15 
stones and mudstones, interstratified with 
layers of slatey-coloured marine mud¬ 
stones. The beds stretch inland for some 
distance, probably underlying the sand¬ 
stones of the hills behind, 'they are also 
continued past Carnarvon for some dis¬ 
tance. The following is a rough estimate 
of the various iayeis at the highest part 
of the cliffs: Barren, yellowish mudstones 
about 20ft., mud-limestones and pure lime¬ 
stones containing all typical fossils of 
this horizon about 10ft„ gieyish barren 
mudstones about 20ft-, limestones about 
10ft., another layer of the greyish mud¬ 
stones 411.. basal mudstones of unknown 
depth. These beds have a slight tilt to the 
northward, and to Dead Island and the 
surrounding shore-line, as well as those 
beds lu the north of Carnal von are all of 
the upper layer, while the end of the 
cliffs near Salety Cove are of the bottom 
layers, all the rest having been worn 
away. The fossils to be found in the 
mudstoms are the usual ones found in this 
system. There are some very good speci¬ 
mens of the producing to be found, and 
there is a marked absence of all larger 
shells, such as the Spiriferu couvoluta, 
the Aviculopectens, and the Kurydesnias. 
The hills at the back of Safety Cove and 
around ihe eaves are composed of yellow 
or red mesozoie sandstones, entirely bar¬ 
ren of fossils. There aie some sandstones 
of the same period at tin* head of Dong 
Bay, in which traces of l’hyllothcca and 
Zeugophyllites were observer!. These evi¬ 
dently meige into the coal measures fur¬ 
ther north. 
The whole of the mountains on the east¬ 
ern side of Port Arthur are formed of 
diabase. They have been formed with 
Cape Pillar and Cape Kaoul as a sill of 
diabase, which lias welled up further to 
the north, filled some fissure in 
the overlying strata, but never 
reached the surface, and forced its 
way between the layers of older strata 
which overlay it for thousands of feet 
above the present summits of the moun¬ 
tains. The flatness of Cape Raoul and 'Tas¬ 
man Island is caused by the moulding of 
the molten diabase by the overlying stra¬ 
ta. The softer rock’ which was above 
them once lias been worn away, but the 
hard, igneous jock has resisted erosion 
and preserved the original flat, sill-like 
structure it assumed in forming, 'The 
columnar structure has been formed at 
the edge of the sill, where the diabase 
stopped either through impediment or 
through coming out of the edge of the 
sandstone. A few patches of this older 
sandstone are to be seen, one near Cape 
D*iliar ami others towards the western 
end of the sill near Wedge Bay. Cape 
Kaoul. Cape Pillar, A rtbur’s Peak, Brown 
Mountain the top of Mount Arthur are 
formed in this way, and are diabase, not 
basalt, as they are sometimes called. 
Now, when this diabase was forced 
through the sandstone stiata at a tem¬ 
perature of about fi.OtlOdeg. Fahr., it pro¬ 
duced remarkable changes on the sand¬ 
stones with which it came in contact, and 
this rnetamorphic rock was by far the 
most interesting formation found. 
The place Where it is best seen is be¬ 
tween the Blowhole and the Caves, where 
the diabase of Brown Mountain meet6 the 
sandstones. In one place the following 
structure can be clearly seen. There is a 
small cliff of sandstones, with conglom¬ 
erates on the top, underneath which can 
be seen the first, effects of the enormous 
heating from below. For a foot or so the 
change is hardly noticeable, and is con¬ 
fined to a hardening of the rock, hut after 
that it changes with increasing rapidity- 
Soon the rook becomes a dull brown, and 
very much harder, and huge specks of 
mica appear. Very soon the rock is so 
hard as to be unaffected by a hammer 
blow, but still preserves its stinlified 
form. Tin through cracks has welled thin 
sheets of diabase as miniature dykes, tell¬ 
ing of the sill not far below. Great masses 
of entirely changed matter are seen mixed 
up with the other rock, which soon loses 
all resemblance to any stratified rock, and 
becomes purely a mass of quartzite. 'The 
whole rock has now been changed in col¬ 
our. Some of it is a pale green, some 
blue, other parts are a shining black; 
some again are like polished marble, and 
all of it. is much harder than the ordinary 
diabase, which conies .iust below it. 
This is continued with great variety all 
along the southern coast between Brown 
Mountain and Cape Raoul, and is a sight 
worth the trip to see. 
The absence of native shell mounds 
along the whole shores of Port Arthur is 
particularly noticeable. The reason is 
probably that there are few shell beds 
near containing the shellfish eaten by the 
natives. There is one large bed at Dong 
Bay, and a few flints were found at other 
places. 
13/2333 
