548 
The former variety, owing to its coarse grain, would be called a nevadite, whilst the 
latter w'ould be best described by the term sanidine trachyte : both, however, are 
merely varieties of one and the same rock. The rock is intrusive through the volcanic 
series, and sends out here and there dykes of no great thickness and of a somewhat 
similar character to the rock forming the main mass ; hardly any apparent alteration 
has taken place in the rocks through which the mass has burst. 
“ On the north side of the Bowen lload, near its crossing of Murray Creek, a 
low hill opposite to Mount Os.sa, known as Hammel’s Hill, is found to consist at its 
base of a coarse volcanic a.sh or agglomerate, made up of trachytic materials, and above 
which a rock not unlike that forming the ‘ Sugarloaf ’ at Seaforth lies. This, seen in a 
bare scaur visible from the road, shows fluxion structure to the unaided eye, and in 
places fragments of the ash appear to have been caught up in the lava when in a molten 
condition, and dragged along with the viscid mass. The whole rock subsequently has 
been pierced by a fine-grained granite, and the agglomerate much altered, rendering it 
often, except ou its weathered face, a matter of some difficulty to distinguish it from 
some forms of the lava beds. 
“The Scrubby Hill, Mount Ossa, behind the house in Selection 1585 is, judging 
from the screes on its face, made up of a rock almost identical in physical characters 
with that forming McKenzie Crags. 
“As a whole, those rocks bear a remarkable resemblance to those of Mount 
Britten. Some of the rocks there are very fine volcanic ashes, whilst others are true 
lavas. The ‘ Stalk,’ a conspicuous pinnacle of rock ou the divide between the waters of 
the Bitzroy and the Burdekin, ‘ possibly one of the vents from which the volcanic 
material of the bluffs in the neighbourhood of Mount Britten was ejected,’ * is almost 
identical with the trachytes of Mounts Barren and Jukes. 
“The Mount Britten rocks have been conjectured by Mr. R. L. Jack to belong 
to the Desert Sandstone series, ‘whose base is often made up of similar volcanic dust.” 
The Mount Funnel conglomerate, merely an outlier of this series, rests upon the 
altered grits and conglomerates of Carbonifero-Bermian [Permo-Carboniferous] age, 
and is distant not less than forty-five miles from any rock its equivalent in age, 
and forms an im]ires8ive evidence of the power of denudation. 
“ The sedimentary rocks at Seaforth overlie a mass of porphyrite regarded as 
being newer than those of the ‘ Volcanic Series,’ and which is well seen in a little bay 
at Cape Aberdeen, a mile to the south of Cape Hillsborough. Here the porphyi’ite is 
well seen in the cliffs at low water. It weathers into rude spheroidal masses, and where 
a freshly-broken surface is examined it is often found to be amygdaloidal, the 
greater part of the cavities being filled with carbonate of lime, though in some leucite 
can be detected. 
“ Overlying the porphyrite, a thickness of grits and fine conglomerate, and, in 
some places, nearly pure white and calcareous sandstones, occur. At one place directly 
overlying the porphyrite a bod of ‘ mudstone’ is seen. Some little distance north this 
covers a great banle of conglomerate, which in turn is succeeded by the main mass of 
grits, &c. 
“The Cape Table-land is made up of about four hundred and fifty feet of 
sedimentary materials, dipping at an angle of about 10° to W.8.W. The base con- 
sists of a thick mass of cavernous and ferruginous sandstones, succeeded by whitish 
conglomerates and breccias with thin beds of banded siliceous matter. AVhether these 
* Report by R.L. J. on the Geological Features of the Mackay District, j). 7. Brisbane : by 
Authority ; 1887. 
