.IV Mfc

“The Tasmanian Naturalist”

--

New Series, Vol. I., No. 1.

It is with the greatest pleasure that the Tasmanian Field Naturalists’
Club presents the first number of the new series of its Journal. “The Tas¬
manian Naturalist*’ commenced publication soon after the inauguration of
the Club in 1904, and ran until 1911, when it gradually became overwhelmed
with financial problems. Its objects during those issues were to*provide a
forum for the promulgation of the work of the Club, and to assist in the ad¬
vancement of the knowledge of Tasmanian natural science.

Since 1911 costs have increased enormously, and the resources of the
Club, in common with those of learned societies throughout the world, have
barely held their own. However, with the assistance of “News Ltd.,” the
Club is making a second endeavour to publish its Journal, and the Committee
look to members for the degree of practical co-operation, and the Club looks
to the public of the State for the necessary sympathetic interest to enable
this Journal to continue its existence.

We, the present and future contributors to “The Tasmanian Naturalist,”
are firmly of the opinion that a knowledge and appreciation of natural laws
and the principles governing the forces that control the world around us are
essential to human happiness and economic progress, and even to the very
existence of life itself.

We are convinced that the welfare and progress of the community are
. based on deeper principles than economic laws. We know that man cannot
fight his environment. He may occasionally guide nature, but in general he
must fit himself into the general scheme. To do this he must know nature-
know what we are, and know the forces that govern life on the globe. There¬
fore these pages will find no room for superstition and that great enemy of
progress in thought, “I believe.” Here there will be no place for any story
but the truth, and the truth tested by all the means at our disposal.

Further, this journal will be devoted to the story which concerns us—-to
the story of our homeland, Tasmania. We leave the daffodil and the nightin¬
gale to those who know them. It will be the vvell-known odour of our home¬
land bush and the free, rustling gusts of our wild mountain tops that will fill
these pages.

Our aim in this Journal is to present our ideas, observation and deduc¬
tions concerning the flowers and trees, the sea shore and inland landscape,
the animals, birds and insects of Tasmania. We conscientiously, think that a
, knowledge of the world around us gives a far truer ideal in education than
the dead past of forgotten peoples, tlie wonders of other lands, whose exist¬
ence scarcely concerns us, and the stories that are called literature, but which
still are mere fiction, and we are of the opinion that to progress we must turn
our back on the past, and look to the wonderful vista of natural science tha^s
daily being unfolded before our eyes.

We know that many slips will be made from time to time, but this is but
a small penalty for progress, and progress is the keynote of our study. We
know that this publication will reach only a few of onr citizens, but it .Will do
good if it brings light to a few who do not consider their education yef com¬
pleted, and indicates that there do exist in the great world out of doors foS^s
and facts whose presence is never dreamed of b_v the Saturday afternoon foot¬
ball crowd. And we shall be more than happy if the revelation of the exist¬
ence of these mysteries will lead an occasional enquiring mind to ask himself.
“Why?” and to go and find the answer, and add his name to the tiny list of
those who are endeavouring to place Tasmania on the scroll of peoples who
have contributed some assistance towards the advancement of civilisation.

THE TASMANIAN FIELD NATURALISTS’ CLUB.

Tasmanian Field Naturalists’ Club

1924-1925

OFFICE-BEARERS

Chairman:

DR. W. L. CROWTHER. D.S.O., M.B.

Vice-Chairman:

MR. J. REYNOLDS.

Hon. Secretary:

MR. CLIVE LORD.

Tasmanian Museum.

Hon. Assistant Secretary:

MR. J. C. BREADEN,

Waverley Avenue, New Town.

Committee:

MESSRS. L. RODWAY, C.M.G.; A. N. LEWIS, M.C., LL.B.; M. S. R.
Sharland; A. R. REID; G. B. DAVIES.

Hon. Auditor:

MR. C.'W. ROBERTS.

©fje (Easmnman J^aturaltSt

THE JOURNAL OF THE

Tasmanian Field Naturalists' Club

New Series—Vol. I. OCTOBER, 1924. No. 1.

Fish Fauna of Tasmania

The fish of Tasmania are of interest.
"Winp to the Southern position of our
island, which, in some ways, form a
connecting 1 link between the fauna of
Australia and the subantarctic regions.

In the grouping of the greater di¬
visions of the zoological kingdom the’
fishes (Pisces) form the lowest <dass of
the vertebrates, or backbone animals,
and the lnncelets, which are * often
grouped with the fishes* realy form a
connecting link between the inverts-
hrates and the vertebrates.

Lancelets are small semi-transparent
marine animals found burowing in the
sand. They are from 30 to 40 mm. long
and an with.ml brain, cranium, or
jaws.

A considerable advancement in de¬
velopment is shown by the lampreys,
which are cold-blooded vertebrates with¬
out limbs or skulls. The mouth lacks
jaws., and is in the form of a suctorial
disc. Both the Short-headed and the
Pouched lamprey occur in Tasmania.

Shark Species.

Above the lampreys are the sharks
(Selachii) which are distinguished by
the absence of a bony skeleton, the ab¬
sence of the true fish-like scales, and the
presence of the five to seven gill open
ings, which are on the sides. The mem
hers of this order constitute the larger
predaceons fishes, representatives of
which are founu all over the world The
seven-giUed and the one-finned shark
Port Jackson, wobbegong or carpet
shark, collared cat shark, varied cat
shark, spotted cat shark, swell shark,
thresher shark, grey nurse and the blue
pointer have all been recorded from Tas¬
mania.

I ho small sharks known as *'dog
fish" are represented by such species as
the piked dog fish, spotted dog fish, and

prickly dog fish, whilst two varieties of
the peculiar saw sharks are met with.

The angel shark, with its fiat depress¬
ed body, approaches, In some respects,
the members of the next order, the rays.

Bays (Batoidea) are immediately dis¬
tinguished from sharks by the disc-like
form of the body and the fact that the
gilj openings are on the under surface,
Tasmanian representatives of this order
include such species as the fiddler, Tas¬
manian numb fish, rough-backed skate,
thorn-backed skate, smooth stingaree,
handed stingaree. green-backed stinga¬
ree. sandy-backed stingaree and the
eagle (nr whiptail) ray.

Ghost sharks (Holocephali) are dis¬
tinguished. apart from their peculiar
iorm, owing to the fact that they have
but one external gill opening. They also
possess an erectile dorsal spine. The
peculiar elephant fish is the more common
Tasmanian representative of the order,
but the ghost shark also appears here.

Fishes proper are distinguished from
the sharks, rays, etc., by the presence of
the operculum, or gill cover. The first
division contains the trout-like fishes such
as herrings, etc. Certain species of cos¬
mopolitan range are grouped within this
order, and in the future certain of these
should prove of great economic import¬
ance, as they are practically identical
with European forms which arc regarded
as of great value.

Australian Anchovy.

The Australian anchovy is practically
identical with the European form. The
pelagic sprats, both tlie blue and the
robust, occasionally appear in shoals off
the coast, whilst the Australian pilchard
is very similar to the European pilchard
or sardine. The beaked salmon (sand
eel of New Zealand) is occasionally taken
in Tasmanian waters It frequents the
muddy bottom of certain rivers, grows

( 1 )

THE TASMANIAN NATURALIST

to about a foot or eighteen inches in
length, with cylindrical body, and a
pointed overhanging snout with two
barbels.

The jollytail is a well-known form com¬
mon in estuaries and creeks. The
Mersey jolly-tail is a variety.
Jolly-tails are really minnows,
and represent the Salmonidue in the in¬
digenous fish fauna of Tasmania.

In the lakes and the higher reaches
of the fresh water streams the jolly-
tails give place to the spotted mountain
trout. The lake trout, which occurs in
the Great Lake and the other lakes and
streams at high altitude, is a variety
of the spotted trout.

The order under review includes sal¬
mon, trout, etc., and many forms which
have been introduced from other coun¬
tries. As examples of species which
have been introduced into Tasmanian
waters the following may be mention¬
ed:— Salmon, brown trout, rainbow
trout. Loch Levon trout, salmon trout,
American brook trout, sebago salmon,
sock-eyed salmon, quinnat salmon.

The Smelt.

