308 LAPLACE. 



by him in this investigation, and still he was not weary 

 of it ! What, in reality, are twenty-two years of labour 

 to him who is about to become the legislator of worlds ; 

 who shall inscribe his name in ineffaceable characters 

 upon the frontispiece of an immortal code ; who shall be 

 able to exclaim in dithyrambic language, and without 

 incurring the reproach of any one, " The die is cast ; I 

 have written my book ; it will be read either in the 

 present age or by posterity, it matters not which ; it may 

 well await a reader, since God has waited six thousand 

 years for an interpreter of his works ? " * 



To investigate a physical cause capable of making the 

 planets revolve in closed curves ; to place the principle 

 of the stability of the universe in mechanical forces and 

 not in solid supports such as the spheres of crystal which 

 our ancestors had dreamed of; to extend to the revolu- 

 tions of the heavenly bodies the general principles of 

 the mechanics of terrestrial bodies, such were the ques- 

 tions which remained to be solved after Kepler had 

 announced his discoveries to the world. 



Very distinct traces of these great problems are per- 

 ceived here and there among the ancients as well as the 



* These celebrated laws, known in astronomy as the laws of Kep- 

 ler, are three in number. The first law is, that the planets describe 

 ellipses around the sun in their common focus; the second, that a line 

 joining the planet and the sun sweeps over equal areas in equal times ; 

 the third, that the squares of the periodic times of the planets are 

 proportional to the cubes of their mean distances from the sun. The 

 first two laws were discovered by Kepler in the course of a laborious 

 examination of the theory of the planet Mars ; a full account of this 

 inquiry is contained in his famous work De Stella Martis, published 

 in 1609. The discovery of the third law was not effected until, sev- 

 eral years afterwards, Kepler announced it to the world in his treatise 

 on Harmonics (1628). The passage quoted below is extracted from 

 that work. Translator. 



