44 A FURTHER NOTE ON OBSIDIAN BUTTONS. 



eye. The ellipsoidal shape, AA'hich is . not uncommon 

 in Australian specimens of the buttons, is inconsistent 

 Avith the theoi'v of a long rotatory flight through the air, 

 for any such volcanic ejectamenta must have cooled too 

 quickly to alloAv of any change of form on reaching the 

 ground. A similar elongation of originally spheroidal 

 cavities in vesicular basaltic lavas is a familiar instance 

 in this connection. 



The general probabilities seem to be in favour of the 

 origin of the obsidian in or near the country in which 

 the " buttons " are found, even if volcanic rocks of the 

 necessary acidic type are not now in evidence : that they 

 have been largely distributed by human agency cannot 

 be doubted. Their reported occurrence in drift gravels 

 in certain localities is still a mystery for the elucidation 

 of which no satisfactory explanation has yet been offered. 



