CHAPTER XII. 
THE PEEMO-CAEBONIPEEOUS SYSTEM— cowCiwwefZ. 
THE LOWEE BOWEN FOEMATION IN THE TYPE DISTEICT. 
In tlie district from which this series receives its naine, and in which it was first 
mapped, the granite, schists, slates, and other plutonic and metamorphic rocks ot tbe 
Clarke Ean-e are succeeded by a thick accumulation of coarse volcanic agglomerate, 
made up of angular or but little rounded pebbles and boulders On this agglomerat^e 
lie thick beds of conglomerate, the pebbles of which are mainly of quartzite and ye 
porphyry derived from the surrounding metamorphic country, but a few are of porp yr . 
&c.; derived from the immediately underlying bed of volcanic agglomerate To the con 
glomerate succeeds a mass of yellow siliceous sandstone, at least fifty feet in tMckn 
Ld probably much more. Soft stratified rocks of a similar character evidently cr P 
out all over the plain which extends southward from a little mountain about three 
below the head of Pelican Creek to Mount Devlin, under whose steep escarpment they 
dip and disappear. As the breadth of this flat is about a mile, a dip of 10 would g 
a thickness of about eight hundred and eighty feet. , ^ 
The Bowen and Sonoma Eoad, between Bolger’s (ruined) Public-house and Stra 
more Creek, crosses the outcrops of several beds of white and yellow sandstones, dipp'^b 
at a low angle to the south-east. This dip would carry the sandstones beneath 
porphyrites, which are first met with near Strathmore Creek, and which presently 
in terraces in the* Mount Toussaint Eange. From their position, resting on the m 
morphic rocks and underlying the bedded traps, there can be no on ^ . jj 
sandstone beds in question are the equivalents of those which, at the hea o 
Creek, dip under the traps of Mount Devlin. 
INTEEBEDDED POEPHYEITES AND BASALTS. 
The volcanic range of Mount Toussaint and Mount Devlin presents the usual 
features characteristic of slightly inclined trappean rocks. The range appears v 
different according as it is viewed from the “ dip ” or “ rise ” side of the beds. 
one case the long gentle slope of the hill generally coincides with the surface o 
In the other the ascent must be made over a series of alternate terraces and a 
perpendicular cliffs. • . r i v soil- 
Over considerable areas basalts and melaphyres decompose to a rich Diac 
The amygdaloidal porphyrites form a lighter but still very good soil. 
The terraced and scarped hills of the Mount Macedon Eange continue 
outcrop of the bedded trap round the north-western corner of the coa,lfield. - 
It is difficult to find, either in the Mount Macedon or Toussaint Eange, a ‘ 
specimen of the trappean rock which has not obviously undergone consicera 
alteration. A specimen from the south end of Mount Macedon, which appeared lu^^ 
than usually fresh, was sliced and examined microscopically. The ground-mass s o 
a tangled web of very minute interlacing crystals of labradorite, the interstices ^ 
up with specks of magnetic iron. The aiigite crystals were generally represented 
zeolitic pscudomorph (prehnite?), although occasionally a nucleus of augite com 