To return to the indigenous fauna of
this order the Argentine or Siel smelt is
occasionally obtained during trawling
operations off the coast, whilst the Aus¬
tralian grayling or “cucumber herring”
is sometimes taken on the north-east
coast. It was very plentiful at one
time, but its numbers have greatly di¬
minished. The small species known as
the Derwent smelt (40-60 mm.) is found
In the Derwent, whilst the larger Tas¬
manian smelt (60-70 mm.) or “white-
bait” also occurs.

Following the herrings are representa-
times of the order Iniomi. Two species
belonging to this order have been re¬
corded from Tasmania, the cucumber
fish, which was secured by trawling off
the East Coast, and the lancet fish. The
latter is rare. It is a very formidable
species, growing up to six feet in length
and possessing “a large barracouta-like
mouthful of teeth.” The dorsal fin is
considerably elevated and extended.

The following group includes such fish
as the European carp, gold fish, and
English tench, which are not native to
our island, but have been introduced at
various times.

The next group to be considered arc
the eels, the first order of which em¬
braces the pigmy eels, which are small
eel-like creatures found under stones, etc.,
along the shore. They have but one gill
opening which is on the ventral sur¬
face.

True Eels.

The true eels (Apodes) have two gill
openings on the sides. Some species are
found in inland waters, but descend to
the sea to breed, the young returning to
the lakes and rivers. The short-finned
and the closely allied long-finned eel may
be mentioned in this regard. The larger
conger eels are found around the coasts,
whilst the little conger, -which is often
referred to as the silver eel in Tasmania,
frequents certain rivers and estuaries.

The minute Tasmanian worm eel has
been recorded from the East coast.

Following the eels is the order Solenich-
thyes , 4 to which belong the sea horses,
pipe fish, bellows fish, and other species
of a like nature. Thu sea horses are
typical of the present group. They pos¬
sess a peculiar elongated tube-like snout.
The body is often encased in a series
of bony rings. Several kinds of sea horses
are met with, including the leafy sea
horse. A point of interest is that the
male has a pouch and carries the eggs
about after they have been deposited by
the female.

Bellows Fish.

Three species of Bellows fish have
been recorded from Tasmania, all of
which possess an elongated snout and
two dorsal fins, the anterior one being
compressed Into a spine.

The Pipe fishes, which are closely re¬
lated to the sea horses, are common in
Tasmanian waters half a dozen o r
more species having been described. Be¬
longing to this order is the Opah, a
giant sea fish. One specimen has been
recorded from Tasmania, and is now i n
the Tasmanian Museum.

Although Included in a separate order
the Dragon fishes approach the previ¬
ous group In that their bodies are en¬
cased In bony rings. The snout is also
produced, but it lacks the tube-like pr 0 .
cess of the Pipe fishes. The Dragon fish
is a small species 50 to 90 mm. lon^
found in many places such as among
'-he shallows of the Derwent estuary, it
is occasionally taken in scallop dredges

Following'the Dragon Fish and the
Garfish, are the Hock Cods, Whipl
tails, etc (Anacanthini). The represen¬
tatives of this latter group have no
true spines in the vertebral fins. Hock
Cod are extremely common in nmnv
localities, but fishermen, as a rule, dn
not distinguish between the three sn P .
cies met with. It must also be remem
bored that in New South Wales the fish
there called the Rock Cod in the ver
naoular, is a species of Gurnet.

Three species of Whiptails are alsn
found in Tasmanian waters, but

THE TASMANIAN NATURALIST

they constitute part of a family of deep¬
water fishes, they are seldom taken ex¬
cept by trawlers.

The next order embraces the Dories
and other similar fishes, whilst follow¬
ing these are the Ribbon Fish. Both
the great Oar Fish and the Ribbon
Fish have been recorded from Tas¬
mania They art- peculiar-looking fish¬
es. eel-like in form, but the body is
greatly compressed.

Flat Fish.

Flounders and similar flat fish con¬
stitute the order Heterosomata. The
flat fishes are those in which the body
is laterally compressed to such an extent
that both eyes appear on one side. The
very young fry are not very different
from the young of other fishes, but they
soon begin to lie on one side and the
lower eye in the proces of growth tra¬
vels over the snout to the upper side.
Three main divisions of the group are
easily separated; one of which has the
eyes on the left side, the second of
which has the eyes on the right side,
whilst the third division has the opercle
and pre-opercle practically fused into
one member, there being no clevage
This third division embraces the soles
The latter are rare in Tasmanian wat¬
ers. being only occasionally taken in
Bass Straits. The so-called “Sole” of
the Tasmanian fishermen is the long
snouted Flounder.

Fifty-Five Families.

Following the fiat fishes comes tin*
order Percomorphi. This division em¬
braces a very large percentage of the
total fish fauna of the island. Many
varied forms arc met with, but they all
agree in having a number of spines in
the anterior’ dorsal fin, whilst the ver.
trals never have more than one spine
and five rays. Forty-two families lie-
longing to this order occur in Tasmania,
and for the purpose of the present out¬
line it may be as well to defer consid¬
eration of these until dealing with each
group in detail.

The following order (Discoeephali) ha-*
but two representatives in Tasmania.
The slender and the short sucker fish.
These have elongate bodies with very
tough skin. The top of the head h s a
sucking disc which enables them to
cling to larger fishes and even ships.

The mailed-cheek fishes (Seleroparei)
are well represented in Tasmania. In¬
cluded in this order are the various gur¬
nets. the richly-colored velvet fish, the
kuma, and other gurnards, as well as
the several species of fiathead.

Cling fishes (Xneoptari) form a small
group of fishes that attract but little
notice owing to their small size. The/
cling to stones, etc., by means of an ad¬
hesive disc which is situated between
the ventral fins.

Following these come the angler fish,
or frog fish, which are distinguished by
having a movable projection at the ex¬
tremity of the snout. They are usually
met with among weeds.

Leather jackets and other such fish
constitute the order Pletognatti, the
distinguishing feature of which is the
absence of the ventral fin. Included in
the order also are the trunk fish and
the peculiar sun fish, which pelagic form
is occasionally met with off the Tasma¬
nian coast.

General Character of Fishes.

The term fish is one that is apt to be
applied in a free and easy manner to
many species of animals far removed
from the true type. For instance, nu¬
merous representatives of the Mollusca
and Crustacea are often referred to as
shell fish. True fishes, however, are
aquatic, vertebrated or backboned ani¬
mals. They are cold-blooded and breathe
by means of gills. Their external limbs
are reduced to a series of fins, the ar¬
rangement and number of which plays
a large part in their classification
Whales are occasionally spoken of as
though they were a species of fish, but
whales are truts mammals, and except
for aquatic habits have nothing in com¬
mon with fish.

The body of a fish is usually describ¬
ed in detail in three main divisions, name¬
ly, the head, the trunk, and the fins. On
each side of the head there is a movable
flap called the opercle. although in some
fishes such as the eels, it is covered with
skin, whilst with the sharks, rays, etc.,
it is absent. The gills, which are situat¬
ed under the opercle, constitute a won¬
derful arrangement by means of which
the blood is aerated as it circulates,
owing to the constant passage of water
through the gills.

The trunks of fishes are usually covered
with scales. The sharks exhibit a lower
form of this development, the scales be¬
ing of such a small enamel nature as to
practically constitute a hard skin. Other
fishes have scales with smooth rounded
edges, technically known as cycloid
scales, whilst the higher fishes *how a
Nti'l further development by having the
edges cf the /rales toothed or covered
with small )>oints. The fins of fishes are
of great importance in the scheme of

( 3 )

THE TASMANIAN NATURALIST

classification, most fishes having the fol¬
lowing:—

A fin on the back known as the dor¬
sal fin.

A tail or caudal fin.

An anal fin situated on the under
side just in advance of the tail.

A pectoral fin situated on the side
just behind the opercle.

The ventral fin situated on the lower
side of the body usually a little below
the pectoral fin; but in some of the
lower fish the ventral fin is far behind
the pectorals.

The ventorals and pectorals are both
paired; that is to say, there is a fin of
similar shape on each side of the body,
while in some fishes the dorsal fin is
divided into several divisions or there
may be one or more dorsals.

Again, portions of the fins may diffei
in character, some being separated by
means of spines, and some by means of
more flexible 'supports.

