BY A. N. LEWIS, AI C. 29 



The size of these cirques has probably been increased by 

 later action of frost, but undoubtedly the ice is responsible 

 for the outline of this rugged stretch of country. Lateral 

 expansion of the Lake Seal glacier, and the upward move- 

 ment of its load as it swung round Mt. Bridges, also had 

 something to do with the forming of its wonderful valley. 



(c) The, Head of the Broad River Valley. 



Returning to the third branch of the main glacier, the 

 one flowing straight down the trough of the Broad River. 

 To the east of Lake Webster the river now flows on the 

 €ast of the lines of ridges of glacial till already described, 

 and for which the Lake Seal glacier was probably respon- 

 sible. Shortly after passing the level of the end of Lake 

 Webster, the glacial deposits in the actual valley of the 

 Bread disappear, and within the general U-shaped valley 

 the river runs for over half a mile down a typical water- 

 worn gully ever a series of pretty cascades. On both sides 

 of this gully native diabase outcrops, and no signs of 

 glaciation exist in the bed of the creek or further east, 

 although a mile to the west, and 400 feet up the side 

 of Mt. Mawson, we see the ridge of glacial till -already 

 mentioned, and glacial deposits abound above this gully 

 as below. Evidently here, with a more abrupt slope in 

 the floor of the glacial valley, the river has had more cutting 

 power, and has cut a small valley of its own out of the 

 floor of the larger valley, a floor probably largely com- 

 posed of loose materials, and cut by the considerable flow 

 of water escaping from the melting glacier, thus giving 

 us an example of a valley within a valley. It does not 

 appear reasonable to suppose that the glacier never pushed 

 down over this section of the valley, and that the glacier 

 lower down came entirely from the Lake Seal Valley, but 

 rather that all traces just here have been removed by sub- 

 sequent water action. 



Once this short stretch is passed, the Broad River Val- 

 ley assumes again an appearance somewhat similar to that 

 below Lake Webster. But here the bottom of the valley is 

 not so flat nor so wide as in the lower reaches, and is clearly 

 the work of a smaller ice-river. The whole floor is covered 

 with till consisting of earth, a quantity of clay, and a high 

 proportion of boulders, especially towards the sides. These 

 erratics increase in size and frequency until the Broad 

 hends west to its source in Lake Dobson. 



