304 MEMOIR ON METEORITES. 



the earth and those of meteorites; and their very dissimilarity 

 of constitution is the strongest argument of their belonging to 

 different spheres. In further refutation of this idea it may be 

 asked, Is it to be expected that a mass of matter detached from 

 Jupiter (a planet but little heavier than water) or from Saturn 

 (one nearly as light as cork) or from Encke's comet (thinner 

 than air) would at all accord with each other or with those 

 of the earth? It is far more rational to suppose that every 

 cosmical body, without necessarily possessing elements different 

 from each other, yet are so constituted that they maybe known 

 by their fragments. With this view of the matter our speci- 

 mens of meteorites are but multiplied samples of the same 

 body, and that body, with the light we now have, appears to 

 have been the moon. 



This theory is not usually opposed on the ground that the 

 moon is not able to supply such bodies as the meteoric iron and 

 stone. It is more commonly objected to from the difficulty 

 that there appears to be in the way of this body's projecting 

 masses of matter beyond the central point of attraction between 

 the earth and the moon. Suffice it to say that Laplace, with 

 all his mathematical acumen,, saw no difficulty in the way of 

 this taking place, although we know that he gave special 

 attention to it at three different times during a period of thirty 

 years, and died without discovering any physical difficulty in 

 the way. Also for a period of forty years Olbers was of the 

 same opinion, and changed his views, as already stated, for 

 reasons of a different character. And to these two we add 

 Hutton, Biot, Poisson, and others whose names have been 

 already mentioned. 



Laplace's view of the matter was connected with present 

 volcanic action in the moon ; but there is every reason to be- 

 lieve that all such action has long since ceased in the moon. 

 This, however, does not invalidate this theory in the least, for 

 the force of projection and modified attraction to which the 

 detached masses were subjected only gave them new and inde- 

 pendent orbits around the earth, that may endure for a great 

 length of time before coming in contact with the earth. 



The various astronomers cited concur in the opinion that a 

 body projected from the. moon with a velocity of about eight 

 thousand feet per second would go beyond the mutual point 



