94 
Geology and Physical Geography: 
Lar^e and small strips and patches are found between the 
Tanjil and La Trobe Rivers and in various portions of South 
Gippsland. A well-defined lead, covered by 200 feet of older 
basalt, has been proved to trend, from between Walhalla and 
Mount Baw Baw, southward to the level country near Toon- 
gabbie. Very extensive sheets of older basalt probably underlie 
parts of the low Upper Tertiary country of Gippsland, as it may 
be seen sloping from the hilly country, and passing under the 
plains at Haunted Hill, Toougabbie, Seaton, Glenmaggie, and also 
at many places on the south side of the La Trobe Valley. The 
basalt of the Dargo and Bogong High Plains has been classed as 
Older Volcanic, because it immediately overlies sedimentary beds 
containing Miocene flora, and its lithological character also justi- 
fies this classification. Here we find many hundreds of feet in 
thickness of lava, for the most part undecomposed, and often 
highly magnetic, showing, in many places, columnar structure in 
a marked degree. Portions of the plains where the rock is bare 
resemble a pavement of five-sided blocks ; while, on the slopes 
below the escarped edges of the plains, acres in extent are covered 
with pentagonal columns of basalt like logs confusedly heaped 
together. 
Similar outliers of basalt, but of less extent, occur at Connor’s 
Elain and Fullarton’s Spring Hill, both points on the Main Divide 
between the Gippsland and Murray River basins, also to the 
southward at Mount Useful and Mount Lookout, the ranges be- 
tween the Aberfeldy and the Thomson, and between the Thomson 
and the Tyers Rivers. A very small outlier occurs on the east 
slope of Mount Matlock, and other patches are found on the 
Southern Spur, between the sources of the Yarra and those of the 
La Trobe. 
The general evidence obtained from observation of the Older 
Volcanic areas points irresistibly to the conclusion that they 
are remnants of extensive lava-flows which poured down the 
valleys of the Miocene period, partially filling in the basins and 
covering the sedimentary deposits in them, and also spreading in 
wide layers over the beds of the estuaries and inlets. Subsequent 
denudation has cut through aud destroyed the continuity of these 
lava-flows ; new channels have been excavated to lower levels 
than the ancient ones, which they filled, and fresh accumulations 
have in many places overspread them. 
