472 ./. T. Jntson: 



Here the river plunges into a deep narrow gorge ; and the 

 stream passes from the slow meanderings indicative of old age 

 to the swift-flowing, rocky-bedded river characteristic of youth. 

 This gorge continues as far as Templestowe, from where the 

 country becomes more open and the river more staid, until 

 at Heidelberg it has a wide-bottomed valley, and the river 

 meanders through its flood-plain. 



At Fairfield the river again becomes youthful in appearance, 

 due to the partial infilling of the old valley by basalt. It main- 

 tains its narrow valley for some distance ; but the valley 

 gradually widens as it approaches Melbourne, becoming once 

 again the mature or old river, which feature it retains until it 

 meets the sea at Hobson's Bay. 



The character of the valley at Heidelberg has been described 

 by Dr. T. S. Hall (5, p. 42) and the writer (6, pp. 165 and 166). 



The tributaries of the Yarra do not present many diversified 

 forms. Those entering the stream on its right bank comprise 

 streams running mainly through silurian country, such as the 

 Plenty, the Diamond Creek, Watson's Creek, Steel's Creek and 

 others near Yarra Glen. They also include the Watts River, 

 the Badger Creek, the Don and the Dee Rivers, and the small 

 streams near Warburton, all of which belong to dacite country. 

 Farther east there are the O'Shannassy and other rivers, which 

 are silurian. 



These tributaries are, with the exception of the small 

 streams at Warburton, deeply trenched, and have, generally 

 speaking, rather narrow valleys. They enter the Yarra with 

 accordant junctions, are well graded, and their development 

 has clearly been determined by the stage of growth of the 

 Yarra itself. In other words, they are normal tributaries. 



The tributaries at Warburton are very short, with steep 

 grades and very narrow valleys. Their waters are very swift- 

 flowing, and they, with similar streams on the opposite bank 

 at the same locality, constitute a group of mountain torrents. 

 Their rocks are dacite on the northern, and mainly grano- 

 diorite on the southern side. 



The affluents entering the Yarra on the left bank are, as a 

 rule, considerably shorter than those entering on the right 

 bank. They comprise Gardiner's and the Koonung Koonung 



