276 ^\ R. Junver: 



Section No. HlOl, one mile S.W. of Muroondah Weir. — Sharp 

 rhombs of dolomite occur in places, associated with secondary 

 quartz and iron oxides. Microscopic veinlets of banded silica and 

 carbonates intersect the rock. 



Fragmental rocks, tuffs and flinty breccias whose fragmental 

 character is only revealed on weathering, also occur to the south 

 and south-west of Mount St. Leonard. 



E . — Rhyoliies. 

 With the single exception of Professor Skeats' reference to quartz 

 l^orphyries and porphyrites occurring near Narbethong and MaryB- 

 ville, there is no mention, in the literature of the area, of extrusive 

 rocks more acid than the dacites. However, at Archer's Look-out, 

 St. Ronan's Well, near Lindt's Hermitage, the Acheron river 

 above St. Fillan's, and at several other points north of the main 

 divide, normal rhyolites outcrop. These rocks are characterised in 

 hand specimens by abundant quartz phenocrysts, and by the paucity 

 of femic minerals. Rhomb-shaped sections of glassy or pearly ortho- 

 clase can be recognised in nearly all hand specimens of these rocks. 

 Fluxion banding is often well developed. A chemical analysis of 

 the rhyolite from Archer's Look-out was made by the writer in the 

 geo-chemical laboratory of the Royal College of Science, London^ 

 and gave the foUoAving result : — 



Sp. (4r. 2.49 

 I. Khyolito, Archer's Lookout. Analyst, N. K. Junuer. 

 II. Rhyolite, Mount Wellington. Analyst, E. O. Thiele. 