Sharks and Rays.

The sharks and rays, although differ¬
ing considerably in general appearance,
are grouped together in the same order
for the reason that they are seen to be
closely related when examined in de¬
tail. Moreover, there .is a connecting
link between the sharks and the rays
in the peculiar-shaped Angel Shark
which is occasionally taken in Tas¬
manian waters. The whole fish class
(Pisces) is easily separated into two dl-
wisdom, of which the . sharks form the
first and the bony fishes the second.

The characteristics of the first divi¬
sion are the absence of the bony skele¬

ton, its place being taken by cartilege.
the absence of the opercle and similar
bones of the head, and the presence of
paired clasperg in the male.

A connecting link between the sharks
and the bony fishes is provided by the
sub-class Holocephali, under which are
grouped the peculiar Elephant Sharks
The Elephant Shark is a common spe¬
cies in Southern Tasmanian waters, and
apart from its peculiar shape is easily
recognised owing to the fact that it has
the gills coneeealed under a cartiligenous
opercle. Most. Tasmanian sharks ha ve
five separate external gill openings, but
there are two species, the seven-gilled
and the one-finned shark, in which the
number is increased to seven. In addi¬
tion to the ordinary gill openings there
is a smaller opening near the eye, gen¬
erally referred to as the spiracle, which
enables the fish to breathe when its
mouth is burrowed in the sand or oth¬
erwise occupied.

Sharks and rays are in the main pre¬
daceous fishes, and as a consequence
they are well adapted for their method
of life. The teeth vary greatly in num¬
ber and shape, and arc placed in rows,
which are continually growing out¬
wards. so that a lost set of teeth i s
quickly replaced. The great majority
of these fishes arc viva parous, that is.
the young are brought forth alive, but
certain of them are oviparous, among
the latter being the Bull-headed or Port
Jackson sharks, and some of the small
er Dog Fishes. The Rays, which are in
the ordinary sense fairly slow moving
creatures, frequenting the sea bottom,
are oviparous.

Clive Lord.

Outlines of Tasmanian Geology

Part I.—Gcoloyicai Processes.

Chapter I.—introductory. The Science of Geology.

Section I.—Geology.

Geology is the great foundation-stone
of science. It teaches us the history
of our planet, the origins of sea and
land, the reasons for our many kinds
of rocks, how our present scenery was
arranged, and the development of life
in its multitudinous forms. It is the
study of the great out-of-doors, with
the whole surface and interior of the
world for its classroom. We insignifi¬
cant mortals crawl on the face of the
earth! and wrangle about prices and

honors. We undertake gieat ventures
optimistically, or spend our lives coax¬
ing a few pence from the unwilling soil,
and we prosper or fail. Mother earth
— this globe we inhabit—gives us our
success, or rebuffs us, and the great
controlling factor in the lives of eacn
and every one of us is

Environment.

High above our politics, our trade,
our wars, our petty lives rises this dom¬
inating influence. Geology is the science
of our environment.

( 4 )

THE TASMANIAN NATURALIST

This is a new science, and still in the
infancy; but little by little its facts are
being uncovered, although today even
the framework is scarcely apparent
Also it is a universal science—its truths
must apply equally well all over the
world, and for all times, cr they are
fallacies. Hence, we in Tasmania have
our responsibilities. We cannot hope to
produce master minds who direct the
whole trend of the worlds ideas, nor
can we compete with the great centres
of scientific research, equipped with
vast paraphernalia In enquiring into the
more abstruse natural laws; but we ^a*i
describe to the world our own natural
surroundings, and the world wants to
know them.

At the recent Pan Pacific Science Con¬
gress held in Melbourne and Sydney
leading American geologists were most
persistent in their request: “Don’t worry
about theories and laboratory tests, we
can do those better than you, but give
us descriptions of your country—we
want that.’' Now, much has been done
in this respect ,but a vast amount

Still Awaits Workers.

We have iv. Tasmania some of the
least known tracts of the Common¬
wealth, but the few interested in this
study cannot cope with the work. These
notes, it is hoped, will serve* to give our
many enthusiastic trippers and bush
lovers sufficient insight into the ground¬
work of the science of geology that they
will realise what they see, as they en¬
joy a holiday in the bush, and that pee¬
ing, they will remember and record. Un¬
fortunately, we have no text book of
Tasmanian geology, and naturally ex¬
amples from Europe and Ameriea do
not appeal to those not specially in¬
terested.

It is hoped that these brief notes will
serve to fill this gap until time and
money are available for something more
worthy, and that sufficient will be hero
found to enable readers to realise the
hidden meaning in the scenery they
gaze on. and the great foundation plan
on which our superstructure of civilisa¬
tion is built. And perhaps some few
may be added to the tiny band who arc
endeavoring to show that Tasmania is
not backward in contributing her quota
to the f, um of knowledge, and always re¬
membering Professor David’s fine sen¬
tence — “No work, conscientiously done,
hr investigation carefully carried out, will
fail to affect the economic life of the
community.’*

Section 2.—Subdivisions of Geology.

Geology as a basal science merges
at many points into other branches of
knowledge. It draws much of its data
from astronomy, chemistry and physics,
and it supplies the historical background
for botany, zoology and ethnology. Again
its many branches have each become
the subject of special studies, but ge¬
ology uses all these sciences, as it re¬
quires their assistance, and unites them
to explain the history of the world and
the landscape and its inhabitants.

In the first place it draws on astron¬
omy to assist in explaining the origin
oi the world as a planet, and the first
branch of our subject is

Astronomical or Cosmic Geology.

But most geologists leave this branch
to the astronomer, as too vague for prac¬
tical study. Next comes geotectonic
geology. This deals with the archi¬
tecture of the earth’s outer shell as a
shell. It is world-wide in its scope,
and although most important, requires
very extended travel for study. This
branch merges into the new science •'(
geophysics—the study of the principles
ot physics that govern the behavior of
the surface of the world—on the one
hand, and into dynamic geology on the
other hand.

It is with dynamic geology that our
subject really starts. This branch,
starting with the shell of the earth as
we find it, examines and explains all the
processes by which it is built up 01
broken down, or in any way affected.
Having mastered the processes, their ori¬
gin and effects, we can proceed to the
next branch, physiographic geology,
which explains by what process a given
landscape has been moulded into its pre¬
sent form. It tells us the history of the
countryside.

Now, during the earth processes that
have built up the surface of the world
as we see it today, rocks have been
formed and remains of plants and ani¬
mals have been enclosed and preserved.
The branch of geology which examines
th( nature, composition, and formation
of the rocks as individual masses of
matter, is called petrology. It has a
large subdivision mineralogy, which ex¬
amines the structure, texture, composi¬
tion, and form of the constituent parts
of those rocks. The branch which ex¬
amines the traces of life Is called palae¬
ontology. Both of these branches have
become separate studies, but both are

( 5 )

THE TASMANIAN NATURALIST

essential to the complete understanding
of the history of our landscape. Fin¬
ally ,when all the information these
blanches can give us is collected, we
can give a

Fairly Complete History.

of our chosen piece of landscape. When
much of the surface of the world is so
investigated we can give a history the
general outlines of which hold good
everywhere. This branch is known as
systematic or historical geology.

Finally when these principles are un¬
derstood, and are worked out for a
given district, they can be applied to
assist the miner, farmer, and engineer,
and to guide the geographer, economist
and politician. This part of our science
i.3 often termed economic geology, and
its various branches are given such names
as mining geology, agricultural geo¬
logy, etc. In reality geology has no
such subdivisions. These are the prac¬
tical application of the principles of the
science to a given set of facts.

A. N. Lewis.

Chapter II.

The Globe

(Astronomic and Geotectonic Geology.)

(Section 3.)

The Early History of the Globe.

This chapter is a summary outline
added solely to make our story complete.
The subject is not of less relative im- •
portance than other divisions, but to
study it, the whole world must be taken
as a single unit, and Tasmania can add
little to what is uow found in standard
text books, to which readers arc referred
for a fuller statement.

The early nistory of our solar system
and of our world as a planet is shrouded
in mystery. Much light has been thrown
onthe dawn of our history by the lessons!)
of astronomy which can show how other
celestial bodies may be born, grow old,
and be extinguished, and physics gives
us a guide as to the possibility or other¬
wise of many processes.

