■'3^6 Morris MorrU : 



in the form of a crescent, but it opens to the south. These phenomena 

 may be explained on the hypothesis, that the eastern pair lie along 

 an anticlinal axis, and the western pair alon*,' a synclinal axis, the 

 fold in both cases pitching south. 



Further, it is owing mainly to these resistant ridges that tlie 

 Yarra has had to take such a long bend to the north after leaving 

 the course set for it in the Warburton Gorge. 



IV. — Late Palaeozoic Igneous System. 



The great revival of igneous activity which occuned at many 

 centres of Victoria in the late Palaeozoic, and produced, among 

 ■other formations, the Snowy River Porphyries, the Strathbogies. 

 and Mt. Macedon, developed in the district under review, into a 

 cycle of three phases — a volcanic phase, including probably five 

 series (of which the last three formed the Dandenong Ranges), a 

 plutonic phase, and a hypabyssal phase. 



Distribution. — The whole system has the foiiii of a rough 

 triangle, with its l)roken apex between Lilydale and Wandin. From 

 this place, it extends south for twenty miles to the Gippsland i-ail- 

 way line, near to which its broad base of about 15 miles is spread 

 out between Dandenong and Pakenham. A line connecting 

 Emerald with a point two miles south of Ferutree Gully divides 

 this triangle into two parts, and, roughly speaking, the southern 

 part contains the plutonic outcrops, <ind the northern part the 

 volcanic rocks of the system. 



This map and paper is chiefly occupied with the northern ex- 

 tremity of the volcanic series, and as this area, though small, 

 •contains all the series of the system, it therefore supplies material 

 for the description of the whole cycle. 



Relation to the Siliir/a/is:. — The part of the system shown on the 

 map is girdled on three sides by the Silurians, of which those on 

 the west dip east, and those on the east dip west. The uptujiied 

 edges of the Silurians dipping at a high angle may be seen almost 

 in contact with the overlying igneous rocks at a (juarry about Ij 

 miles from Lilydale, along the railway line to Coldstream, and 

 also at a small quarry about 200 yards north-east of Gave Hill. Tlie 

 igneous rocks therefoi-e occupy a denuded syncline. 



A. — The Volcanic Phase. 

 The volcanii' rocks are represented by five series. Using Hatch's 

 classification, but with reasonable elasticity, these series are as 

 follows, naming them in the order of extrusion : — 



