Obsidian BoniJis ii> Ausindin. 45 



they have been transported to where they are now found, it ought 

 to follow that where we have had extensive volcanic acti\ity of 

 this nature we may reasonably expect products similar in all 

 respects. The nearest occurrence of this kind is in the North 

 Island of New Zealand, where obsidian is very connnon in the 

 rhyolite series, and an abundance of pumice occurs, but Sir James 

 Hector states that he has never seen obsidian bombs^ there, and 

 Professor Ulrich says he has never heard of any such button- 

 shaped bombs as the "Victorian ones being found in New Zealand. 

 But in regions whei'e basic flows have taken place, bombs occur 

 similar to those of the same nature found here, which are always 

 more or less vesicular. 



This fact opens the question whether solid bombs, either acidic 

 or basic, are ejected by volcanoes. In speaking of bombs, I refer 

 particularly to true bombs or masses of lava which have assumed 

 a more or less regular shape through their gyrations in the air 

 whilst in a molten state. I say this advisedly, because not only 

 blocks and fragments of solidified lava may be ejected, but also 

 pieces of foreign rocks through which the pipe burst, and which 

 may differ totally both in physical and lithological character from 

 the ordinary products. In this respect then we have just seen 

 that in New Zealand solid bombs are not known, and it is 

 hardly likely that where such extensive volcanic activity has 

 been displayed they would not have been noticed if they existed. 

 Tlien, referring to Professor Stelzner's paper, in which he gives 

 a number of analogies, the only ones which can be taken as 

 undoubtedly composed of dense obsidian are the moldavites and 

 the obsidian balls from Mount Patak. 



But the strange feature in, anyway, the first instance is that 

 their origin, like the obsidianites, is enveloped in obscurity. 



With regard to the second instance, Beudant says that the 

 form of the obsidian specimens presents itself everywhere, which 

 indicates necessarily a like cause in all localities. These speci- 

 mens were found at the foot of hills composed of pumice and 

 trachyte conglomerates, the latter overlying the former. It is 



1 Professor F. W. Hutton, under the heading of obsidian, mentions a black \itreoiis 

 volcanic bomb, highly vesicular inside, with a thin cracked vitreous skin on the outside, 

 from Mount Haroharo, Lake Rotoiti, Taurauga Co. Trans. Ro.val Soc. of N.S.W., vol. 

 xxxiii., p. 23. 



