THE STABILITY OF THE SOLAR SYSTEM 299 



man, who lived chiefly upon nuts and fruits, planned methodi- 

 cally each day what he should do the next, who cared nothing 

 for place nor the glitter of the court like Laplace, who lived 

 to calculate, to meditate, incidentally to render into very ad- 

 mirable prose the famous poem, On Nature, of Lucretius. This 

 was Lagrange. He was thirteen years the elder of Laplace, 

 and is often thought to have been the more solid, as he was 

 certainly the less showy man. 



It is an idle speculation ; both were men of prodigious power 

 in analysis ; their peculiar abilities seemed to be a kind of com- 

 plement one to the other. It was Lagrange who worked out 

 the problem of the changing shape of the earth's orbit, dis- 

 covered by Laplace. It was Lagrange who showed why it is 

 that the moon turns towards us always the same face ; he 

 figured out that the moon must bulge a little, just as the earth 

 does, and that this would act as a sort of a brake on the revolution 

 of the moon, so that it would eventually come to a standstill. 

 It was Lagrange. who worked out the general method connecting 

 the rate of change in the variations of planetary orbits with the 

 disturbing forces. But in general they worked so closely to- 

 gether, the one taking up the problems of the other, and vice 

 versa, that their names are usually linked in any account of the 

 achievements of the period. 



This peculiar relationship was in no wise disturbed by the 

 translation of Lagrange to Berlin in 1766. Students of the 

 period and it was a heyday time for philosophers and men 

 of science in general will recall that the fat Frederick, sur- 

 named The Great, was then doing what he could to Parisianise 

 the German capital. He had established an Academy like unto 

 that which has rendered such signal services to France, and as 

 there was a dearth at that time of native material, he imported 

 half the great figures of France Voltaire, Maupertuis, Lamettrie, 

 d'Argens, and many another. 



There came a vacancy in the mathematical section. Frederick 

 had a taste for fine phrases as well as an excellent opinion of him- 

 self ; he even wrote verses, whose halting metre a wit of the 

 time remarked would limp after him in history. In his invita- 

 tion to Lagrange to come and fill the vacant post, he explained 

 that the greatest king of Europe wished to have the greatest 

 mathematician in Europe at his court. It was a fine place to 

 go ; an invitation couched in such language was hardly to be 



