KINETIC THEORIES OF GRAVITATION. 239 



withstanding everything occurs as though bodies mutually attracted 

 each other, it is incontestably true that bodies do not so attract. New- 

 ton, as Euler, — as every philosopher worthy of the name, — has seen in 

 nature but two things, inertia, and motion originally impressed by a 

 free Will, the first and infinite Mover. And it is with these two great 

 facts of inertia and movement that advancing science shall ultimately 

 explain all the phenomena of the physical world. Already courageous 

 thinkers have endeavored to explain by inertia and motion the great, 

 the capital fact of universal attraction, but these explanations are neither 

 so distinctly formulated nor so plausible as to enable us to give a correct 

 idea of them." Abbe Moiguo, as Seguin's interpreter, proceeds: "The 

 secret of cohesion has been pursued by one of our most illustrious com- 

 patriots, M. Seguiu, senior, for the last twenty years, and he has cer- 

 tainly discovered it. It consists most essentially, as we shall proceed 

 to show, in the incontestable fact that the molecules of bodies exceed 

 in number and minuteness anything that could have been imagined."* 



This theory of cohesion is then set forth at some length, the funda- 

 mental assumption being that there are two classes of dynamic monads 

 occupying the universe, the one in a state of relative repose, exhibiting 

 the various phenomena of attraction, and commonly called the ponder- 

 able elements, and the other class entirely free or independent, (improp- 

 erly called imponderable elements,) actuated with extreme velocities of 

 translation, of rotation, and of vibration, continually traversing the 

 systems of ponderable monads in all directions.! 



Although the admiring editor avows himself a pupil of Seguin, it 

 is doubtful whether he has cautiously followed him, in so enthusiasti- 

 cally proclaiming his development of " a vast theory from the admission 

 of but a single principle in the universe, — the attraction of two monads 

 in the inverse ratio of the distance squared, without recourse to any 

 hypothetical force of mysterious attractions or of impossible repulsions." 



In 1858, Seguin published in the Cosmos a somewhat elaborate essay 

 "On the Origin and Propagation of Force," in which he seems to have 

 abandoned a kinetic theory of gravitation. It is true that he there 

 holds : " Matter is inert; that is to say, it does not harbor in itself the 

 power to put itself into movement, and still less a fortiori to communi- 

 cate it, since a thing to be transmitted must first exist."| And it is 

 also true that he repeatedly speaks of " the great principle of the inde- 

 finite conservation of motion " as being " the foundation of all me- 

 chanics ;"§ and regards " the possibility of the destruction of motion 

 as equivalent to " the annihilation of force,"|] which is the very shibboleth 

 of kinetic theorists; and further that he disputes Poisson's proposition 

 that two spheres of equal mass and velocity, devoid of elasticity, if 



* Cosmos, November 14, 185-2, vol. i, pp. 693, 694. 

 t Cosmos, vol. ii, pp. 371-382, and pp. 625-632. 

 t Cosmos, October 15, 1658, vol. xiii, p. 485. 

 § Ibidem, pp. 503, 505, 515, 518, 527. 

 || Ibidem, p. 509. 



