426 . H. S. Suniiners : 



V. — Obsidianite from near Coblgardie, Western Australia. 

 Analysed by A. Hall, 1907. — Records of the Geol. Survey of 

 Victoria, Vol. II., Part i, 1908, p. 205. 



VI. — Obsidianite from near Kalgoorlie, Western Australia. 

 Analysed by E. S. Simpson, 1902. — West Aust. Geol. Survey. 

 Bulletin No. 6, 1902, p. 79. 



VII. — Obsidianite from near Uralla, New South Wales. Ana- 

 lysed by J. C. H. Mingaye, 1897. Proc. Roy, Soc. of Victoria, 

 Vol. XL, N.S., Part I., p. 30. 



VIII. — Obsidianite from the Upper Weld, Tasmania. Analysed 

 by W. F. Hillebrand, 1905. — Report of the Secretary for Mines, 

 Tasmania, for 1905, p. 21. 



IX. — Obsidianite from Pieman, Tasmania. Analysed by W. 

 F. Hillebrand, 1905. — Report of the Secretary for Mines, Tas- 

 mania, for 1905, p. 21. 



By dividing the percentages by the molecular weights of the 

 oxides the molecular proportions of the principal constituents are 

 obtained, as under : — 



The classification of the analysis of the obsidianite from near 

 Mount Elephant may be given as an example of the method 

 used. The molecules in thtMi- right pi'oportions are distributed 

 among the " normative" minerals with the following result : — 



