ASTRONOMY 1 



In all branches of Astronomy in Geodesy, Observa- 

 tional Astronomy, Astrophysics, and Celestial Mechanics 

 -France has made noteworthy contributions. In the 

 first three named, she has kept abreast of all progress 

 and has often led the way; and in Celestial Mechanics, 

 or Mathematical Astronomy, she is well-nigh supreme. 

 Her work in Mathematics, in developing methods of 

 analysis and lines of attack; and in Physics, in estab- 

 lishing standards of wave-lengths of light, in fact in the 

 whole field of radiation; is reflected in the progress of 

 Astronomy. It sometimes happens, moreover, that 

 noteworthy advances follow achievements in fields quite 

 apart from that of the direct research; and as one such 

 instance, GUILLAUME'S discovery of invar, in relation to 

 the errors, due to temperature effects, which creep into 

 all instrumental observations, must be regarded as one of 

 the indirect influences promoting advances of prime 

 importance. 



Celestial Mechanics. Since the publication of New- 

 ton's Principia in 1686, the contributions of all other 

 nations combined would scarcely equal in this field the 

 contributions of France alone. 



It was CLAIRAUT (1713-1783) who first published the 

 differential equations of motion for the problem of 

 three bodies, and their ten integrals. The formidable 



^Drafting Committee: PHILIP Fox, Northwestern University; G. E. 

 HALE, Carnegie Institution; F. R. MOULTON and W. D. MACMILLAN, 

 University of Chicago; H. N. RUSSELL, Princeton University. ED.] 



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