Three great schools of thought have
held sway during the last sixty years.
These, in order, have been: — (1) The
Nebular Hypothesis, first put forward by
Laplace. This theory assumed, first a
great gaseous nebula sufficiently exten¬
sive to cover the whole of our solar
system and containing all the elements
of the minerals we now know, but so
intensely hot that they existed only
in the form of gases. Nebulas
certainly exist in t he heavens,
hut it is doubtful whether
they consist of gaseous material. Our
parent nebu’.a was supposed by cooling
and by the action of “gravity*' to have
gradually commenced to revolve. As the

process continued, the materials sepa¬
rated into rings and later into separate
todies revolving round a nucleus. These
bodies, by the same process, became more
and more compact. Our globe, as a typi¬
cal one, in time cooled sufficiently to
form a hard crust covered with water,
arul with a .still molten interior. As the
globe cooled, still more, it shrank and
thus buckled the crust into continents
and mountains. This theory necessitated
the idea of a cooling and shrinking globe.
Today we know that almost every de¬
tail of this hypothesis is unsound.

(2) The Metcoritic Hypothesis.—This
was favored oy Lockyer and Darwin. It
explained the origin of the solar system
to the collection of meteorites or .simi¬
lar small bodies moving freely through
space, and continually augmented by n
rain of similar particles. The particles
were at first cold, but by continual fric¬
tion the temperature rose to a great
heat. Later the world started to cool
down. This theory also is known now
to be untenable,

(3) The Planetesimal Hypothesis, ad¬
vanced at the beginning of this century
by Chamberlain and Salisbury, two great
American geologists, and both still living.
This theory postulates the origin of the
solar system, from a nebula consisting
not of gases, but of small solid bodies
revolving in slightly different courses
round a central core. The nebular th»ew
out great spiral arms and the particles
in these, colliding from time to time
gradually formed knots which in the

( 6 )

THE TASMANIAN NATURALIST

course of time collected the material
of the arms of the spirals round them,
and consolidated into the planets, with
the central mass of the nebula
as the sun. This theory implies that
the materials that formed the planets
were originally cold and that heat was
produced by friction and pressure. The
Planetesimal Hypothesis has proved the
preceding ones to be wrong, and today
scientists consider it contains itself many
elements of untruth. As yet, no compre¬
hensive theory has been propounded to
replace it. and our ideas ns to the early
history of the planet are in the melting
pot.

Section 4.—The Globe.

Although we have so little accurate
knowledge of the early history of the
world, and although we know more
about the moon, the sun, and stars mil¬
lions of miles away than we do about
what is five miles below the surface of
the planet on which we live, still, we
do know certain basic facts about the
globe which 'arc the foundations for
much of the science of geology. These
may be summarised as follows:—

(1) The earth is rigid. It does not con¬
sist of a '‘crust" surrounding » molten
interior. The speed with which the im¬
pulses given by earthquake shocks are
transmitted through the earth (they
travel over 8000 miles In 21 miiutc 3 )
in relation to the spe d they travel round
the surface, is sufficient to indicate that
the interior of the globe is of much
greater rigidity than the finest steel,

(2) The interior of the earth is at a
far higher temperature than would he
necessary to melt the materials at the
surface. This temperature i> induced
primarily by pressure, and it is the same
pressure which keeps the. globe ng cl.

(.‘0 While the earth is very rigid, still
it is plastic, and will yield to a change
of pressure.

60 The average density of the whole
globe is greater than the average den¬
sity of the rocks at the surface, rs >
o.5 ns against 2.7). The lighte” mat rials
form a covering around the heavier ones
towards the centre, but ire of insuffi¬
cient quantity to cover the v/nole sur¬
face of the globe. These bln.k^ of light¬
er material form the continents. ^On
account of this, blocks of the surface
of the world occupied by continents do
not exert more pressure on the under¬
lying core than blocks occupied by
ocean depths. Owing to the difference
of specific gravity, the whole crust ex
erts equal pressure on the core, each

block is in, what is called isostatic equili¬
brium.

(5) If this is upset, the plastic core
yields to the pressure, and great geo-
tectonic and continent building move¬
ments result.

(G) Volcanoes and similar thermal
activities are not connected with the
molten interior, but result from a re¬
lease of pressure resulting in the fusing
of portion of the rocks near the sur¬
face.

(7) The mass of the world consists of
one type of rock material. Existing dif¬
ferences in rock types are due to local
and superficial causes.

(8) Change, and not stability, i.^ the
order of creation. The surface of the
world is continually changing, but is not
changing in a haphazard way. It is
growing, and. being built according to
a plan which can be recognised.

(9) The general relative positions of
the great land masses have always been
much as we now know them, but they
are continually being augmented round
their exterior edges.

(JO) Whatever was the original condi¬
tion of the world, it has not grown ap¬
preciably colder during the long course
of geological history. At the very dawn
of history (say. 1000 million years ago),
we find ice covering a far greater area
of the world’s surface than it does to¬
day, and the seasons alternating in
major and minor cycles much as we
know them

Section 5—Continent Building.

As we have indicated, the great land-
masses of the world appear to have been
relatively permanent since the dawn of
geological history. The core of each of
the continents consists of the very oldest
rock we know, and these cores have
not been greatly altered since the earli¬
est times. Kuund these cores the con¬
tinents have been built by the addition of
successive layers of material crushed
against the older and stable rocks from
the outside. In this core we find the
oldest known rocks of the surface of the
earth. They are so affected by com¬
pressive movements that their original
form is unrecognisable. If later rocks
occur on top of the older ones, these have
not been affected by great compression.
Farther out towards the edge of the con¬
tinent we find more recent rocks as com-
>uvssed and contorted ns those of the core.
If these, in their turn, are covered by
still newer beds, we find these have not
been so affected, and so on, until in many
places op the outer rim of the continents
we find the building process continuing,
or, for the moment, just completed.

THE TASMANIAN NATURALIST

It is recognised that pressure is con¬
tinually being exerted towards the centre
of the earth. Whether this is due to that
indefinite and little understood force we
call gravity, whether in response to pres¬
sure iron; outside, whether it is due
to molecular attraction of the constitu¬
ents of the earth or whether the process
is. just one of crystallisation, we do not
know. But we are justified in assum¬
ing that the materials of higher specific
gravity have a tendency to move towards
the centre of the earth and to squeeze
the lighter materials up into ridges and
prominences. The portions of the earths
surface occupied by the great ocean depths
are evidently those portions with the high¬
est specific gravity, and they have a ten¬
dency to move towards the centre of
the earth, forcing, in the process, the great
land masses, representing the areas of
material of lower specific gravity, higher-
above the relative level.

For some reason, not yet adequately
explained, certain centres of the earth’s
surface

Reached Stability Very Early.

As tiie portion sof the surface represented
by the ocean depths progressed in this
gradual movement towards the centre, the
edges of these land masses warped in a
great incline towards the surface of the
sinking masses. These inclines, being one¬
sided folds and being of very considerable
length, are known as geomonochlies. (ge
the earth, mono-single, cline-fold.) These
produced, under tire sea bordering the
shores of the continents, great submerged
plains, known as the continental shelf, on
which all the sediments worn from the
land were deposited.

As the sinking process went on these
blocks of the euth of necessity had to
fit into a somewhat smaller space than
'hey had occupied before, and naturally
V more dense segments squeezed those
f fighter materal out. The pressure
ws greatest between the sinking segment
under the ocean depths, and the already
stabilised land mass, that is on the geo¬
monoclines where these great deposits of
sediments had accumulated.

When the pressure came on these
great beds of newly-formed rocks they
tended to move horizontally in response,
and would have done so had they not
been prevented by the mass of already-
formed land. As it was, they started
to fold and buckle, the portion next to
the stable mass bending upwards into
fold or geanticline, while the next por¬
tion folded downwards into a trough or
geosyncline. This folding continued un¬
til the compression of these rocks gave
the moving pigment all the room it re¬

quired. If the pressure continued long
enough these folding portions were com¬
pressed against the land mass until they
were compressed to their utmost, when
a second and even more series of folds
formed out towards the oceans.

