THE VICTORIAN NATURALIST. 75 



forming a regular line along both sides of the valleys under the 

 basalt, and at some places Older Volcanic rocks. 



These Older Volcanic rocks are divided into two groups in the 

 geological survey maps — Older Volcanic and Lower New Volcanic. 

 The largest area near Melbourne lies along and to the east of the 

 Saltwater River, and reaches down to Melbourne, reappearing 

 beyond the Yarra as Emerald Hill. The greater part of it is 

 coloured and lettered on the maps as Older Volcanic, the south- 

 east end is coloured and lettered as Lower New Volcanic, and 

 the middle is coloured Lower New Volcanic and lettered Older 

 Volcanic. It appears to be overlaid at South Melbourne by the 

 same Tertiaries as on the Saltwater River, and though a small 

 patch of clay coloured as Tertiary is shown underlying one part, it 

 is a deposit containing fossil leaves quite different from that over- 

 lying the other part. As a rule the basalt is much decomposed, 

 often weathering in concentric shells, as at North Melbourne. On 

 the Moonee Ponds Creek, near Essendon, it may be seen in some 

 quarries undecomposed — a dense black basalt. Other small areas 

 of Older Volcanic rocks occur higher up the Saltwater. At the 

 Green Gully, south of Keilor, the relations of the Silurian, Older 

 Volcanic, Tertiary, and New Volcanic may be well seen. 

 Another small patch occurs in the Spring Creek, east of Keilor, 

 and a small patch in the Saltwater above that township. It also 

 appears in a gully south-east of Sunbury Hill, where it is not 

 shown on the maps, and the maps show three more small patches 

 on the Emu Creek, east of Sunbury. In a quarry on the side of 

 the Moonee Ponds Creek, above Broadmeadows, the columnar 

 structure is distinctly seen; and also in the bed of the creek, just 

 above this, there are very small columns, up to two inches diameter, 

 of dense black basalt. Another patch occurs on the same creek 

 at Pascoe Vale. A small area on the Deep Creek, above Bulla, 

 is marked as Lower New Volcanic. 



Several small outliers of basalt occur near Greensborough, on 

 the Plenty River, where they are considered to be Lower New 

 Volcanic as they seem to overlie the Tertiaries (though this is not 

 certain), and have evidently been deeply eroded before the lava 

 streams covered the plains, as these extend into some of the 

 valleys between them. These are remnants, probably, of a once 

 more widespread lava stream. The Sugarloaf Hill north of 

 Heidelberg appears to have been once the bottom of a valley 

 which has been filled by a lava stream. The basalt has since 

 been removed, but the bed of the stream, with the drift in the 

 hollows of the rock, all much hardened, remains as the top of 

 the hill. Other small areas of volcanic rocks occur higher up the 

 Yarra Valley, and at Lilydale there is a well-defined point of 

 eruption. On the other side of the Dandenong Ranges Older 

 Volcanic rocks occur at Harkaway and Berwick. At Wilson's 



