THE ORIGIN OF WORLDS. 3 



directions. This rule will evidently need but slight modifications, when, 

 instead of being so extremely unequal, both bodies have the same rela- 

 tion of size as that subsisting between our earth and moon, or even such 

 as is represented in our diagram. In this case, however, the lesser body 

 would bear a somewhat greater disturbing influence ; but its dismem- 

 berment, though of a paroxysmal and a very extensive character, would 

 be confined to the side next the primary. On losing a large portion of 

 its mass, the satellite would swing into a wider orbit ; its distance from 

 the primary would for a long period be increased by tidal action, and 

 many ages must elapse before they again became near enough to give 

 occasion for a like convulsive rupture. The incorporation of a large 

 celestial body with a greater one around which it previously revolved 

 would thus be effected by a number of paroxysms, and would not be 

 completed before many billions of years. 



The intermittent character of these rare events would be very de- 

 cided, except, perhaps, when the subordinate body were, like a comet, 

 composed of a profusion of exceedingly rarefied gas surrounding a small, 

 dense, central nucleus. Such differences of density as may be naturally 

 expected in the internal and superficial matter of a satellite would tend 

 to give the convulsive dismemberment a somewhat reduced scale, and 

 to make it recur after less remote periods of time. But this influence 

 would be more than counterbalanced if the incorporating body were 

 solid, as the planetary structure would be preserved for a longer time ; 

 but, when the rupture took place, the ruin would be more extensive. 

 Indeed, in the cases most likely to occur, the doomed planet would meet 

 its fate in successive stages, of which the number and magnitude may be 

 estimated with tolerable accuracy. If our moon were made to revolve 

 about 4,500 miles beyond our atmosphere, its coalescence with our 

 globe would be inevitable, and it would take place by about six or eight 

 paroxysmal stages extending over a vast immensity of time. Two or 

 three times the number of such terrific convulsions may be expected in 

 the union between Algol and the large planet which causes his varia- 

 bility ; and the same estimate will serve for the binary systems or the 

 physically double stars when after long ages they become close enough 

 for the incorporation of the less with the greater. 



It is the terrific conflict of matter on such rare and stupendous 

 events, that awakens the power which is mainly concerned in giving 

 birth to worlds. Large primary planets would be called into being if 

 one or both of the celestial objects undergoing these violent stages 

 of combination had the rank of a sun. The vast mass of matter pre- 

 cipitated to the greater body on these occasions would sweep along its 

 equator with furious velocity. But on the subordinate one, especially 

 in its equatorial regions, the more superficial parts would slide over the 

 internal nucleus in an opposite direction, in consequence of the tidal 

 action, which in the new orbit must be powerful enough to produce not 

 merely waves, but even progressive movements at the rate of many 