The folds thus caused formed a

Fringe of New Land

along the outer edge of that already
existing, and against which the pressure
had been exerted. Very often the folds
were raised into lofty mountain chains
bordering the coast of the older land and
succeeded out to sea by a great '‘deep/’
which in turn was succeeded by the next
fold rising in succession, often represent¬
ed by a chain of islands.

This process is a continuing one. It
has been at work from the earliest times,
and is still going on; but because it is
working on huge masses of solid rock
which offer great resistance, the tendency
is for it to move in spasms. The pres
sure increases until it is sufficient to over¬
come the resistance, and then follows
one of the great periods of mountain
building which have occurred at inter
vals throughout the world’s history.

The picture we thus get is of a nucleus
of solid rock succeeded outwards by a
succession of folds decreasing in size and
gradually reaching the level of the great
ocean deeps. The nucleus has become
stabilised, and is solid enough to resist
the pressure. The segment of the earth’s
crust under the ocean deep is exerting
the pressure. Between these is a great
mass of yielding rock. The upper por¬
tion. known ns the zone of fracture, is
bending, and after breaking under the
strain, and in many place* is being raised
into mountain ranges. The lower por¬
tion. known ns the zone of flowage. is. as
a result of this tremendous pressure he¬
rn** squeezed into conformity w’th the
folding. and is nlferiiu* it* nature to op
"imv the less snace allowed it.

These processes can be clearly seen in
various stages in Australia. Near Bro¬
ken Hill three separate series of such
foldings have been successively folded into
older land masses. Later another groat
mass, with its centre at Cobar, was
folded against them. This was followed
hv another farther east, and finally wo
have the

Great Dividing Range

on the coast. The Pacific Ocean is one*
of these areas of greater density, and is
continually forcing the rocks of the geosvn-
cline against the continent masses. The
Rocky Mountains and the Andies are the
most recent examples of this work on its
eastern border, and in Japan and the

( 8 )

THE TASMANIAN NATURALIST

East Indies and New Zealand the process
is going on under our eyes.

The result is that, apparently, our con¬
tinents are being continually augmented
from the outside as the ocean deeps con¬
tinually sink. Round the borders of the
great oceans deposits from the shore
are being continually folded into great
mountain chains for the processes of
erosion to level again, thus building the
continents. When once a land mass has
reached stability, it is never again sub¬
jected to great contortions, and hence all

our existing high mountain ranges are of
relatively recent age, and the volcanic and
earthquake regions of the world are the
places where continent building is pro¬
gressing today.

But much of this is speculative as yet.
Our science really starts with the land
masses as we find them. The phenomena
that mould these continents, however
formed to the landscape, we now see are
well known, and we will now start to
describe them.

A. N. Lewis.

The Gum Tree

Amongst the earliest records that ex¬
plorer? made of their experiences in
Australia was the fact that a large
part of the land was covered by trees
which produced a timber of hard, heavy
•and durable quality, and which wa«
peculiar for having veins of dark red,
resinous gum throughout the wood.
For this reason they called the trees by
the popular name, which they still bear,
of gum trees. Botanists following in
the wake of the explorers grouped these
plants into genus, to which they gave
the name of Eucalyptus. The chief
peculiarity noted in this group was that
the flowers had evolved an unusual
form, in that the colored portion, or
corolla, was apparently absent, and its
place taken by a cap which fell off
at maturity, exposing very numerous
stamens.

Research throughout Australia has
discovered about two hundred sp cies
of gum trees, yet though so numerous,
only very few forms have been found
beyond the confines of the continent.

The gum tree is the typical tree of
Australian forests, and therefore should
be recognised as

The Australian Emblem.

Tt well deserves this position, not only
from its many forms, which i re almost
confined to Australia, but from its uni¬
versal distribution throughout that area,
and above that, for the enormous size
which many of them attain. Some
euealypts reach dimensions which vie
with the giant trees of California in
being the tallest trees of the wor’d. and
in favorable situations it is not at all
unusual for trees to exceed the extra¬
ordinary height of 300ft. The timbers
of euealypts are varied, but always
hard and heavy, and the woods produc¬
ed by this genus are fit to take the place

of any hardwood timber of the world,
whether oak, ash or mahogany.

In Tasmania we have about twenty
different species, and some of these are
amongst the noblest spec'mens of plant
life to be found anywhere in the world.
The blue gum (Eucalyptus globulus)
grows to a very big tree wherever con¬
ditions are favorable, and it does so in
record time. Fef, if any, trees of other
parts of the world produce such a great
quantity of wood in a given time as
thi stree. and this wood when prope.ly
mature is of most excellent toughness
and durability. Blue gum may be read¬
ily known by its long sickle-shaped
leaves and large, solitary flowers. An
interesting matter concerning this tree
is that in its young condition, as well
as in response to injury, the leaves are
large, have no stalks, and are placed
square to the sunlight instead of be¬
ing pendulous. This is generally con¬
sidered to indicate that once the tree
lived

In a Less Bright Atmosphere.

and as climatic conditions changed to
intense isolation, the tree responded by
changing from the broad, spreading fo¬
liage to the pendulous condition now ex¬
isting. in order to avoid the evil effects
of too intense a light.

The various forms of w'hite gum be¬
have similarly. This tree does not at*
tain the gigantic conditions of the last*
mentioned, and may always be recog¬
nised by the flowers being small, and
with three together in the axils of the
leaves.

Stringy-bark. or messmate, is one of
our most useful trees. It attains ma¬
turity of timber quicker than does
bluegum. and is more easily split into
thin slabs. It may be recognised, not
only by its thick, fibrous bark, but

( 9 )

THE TASMANIAN NATURALIST

also by the flowers being many
together, and the characteristic leaves,
which arc very unequal in size, on rach
side of the mid-rib. The thickness of
bark has a direct purpose. It protect®
the tree from destruction by Are. A
bush fire must be very intense to kill
a stringy-bark.

Gum-topped stringy is our commonest,
and perhaps most useful, tree. It is
very similar to messmate, only the
clothing of fibrous bark is thinner, and
does not extend as far along the
branches. It is an excellent substitute
for European ash.

Mountain ash grows to a gigantic
tree, and has similar leaves and flow¬
ers to messmate; but the mark is smooth
from the base. It readily falls

A Victim to Fire.

The wood is straight-grained and fis¬
sile, but is less durable than that of
related species. It is commonly called
sWamp-gnm, which is an unfortunate
name, as it leads to the belief that it
produces inferior timber, whereas for.
the purpose for which it is best suited
it would he difficult to find its superior.

There is a group of glims, consisting
of about half a dozen species, which
haie a very close affinity to cider gum
This latter is very like white gum. wit i
three flowers in each flowering axil; hut
the leaves are equal-sided, and not
sickle-shaped, as in that species. The
members of this group vary greatly in
-he shape of the capsules. Cider gum
has small, oblong fruits. Yellow gum
which bears the strongest, most durable
and elastic timber of any Tasmanian
eucalypt. is very similar to cider, onl
the capsules arc rather larger; heait
leaved gums, with large, globular cap
stiles, and always opposite, stalkless
leaves. Urn-gum, with capsule-shaped,
like a Grecian urn. and dwarf-gum. with
small box-like leaves, which s -ldom
grows more than 3ft. high.

The peppermints arc always sana'l
trees, but they have two good qualities:
they will grow in

Soil Too Poor.

for any other tree, and their timber is
most durable. There ore three pepper¬
mints, black, white, and blue. Black
peppermint has narrow leaves,
many flowers in the bunch, and fibrous
bars. White peppermint is a varia¬
tion of this, with smaller flowers and
narrower leaves, but the bark is smooth
from the base. It grows principally on
hills. Blue peppermint is very d ffer-
ent. The fruit is larger, and the juven¬

ile leaves and also all the leaves on trees
growing on poor, dry soil, are opposite,
and connate across the stem. The form
of blue peppermint which retains the
juvenile form of leaves, even when ma¬
ture, is often called the Risdon gum.

Eucalyptus appear to have one disad¬
vantage, in that they bear very small
seeds, and therefore have not a large
store of reserve for the young plant to
draw upon till it shall be able to con¬
struct. food for itself The effect of this
disadvantage is greatly increased by the
peculiar constitution of the plant demand¬
ing for it a full exposure to sunlight. As
a rule, owing to the gum trees having
pendulous leaves, the light of the sun is
but little impeded in its passage through
the overhead foliage, with the conse¬
quence that below cucalypts the soil
maintains a copious vegetation of shrubs
and small trees.

