430 Mr. R. P. Greg on the Lunar Origin of Aerolites. 



been said ; in fact no mineralogist can dispute the great resem- 

 blance of these minerals to those of terrestrial volcanoes, they 

 having only sufficient difference in association, to establish that, 

 although igneous, they are extra-terrestrial. The source must 

 also be deficient in oxygen, either in a gaseous condition or com- 

 bined as in water : the reasons for so thinking have been clearly 

 stated as dependent upon the existence of metallic iron in mete- 

 orites ; a metal so oxidizable, that in its terrestrial associations 

 it is almost always found combined with oxygen, and never in its 

 metallic state. 



" What then is that body which is to claim common parentage 

 of these celestial messengers that visit us from time to time ? 

 Are we to look at them as fragments of some shattered planet 

 whose great representatives are the thirty-three asteroids between 

 Mars and Jupiter, and that they are ' minute outriders of the as- 

 teroids ' (to use the language of Mr. E. P. Greg, in a late com- 

 munication to the British Association) which have been ultimately 

 drawn from their path by the attraction of the earth ? For more 

 reasons than one this view is not tenable ; many of our most di- 

 stinguished astronomers do not regard the asteroids as fragments 

 of a shattered planet ; and it is hard to believe if they were, and 

 the meteorites the smaller fragments, that these latter should 

 resemble each other so closely in their composition ; a circum- 

 stance that would not be realized if our earth was shattered into 

 a million of masses large and small. 



" If then we leave the asteroids and look to the other planets, 

 we find nothing in their constitution, or the circumstances at- 

 tending them, to lead to any rational supposition as to their 

 being the original habitation of the class of bodies in question. 

 This leaves us then but the inoon to look to as the parent of 

 meteorites, and the more I contemplate that body, the stronger 

 does the conviction grow, that to it all these bodies originally 

 belonged." 



Dr. Smith then notices the similarity existing between the 

 respective densities of the moon and aerolites, but does not lay 

 great weight on that point ; though he thinks their chemical 

 composition a strong ground in favour of their lunar origin. He 

 goes on to say, — 



" Laplace's view of the matter was connected with present vol- 

 canic action in the moon, but there is every reason to believe 

 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 independent 

 orbits around the earth, that may endure for a great length of 

 time before coming in contact with the earth, 



