26 
C. G. THORP, M.B., C.M. : 
Until the last few days I was of opinion that the facetted 
portion of the conical and dumb-bell forms were on the inner 
side of the sharp ridge, but 1 am now quite convinced that the 
large rounded disc on one side of the ridge is the hanging drop 
inside the bubble, while the facets and small flatter disc are 
towards the outside. In every case the curvature of the dumb- 
bell is towards the facetted surface (Plate XX, Fig. 17), and it is 
inconceivable that the dumb-bell should curve away from the 
bubble, and as the dumb-bells shown approach very closely the 
lens form (Plate XX, Figs. 13, 14 and 15), so I am convinced 
that it is from a body of that shape that our West Australian 
conical Australite has been produced, though why it should 
sometimes chip in this way and sometimes leave the body in the 
tabloid form, is not at present explainable.* 
Our West Australian conical Australites, when they are 
found, have the apex of the cone pointing down and stuck in 
the sand or mud, thus furnishing a further reason for believing 
that the cones pointed outward in the bubbles. 
I now thought that a most useful line of investigation would 
be to blow bubbles that would last long enough to allow the 
bleb to be photographed, and I wrote to Nature, asking for 
advice as to a material that could be used for this purpose. 
Professor Boys courteously gave me the recipe asked for, but 
in the meantime at Mr. Curtis’ glass foundry they very kindly 
blew some glass bubbles for me. which gave me roughly the 
information that 1 required at the time (Plate XIX, Fig. 3), so 
I have never blown my bubbles with Professor Boys’ material. 
Professor Kerr Grant, of Adelaide University, seeing the 
answer to my enquiry in Nature, very thoughtfully sent me a 
copy of a paper he had read before the Royal Society of Victoria, 
in support of the contention that bubbles cannot possibly be 
formed from Obsidian, and that therefore these bodies must be 
of meteoric or extra terrestrial origin, giving many arguments in 
support of this contention. 
The divers deductions different persons can draw from the 
same premises is a very interesting study. I took the liberty of 
* Since reading the above, I have thought of an explanation that would 
account for all the many divergent modifications of the few typical shapes 
in which Australites occur. It appears to me to warrant further thought • 
in fact, I may say that several arguments in favour of it have presented 
themselves to my mind. Roughly, I may say that it is that on the surface 
of the molten glass, when it comes in contact with the air, a thin pellicle or 
scum forms, and the masses of gas on rising lift pieces of this skin of different 
sizes and shapes, according to the size and shape of the gas, and this dragging 
after of glass from their edges would form blebs on the summits of the bubbles, 
I hope in the near future to be allowed to read another paper on the aibject. 
when 1 will be able to show you many reasons for believing this to be the 
true explanation. 
