A CONTRIBUTION TO THE STUDY OF AUSTRAI.ITES. 
21 
of comparison. It will be noticed that the composition of Austral- 
ites and Billitonites are identical, while that of Moldavites differs 
materially from them. 
Australitcs, Billitonites and Moldavites are three somewhat 
similar bodies, found respectively in Australia, in the East Indian 
Islands, and Malay Peninsula, and named after Billiton, an island 
to the south-east of Singapore, where there are tin mines, and in 
Bohemia and Moravia, being named after the river Moldau, in 
Bohemia, where they were first found. It is my intention to 
discuss iu this address their similarities, their differences, and 
the problem of the formation of the two former. Similar bodies 
have been recovered from Columbia and Arizona, in America, 
and in the localities mentioned by Dr. Munn in his paper, published 
by the Geological Survey of Victoria, but few particulars are 
available here. 
The composition of Australitcs and Billitonites is peculiar, 
in that it differs from that of most known Obsidians, 1 understand, 
by combining with a high lime content always more, and some- 
times considerably more, potash than soda. As Moldavites 
with a smaller proportion of lime, contains a still greater proportion 
of potash to soda, this would probably show that Obsidians of 
this character are more viscid when fused, or otherwise better 
adapted to form these objects. This may perhaps be the reason 
why they are not more universally produced, and may also lead 
to the discovery of the volcanoe, or volcanoes, whence they are 
derived. The high lime content is apparently the most important 
factor, as may be judged by the much more perfect shapes con- 
stantly presented by Australitcs when compared with Moldavites. 
If a glassy lava of this composition were erupted in a large 
flow it would probably maintain its heat sufficiently long to permit 
some crystals to separate out, and in time, as has been observed 
elsewhere in other Obsidians, the molecular structure might so 
alter that the entire mass would become crystalline. From this 
I infer that Australites and Billitonites have been suddenly 
chilled from a fluid state, even though the volcano that produced 
them might not discharge apparently a perfectly glassy lava. 
Two theories have been propounded to account for the 
formation of these glass bombs and their deposition in the places 
where we find them, viz. : the Meteoric and the Bubble theories, 
both hypotheses being supported by well-known sound scientific 
men ; and while I hold most strongly to the latter, and must 
confess my total inability to appreciate the validity of the argu- 
ments in favour of the former, and against the latter, it is im- 
possible not to acknowledge that there are difficulties, very hard 
to explain, and that there has been no actual proof. Thus it 
can only be regarded as the best working hypothesis at the 
