12 INTRODUCTION. 



applying the experimental method to them directly ; 

 our laboratories are too small. But analogy with the 

 phenomena which these laboratories enable us to reach 

 may nevertheless serve as a guide to the astronomer. 

 The Milky Way, for instance, is an assemblage of suns 

 whose motions appear at first sight capricious. But 

 may not this assemblage be compared with that of 

 the molecules of a gas whose properties we have 

 learnt from the kinetic theory of gases? Thus the 

 method of the physicist may come to the aid of the 

 astronomer by a side-track. 



Lastly, I have attempted to sketch in a few lines the 

 history of the development of French geodesy. I have 

 shown at what cost, and by what persevering efforts 

 and often dangers, geodesists have secured for us the 

 few notions we possess about the shape of the earth. 

 Is this really a question of method ? Yes, for this 

 history certainly teaches us what precautions must 

 surround any serious scientific operation, and what 

 time and trouble are involved in the conquest of a 

 single new decimal. 



