202 Prof. Norton on Molecular Physics. 



- two alternations of the effective force will subsist. The forces 

 m 



may also experience losses, to a certain extent, in their propaga- 

 tion, and this general principle still hold good. 



It should also be observed that when two particles are remote 

 from each other, as in the case of a particle of cometic matter 

 repelled by the sun, we must suppose the intervening space to 

 be occupied by the universal sether only. In such a case, then, 

 both the attractive action and the electric repulsion will be want- 

 ing, and the only force remaining will be the (Ethereal or heat- 

 repulsion ; which should operate at indefinite distances, accord- 

 ing to the law of inverse squares. A discussion of the pheno- 

 mena of evolution of cometary envelopes, and of the outstreaming 

 of jets of nebulous matter from particular parts of the surface 

 of the nucleus, must be had before we can decide how far the 

 electric repulsion maybe in operation in the processes of ejection 

 of cometic matter from the nucleus >!< . 



The general law of the variations of the force of effective 

 molecular action is graphically represented by the curve r a m 

 en in fig. 1. The abscissas represent the comparative distances 

 between the electric atmospheres of the two molecules, and the 

 ordinates the intensities of the effective force corresponding to 

 these distances. When the ordinate lies above the axis of 

 abscissas, the force is attractive ; when it lies below, the force is 

 repulsive. The two axes are asymptotes to the curve. The 

 curve has been constructed from the calculated results obtained 

 on the supposition that/=0 when x = 5r. 



There are four points, marked a, b, c, d, to be especially noted. 

 a and c } where f=0, represent positions of equilibrium, a being 

 a position of stable, and c of unstable equilibrium. When the 

 atmospheres are separated by the distance b the attraction has 

 its maximum value, b m ; and when they are at the distance d, 

 the repulsion, beyond the outer limit of the attraction, has its 

 maximum value, dn. In order that two particles may unite 



* In the memoir by the author ' ( On the Theoretical Determination of the 

 Dimensions ofDonati's Comet," published in No. 87, vol.xxix., and in No. 

 94, vol. xxxii. of Silliman's American Journal, the conclusion was reached, as 

 one result of the computations, that "the repulsion exerted by the sun, 

 and also by the nucleus (of the comet), is not a property belonging to all the 

 particles of" the mass, like the attraction of gravitation ; and is probably 

 therefore a force emanating from the surface of the body, or from a portion 

 only of its mass." We now see that the existence of such a force is also a 

 legitimate deduction from the theory of molecular forces under considera- 

 tion, and that it consists in the force of oethereal repulsion, which we have 

 denominated heat-repulsion. Its impulses constitute the entire force of 

 radiant heat given otr by the body into free space, and vary in intensity or 

 amount with the temperature. 



