478 PROCEEDINGS OF THE ACADEMY OF [August, 



low momentum and greater air resistance in proportion to their mass 

 would make them early losers in the race, while the air pressure 

 encountered would usually smash them into small pieces. 



I think it quite probable that the stony matter of the earth is merely 

 an outer layer over an iron centre, and in the smash up of any body 

 due to partial collisions or actual collisions the stony matters must 

 be dissipated, as well as the iron masses, to be gathered up again 

 by the approach near to a large gravitating body like a planet or a 

 sun. 



Your expression of "celestial cobblestones" is very expressive and 

 pertinent to the case of the shale-ball masses, and your observation 

 that pieces of apparently broken-up shale-balls are curved indicates 

 a similar origin for all of them. The flight of a cluster of small and 

 large meteoric masses, more or less rounded through our air, would 

 naturally be a sifting-out process, as the smaller bodies would lag 

 behind in the flight. 



