577 
Island, in Western Port Bay, consist of Older Volcanic rocks, in places nndecomposed, 
and consisting of hard, dark, dense basalt. This rock, more or less decomposed, occupies 
a strip extending from Griffith’s Point along the east coast of Western Port Bay, and I 
believe this to be portion of and continuous with the French Island and Phillij) Island 
layers, and to be united, beneath the ISTewer Tertiaries, with the Older Volcanic rocks 
which occupy so extensive a tract in the Neerim and Buln Buln district. 
“ Large and small strips and patches are found between the Tanjil and La Trobe 
Ilivers, and in various portions of South Gippslaud. A well-defined lead, covered by 
two hundred feet of older basalt, has been proved to trend, from between Walhalla and 
Mount Baw Baw, southward to the level country near Toongabbie. Very extensive 
sheets of older basalt probably underlie parts of the low Upper Tertiary country of 
Gippslaud, as it may be seen sloping from the hilly country, and passing under the plains 
at Haunted Hill, Toongabbie, Seaton, Gleumaggie, aird 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 fiora, and its lithological character also justifies 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 Plain and 
Fullarton’s, Spring Hill, both points on the Main Divide between the Gippslaud and 
Murray Kiver basins ; also to the southward at Mount Useful and Mount Lookout, the 
ranges between the Aberfeldy and the Thomson, and between the Thomson and the 
Tyers Elvers. 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 Tarra and 
those of the La Trobe. 
“ The general evidence obtained from observations of the Older Volcanic areas 
points irresistibly to the conclusion that they are remnants of extensivo 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 and destroyed the con- 
tinuity of these lava-flows ; new channels have been excavated to low'er levels than 
the ancient ones, which they filled, and fresh accumulations have in many places over- 
spread them.” 
Under the head of Upper Tertiary, Mr. Murray says,* “ are included all aqueous 
deposits marine or fluviatile, and associated lava-flows, younger than the Older Volcanic 
and older than the Newest Volcanic rocks, which latter are taken as the latest products 
of the Tertiary period ; deposits newer than they being regarded as Post-Tertiary and 
Eecent.” ^ 
“ The basalts, or anamesite and dolerite lavas, familarly known as ‘ bluostone,’ 
occur in sheets or strips of varying breadth overlying a large extent of the central 
western portion of Victoria. The great plains of the Western district, from Geelong to 
Hamilton, and from Colac to Ararat, are nearly wholly of volcanic origin, while rnost of 
the ancient river-beds or leads trending north and south from the Main Divide are 
more or less filled in and covered by lava-flows, which, though often confined between 
elevated Silurian ridges near the hilly country, spread out and unite with the wide sheets 
2n 
Z/oc. cit, p. 113. 
