ASTRONOMY AND METEOROLOGY. 377 



There being no longer any unyielding coherence between the par- 

 ticles of the inner and outer edges, they have not necessarily the same 

 period of rotation about Saturn. A continual flow of the inner par- 

 ticles past the outer may be supposed, by which centrifugal force will 

 be brought into equilibrium with the other forces. And even should 

 an accumulation of disturbances, of which the absence of inequalities 

 lessens the probability, bring the rings together, the velocities at the 

 point of contact will be very nearly equal, and the two will coalesce 

 without disastrous consequences. If in its normal condition the ring 

 has but one division, as is commonly seen, under peculiar circum- 

 stances, it might be anticipated that the preservation of their equilib- 

 rium would require a separation in some regions of either the inner or 

 outer ring ; this would explain the fact of occasional subdivisions being 

 seen. Their being visible for but a short time, and then disappearing, 

 to the most powerful telescope, is accounted for by the removal of the 

 sources of disturbance, when the parts thrown off would reunite. 

 Finally, a fluid ring, symmetrical in its dimensions, is not of necessity 

 in a state of unstable equilibrium with reference either to Saturn or to 

 the other rings. 



At the meeting of the American Association, Cincinnati, the follow- 

 ing remarks were made by Prof. Peirce, of Harvard, in relation to the 

 discoveries made by the Messrs. Bond, and the supposed fluidity of 

 Saturn's rings : 



1. The author of the Mecanique Celeste proved that Saturn's ring, 

 regarded as solid, could not be sustained about the primary, unless it 

 had decided irregularities in its structure. But the observations of 

 Herschel and others have failed to detect any indications of such ir- 

 regularity ; and Mr. Bond's observations have finally convinced him of 

 the utter improbability of any serious irregularities, and he has, there- 

 fore, adopted the conclusion that Saturn's ring is not solid, but fluid. 

 Mr. Bond's argument is chiefly derived from observation ; but a new 

 investigation of the mechanical conditions of the problem has led me 

 on a step farther. I am now satisfied that there is no conceivable form 

 of irregularity, and no combination of irregularities consistent with an 

 asfcreal ring, which would permit the ring to be permanently main- 

 tained by the primary if it were solid. Hence it follows, independent 

 of observation, that Saturn's ring is not solid, but fluid. Adopting as 

 the basis of the calculations the mass of the ring which was deter- 

 mined by Bessel, the thickness from Bond, and the other dimensions 

 from Struve, the density of the ring will be found to be about one 

 fourth greater than that of water. The ring of Saturn is, then, a stream 

 or streams of fluid, rather denser than water, flowing about the pri- 

 mary. 



2. Mr. Bond next undertook a series of very curious and novel com- 

 putations, in order to determine, from theoretical considerations alone, 

 whether the ring was one or many ; and arrived at the remarkable 

 result that neither hypothesis could be maintained. He is, therefore, 

 disposed to reconcile the discrepancies of observation in this respect, 

 by supposing the constitution of the ring to be variable ; and that, 

 although the principal division, which has been always observed, is 



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