Obsidianites. 433 



consideration of the chemical composition shows that such a 

 belief is untenable. The analyses show that if the obsidianites 

 be artificial, they must have come from a common source, and 

 are either the result of the melting down of some substance 

 having the requisite chemical composition, or else are the pro- 

 ducts of high-class metallurgical works. The occurrence of the 

 buttons over such a large area shows that the distribution from 

 this common source must have commenced long before the dis- 

 covery of Australia, so that to believe in the artificial origin of 

 obsidianites we must believe that among the Australian 

 aborigines were first-class metallurgical chemists who had con- 

 trol of temperatures of over 1300 deg. C. 



(b) Volcanic Products. — 



Most of the earlier writers on this subject believed that the 

 obsidianites were a peculiar form of volcanic boml), and this 

 opinion is still held by many. Various places, such as the 

 volcanoes of New Zealand, South Victoria Land, and the Malay 

 Archipelago, and the extinct volcanoes of Victoria, have been 

 named as the source from which the bombs were derived. Un- 

 fortunately, no reliable analyses of Victorian basalts have been 

 recorded, but analyses of rocks from the other areas are given 

 below, together with the analyses of the Coolgardie obsidianite 

 for convenience in comparison. Only the more important con- 

 stituents are quoted. 



