MICROSCOPIC STRUCTURE OF SOME AUSTRALIAN ROCKS. 213 



have failed to reduce the spheerulites to a degree of tenuity which 

 would permit light to pass. I have collected some few, and have 

 seen other examples of basalt-glasses, many showing clear absorp- 

 tion spaces around the globulites • but altogether the Carcoar rock 

 is the most beautiful example I know. The general appearance 

 of slices of this rock under the microscope is shown in Plate xx., 

 figs. 1 and 2. 



Slice 49. — Tachylyte from Vegetable Creek, New England, 

 New South Wales. This resembles the Carcoar rock generally 

 in the microscopic slide. In hand specimens, the New England 

 rock shows a bright blue skin which gives it a very remarkable 

 appearance. Like the Carcoar rock also, it is easily fusible and 

 its powder is not magnetic. Sphserulites are well developed and 

 have the appearance of globulites massed together. But there is 

 no halo around them free from globulites which gives the Carcoar 

 rock so interesting a structure. The globospherites are quite opaque 

 and the glass is of a rich brown colour. In the Vegetable Creek 

 specimens, the globospherites are large and well developed both 

 as individuals and congregated in masses, set in a dark brown 

 glass, but as already stated with no clear space surrounding them. 



Slice 84. — At the Battery Hill, Lachlan River, above Cowra, 

 pieces of basalt-glass are frequently found, but I have not been able 

 to discover whence they are derived. The fragments occur in the 

 drifts, sometimes being two and three inches in diameter. The 

 surfaces of these specimens are pitted in a very curious fashion 

 and show a peculiar etched-glass appearance suggestive rather of 

 corrosion than of weathering or attrition. The Battery Hill basalt- 

 glass is easily fusible before the blowpipe and the powdered stone 

 is magnetic. Under the microscope incipient sphaerulites are 

 plentiful as well as flakes of a monoclinic pyroxene. A little 

 magnetite is also present. The colour, by transmitted light, is 

 a deep brownish-yellow. At Monkey Hill, near Hill End, frag- 

 ments of a basalt-glass may be collected. I saw a few specimens 

 six inches in diameter. Slice 84a is prepared from one of these. 

 Under the microscope, it shows a rich red-brown shade. Before 



