290 PROCEEDINGS OF SECTION C. 



3. That then no more dust fell during the accumulation of the 



upper part of the Estheria Shales, and the bulk of the 

 succeeding Narrabeen beds. 



4. That then fresh showers of volcanic dust fell and became 



interbedded with the basement beds of the Hawkesbury 

 Sandstone, as proved by the thin layers of tuffaceous grit 

 in the core from the Moorbank bore. 



5. That these tuft'aceous grits belong to a geoloijical horizon 



ditlerent from that of the Holt-Sutherland, Heathcote, and 

 Bulli tuffs, and therefore should probably be correlated 

 with the Newington cupriferous shales. 



ACKNOWLEDGMENT. 



My thanks are due to Mr. J. Waterhouse for kindly allowing 

 me to examine the specimens of the Newington bore : to Messrs. 

 Jones, Black and Tidswell for doing me a similar favour with 

 regard to the Liverpool core ; and to Mr. W. J. Slee, Superin- 

 tendent of Diamond Drills, for the facilities he afforded me for 

 examining the Heathcote core at the drill stores belonging to the 

 Department of Mines. 



3.— MICROPETROGRAPHICAL NOTES ON SOME OF 

 THE HYDROTHERMAL ROCKS OF N. S. WALES. 



By T. W. Edgeworth David, B.A., F.G.S., Geological Survey of 

 New South Wales. 



I Abstract.] 



L J 



These rocks are divided according to ultimate chemical composition 

 into ulti'a-basic, basic, intermediate, and acid igneous. 



Of the ultra-basic group there are two ex ti-a-ter rest rial repre- 

 sentatiyes in the Bingera, and Barratta Meteorites, described by 

 Professor Liversidge. Of terrestrial ultra-basic rocks the chief 

 representatives in New South Wales are serpentines, which rocks, 

 near Gundagai, are considered to be formed from the extreme 

 metamorphism of talc schists. 



Of the basic group there are numerous representative varieties, 

 ranging from glassy tachylites to coarse dolerites. A remarkable 

 intrusive C'herzolite basalt occurs near Bulli. This is composed of 

 fragments of granular ciystalline olivine one to four inches in 

 diameter, and black crystals of augite, half to two inches in 

 diameter, interlaced with anamesite basalt. Leucite basalt has 

 been discovered lately at Byerock and at El Capitan, near Cobar. 

 True gabbros, composed of diallage and a felspathic mineral 

 resembling saussurite have lately been found at the Canoblas 

 near Orange. 



