280 PROCEEDINGS OF SECTION C. 
I merely mention this to show that every conceivable ex- 
planation has been thought of. The analyses of Australian 
specimens show thac the substance of the bombs is not 
hydrated silica. There is consequently no need to dwell 
upon the complete absence of any signs of geyser-action in 
the districts of the respective discoveries. 
At first I could see no other source open than New Zealand 
or Antarctic volcanoes. I must confess, however, that the 
great distances involved are unfavourable to the theory. 
The non-discovery of such bombs in New Zealand in the 
vicinity of the mountains which are, on this theory, pre- 
sumed to be the points of origin, is disconcerting. The — 
conclusion after all seems irresistible, that if the buttons are 
of terrestrial origin, they must be derived from some near 
source. We know that quartz-basalts occur in California, 
and quartz-diabase in Europe and Canada. The former have 
a quartzless ground-mass, and contain porphyritic crystals 
of quartz; the latter has granophyric aggregates of quartz 
and felspar, and occurs sparingly in Tasmania. The pres- 
ence of the quartz in basalt is generally explained by sup- 
posing a mixture of dacite and basalt magmas to have taken 
place. If this had happened in Tasmania, it is just con- 
ceivable that siliceous glass might have separated and given 
rise to these bombs. It is, on the other hand, very unlikely 
that all such material should have gone into the bombs, and 
none be left behind in the basalt sheets. None of these 
objects have been found in the basaltic lavas, and no quartz 
has ever been seen in any of the numerous slides of basalt 
which have been prepared. Moreover, their presence in 
the infra-basaltic gravels indicates an older date for them 
than that of the basalt outflows. They are found, too, in 
non-basaltic districts, ¢.g., Schouten Main. 
From this brief review of terrestrial theories, it will be 
seen that every suggested explanation is surrounded by 
grave difficulties. At present the extra-terrestrial theory 
is most in favour. Dr. Suess of Vienna published a treatise 
in 1900 on the origin of moldavites and allied glasses, 
strongly supporting a meteoric origin. He has given the 
objects the general name of Tektites, distinguishing the 
varieties found in Europe, Billiton, and Australasia as Mol- 
davites, Billitonites, and Australites respectively. Mr. R. 
H. Walcott of Melbourne had previously called our bombs 
“ obsidianites.”’ Their occurrence in Australia, both in 
drifts and on the surface far distant from-any volcanic 
centres, and here as there, in a manner independent of 
local geology, their similarity of type, even though. scattered 
all over the vast area of Australia, lend undeniable weight 
