately brought his completed 

 labors into a system, and incorporating with them the 

 labors of his contemporaries, produced in the Mecanique 

 Celeste the undisputed mathematical monument of the 

 century, a fitting complement to the Principia of New- 

 ton, which it supplements and in a sense completes. 



In the closing years of the century Laplace takes up 

 the nebular hypothesis of cosmogony, to which we have 

 just referred, and gives it definitive proportions; in fact, 

 makes it so thoroughly his own that posterity will al- 

 ways link it with his name. Discarding the crude no- 

 tions of cometary impact and volcanic eruption, Laplace 

 fills up the gaps in the hypothesis with the aid only of 

 well-known laws of gravitation and motion. He assumes 



15 



