156 Notes on the Geology of the 



grits and cements. It also forms a range of hills on the 

 north side of the West arm, called Stockyard Hills. This 

 greenstone is followed to the west by rocks of carboniferous 

 age, dipping north-easterly under it, and much obscured 

 (except along the coast line, and at the heads of the arms) 

 by both older and newer tertiary drifts. Further west 

 again follow the silurian rocks, forming ranges of hills, with 

 a general north-westerly trend, against the eastern flanks of 

 which the carboniferous rocks lie un conformably. Beyond 

 these again come the metamorphic rocks. Bays, as it were, 

 of the carboniferous rocks run up the valleys of Anderson's 

 Rivulet and the Middle Arm Creek, the boundary of the two 

 formations (silurian and carboniferous) following a contour 

 line at one general level. The serpentine occupies an oval 

 or lenticular-shaped mass about three miles long by one mile 

 wide, in the valley of Anderson's Rivulet, having its northern 

 extremity near the junction of the silurian and carboniferous 

 formations, and the whole of its length entirely in the 

 former. 



I will now proceed to describe the different formations in 

 their order of superposition, from the oldest upwards. 



The metamorphic rocks, the lowest and oldest in geological 

 position, form the highest ranges in the district, and the 

 watershed between the River Tamar and the Port Sorell 

 River, and lie at from four to seven miles west of the former 

 river. Their general direction is from N. 20° — 30° W., which 

 determines the strike of the other formations and the course 

 of the river. They are chiefly composed of mica schist, 

 quartzite, grit, and clayslate; but, owing to their densely 

 scrubby character, and the prevalence of heavy bush fires, I 

 did not examine them, and will pass to the next formation 

 in ascending order, the lower silurian (of Gould). 



This forms a series of nearly parallel ridges, composed of 

 silicious sandstones, grits and conglomerates, micaceous sand- 

 stones, shales, slates, and limestones, &c; the harder 

 indurated silicious rocks forming the summits or backbones 

 of the ridges, the shales and sandstones the flanks of the 

 ranges, and the limestones the valleys. From their associa- 

 tion with large limestone belts, I should be inclined rather 

 to class them as upper silurian, in the absence of any fossil 

 evidence of their age. The conglomerate is locally called by 

 the Brandy Creek, or Beaconsfleld, miners, " Cabbage-tree," 

 from the range of that name there. The matrix of this con- 

 glomerate contains occasionally specks of chromite (which is 