The seeds falling from the capsuls reach
the soil beneath these shrubs are euhe.
do not germinate or. if they do, they
are smothered in their infancy. This is
why so few young trees are found in a
normal gun forest. To combat this
eucalypt trees have evolved an effective
means of reafforestation. When they
have flowered, and set seed in their cap¬
sules these

Capsules Do Not Open

ami allow the seed to escape, but re¬
mains closed during the life of the stalks
bearing them. Now if a bush fire comes
along it destroys not only all undergrowth,
but kills at least all the small brunch¬
es. This *uts off the moisture supply
of the capsules: they dry up, open their
valves, and the enclosed seeds fall out
on to the now bare soil.

Eucalypt seeds germinate very rapidly,
and usually get n fair start from the
weeds. There :s now a struggle for ex¬
istence. If the seeds of rapid and dense
vegetation happen to be present the
young gums will probably have a bad
time. On the other hand, if there is
any delay, ami the eucalypt once get a
chance, they being rapid growers, the
probability is that there will be a dense
crop of young gums, which, in its turn,
will for a few years inhibit the growth
of underscrub.

The condition of Tasmanian forests is
that of most woodlands which have been
raised under purely natural conditions
They consist of trees of various ages.
Some long past their ^Wme with dead
boughs and rotten heart, which are of no
service but to supply firewood : a few are
in a good state for the axe, and many
too young for anything better than poles
This is what you always got where trees
have been left to

( 10 )

THE TASMANIAN NATURALIST

Fight Out Their Lives

for themselves. There is only one way
to secure a better condition, and that is
to clear practically everything off the land
and raise a new crop all of the same
age.

This is hardly reasonable in the pro
sent, but with (he rapid elimination of
soft wood, I he duy must come when

hardwood forests will be of much greater
consequence than in the present. Some
oi' our. choicest timber: such, for instance,
as the yellow gum of Uxbridge, grows
in small numbers in out-of-the-way pla¬
ces. It would be a useful thing to plant
small experimental areas under pure
forest conditions as a test of what can be
done with good trees and waste places.

L. Rodway.

Chapter III.

Features of the Landscape

(Dynamic Geology.)

Section 6.—Mountain Building.

Mountains are elevations on the earth’s
surface which rise above the general
level of the country. Height, size and
shape are immaterial and of infinite
variety. A large extent of high, but
relatively level, country Is not called a
mountain, but a plateau, e.g., the cen¬
tral plateau of Tasmania: in Victoria
the term "high plains’' is common, and
prominences attaining a lesser elevation
are called hills. The principles which
govern the formation of these three fea¬
tures are similar and the following re¬
marks will, in general, apply to all.

Mountains may be classified Into:—

(a) Formation mountains (he., por¬
tions of the landscape that have been
raised to a higher level than the sur¬
rounding country by some geographi¬
cal process).

(1) Folded mountains (i.e., those
formed by the folding of portion of
the earth’s crust in response to lateral
pressure).

(2) Block mountains (i.e.. blocks of
the crust that have been raised bodily
above the surrounding country).

(3) Domed mountains (i.e., those
formed by pressure from below bulg¬
ing the surface into a dome).

(4) Volcanic mountains (i.e., those
formed by outporings of lava or vol¬
canic ash).

(b) Residual mountains (i.e., those
formed from a once extensive elevated
tract of country by the removal or
sinking of -the balance ol' the land¬
scape).

(1) Mountains of circumerosion (i.e,
the elevated areas left when the bulk
of the original plateau has been worn
away).

(2) Residual block mountains (Le¬
the portions of a once elevated plateau

that have been left when the bulk of
the country has sunk).

The formation of residual mountains
is really the story of the formation of
the valleys that separate them. We
will leave this class therefore until
We discuss the development of valleys.

Origin of Mountains.

All the mountains included in the
class “formation mountains’' owe their
origin in some way or another to the
same cause. That cause is the same
series of earth movements which wo
have seen is responsible for the addi¬
tion of belts of new land to the older
continent masses, the squeezing of ac¬
cumulations of sediments, deposited off
the coasts of the continents, against the
older stable core of the great land
masses by the sinking of the blocks of
the earth’s crust of higher density than
the average and which are represented
by the floors of the oceans.

A mountain, whether an isolated peak
like Mount Wellington or a continental
cordillera like the Rocky-Andean chain
is essentially a feature of relativelv re¬
cent growth. Immediately on elevation
the weather starts its work of breaking
down the newly formed mountain, and
after a space of time, by no means long
according to the geological scale, the
mountain range is reduced to a suc¬
cession of rolling hills—"downs,” as they
are termed in England and north-wes¬
tern Tasmania; plains as they are call¬
ed in Australia, and prairies as they are
called in America.

All the great mountains we now' see
on the map of the world arose during
the more recent epochs of geological
time and from the mere existence of a
mountain at the present day we can
argue the ocurrence of great earth
movement at that spot in the no very
distant past.

THE TASMANIAN NATURALIST

Further, we see from our atlas that
all the great ranges of the world are
grouped along the outer edges of the im¬
portant land masses. They are, in fact,
the newest layers of land added to the
continents, and are the ridges of rock
compressed against the older cores of the
continents, which the weather has not
yet had time to level to a maturer con¬
tour. Also we see that the lines ot
these newly-formed mountain chains are
also the lines of volcanic activity at the
present time, and also mark the por¬
tions of the earth's surface afflicted by
earthquakes. These new mountain ran¬
ges, volcanoes, and earthquake shocks
are all phenomena resulting from the
same cause, and are ali indications of
the building of new land.

Folded Mountains.

When pressure is applied, as above
explained, to a bed of newly-deposited
and relatively horizontal strata, the first
impulse of this bed is to yield laterally.
This inclination is resisted by a block of
the earth crust more stable than the
bed of strata, and if the pressure con¬
tinues, and is sufficient to overcome the
resistance of the strata, folding begins,
and the strata are crushed against the
stable section, known in this connection
as a “remanier block.” Folding, there¬
fore, implies pressure, and a stationary
mass or anvil against which the pres¬
sure is exerted. In any one region pres¬
sure comes, as a rule, fr^m one side, and
is exerted in one direction, although it
is possible for pressure to be exerted
from both sides of a block of strata,
each locus of pressure acting as the re¬
in anier block to the other.

The first tendency is tor the edge of
the block of strata nearest the re-
raanier block to buckle into a fold. This
fold will be at first broad based and flat.
As the process continues it will rise into
a sharper ridge, and we will s?e the gra¬
dual growth of our Fountain range. The
fold will seldom be uniform-sided, be¬
cause the movement, being all from
cne side, will tend not merely to bend
the strata, but t. • li outside portions
under the interior ones.

The pressure will be coming from be¬
low and from the outside, not from
above, or in an absolutely horizontal
plane. This tends to overturn the folds
on the older formed rock or on earlier
stages the shapes of regular, broad-bas-
great beds of the outer portion of the
folding strata over, under, or through
the inner portions. Thus we got fold¬
ed mountains assuming in their earlier
stagesthe shapes of regular, broad-bas¬
ed, domed ridges, but as the process con¬

tinues these folds steepen and finally
overturns and breaks, leaving ragged
edges and broken escarpment, and the
grander features of our more letty
mountain ranges.

In Tasmania we have no mountains
whose existence in their present torni
can he ascribed to this process oi tout¬
ing. Certainly the rocks of the west¬
ern highlands are intensely folded. Pro¬
bably they formed portion of an anci¬
ent mountain chain, but this range has
long since disappeared, leaving a mere
core of folded and contorted strata.
These strata have been raised some¬
what, and then blocks have been isolat¬
ed into the existing mountains at a
later date, and by very different pro¬
cesses than the ones that originally
folded the rock.

Block Mountains.

