7 4 2 THE POPULAR SCIENCE MONTHLY. 



nearly in a straight line out and back again into the sun. If in its 

 course it enters the earth's atmosphere, its relative motion, that which 

 we see, should be in a line parallel to the ecliptic, except as slightly 

 modified by the earth's attraction. A large number of these meteors 

 that is most, if not all, well-observed fire-balls have certainly not 

 traveled in such paths. These did not come from the sun. 



It has been a favorite hypothesis that the meteorites came from 

 some planet broken in pieces by an internal catastrophe. There is 

 much which mineralogists can say in favor of such a view. The studies 

 of M. Stanislas Meunier and others into the structure of meteorites 

 have brought out many facts which make their hypothesis plausible. 

 It requires, however, that the stone-meteor be not regarded as of the 

 same nature as the star-shower meteor, for no one now seriously claims 

 that the comets are fragments of a broken planet. The hypothesis of 

 the existence of such a planet is itself arbitrary ; and it is not easy to 

 understand how any mass that has become collected by the action of 

 gravity and of other known forces should by internal forces be broken 

 in pieces and these pieces rent asunder. The disruption of such a 

 planet by internal forces, after it has by cooling lost largely its original 

 energy, would be specially difficult to explain. 



We can not then look to the moon nor to the earth, nor to the sun, 

 nor to any of the large planets, nor to a broken planet, as the first home 

 of the meteoroids, without seeing serious if not insuperable objections. 

 But since some of the meteoroids were in time past certainly connected 

 with comets, and since we can draw no line separating shooting-stars 

 from stone-meteors, it is most natural to assume that all of them are 

 of a cometary origin. Are there any insuperable objections that have 

 been urged against the hypothesis that all of the meteoroids are of like 

 nature with the comets, that they are in fact fragments of comets, or 

 it may be in some cases minute comets themselves ? 



If such objections exist, they ought evidently to come mainly from 

 the mineralogists, and from what they find in the internal structure of 

 the meteorites. Astronomy has not as yet furnished any objections. 

 It seems strange that comets break in pieces, but astronomers admit 

 it, for it is an observed fact. It is strange that groups of these small 

 bodies should run before and follow after comets along their paths ; 

 but astronomers admit it is a fact in the case of at least four comets. 

 Astronomically there would seem to be no more difficulty in giving 

 such origin to the sporadic meteor, and to the large fire-ball, and to 

 the stone-meteor, than there is in giving it to the meteor of the star- 

 shower. If, then, the cometic origin of meteorites is inadmissible, the 

 objections must come mainly from the nature and structure of the 

 meteoric stones and irons. Can the comet in its life and history fur- 

 nish the varied conditions and forces necessary to the manufacture or 

 growth of these peculiar structures ? It is not necessary, in order to 

 answer this question, to solve the thousand puzzling problems that 



