147 
DISCOVERY OF GLACIATION IN THE VICINITY OF MOUNT 
TYNDALL, IN TASMANIA. 
By T. B. Moors, F.R.G.S. 
_ (Map-) 
A most important and extremely interesting discovery of glaciation 
was made by Mr. E. J. Dunn, F.G.S., of Victoria, in the first week 
of October, 1892, on the high plateau in the vicinity of Lake Dora, 
Tasmania. Having been with Mr, Dunn atthe time of his discovery, 
and as it was his intention to write on the subject, I_now wish to record 
in the proceedings of our Royal Society the result of a more extended 
search made by me on the high peaks and surrounding tableland, 
and illustrate the most important features of the glacial action on the 
accompanying sketch map compiled from prismatic compass bearings. 
The Tyndall Range and Mount Sedgwick have been the principal seats of 
the prehistoric glaciers ; respectively these mountains are about thirteen 
(13) and nineteen (19) miles in a direct line from the town of Zeehan, 
and twenty-two (22) and nineteen (19) miles from the port of Strahan. 
They rise 1,500ft. to 1,600ft. above an elevated plateau, on which are 
situated Lake Dora and numerous other lakes and tarns at an altitude 
of 2,400ft. above the sea level. The plateau is drained on the north by 
the Anthony River, a tributary of the River Pieman, on the west by 
the Henty Kiver and its tributaries, and on the east and south by the 
head branches of the King River. The formation of the higher land is a 
quartzose conglomerate, probably Devonian. A band of sliurian schist, 
overlaid in places with a schistose conglomerate over a quarter of a mile. 
in width, adjoins on the east, to which I shall allude in this paper as the 
Devonian conglomerate, and further east, as far as the North Eldon 
River, close-grained quartzites and conglomerate occur. The summit 
of Mount Tyndall beautifully illustrates the direction in which the 
glaciers have retired. The Devonian conglomerate rock shelves off at 
different points of the compass,is worn perfectly smooth,and within 20ft, 
of the summit the rock is polished and striated. The glaciers descend- 
ing from the higher peaks have flowed in many directions down the 
numerous valleys, in their course beautifully polishing, grooving, 
striating, and moutonnising the Devonian conglomerate, deeply grooving 
and furrowing the softer silurian schists, and scooping out the rock 
basins now forming the present lakes and tarns; then in places rasping 
over hard quartzite and conglomerate ranges 400ft. and 500ft. higher 
than the lower land over which they have travelled, indicating on all 
rocks the direction each flow has taken by the striz and the erratics and 
perched blocks left behind. The largest erratics and blocks are 
composed of Devonian conglomerate. Some examples are 20ft. high by 
about 15ft. broad and long respectively, many are planed and striated 
splendidly, and are often found forming segments of circles at the edge 
of the morainal matter, or scattered in confused masses over the 
moraines. Mount Sedgwick (4,000ft.) is even more interesting than the 
Tyndall country. Greenstone forms a cap to the mount, 800ft. to 1,000ft 
above the lower surrounding Devonian conglomerate ; naturally the 
trap rock has weathered, yet deep grooves and {furrows are perceptible 
to within a short distance of the summit. (Mount Dundas is the only 
other eminence in the West Coast range capped with a simiJar formation, 
but without signs of glaciation.) The elevated country round Mount 
Sedgwick, especially to the east, has been swept bare, and, with the 
exception of a few small boulders, all other morainal matter has been 
carried down the steep slopes and river valleys, The quartzite and 
conglomerate rocks show the striz polishing, etc., similar to those round 
