THE VICTORIAN NATURALIST. 43 



dykes have been forced through the Silurian to the under surface 

 of the glacial beds. In all cases where the junction has been 

 observed the hard dyke rock shows striation and polishing by 

 ice action. 



As the visible eastern boundary of the Granite is approached 

 the Silurian rocks show contact evidence at a distance of i8 

 chains. It is therefore my intention to give a more detailed 

 account of the section between the junction of the Myrniong 

 Creek and the Granite country on the west. 



From the junetion up the river to the first anticline, 8.17 yards 

 distant, the normal features of the Silurian are observed. On the 

 south bank the anticline is seen in section, exhibiting radiating 

 jointing or cleavage, with the usual quartz films. The pitch is 

 S. 10° W. at 15°. Proceeding up the river the dip suddenly 

 increases from 75° to 90°, and continues for 2.50, when it 

 becomes inverted, and dips east at 75°. The massive sandstone 

 and quartzite forming this fan-like structure are seamed with quartz 

 veins and spurs, with here and there strings and threads of 

 granite. Following closely upon the overturned strata, a syncline 

 is observed overthrown 25° W. Within two chains and a half 

 two anticlines and a syncline are developed, with the same angle 

 of overthrow. A quartz reef three feet in width passes through 

 the bedding, and can be traced to the top of the hill, 400 

 feet in height. 



At the spot where we should expect to find the second anti- 

 cline a steep gully runs up the face of the section. The rocks on 

 either hand of this gully are greatly altered, and contain very 

 numerous flakes and spangles of whitish mica, quartz and felspar 

 crystals ; fine threads of granite and quartz penetrate the walls of 

 Silurian. Parallel jointing is strongly developed, dipping at 30° W. 

 In the bed of the gully, when cleared from fallen rock fragments, 

 granite is exposed. I think there can be little doubt that the 

 granite is part of a dyke which has weathered out, leaving the 

 altered rocks on the east and west. 



Westerly for seven chains purple slates and quartzites, con- 

 taining patches and nests of schistose rock, together with strings 

 and a vertical dyke of granite 9 to 12 inches wide. Contortion 

 and pseudo-ripple markings are well developed ; the latter appear 

 more extensively in localiiies which have been subjected to the 

 greatest strain and pressure. 



In sheltered places sulphate of copper and other mineral salts 

 (some extremely acid) coat the surface of the rocks. Shallow 

 caves and hollows have been formed by the continued action of 

 these salts, which have probably been derived from the decom- 

 position of copper pyrites. At the large bend in the river a 

 syncline occurs, the dip being W. 90° E. 60°, and continues at the 

 latter angle to the junction with the Granite, off which they lie. 



