Vol. XXVII. 

 I9I0 



J Armitage, Country about West Essendon. 87 



these basic lavas and ash beds are up to 4,000 feet in thickness. 

 So that, as regards area covered, as well as thickness of flows, 

 our lava plains, it seems, must take at least fourth place. 



The points of eruption from which the Newer Basalt of West 

 Essendon proceeded cannot be positively indicated, although 

 it is interesting to note that Mr. R. Brough Smyth (8) has stated 

 that " the basalt through which the Saltwater River has cut a 

 channel has undoubtedly proceeded from Mount Aitkin [? Aitken] 

 and the neighbouring peaks." To the north of the granitic 

 rocks in the Broadmeadows district are several volcanic hills, 

 from one of which, according to Mr. T. S. Hart (3), " the lava 

 streams probably extend round the granitic area to the south- 

 west side of the Moonee Ponds Creek." Portion of this lava 

 stream may have provided the Newer Basalt in the vicinity of 

 the Bend. But on the large geological map (9) of Victoria four 

 cones are marked near Diggers Rest. These cones are all within 

 12 miles, in a north-westerly direction, of West Essendon, and 

 may quite credibly represent the points of eruption from which 

 the lava flows that provided the Newer Basalt of the locality 

 under discussion originated. Immediately to the south of 

 Diggers Rest the flows have an elevation of about 650 feet. 

 This would give a grade of about i in 200 from Diggers Rest to 

 West Essendon, and this slope would be quite sufficient to allow 

 of the flowage of basalts so highly fluid as ours were. 



In the vicinity of the Bend the Newer Basalt is a fairlv fresh, 

 coarse, vesicular, bluish rock, which in places has undergone 

 partial decomposition, especially along joint planes. On the 

 cliff-face north of the Bend good exposures, showing spheroidal 

 weathering, may be noticed. In places, nodular concret.ons of 

 hard secondary magnesite are present. In the neighbourhood 

 of the Bend, at least four outliers of Newer Basalt are present. 

 One immediately south of the unsymmetrical terraces previously 

 noticed, and another (Quarry Hill) near the Maribyrnong Bridge, 

 are both marked on the Quarter Sheet ; but a small outlier at 

 the Sand Pits, covered with Newer Basalt, and another larger 

 one a short distance east of the Sand Pits, stretching half a mile 

 from north-west to south-east, and a couple of hundred yards 

 wide, are not shown on the Quarter Sheet. It appears, in con- 

 nection with the latter, that an omission from the Quarter Sheet 

 of the pink colour to represent the Newer Basalt has inadvertently 

 occurred. On Quarry Hill are to be seen some of the best ex- 

 amples of spheroidal weathering of basalt in Victoria, or, in 

 fact, anywhere in the world. The basalt of the two outliers 

 c ose to the Bend is very coarse and vesicular, approximating 

 to the kind forwarded to Melbourne from Malmsbury for 

 monumental work (see Petrographical Note No. 2). This 

 Newer Basalt is probably of Werrikooian age, resting in this 



