Glaciation of Western Highlands, Tasmania. 137 



testimony to the forces they have been subjected to. Many of 

 the small pebbles detached from the blocks of Devonian or 

 schistose conglomerates are remarkably ground down, polished, or 

 striated. Some of the pebbles from the Devonian conglomerate 

 are sheared in a remarkable manner ; this was done while in their 

 parent mass, the glacial markings have been added since. 

 Curiously enough, at Prince Albert, in Cape Colony, sheared 

 pebbles of precisely similar character occur in the older glacial 

 conglomerate (Dwyka conglomerate) of that region that also 

 show glacial markings, and they, too, are derived from a conglo- 

 merate of supposed Devonian age. 



Tarns. 



Lakelets from several miles in length down to mere ponds are 

 met with throughout these highlands ; they occupy rock-basins 

 that the ice mass ground out where the bed-rock happened to be 

 softer than usual. It is noticable that many of these basins 

 have the longer axis in the direction of the strike of the rock, 

 and they appear to occur most frequently on schist country. 

 Nowhere do these tarns appear to be more than a few feet deep, 

 they occur at many different altitudes. The outlets are some- 

 times over bare bed-rock, in other cases morainal matter dams the 

 water back. Small rocky islets dot some of the tarns, and on 

 them and around the edges of some of the tarns ti-tree and other 

 small trees grow, greatly enhancing their beauty. Now that the 

 iiexibility of ice inasses is well undei'stood it is easy to understand 

 how such rocky basins could be eroded. 



Extent of Glacial Action. 



It appears highly probable that the central highlands around 

 Lake St. Clair, and in fact the greater portion of the island above 

 the 2,000 feet level should also contain evidences of glacial action 

 if searched foi^, and I'emains in abundance may be expected in the 

 iiigher country east of Lake Dora. 



Age. 



There are no direct evidences by which the age of this glaciation 

 can be determined ; so far as the appearance of the moraine, 



