AND THEORY OF THE HEAVENS. 125 



come the said cohesion. But it will not overcome it as 

 long as the excess of the centripetal power which it 

 exerts in an equal period of revolution with the lowest 

 particles does not exceed the central force of their 

 position or that adhesion among them. And for this 

 reason, in a certain breadth of a band of this ring, 

 although the further particles must exert a tendency to 

 tear themselves away from the lower particles, because its 

 parts perform the revolution in the same time, yet the 

 coherence must subsist but not to a very great breadth. 

 Because, as the velocity of those particles that move in 

 equal times increases with the distances, and therefore 

 more than it should do according to the laws of the 

 central forces, when the velocity has exceeded the degree 

 which the coherence of the vapour particles can offer to 

 it, they must be torn away from the other particles and 

 assume a position at a distance which is conformable to 

 the excess of the centrifugal force over the central force 

 of that place. In this way the interval is determined 

 which separates the first band of the ring from the others; 

 and in like manner the accelerated motion of the more 

 distant particles produced by the rapid revolution of the 

 nearer particles and their coherence which tends to hinder 

 the separation, make the second concentric ring, from 

 which the third is removed by a moderate interval. The 

 number of these circular bands, and the breadth of their 

 intervals, could be calculated if we knew the degree of 

 the cohesion which attaches the particles to each other. 

 But we may be satisfied with having divined generally, 

 and with good grounds of probability, what the nature of the 

 composition of Saturn's ring is which prevents its destruction 

 and keeps it revolving by the free movements of its parts. 