The existence of folded rocks is usu¬
ally an indication that these rocks were
at a considerable depth, and hence under
great pressure when the pressure was ap¬
plied, otherwise they would have mere¬
ly broken. A bed of rock on the sur¬
face is in general too friable to bend,
but if the pressure was sufficient, would
buckle, and break into blocks which
would yield to the pressure, and, if ne¬
cessary, slide over each other. It is
only when the pressure is so great that
no movement is possible that a solid
mass of rocks will fold. Although this
is the rule, folding occasionally occurs
at the surface in peculiarly favorable
conditions, and is now occurring in
Papua, New Britain, and British New
Guinea.

When the pressure due to depth, and
the pressure due to lateral forces are
very considerable the rock mass may be
reduced to a plastic condition, and as¬
sume the qualities of a liquid, flowing
In any direction possible. Areas and
zones in the crust where this condition
exists are known as

“Zones of Flowage.”

They can only occur where the pressure
is sufficient. In them all pores and
fractures are closed, the rocks often
take on different forms, and the strata
conforms to such shapes as the pressure
imposes.

Nearer the surface the rocks are freer
to move, and to yield to pressure. The
portion of the crust is known as the
“Zone of Fracture.” Here the beds of
strata are not folded, but break. When
pressure comes on, this portion, or where
the folding of rocks below it, nearer the
centre of the earth, exerts forces from

( 12 )

THE TASMANIAN NATURALIST

below, the strata of this zone of
fracture tends to conform to great
masses of the landscape, are forced
more or less vertically upward, above
the general level, and other great blocks
tend to sink. Hence we get the for¬
mation of the type of mountains we have
called “Block Mountains/' They are
characterised by abrupt faces descending
to the neighboring valleys, but their
rocks have been pushed up as a whole,
and although probably tilted to a greater
or less degree in the process, and often
much broken, they are not folded or
compressed at all.

Block mountains are probably very
often the mere conformation of the sur¬
face beds of strata to the foldings going
on very far below. The portions of the
surface, over the upward arch of a fold,
being free to move, are forced to a block
to a greater or less elevation above the
surrounding country and the portions
over the downward arch of the strata
drop below the general level. But it is

By No Means Certain.

that all block mountains are so formed.
The surface of the crust may often ad¬
just itself to differing conditions, or to a
general shrinking by breaking into such
blocks, some of which are forced up,
while others remain stationary or drop,
without any corresponding folding below.
But, on the whole, it is unlikely that
block mountains could be formed on any
scale without folding of the strata be¬
low.

Block mountains tend to result in
plateaus and flat-topped ranges rather
than the jagged, fantastic peeks and
ra'or-backed ridges that folding gives
us. Most of our Tasmanian mountains
in common with the whole of the Great
Dividing Range running the length of the
eastern coast of Australia, belong to this
type.

Mount Wellington, Ben Lomond, the
Central Plateau, and all the mountain
groups of the south and of the middle
west and north-east of Tasmania, show
the typical form of block mountains.
They have all flat, plateau-like tops, and
steep sides, dropping to, usually, broad
flat valleys. They are evidently blocks
of the surface strata of this portion of
the earth's crust that have been forced
up to their present elevation as blocks.
There is often a certaih amount of tilt¬
ing, but no folding.

It is unknown, as yet, whether these
block mountains represent merely an at¬
tempt of the surface strata to adjust it¬

self to a smaller space necessary through
the general shortening of the earth crust,
or whether the pressure from the east¬
ward or south-eastward—that is from the
Pacific basin, more particularly the Tas¬
man Sea basin—has

Squeezed These Blocks

up to form the mountains we now see.
The writer suggests the latter alterna¬
tive is the more probable.

Perhaps our more important mountain
ranges are merely the surface indications
of great folding movements that have
occurred deep down in the earth. It
seems quite possible that pressure origin¬
ating as has been described was applied
from the south-east and east on the great
deposits of sediments washed from the
ancient land that once existed to the
west, of which our West Coast mountains
are a fragment, and deposited off the
coast of this land. The ancient rocks
of the West Coast, supplied the remanier
block against which these sediments were
squeezed. Deep down in the crust, fold¬
ing resulted, which has not yet been ex¬
posed, it having occurred in relatively
recent times. The largest fold occurred
nearest the old and stable rock masses.
Farther east this was followed by a
great trough with a lesser fold, and a
lesser trough farther east, and finally
the smallest fold of the three in tile
vicinity of our present Fast Coast. These
folds, as is usually the ease, were by no
means regular, but more pronounced in
some places than others, and were broken
by many transverse folds at approximate-
ly^ right angles to the main lines.

The surface strata not being restrained
by any pressure or weight of superim¬
posed rock, did not fold, but broke into
great blocks in conformity, giving us
elevated tracts or block mountains over
the upward folds, and

Dropping to Deep Valleys

over the downward folds. Thus, where
the largest fold occurs nearest the ancient
rocks of the western side of Tasmania
we have the most elevated blocks of these
newer mountains — La Perouse. the Hartz
Mountains, the Snowy Mountains, and
Mount Wellington, Mt. Field Ranges, Mt.
Cell and its neighboring ranges, Mt.
Olympus, the Du Cane Ranges, the
Pelions to Barn Bluff, and Cradle Moun¬
tain.

This mass is followed by a line of
great valleys—D’Eutreenstreaux Channel,
the Lower Huon. the Derwent and the
Forth Valleys. Farther east, there is a
lower and less defined series of moun¬
tains, Bruny Island, the mountains east
of the Derwent and the Central Plateau
being the most striking.

( 13 )

THE TASMANIAN NATURALIST

These in turn are followed by another
line of valleys—Pefcta Water, the Coal
River Valley, the Midlands Valley, drain¬
ed by the Macquarie River, the lower
South Esk Valley and the Tamar. Finally,
along the East coast there is a line of
mountains, also decidedly of the block
typo, but of less altitude than the others,
and from which the East coast drops
sharply. In the north-east corner of
Tasmania, there are also some older rocks,
and against these pressure has also been
applied, giving us the

Ben Lomond-Mt. Victoria Plateau,
separated from the East Coast tiers by
the valley of the Upper South Esk.

This theory to explain the origin of
our mountains is advanced here for the
first time. It is still only a theory, and
has yet to be proved, but all earlier
theories attempting to explain the reason
for our mountains are more or less
erroneous and this one avoids some of
the worst objections that can be raised
t 0 the others. It is here only given in
barest outline; in fact, only as an indica¬
tion of a possibility and must not at pre¬
sent be stated as if it were an established
fact.

We must now pass on to our next
type.

Domed Mountains.

Great beds of strata arj seldom of the
same material throughout, but more
usually hard and soft layers alternate.
When pressure is applied during folding
movements, naturally, layers of different
hardness respond differently. The layers
of hard rock tend to fold, pucker, and
sometimes to break and overthriist other
layers. If the stress is so tremendous that
the relief given by these movements can¬
not accommodate the rocks to their re¬
stricted space, the individual particles and
minerals tend to re-arrange themselves,
and alter so as to occupy less space. On
the other hand, soft rocks cannot stand
the strain which would merely bend hard
layers, and are crushed beyond recog¬
nition without much opportunity to fold,
and are squeezed between the moving
layers of hard rock and forced into
cavities where they occur.

It is well known that although ordinary
water turns into steam at 100 deg. C,
water in ordinary engine boilers attains
a temperature double that degree before
turning to steam, and special appliances
can be made wliereby the temperature of
water can be raised to 1000 degrees or
more without it turning to steam. This
iz

Because of the Pressure

it is under, and the greater the pressure
the greater the temperature the water

can attain without turning to steam. But
immediately the pressure is released water
over the temperature of 100 degrees will
forthwith become steam.

Similar principles hold good with rock
masses. During folding processes a heat
is generated by the pressure far in ex¬
cess of what would be required to melt
these rocks at the stir* ace, but the same
pressure prevents their fusing. But often
spaces, pockets or fissures, will occur.
Often a hard layer will arch as the result
of the pressure and leave a cavity below.
It is the softer rocks which are feeling
the stress of the pressure most and often
when this pressure is released, by, per¬
haps, the arching of a layer above, or
the slipping of some higher bed across
another, or by the rising of a block of the
crust as the result of the pressure, some
of this soft rock will fuse; that is, be¬
come molten.

