28 Proceed rii(j.s of tJte Royal Society of Victoria.. 



also made to the obsidian balls from Mount Patko, Hiingaiy, 

 pieviously mentioned as being described by F. S. Beudant. 



Darwin considers the form of the bombs to be due to rotatory 

 flight, in the centrifugal force engendered thereby, and in the 

 final bursting of the bomb ; but with this view Professor Stelzner 

 does not agree, and he regards the final bursting as really 

 objectionable. He admits, however, that rotation may ha\p 

 taken place, although he does not think it necessary. 



According to him, the outline form of five specimens can be 

 deduced from that of a sphere, and that of one to a triaxial 

 ellipsoid. He considers that the approximately spherical form 

 was produced in two very different ways. In the one case — 

 that of the hollow ball — it has been produced by the expansion 

 of a thread of lava rich in gaseous components ; in the six solid 

 bombs the form is referable to the same causes which induce the 

 shape of a drop of water, or fluid lead descending from a tower 

 or into a shaft, and forming shot globules. He further states 

 that the shape must have been likewise influenced by the 

 resistance of the atmosphere which the rapidly moving bomb had 

 to surmount. In tliis the explanation of the special form and 

 the more delicate surface sculpture has to be sought for. He 

 then goes on to compare the obsidianites with meteorites, and 

 considers it perfectly admissible. In this he mentions the black, 

 glassy crust, the pittings and the analogy to the expansion rims 

 and streaked friction planes which Daubree^ obtained in his 

 experiments. Finally, he thinks their origin is to be sought for 

 in Australia, but leaves it to Australian geologists to settle. 



Professor Tate and J. A. Watt, in their report on the Geology 

 of the Horn Expedition, 1897, in referring to the numerous 

 obsidian bombs, which most frequently occur in an eroded state, 

 and unrolled agates found between the Stevenson River and 

 Charlotte Waters, say — "In the first place, the occurrence of 

 [sic) the obsidian bombs and agates on the Desert Sandstone 

 plateaux and their slopes could not have been transported there 

 by water, unless in the form of ice (an hypothesis incompatible 

 with the co-ordinate features)." They therefore assume that 

 these agates and bombs are all that now remain of a supposititious 



Etudes s.vnthi'ti(|ues de :4-<'ologie exiK-i-iiiientale, 1S7:). 



