676 
sometimes distinctly columnar structure, and composed cliiefly of augite, labradorite, 
olivine, and specular iron. Tliey are, however, as a rule, either wholly or partly decom- 
posed. In the former condition they consist of red, yellow, purple, brown, and nearly 
white amygdaloidal clays, containing hard lumps of less decomposed rock showing 
concentric structure ; in the partly decomposed state, the rock exhibits in sections the 
appearance of a conglomerate of such concentric masses in a clay matrix. 
“In every locality throughout the Colony where the Older Volcanic rocks are 
at the surface, the soil immediately resting on or derived from them is of great fertility 
and of exceptional value for agriculture. In the iNeerim, Brandy Creek, and other 
districts in Gippsland, the natural vegetation growing on such soil is of a most 
luxuriant, sub-tropical character, forming a serious impediment to the labours of the 
selectors, who, during late years, have eagerly taken up every available acre of such 
land. 
“ The sources whence the Older Volcanic lava streams issued have not yet been 
distinctly recognised ; no well-marked points of eruption, such as are common in the 
Newer Volcanic districts, have been observed, and it would appear that the original 
volcanic cones have been entirely removed by subsequent denudation, so that it would 
only be in what are now narrow or small pipe-shaped dykes, easily passed over 
unobserved, and pirobably far distant from where the Older Volcanic rocks remain in 
considerable area, that we might look for the vents whence the flows were poured forth. 
The original extent covered by Older Volcanic rocks was once very much greater 
than now. The areas we now see occupied by them are, for the most part, disconnected 
vestiges of what were once long, continuous, and frequently also widespread sheets, 
which have been cut into and through by subsequent denuding agencies, so th.atinmany 
places the Older Volcanic rocks, which, at the time they were poured forth as lavas, 
flowed down and partly filled in the valleys of the period, .are now the cappings of 
ranges, owing to the erosion of still deeper valleys on either side. Enough still remains 
to enable some conjectures to be formed as to the areas once occupied by the Older 
Volcanic rocks. The conclusions arrived at will, however, be better understood after 
the existing Older Volcanic areas have been described, and will, therefore, be included 
in the general sketch history of the Tertiary period, given in a subsequent chapter. 
“ Older Volcanic rock occurs in j)atches, filling hollows in Miocene and other 
older formations in the neighbourhood of the Moorabool River, near Maude, and in one 
place as an intercalated band between marine Miocene beds ; it also constitutes a 
considerable area of the Bellarine district, south of Geelong Harbour. 
“ From between Balkan and Blackwood down to near Bacchus Marsh the Older 
Volcanic rock occurs in a number of localities, especially on the Pentland Hills, where 
some of the undecomposed basalt of this age is highly magnetic. 
“ Prom near Romsey down to Melbourne there are several exposures of this 
rock in beds and banks of creeks that have cut their, way down to it through newer 
overlying formations. Near Flemington is an area consisting of Older Volcanic 
decomposed basalt, which maybe seen in natural section on the bank of theSaltwater River, 
passing under Upper Tertiary ferruginous deposits, capped with basalt of Newer Volcanic 
age. From Hoddle’s Creek, a branch of the Upper Tarra, a series of disconnected 
patches, in some places underlaid by auriferous gravels, are traceable, in the direction 
of Melbourne, as far as Lilydale. Other patches occur between the Tarra and the 
Plenty, near the Kangaroo Ground. This formation occurs again at Berwick and 
Cranbourne, and has been proved by boring operations to exist bene.ath some two 
hundred feet of Upper Tertiary deposits near Frankstou. Cape Schanck and portion 
of the country between Western Port and Port Phillip, also Phillip Island and French 
