[Pk.>,. Rot. Soc. Victoria 28 (N.S.), Part II.. L916]. 



Art. XVI. — Additional Notes on Australites: Darwin Glass. 



JJv E. J. DUNN, F.G.S. 



[With Plate XXIII.J. 

 (Read November 11th, 1915). 



Since my notes dated 4/7/13, and published in Records of the 

 Geological Survey of Victoria, Vol. III., Part 3. were penned, 

 further examples of Australites have come to hand that demand 

 attention as affording valuable evidence of the manner in which they 

 were formed. Among those dealt with are probably the smallest 

 pet described ; their importance, however, is not to tie measured 

 by their size, for the series, as illustrated, affords useful data not 

 liitherto obtained. Apparently they show the progressive steps by 

 which the original drop of fluid glass became moulded hit" the 

 symmetrical australite. The several examples show individuals 

 arrested at different stages of the process. The glass of which they 

 ■uiisisi having become rigid in some cases at an early stage, in othei; 

 sases at later stages. In three examples they are deformed, and 

 appear to have reached the surface of the earth while still in a 

 semi-plastic condition. 



The smaller figures in the illustration are natural size. The larger 

 figures are the same objects magnified two diameters. 



Fig. I shows an early stage, the drop of glass has assume! a 

 liscoidal form, there is a short line in the centre of the upper sur- 

 face, and the outer edge of the rim is turned slightly up. There 

 must have been a stage preceding this in which the molten glass was 

 drop like. In Fig. 1 the thin short line is the only indication of a 

 3ore. It seems as though a rotary impulse had been imparted to 

 die dro]) of molten glass, and that the small body through loss of 

 heat became rigid at this stage, and fell to the surface of the earth. 



Fig. 2 shows an advance on Fig. 1, for a small conical pit has 

 formed in the centre of the upper surface, but there is still no 

 actual core present. This example may have rotated longer while 

 ■^t i 1 1 in a molten or plastic condition than was the case with I'd-. I. 

 The rim has become more defined also. 



Fig. 3 shows an advance on Fig. 2, and a small core appeal- in 

 the centre, where only a pit existed in Fig. 2. This example may- 

 have rotated still more than was the case with Fig. 2 before the glass 

 became rigid. 



