Vol. 60.] THE GLACIAL GEOLOGY OF TASMANIA. 45 



large that I could understand their being regarded as of glacial 

 origin. Absorbed in the interesting problems of the Mount- Lyell 

 mining-field, I had dismissed glacial questions from my mind, 

 especially as I found only talus-boulders at the old mine-workings, 

 where Moore had described a moraine. I was therefore led to 

 accept the view of Officer, Balfour, and Hogg, that Moore had mis- 

 taken coarse talus for glacial deposits. I was according surprised, 

 when having occasion to cross the hill on which Gormanston is 

 situated, to find on its western face some beds of tough, fine, well- 

 bedded glacial clays, with ice- scratched boulders. Above this 

 deposit were beds of typical boulder-clay. One of the boulders in 

 the bedded clay was a foot long, aud was standing on its edge ; it 

 had compressed the layers below it, and had evidently fallen through 

 water from floating ice ; near it were a few scratched stones. The 

 boulder-clays, moreover, were clearly of recent origin, and formed 

 later than the excavation of the Linda Valley ; they occurred as a 

 bank projecting from the southern side of the valley, and nearly 

 damming it across, like a delta. A short examination showed that 

 Moore was right in his view that the town of Gormanston 

 stands on a glacial moraine of recent geological age. 



This moraine occurs now in a fan-shaped hill, a mile long by 

 half a mile wide : it rests against the southern bank of the Linda 

 Valley at the Gormanston Gap. The top of the moraine is. in 

 places, fairly level, and at the height of 320 feet above the Linda 

 Creek. For it has been planed down by the southern tributaries of 

 the Linda, which flows round its northern edge. The moraine 

 must once have extended right across the valley to the southern 

 foot of the ridge of Mount Lyell, where patches of it still occur. 

 But the moraine has been cut through by the Linda. Excellent 

 sections of the glacial beds are exposed in the banks of the creeks 

 which run from the Gormanston Gap to the Linda township, and 

 along the eastern side of the deposit ; and also in the railway- 

 cuttings of the Xorth Mount-Lvell Railway, on the northern face of 

 the moraine. The moraine is composed mainly of typical boulder- 

 clays. The bedded clays are best exposed on the western side of 

 the deposit, as if they had accumulated in a glacier-lake that 

 occupied the upper part of the Linda Valley, above the moraine- 

 dam. 



The bulk of the moraine is formed of unstratified clay, crowded 

 with boulders and pebbles. The majority of the included frag- 

 ments are quartzites, derived from the conglomerates that form the 

 summits of Mount Lyell and Mount Owen. These hard materials 

 frequently retain their original form, but some of them show signs 

 of facetting, suggesting ice-action. Some of the boulders are rocks 

 not found in the immediate neighbourhood. There are coarse blocks 

 of hard blue stone, exactly similar to the Mesozoic diabase which caps 

 the central plateau of Tasmania, and forms the crests of the Eldon 

 Rauge and the peak of Mount Sedgwick. There are also boulders 

 of quartzite and sandstones, probably derived from the Silurian 

 rocks to the east of the Xing River, and some blocks of hard slate 



