32 
C. G. THORP, M.B., C.M. : 
conceivable natural agency. They certainly do form a very 
convincing argument for the truth of Mr. Dunn’s bubble theory, 
but, as 1 have said previously, it is not possible that these very 
large extremely fragile bodies can have lain on the surface of 
the ground for any great length of time, and most certainly not 
since tertiary or even early recent times. 
It is very greatly to be regretted that in the opening of both 
these remarkable specimens no means were taken to ascertain 
what the contents had been. Possibly the smallest trace of water 
and watery vapour or one of the simplest gases, such as hydrogen 
or even helium, as the internal heat of a volcano producing a 
fluid glassy lava, must be very high, and at that temperature 
water would be very easily decomposed with the production of 
free hydrogen, while if volcanic action is associated with radium, 
as some seem to believe, that would account for the piesence 
of helium. In any case, however one would expect the pressure 
to be a minus one. 
The next argument brought forward is, to my mind, the 
strongest that 1 have heard against the meteorite theory. Pro- 
fessor Kerr Grant says : - 
'• The average velocity of meteors which enter the atmosphere may be- 
taken as about forty miles per second. If only one per cent, of the energy 
which such meteors possess were, under the influence of the air friction, 
converted into heat and retained by the body it would probably be sufficient 
to raise the substance of an obsidianite to the melting point and render it 
completely liquid. T he melting point of the material and its specific heat 
have been determined in the Physical l.aboratory, Melbourne, as 1.324° f . 
and .21 respectively. The remarkable homogeneous quality of the glass of 
which obsidianites are composed renders it certain that they have, piior to 
assuming their present form, been fused throughout. 
When a meteorite enters our atmosphere from space it is 
generally travelling with such a velocity that, even at one hundred 
miles above the earth, it may already have produced such friction 
as to have become heated so as to glow and become visible. 
Small siderites have fused and been converted before they reach 
the globe into the microscopic so-called “ cosmic dust, ' consisting 
of minute metallic spheres or shot-like bodies, found on the 
snow in arctic regions, and on the bottom of the profoundest 
depths of the oceans. 
It is only masses of considerable size, or fragments of such 
masses, that are ever found as distinguishable meteorites. I have 
never heard of siderites being found so small as to be in any waj- 
comparable to the average size of Australites, not to speak of the 
smaller ones.* 
* U should be said here that meteorites meeting the earth in its flight 
may travel considerably more than 40 miles per second. Those, however, 
travelling in the same direction only a little faster that overtake it may be 
effectively travelling through the atmosphere at only a mile or two pet- 
second. 
