FORMA TION OF ME TEO RITES 373 



and planet-like bodies are concerned, the sphere of disruption 

 has a cross section from 5 to 7.5 times as great as the central 

 body It follows from this, that to a passing body the sphere of 

 disruption exposes a disk five to seven times as great as the 

 central body, and hence there are from four to six times as many 

 chances that the passing body will invade the sphere of disrup- 

 tion without collision, as that it will strike the central body. In 

 other words, the fragmentatio7i of a small body by near approach to 

 a large one of the nature of the planets zvill be from four to six ti?nes 

 as imminent as actual collision. 



That disruptions or explosions of some kind actually take 

 place in the heavens, and that not uncommonly, seems to be 

 implied by the sudden appearance of new stars, often with great 

 brilliancy, followed by rapid decline to obscurity or extinction.^ 

 Five such new stars have been recorded during the last decade, 

 and the survey of the heavens during this period has not been 

 entirely exhaustive. The appearance of such new stars has been 

 referred to collision, but their frequency has been felt to be an 

 objection to this view, and other explanations, of the nature of 

 eruptions or explosions, have been offered, but usually without 

 assigning any probable cause for such extraordinary explosive 

 action. The numerical objection is, in some measure, removed 

 if the possibilities of disruptive approach be added to those of 

 collision ; and it will be seen further on that special condi- 

 tions giving rise to distant approaches that are merely disturb- 

 ing at the outset, may ultimately give rise to large possibilities 

 for disruptive approaches. 



That bodies pass within the disruptive sphere of other bodies 

 is known from the fact that at least four comets have been 

 observed to pass within the Roche limit of the sun, and these 

 would quite certainly have been torn into fragments if they had 

 not already been in that condition. There are, therefore, some 

 observational grounds for the view that instances of bodies pass- 

 ing through the disruptive spheres of other bodies are not so 

 rare as to render their results unimportant. 



' A fact which has become very familiar and impressive, since this was written, 

 by the appearance of Nova Persei. 



