GENEALOGY. 5 8 3 



In the limited number of cases which one system is capable of af- 

 fording, we cannot expect to see the last struggles of a satellite to 

 maintain its planetary structure when moving in a very close proximity 

 to its primary. But the wonderful annular girdle around Saturn shows 

 evidence not only of a great conflict for planetary existence in past 

 times, but even of lesser ones, on an extensive scale, at the present day. 

 From the investigations which I have published on the subject in the 

 Philosophical Magazine, it appears that in the zone of the outer ring 

 a satellite as dense as Saturn could not hold its parts together, and that 

 one twice as dense could not move in safety in the central zone of the 

 inner ring. If, in treating on stability in small orbits, I have generally 

 supposed the satellite fluid in my papers on the subject, it was because 

 they were chiefly intended to decide whether or not it was possible for 

 the matter of the rings to unite and form two secondary planets. 



The long-cherished idea that the rings are two integral solid masses 

 is now generally abandoned. For such a constitution the nearer ring 

 would require to be composed of materials over 200 times as strong as 

 wrought-iron, in order to escape rupture ; but even this condition could 

 not avert destruction from other dangers to which it is exposed. From 

 the estimates and observations of Bond, as well as from the theoretical 

 researches of Pierce and Maxwell, it appears certain that the innumerable 

 parts of Saturn's ring cannot be all connected together, in a rigid or per- 

 manent manner, but must move independently around the great planet. 

 But, while affording much valuable negative information on the subject, 

 the investigations of these eminent mathematicians do not show how 

 the floating matter eternally circulating in these extensive zones is kept 

 from concentrating into two satellites by the impulse of gravity. The 

 cause which prevents this aggregation is to be found in the proximity 

 of Saturn, whose tidal action either annuls gravity or reduces it so 

 much in two directions as to render a planetary structure unstable ; 

 and though an incipient satellite may constantly grow by appropriating 

 the floating matter around it, yet it must fall to pieces before it has at- 

 tained any considerable magnitude. The state of the rings thus depends 

 not on accidental but on -inevitable circumstances ; and, with this basis 

 for our inquiries on the subject, we may arrive at very important in- 

 formation in regard to the past and the future condition of worlds. 



GENEALOGY. 



By JOHN AMP H LETT. 



THERE can be no doubt that, as each person now living has had 

 a father and mother, grandfathers and grandmothers, and so on, 

 every one really comes of as old a family as every one else. Moreover, 

 every living eldest son is the heir male of either the senior or a junior 



