44 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
Thus regarding each constituent element of the ring as having 
its own independent rotation, (a condition absolutely essential to 
the stability of the system,) we may consider that from the compli. 
cated and variable perturbations by the exterior satellites, no one 
particle can revolve in a circular orbit, and hence that in a space 
so crowded there must be a considerable amount of interference, 
The collisions at intersecting orbits may result in heat or in disin- 
tegration; but in any event they must tend to a degradation of 
motion, and hence to a slightly shortened mean radius-vector and a 
shortened period. 
Theoretically then such an effect as that indicated by Struve 
would seem inevitable, whether as a matter of fact it has been 
sufficient in a couple of centuries to be detected or not. And this 
involves a modified conception as to the earlier condition of the 
Saturnian rings. To suppose a fine web of nebulous matter con- 
tinuously spun out from Saturn’s equator, with an unchanging 
balance of centrifugal and centripetal forces during the long ages 
while the planet was slowly contracting to one-half its radius, is 
certainly no easy task or plausible theory. If, however, we are 
now beholding but a stage of transitional development of the ring, 
we shall have to imagine its primitive radius considerably larger, 
and its width as probably very much narrower—so narrow indeed 
as to have a planetary or satellitic status, revolving in a single 
definite period—possibly that of Mimas the nearest satellite. Such 
a ring would present a condition of comparatively great stability ; 
and it may have been that only the secular recurrence of rare and 
remarkable conjunctions commenced upon it the work of disturbance 
and disintegration. 
When Galileo, the first to see the strange appendages to Saturn, 
(though without being able to distinguish the anse as parts of a 
ring,) observed, in 1612, that they had entirely disappeared, he 
wrote in some dismay, “ Has Saturn possibly devoured his own 
children?” * So may perhaps the future astronomer, seeing but an 
airy trace of the historic ring, repeat the saying, Saturn has indeed 
devoured his offspring; not indeed completely, for*a part will © 
probably still remain ; nor with violent catastrophe, for the scattered 
fragments falling by their eccentricity will be absorbed as gently as 
are the meteors daily falling on our earth. 
* Third letter to Marc Velser, December 1, 1612. Ofjere di Galileo. 4toi 4 
vols. Padua, 1744: Vol. II, p. 123. 
