So far as could be ascertained, the 
series exposed in the district is as fol¬ 
lows : — 
9. Slag heaps. 
8. Native shell mounds 
7. Raised Beaches. 
6. Diabase. 
5. Fin gal series. 
4. Ida Bay series. 
3. Southport series. 
2. Limestone. 
1. Quartz grits. 
1. These quartz grits were found appar¬ 
ently underlying the limestone at the Ida 
Bay caves. They are composed of quartz 
particles cemented together by a sub¬ 
stance like kaolin. They are not well 
exposed, owing to the vegetation. 
2. At various parts of Tasmania, not¬ 
ably at the Great Bend of the Gordon 
River, we find exposures of limestone. 
This limestone is of lower Ordovician age. 
and has been named the Gordon River 
limestone. It is generally of a dark grey 
colour, regularly bedded, and somewhat 
argillaceous. At Mole Creek. Gunn’s 
Plains, Ida Bay. and elsewhere, caves 
have been worn in it by surface waters. 
Those at Ida Bay were visited by a canri 
party. At this point the rock is of a 
dark grey colour, with signs of metamor- 
phism. It is hard and brittle, with veins 
of ealcite. Though usually of fine tex¬ 
ture, it may become of a fairly "oarse 
crystalline structure when it is lighter 
in colour. No organic remains were ob¬ 
served, but it may be that the microscope 
would reveal them. 
Tire caves themselves form a channel 
for a stream which flows into them. The 
outlet end of the caves is unknown. It 
would appear that a tributary of the 
Lime River, ; n the process of base-level¬ 
ling its valley, exposed these rocks, which 
were sufficiently porous to absorb it. The 
water gradually dissolved the rock away, 
until a small inland drainage basin was 
formed. The track to the caves goes 
down what was seemingly the old eTeek 
valley. 
A somewhat similar example can be 
seen forming at Circular Ponds, near 
Mole Creek, in the same limestone. 
The eaves take the form of a series 
of large hahs, rather hare of stalactites, 
but with one or two massive examples. 
These stalactites are formed by surface 
waters percolating through the rock, and 
dissolving it. When exposed to the air 
in the caves they deposit crystalline eal¬ 
cite. both on the roof and floor. These 
projections continue to grow till they 
meet. The white secondary material con¬ 
trasts strongly with the dark colour of 
the massive rock. One very interesting 
specimen was secured consisting of a 
waterworn fragment of a stalactite. It 
showed the erme-iu-cone structure, as well 
as the undulating surface produced by 
the water in partially re-dissolving it. A 
soft pink inerusting mineral found near 
tile cave month was tested, and proved to 
be montmorillouite (Hydrous aluminium 
silicate). 
3 At Southport, sandstones, mudstones, 
grits, and shales are exposed of Permo- 
curboniferous age. The sandstones are 
light-col on red, and show spangles of mica. 
Tim sh-.les are of a grey colour. These 
beds resell 1 hi* the Knoeklofty series, 
which come between these and the Ida 
Bay series in point of age. 
1. Th Ida Bay series were not inspect¬ 
ed bv camp members. They consist of 
coal-bearing shale and sandstone. 
5. Immediately above the Tda Bay 
series are the beds belonging to the 
Recherche basin of the Fingal series. 
Tltese are known as the upper coal 
measures. A party visited the Catamaran 
colliery, and by tile courtesy of the maria 
ger were shown round underground. The 
collierv is situated about a mile from the 
bay. The 'beds consist of sandstones and 
shales, with coal seams dipping north¬ 
west at about Ifldcg. Two seams are 
known, an upper one 9ft. thick, and a 
lower one 6ft. thick. Only 5ft. of the 
upper s, am is at present being worked. 
Bands of "lay occur in the coal, hut are 
capable of easy separation. The coal is 
bright, and hard, and assays 66 69 per 
cent, fixed carbon, 25 -27 per cent, voln 
tile matter, and under 4 per rent. ash. It 
is c laimed f ir this coal that il is the best 
in Tasmania the assay of the coal from 
the Cornwall and Mount Nicholas col¬ 
lieries being 57—61 per cent, fixed car¬ 
bon. 18—27 per cent, volatile matter, and 
8—15 per cent. ash. 
An interesting feature observed by the 
party was the local crushing in of the 
floor by reason of the superimposed 
weight. 
6 Some time after the deposition of the 
upper roal measures the island was sub- 
iected to a great intrusion of diabase. 
This rock is taken to he of upper meso- 
zoic age. It occurs in quantity in the 
south-east as the caps of hills. It forms 
the great central tableland, and is found 
m ‘he north at Mersey Bluff, Port SorelJ 
Point, and elsewhere. It is of medium 
grain and dark colour. No flow structure 
is risible. It is composed essentially of 
pyroxene and a basic felspar (Lnbrador- 
ite). While il is of basic composition, its 
silna contents being 52—57 per cent., it is 
typically free from olivine, which is a 
useful guide iti field work us distinguish¬ 
ing this rock from tertiary basalt. 
The rock has solidified in the form of 
dykes, laccoliths, and sills in the midst 
