124 
The Australasian Scientific Magazine. [Nov. i, 1885. 
agree with you, my friend, the rocks are entirely dissimilar, but still we must 
not judge too rashly. We will now stroll round the edge of the limestones 
on the fall towards the Tambo river. Stay ; here is an alteration in the 
rocks, the conglomerates are becoming porphyritic, i.e., they are seen to 
contain small translucent quartz crystals associated with the base or mag- 
ma which binds together the conglomerate mass. Let us carefully ex- 
amine that bluffy outcrop of red or purple-coloured rock to the east of us. 
It is certainly a prophyry without doubt, and evidently a plutonic mass 
quite distinct in mineral character and mode of occurrence from 
the sedimentary rocks we are examining. The mass is pointed but 
is certainly unstratified. We have here a short, sharp, clear and definite 
passage from the comparatively unaltered conglomerates to the densely 
crystalline quartz porphyry. And there is no doubt that the latter is an 
intrusive rock — i.e., a once molten mass injected into the earth’s crust 
from probably deep-seated sources, melting and absorbing the other rocks, 
in its upward passage, and consequently younger in point of age than the 
sedimentary rocks it has replaced as well as displaced. 
Our talented friend, Mr. Howitt, F.G.S., has informed us* that the great 
mass of “ Snowy River Poryphyries” to the east of us “ are older than the 
middle Devonian Buchan beds which rest upon them and which may 
represent the Lower Devonian formations, hitherto unrecognised in Vic- 
toria, so that our intrusive porphyry is hardly identifiable with the Snowy 
River trap rocks. Let us ramble down this small gorge to lower levels — 
to where the limestone beds are seen to present a somewhat cliffy aspect. 
There we have another proof of the intrusive character of our quartz por- 
phyry in the induration and alteration of the limestone beds at contact. 
See how they have been converted into whitish crystalline and sub- 
crystalline marbles for a distance of 10 or 1 2 feet from the contact, f Now 
it is evident that our porphyritic rocks are dissimilar in character to those 
at Buchan, and that they have an important bearing upon the past history 
of this part of the earth’s crust. This gully we are now ascending will 
bring us to a spur dividing theBindi Creek from Old Paddock Creek, and 
near the crest of the ridge we will examine more closely the sequence of 
the limestones, shales and conglomerates. That was a stiff climb, and 
you say you feel a slight sensation of nausea. It will soon pass away, and 
you will feel better and breathe more freely in a short time. While we 
are resting, do you know that it is stated that this mountain sickness is net 
unusual with tourists at Alpine heights, and has been ascribed to diminished 
pressure of the atmosphere, and an insufficient supply of oxygen to remove 
effete matters from the system J I have felt it when making rapid ascents 
of the higher regions in the Australian Alps, when anxious to get over as 
much ground as possible in a limited time. Here is a small cliff section 
laid bare by the denuding action of the rains, frosts and snows. The 
lower calcareous bands are brownish earthy limestones resting conformably 
on soft yellowish shales, while the latter rest also conformably on the 
brownish grey and purple conglomerates. Now to what conclusion would 
* " Diabase Rocks of tlie Buchan Dist.” Trans. Roy. Soc. Viet., 1881. A. \V. 
Howitt, T’.U.S. 
t“ Notes on the Bindi Marble Reds.” Prog. Rep. Geo. S : ur, Viet. Vol. vii., p, 
107. J. Stirling. 
t Dr. Tripe, on Relations of Meteorological Phenomena to Health.” Q. T.. Mel. 
Soc. Vol. it)., p. ”77. 
