286 M. Faye on Solar Repulsion. 



M. FAYE ON SOLAR REPULSION * 



It follows from a consideration of all the facts relating to the 

 acceleration of comets,, and of the forms they assume, that there 

 exists in celestial space a repulsive force., exerted by the surface 

 of the sun ; that this force is due to incandescence, and operates 

 like attraction at all distances. The physical phenomena which 

 surround us afford striking indications of a force of this 

 nature, and we can put them in evidence by causing an incan- 

 descent surface to act under the conditions which are revealed 

 to us by the study of astronomical effects. There is thus an 

 identity between the two forces which have their origin in heat, 

 just as there is an identity between celestial attraction and 

 terrestrial attraction, as shown by the fall of heavy bodies in the 

 celebrated experiments of Maskeleyne and Cavendish. But 

 repulsion exerted at a distance by an incandescent surface can- 

 not be a different thing from the molecular repulsion which is 

 equally due to heat, the force to which physicists attribute the 

 phenomena of dilatation, of changes in the state of bodies, and 

 their elasticity in the gaseous form. We arrive, then, at the 

 conclusion that there exists in nature a force not less general 

 than attraction, and which, like attraction, manifests itself in 

 celestial spaces as well as in molecular intervals. 



There is, however, a difficulty which seems to oppose this 

 complete identification. The molecular repulsion due to heat 

 has always been considered as a force which disappears at any 

 appreciable distance from its centre of action, and it has this 

 character, whether we admit with Newton an interruption of 

 continuity, or prefer to have recourse with Laplace to the remark- 

 able hypothesis of forces whose sphere of activity docs not 



extend to sensible distances Laplace thus expresses 



himself on this subject. After having calculated the pressure 

 in a gaseous mass, bounded by a spherical envelope, in accord- 

 ance with the hypothesis of a repulsive force with an indefinite 

 sphere of activity ; he shows that the law of repulsion adopted 

 by Newton is far from representing the conditions which this 

 constant pressure exhibits, and he then remarks, " This great 

 geometer does indeed assign to this law of repulsion an insen- 

 sible sphere of activity ; but the manner in which he explains 

 its wants of continuity is little satisfactory. We must, without 

 doubt, admit a repulsive force between the molecules of the air, 

 which is onry operative at imperceptible distances. The diffi- 

 culty consists in deducing from it the laws of elastic fluids, and 

 this can only be done by the following considerations. " These 

 considerations take for their point of departure, the formulas 



* Translated from the Comptes Sendus, 10th March, 1862- 



