464 Dr. Boase on M. Faye's Memoir on the Existence of a 



ferent specific gravities in the atmospheres of comets : the 

 repulsive action of the sun, operating on them after the manner 

 of the metallurgical washings of ores, would arrange them in 

 trains more or less curved in the rear of the general motion 

 according to the greater density of these substances. The repul- 

 sive force exercised by the sun on substances reduced to a great 

 tenuity in cometary nebulosities, also explains the most general 

 and important facts concerning the curvature of their tails, of their 

 multiplicity, and of their form, not conical, as Arago supposed, 

 but flat and fully displayed in the plane of their orbit, &c. The 

 difficulty which so long attended the study of their heads and 

 their atmospheres has disappeared as by enchantment. 



In conducting his experiments in verification of the repulsive 

 force, M. Faye was guided by the memorable experiment of 

 Cavendish on the mutual attraction between two solid bodies; 

 in which the scientific world, he says, did not see so much the 

 indispensable confirmation of the Newtonian theory, as an inge- 

 nious method of ascertaining the density of the earth. In expe- 

 rimenting, however, on the repulsive force, the question assumes 

 a different aspect, as the earth no longer exercises this force in 

 a sensible manner ; for at the present day the sun alone pos- 

 sesses this property, since it alone, in our little world, has pre- 

 served its primeval incandescence. Nor can we experiment on 

 the solar action, because its repulsive force does not come within 

 our reach; it is dissipated on the superior beds of the atmo- 

 sphere, in consequence of its incapacity of acting through all 

 matter after the manner of gravitation. So we are reduced to 

 study the feeble forces which can be produced by artificial means. 

 In experimenting on the attraction between two bodies, the 

 influence of the air and of its currents is a great obstacle to suc- 

 cess ; and the same influence is still more obstructive in the case 

 of the repulsive force, since one of the bodies employed requires 

 to be in a state of incandescence. This is the reason why all 

 the attempts have miscarried up to the present time. He then 

 refers to the arrangements which he adopted for surmounting 

 these difficulties, and announces a new series of experiments in 

 hand, the incandescence being produced by the voltaic current 

 in a vacuum rendered more perfect by chemical action ; and he 

 hopes to be able, not only to demonstrate repulsion at a distance, 

 but also to measure it. 



Lastly, M. Faye thus sums up the conclusions at which he 

 has arrived by his labours. The celestial world does not obey 

 one force alone, attraction, but a duality of forces, attraction 

 and repulsion. The former depends solely on the mass, the 

 latter on the surface and heat. The one is propagated instanta- 

 neously, the other successively. The one acts through all matter 



