58 



explanation can be given in reference to some of the places 

 where they have been found in Tasmania. The theory that 

 they may have come from lunar volcanoes, or even from 

 distant terrestrial volcanic centres such as those of New- 

 Zealand, should not be seriously considered until all other 

 hypotheses on the subject have been exhausted. 



Since the above paper was written, I have received 

 from Sydney a copy of the passage in Darwin's Geological 

 Observations on Volcanic Islands, to which reference was 

 made in connection with the discovery reported by him of a 

 "volcanic bomb " in the interior of Australia. The follow- 

 ing extract completes the early history of obsidian " buttons" 

 in Australasia : — 



" Sir Thomas Mitchell has given me what at first appears 

 to be the half of a much flattened oval ball of obsidian ; it 

 has a singular artificial-like appearance, which is well repre- 

 sented (of the natural size) in the accompanying woodcut. 



" It was found, in its present state, on a great sandy plain 

 between the Rivers Darling and Murray, in Australia, and at 

 the distance of several hundred miles from any kuown 

 volcanic region. The external saucer consists of compact 

 obsidian of a bottle-green colour, and is filled with finely- 

 cellular black lava, much less transparent and glassy than 

 the obsidian. The external surface is marked with four or 

 five not quite perfect ridges, which are represented rather too 

 distinctly in the woodcut." 



