FLANGES OF AUSTRALITES (TEKTITES) 13 
may even occupy the bulk of the interior, as in a hollow sphere 
from Hamilton, Victoria, described and figured by Dunn (1912 b) . 
In thin plates, all the smaller bubbles have dark borders. Barnes 
(1940) regarded similar spherical bubbles in tektites (bediasites) 
from Texas, U.S.A., as formed later than flow structures; but in 
australites elongated bubbles and flow structures bending round 
spherical bubbles indicate that bubbles were formed prior to flow. 
It is therefore likely that bubbles continued to form throughout 
the development of australites, and that bubbles with dark borders 
are primary. Small secondary cavities lacking dark borders are 
confined to posterior surface regions of the core near its union 
with the flange; they were originally pits, but some are either 
infilled with or partly enclosed by glass from the flange (PL II, 
8 and 11, and PL III, 5 and 7). In thin plates such infilled 
cavities are delimited by differences between the refractive index 
of the walls and that of the infilling glass. Infilled cavities are 
sometimes tubular with rounded bases and with openings to the 
posterior surfaces of the cores, as shown by some of the dark 
areas (infilled with ferruginous clay) in Pl. II, 5. 
Most bubble-pits are semi-circular in section (Pl. I, 1 and 12, 
and Pl. III, 7), but a few are tube-like or funnel-shaped. In 
sections of cores numerous bubble-pits in close proximity give 
rise to jagged outlines in sections through the posterior surface 
(Pl. I, 7). 
Bubble-pits are rarer on anterior than on posterior surfaces. 
Many pits on anterior surfaces are wider at the base than at the 
opening, and they may have a central pyramid of glass (Pl. I, 4) ; 
some of the larger pits are irregular in shape (Pl. I, 5). 
The minute glassy particles (Fig. 3) are microscopic in size, 
pale pink where embedded in glass, but colourless where pro- 
truding, and their refractive index (1 460) is lower than that 
of the surrounding glass (1510). They are numerous in those 
parts of flanges contorted by flow structures, but are also common 
along line of union c; infrequent in central cores and scarce in 
the less disturbed regions of flanges. They form rounded or 
irregularly-shaped blebs, granules, elongated threads, and ribbons. 
Ribbon and thread-like particles may be coiled and contorted 
(Fig. 3, A, B and L), some only slightly (Fig. 3, C and K), 
others in complex fashion like examples from bediasites figured 
by Barnes (1940). Some associated with flow directions are 
elongated, others are neither distorted nor elongated. Occasional 
bleb-like particles are hooked (Fig. 3 E), curled (Fig. 3 G-) or 
bean-shaped (Fig. 3 F), and some are lens-shaped particles with 
tapered plane spiral processes (Fig. 3 I). Some granular particles 
