THE VICTORIAN NATURALIST 123 
with granite, as is often the case with this rock in other parts of 
the world, for though there is granite not far frem it in the north, 
there is none in any other part of its outcrop; it is probably an 
independent igneous rock, but whether it was formerly overlaid 
by more basic lavas cannot now be determined. — It is, at any rate, 
of very ancient date, and las undoubtedly been greatly denuded. 
About Cavendish, and thence on to the Grange Creek, it is 
frequently covered by doleritic basalts, probably pliocene, but in 
the bed of this stream other sets of strata intervene between the 
basalt and the poryhyry. These are the celebrated Muddy Creek 
beds, of miocene or oligocene age, and an actual junction of the 
two formations is plainly visible. Above is the limestone, crowded 
with fossils, while immediately underneath is the porphyritie trap. 
Tt is very much older than the limestone, for not only is this last 
wholly unaltered, but must have been laid down on the trap after 
the removal of all the upper portions of the original volcanic or 
plutonic deposit, of which in all probability, the porphyry is merely 
a remnant; this means an immense amount of denudation, which 
would require extended periods of time for its accomplishment. 
The junction of the trap rock with the Dundas sandstone cannot 
be clearly made out, owing to the quantity of débris at the foot 
of the range, but my observations do not show the least sign of 
any alteration where the two formations meet, and at the foot of 
Mt. Melville, (a peak of the Dundas chain), one is very near the 
actual junction, which is concealed only by such a narrow sandy 
belt, that it is possible to pass from porphyry to sandstone within 
a few yards, so that, if any alteration of the sedimentary rocks 
had been produced, it could scarcely escape notice. 
The precise age of the trap formation is doubtful, the only 
definite conclusion which can be arrived at being that it certainly 
antedates by a long period the tertiary era—further research is, L 
believe, likely to throw considerable light on this interesting question. 
The granite which was mentioned just now as occurring to the 
north of the porphyry, is at some distance from the existing main 
ranges, but near it, there is an existing outcrop of very ancient 
looking, and probably metamorphic strata. The chief locality in 
which these rocks are developed is Frenchman’s Creek, a small 
stream entering the Glenelg a few miles to the east of Balmoral 
after a northerly course of about ten miles. The beds are eminently 
micaceous and gneissose, the mica being always muscovite of a 
glistening white colour. Plates of this as large as the palm of the 
hand are common. and so abundant is the mica generally in the 
formation, that the roads in the neighbourhood sparkle in the sun- 
light, as if strewn with jewels. Pure white quartz, either amorphous 
or crystallized, jasper, agates, and clearly cut crystals of orthoclase 
felspar, as well as specimens of pegmatite, or graphic granite, are 
