296 THE WORLD MACHINE 



He had the gift of great personal charm ; he liked to use it, 

 and he formed one of those distinguished and supple-minded 

 figures which graced the salons of the period, and lent solidity 

 as well as brilliancy to a mode of human congregation whose 

 disappearance from present-day society, lovers of the varied 

 life may scarce view without regret. 



Clairaut found a rival as aggressive as he was polished and 

 suave in the foundling, Jean-le-Rond d'Alembert. Left as an 

 infant on the steps of a church in Paris, and growing up to a 

 gloomy view of the world, d'Alembert lives for us now chiefly 

 as the collaborator, with Diderot and Voltaire, in the production 

 of the famous Encyclopedic, and as the luckless victim of the 

 versatile affections of another waif of fortune, Julie de 1'Espinasse. 

 He undoubtedly exercised a very considerable influence upon 

 the political and philosophical thought of the time ; but he was 

 primarily a mathematician, and worthy of rank with the highest. 



It was a rather curious coincidence that three of this group, 

 Euler, Clairaut, and d'Alembert, all succeeded in obtaining in- 

 dependently, and very nearly simultaneously, the solution of 

 the problem of three bodies the means of calculating the 

 mutual share of three planets, for example, acting one upon 

 another by the force of gravitation. 



They did not reach the larger problem : whether or no our 

 system will endure. That was the work of their successors in 

 foremost line Lagrange and yet another mathematical genius 

 whom the French are proud to class with Newton himself. This 

 was that Baron Laplace who, through .all the stormy times of 

 the downfall of the ancient regime, the Revolution, the Empire, 

 the Restoration, managed to balance himself with such dexterity 

 as always to keep a comfortable berth and retain the favour of 

 the whilom reigning powers. 



Laplace had come up from the soil like all the rest ; he 

 was merely a peasant lad in the fields of Normandy, the son of 

 a poor farmer. Some of the neighbours, or perhaps the parish 

 cure, discovered his amazing genius for calculation, and gave 

 him a start. After that his own abilities, alike as a politician, 

 which were unsurpassed, and as a mathematician, which were 

 of the highest order, were sufficient. 



There is a story of how, at eighteen, he came up to Paris 

 with a letter to the then reigning mathematician, d'Alembert, 



