SCIENCE AS A SYMBOL AND A LAW 7 



Such was the state of science when Laplace, in his 

 Systeme du Monde, and Lagrange in the Mecanique 

 Analytique, attempted to construct a theory and his- 

 tory of the universe by means only of the general and 

 accepted laws of the two mechanics: celestial, which 

 concerns the heavenly bodies, and terrestrial, those on 

 the earth. Their problem has been stated in many 

 ways, but this may serve : Given the positions, masses, 

 and forces of a system of bodies at any time, to find 

 the configuration of the system at any other time, previ- 

 ous or afterward. 



By the aid of the principle of centers of inertia, each 

 celestial body could be replaced by a mathematical 

 point, at which the whole mass was concentrated, and 

 endowed with a force of attraction according to New- 

 ton's law of universal gravitation. In a similar way 

 each terrestrial body was divided into a great number 

 of small elastic particles, or atoms. These were con- 

 sidered to be invariable and indivisible, and they were 

 arbitrarily endowed with the same force of universal 

 gravitation, acting through their centers of inertia. 

 This force could be assigned to these imponderable 

 masses, separated by insensible distances, with some 

 probability of truth, although it could not be scien- 

 tifically verified by experiment, because it was known 

 to be a property of ponderable bodies separated by 

 sensible distances. This conception of matter was 

 generally accepted, as the original atomic theory of 



