Age of Metamorphic Rocks, Victoria. 131 



their crystalline character it will be safer to regard them as even 

 older, and as Victorian representatives of the archean group. 



DESCRIPTION OF FIGURES. 

 PLATES XIX., XX., XXI. 



Plate XIX. 

 Locality Plan. 



Showing the relation of the metamorphic rocks, ordovi- 

 cians and granites, from the Geological Survey 

 map. 



Plate XX. 



Fig. 1. — Contorted gneiss, from the bed of Twist Creek, near the 

 junction with Sawpit Gully [No. 57]. Magnified 

 15 diam. Ordinary light. Most of the figure shows 

 one of the dark bands which is much contorted, 

 and the contortions are broken by a series of 

 parallel microscopic faults. 

 ,, 2. — Mylonitic quartz grit; western side of Twist Creek 

 [No. 56]. Magnified 20 diam. Ordinary light. 

 The rock is composed in the main of large quartz 

 grains, in a base of fine quartz mosaic. Owing to 

 pressure a flow has been produced in the rock, 

 causing a roughly parallel arrangement of the 

 quartz grains, and a flow of the base around them. 



Plate XXI. 



„ 3. — [No. 58] Quartz grit; the bed of Twist Creek, further 

 from the junction. Magnified 20 diam. Ordinary 

 light. The quartz grains are angular, and the flow 

 structure of Fig. 2 has not been developed. 



„ 4. — [No. 54] A fine grained grit; the bed on Twist Creek, 

 still further from the metamorphic series. Mag- 

 nified 45 diam. Ordinary light. The rock consists of 

 grains of quartz and plagioclase, with flakes of 

 mica, in a fine argillaceous base. 



