476 J. T. Jatsoii : 



The Senkungsfeld is bounded on the west by a line running 

 north-easterly from about Springvale to the Dandenong Creek 

 (just west of the Bayswater railway station). Crossing the 

 creek it continues in the same direction as far as Burt's Hill. 

 It then iims a little to the west of north to the Yarra at the 

 mouth of the Brushy Creek, then north-easterly to Yarra Glen. 

 From here the boundaries have not been definitely traced, but 

 probably it trends eastward (a little to the north of the Yarra) 

 to Healesville, thence southward close to the great dacite 

 masses of Mounts Riddell and Toole-be-wong to the east of Kil- 

 lara, thence across the valley of the Yarra at the latter place 

 to the Warramate Hills, thence northward along their eastern 

 edge, thence westward to Lilydale, and southerly along the 

 western edge of the Dandenong Ranges and adjacent hills to 

 Dandenong. 



Thus this depressed area consists of a long north and south 

 valley running through Croydon to Dandenong, the low 

 countrj^ about Yarra Glen, and the narrow valley between 

 Mount Toole-be-wong and the Warramate Hills. Mr. Thiele in 

 his suggestive and interesting little paper (7, p. 103) has noted 

 the depression of the Dandenong Creek area ; but suggested 

 no reason for its existence. 



The depth of the original surface of the Croydon Senkungs- 

 feld below the general level of the Yarra Plateau is at Croydon 

 about 140 feet (by aneroid), and at the gorges subsequently 

 described as the Yering and Warrandyte Gorges, about 200 

 feet by the same instrument. At the " Kopje " it is only about 

 85 feet. Elsewhere the heights have not been determined. 



The Lilydale basalt, although higher than most of the de- 

 pressed area, cannot be separated from the latter. Its greater 

 height is due, in the writer's opinion, to its greater resistance 

 to erosion than the softer neighbouring rocks. The relations 

 of the higher country chiefly occupied by the pyroclastic rocks 

 of Evelyn and surrounding country' (which are regarded as re- 

 lated to the dacites), to the Senkungsfeld and the Yarra 

 Plateau, have not yet been determined. 



So far as its boundaries have been definitely traced, the 

 Senkungsfeld is mainly due to faulting ; it is therefore a fault- 

 block. 



