Art. III. — Tlte Occurrence of So-called Ohsiclian Bombs 

 in Australia. 



By R. H. WALCOTT, F.G.S. 



(Plates III. and IV.) 



[Read 9th June, 1898.] 



In writing this paper I have been mainly influenced by a 

 desire to draw attention to these most interesting and, in many 

 respects, remarkable objects, in order, if possible, to satisfactoi'ily 

 solve the mystery surrounding their origin. It is, without 

 doubt, a subject which presents many difficulties, and I do not 

 purpose attempting an explanation to account for them, simply 

 because at the present time sufficient data are not obtainable to 

 establish detinitely any acceptable theory. I will, therefore, only 

 discuss the explanations put forward by others, and give the 

 conclusions which I have drawn from my own observations. 

 The term " boml:) " has been generally applied to these objects, 

 but I think it is justly open to objection, inasmuch as it conveys 

 the idea of a terrestrial volcanic body ; and as we have no 

 positive proof tliat they are products of this nature, the name 

 may be misleading. As long as this uncertainty exists, some 

 other name would be more appropriate, and I suggest and will 

 refer to them in this paper as " obsidiatiites," a term which will 

 at least not be open to this objection, and will be more convenient 

 for use. As far as can be ascertained, little seems to have been 

 done in the past towards uni'avelling the true nature of 

 obsidianites — no doubt owing to the obstacles which are at once 

 encountered. They appear to have been first mentioned by 

 Charles Darwin,^ who described a button-shaped specimen which 

 had been given to him by Sir Thomas Mitchell. It was found 

 on a great sandy plain between the rivers Darling and Murray, 

 and at a distance of several hundreds of miles from any known 

 volcanic origin. He states : " It seems to have been embedded 



1 Geological Observations on Coral Reefs, Volcanic Islands, and in South America, 1851 

 ed., pp. 38, 39. . 



