Obsidian Bombs in AnxtraJin. 29 



volcanic formation, but admit that " the theory seems wild in 

 the extreme, because of the widespread silicification, and the 

 absence over its area of any traces of actual volcanic outbursts." 



lu "Nature " of 13th May, 1897, there is a review of a paper^ 

 by Mr. R. D. M. Verbeek, in which he dealt with the glass balls 

 of Billiton : — " In the quaternary or, perhaps, pliocene tin ore 

 deposits of Billiton there occur peculiar rounded glass balls with 

 grooved surfaces ; they are also found, though very rarely, in 

 certain quaternary tuff strata in Java and in the equally quater- 

 nary gold and platinum mines of South-eastern Borneo." The 

 author classed these objects with the Bouteillenstein of Bohemia 

 and the quaternary glass balls found in Australia. He believes 

 that they cannot be of volcanic origin, because the nearest 

 volcanoes are too far distant, and have, moreover, produced 

 glassy rocks of quite a different nature. For various reasons 

 they cannot be artificial either ; he therefore takes them to be of 

 non-terrestrial oiigin, and considered it probable that they are 

 thrown out by lunar volcanoes during the quaternary and, 

 perhaps, already during the pliocene period. The most recent 

 paper on this subject, by Messrl W. H. Twelvetrees and W. F. 

 Petterd, was read before the Royal Society of Tasmania at 

 Hobart in August last. Obsidianites have been found on both 

 east and west sides of the island, as in the tin drift at Thomas' 

 Plain and at Long Plain, near Waratah. The authors state 

 that " the strange feature of the Tasmanian occurrence is that 

 no glass of similar igneous rocks was known in the island, nor 

 any trace whatever of tertiary or recent rhyolite or trachyte.'' 

 They consider that they are unquestionably volcanic products, 

 but think that the inference that the volcano was a lunar one 

 was unnecessary, and was open to objection. The terrestrial 

 volcanic hypothesis " only requii^ed that the molten spray should 

 have been carried by winds as far as Tasmania and Australia." 



Before considering these papers, it will be well to settle, as far 

 as possible, the chemical nature of obsidianites, moi'e especially 

 as doubts have been expressed on this point, and to give a 

 description of the various forms met with. As far as is known, 



1 Read before the Koninklijke Akademie van Wetenschappen, Amsterdam, 27111 March, 

 1897. See also .Jaarboek \an het Mijnwezen, in Nederlandsch Oost-Iiidie, Amsterdam, 

 pp. ■235-272, pi. i.,lS97. 