This, in its turn, tends to relieve the
strain, due to the folding. Instead of
having to squeeze solid rock, there is only
the resistance of a liquid to be overcome.
The pressure exerted against this forces
it through cracks and weak points in the
surrounding rock. Its own heat tends to
melt more and more of the surrounding
strata, and thus a ‘‘magma pocket” is
formed. These, as can be seen, usually
occur under the upward arches of the
folds. As the pressure continues, quan¬
tities of this molten magma are forced
through the surrounding rocks, in large
sheets (sills), or upward pipes (dykes), or
irregular-shaped masses (laccoliths). Hie
force of the pressure is much more effec¬
tive on this molten matter than on the
resistant Bold rock, ami where it can

Merely Fold and Twist

the latter it can force the molten material
right out of the affected area.

Often this molten magma is formed near
the surface through the release of pres¬
sure caused by the displacing of a surface
block of strata, or again it may be forced
towards the surface by the great pressure
below. When it reaches a spot where its
own pressure is sufficient to bend the
strata above it, it forms a “domed moun¬
tain.” This type of mountain always
has a core of rock that has been once
molten, called igneous rock, which, of its
own power, has forced the overlying rock
up into the mountain we now see. and
this overlying rock is bent round the
igneous rock. Such mountains are termed
laccoliths when the igneous material is
in the form of. a definitely bounded
magma pocket, and a batholith when the
igneous material has no ascertainable
bottom.

Naturally, rock may fuse and form
pockets, or sills, of igneous material with-

( 14 )

THE TASMANIAN NATURALIST

out having sufficient power to bend the
superimposed strata. It then does not
form a domed mountain, but is found
merely, as a mass of igneous rock em¬
bedded in rock of different structure.

Most of our mountains of central, east
and south Tasmania’ are of these natures.
Few definite laccoliths or domed moun¬
tains have yet been identified. The Do¬
main, Hobart, is probably a laccolith, and
similarly many smaller hills of the East
Coast. Trinity Hill, Hobart, certainly
appears to have been formed by the
strata being bent by igneous rock from
below. But most of our mountains in this
part of Tasmania are masses of igneous
rock thus formed, but which have not
had any definite effect on the overlying
strata. They stand in their present posi¬
tion not through doming the surrounding
rock, but either through raising it bodily
as the result of being squeezed upward
by the same process as originally fused
the original rock, or by being lifted bodily
by later, though similar, forces, after
having entered and transgressed the
earlier sediments.

Volcanic Mountains.

As is natural, when the molten magma
is being squeezed and pressed through
overlying rocks, some will often reach
the surface. We then have a volcano.
These are important, but quite subsi¬
diary, agents of mountain building. The
molten material usually works along a
weak bed of strata or up a crack or weak
place in the fold. Usually these are
found on the forward side of the folds;
that is, the side opposite from that from
which the pressure is being exerted. It
is the continuance of tb< pressure due
to the folding process that forces the
molten material out on to the surface,
and causes volcanic eruption.

If the molten rock pours out on the
surface, we have lava flows. These are
often of great extent. In the Deccan, in
India, one ancient lava flow covers 200,000
square miles to a depth of over a mile.

A third of Victoria is covered with
an ancient lava flow, and similarly most
of the North-West and North coasts of
Tasmania. If the lava is viscid on reach¬
ing the surface, it often piles up into
hills of considerable height. Many hills
round Melbourne are so formed, but in
Tasmania there have been no volcanoes
of very recent date, and with our heavier
rainfall the

Ancient Lava Flows

have been greatly reduced, so there are
few hills which we can definitely say were

due solely to a lava flow. The hills of
Droughty Point, south oi Bellerive, are
due to this cause, and the hilly country
round Deloraine, between Devouport and
the Forth, from Burnie to Waratah, and
round Stanley and the extreme North-
West, are all relics of old lava flows,
much cut into, however, b.» the numerous
streams which cross them.

Often very little lava pours from the
vent of the volcano, but from the crater
showers of stones, ashes and mud are
thrown into the air. These in time build
up very considerable mountains, known
as volcanic cones. Mt. Egemout, Mt.
"Ruapehu, and Mt. Tangariro in New Zea¬
land are so formed, and are sufficiently
high to be permanently snow-capped. In
Tasmania, we evidently had at one time
many of such mountains, but they have
not survived our rigorous climate. Cor¬
nelian Bay cemetery, the recreation
ground at Eindisfarne, Fort Alexandra
Hill at Sandy Bay, were once volcanic
cones, and there were dozens up the Der¬
went Valley and through the Midlands
and along the North coast; but such
mountains composed of fine ash and min'
are very soon levelled by the action ot
the weather.

Thus the ancient idea ot a volcano as
being a pipe connecting the mountain with
the molten core of the earth, or as being
a natural safety valve is quite erroneous,
and we have endeavored to explain that
all mountains are built by the processes
generated by the sinking of the heavier
blocks of the earth’s surface, squeezing
lighter portions out and upwards. Some
writers use the terms “epeirogenic,” or
continent making, movements to describe
the formation of block mountains and
“orogenic/’ or mountain making, move¬
ments to describe the formation of folded
mountains; but these terms are mislead¬
ing. As we have endeavored to explain,
all types of mountains arc but different
aspects of one great process; all are but
different results of the one cause. Finally
these processes are infinitely slow. No
mountain is formed by them alone. As
soon as a mountain begins to raise ita
head above the surrounding country run¬
ning water and the weather begin to at¬
tack it, and these forces really give the
figure to the surface, and determine the
details of its outline; the mountain build¬
ing forces merely giving its general sub
stance.

( 15 )

THE TASMANIAN NATURALIST

Section 7.

Folds

Having seen how these features have
their origin we must now discuss them in
somewhat greater detail and determine
their peculiarities so that we may recog¬
nise them when we meet them in the
field.

They may be of any size, from a bend
a few feet high such as can be easily
studied in a road cutting, to one many
thouasnd feet in radius and covering seve¬
ral miles, in which case it isoften only
po-ssible to detect its existence by mea¬
suring the dip of the rock in many places
and tracing one layer of rock over a
large area. The arch or upward bend of
the fold is known as an “anticline,” and
the trough or downward bend as a “s yn-
cline.” Where one occurs the other is
usually to be found on one or both sides.
Greatly folded rock is a succession of
anticlines and synelines. When the strata
is only slightly folded into long induc¬
tions the folds are spoken of “open folds.”
With further compression “close folds”
may be formed, and if the compression
has been so intense that the different
ayers are bent into a series of parallel
vertical bands the folding is isolimial if
each side of the folding is at the same
inclination the folds are termed “symme¬
trical.” Often one side

Is Pushed Over

owing to the pressure coming from one
direction. The fold is then known as an
“overturned fold,” and if the process has
been continued to its utmost limit it is
called a “recumbent fold.”

In regions that have been subjected to
much folding, the larger folds often have
smaller ones superimposed on them, and
these in turn may have still smaller ones
down to tiny “foliations/' With folding
there is a tendency for the particles to
become separated and even individual
minerals to develop stress cracks known
as “rock cleavage.” Often cracks develop
and these become filled with minerals of
;i different nature forced into them under
pressure, or deposited from circulating
water.

All these types of folding can be seen
and examined in any short section of our
West Coast. In a cutting just south of
the Zeehan station is a splendid example
of a symmetrical close folded anticline,
barely four feet high, and with a base of
.•similar measurement, a perfectly regular
curve. Along the north coast from UI-

verstoue to past Table Cape can be seen
a splendid series of folds outcropping on
the beach. As you go along in the train
you can notice that the jagged edge of
the strata appears to be dipping at a very
steep angle. Further along these rocks
gradually assume a steeper and steeper
angle until they arc standing vertically
and finally turn over, and are to he seen
dipping in the opposite direction. This
is repeated many times along this section
of the coast. It is an indication that we
are looking at a

Series of Huge Folds,
the tops of which have been worn off.
Many of these folds are several miles
across. Just west of the Coo-ee sale
yards, a mile or so west of Burnie, they
can be seen to perfection. Here are
many small synclines and anticlines. The
top of one anticline is so perfect that it
resembles the top of u circular concrete
drain running out to. sea. We here see
excellent examples of both open and close
folds.

East of Maria Island ancient rock has
been twisted to such an extent that once
horizontal bands of strata are now to be
seen with a sharp bend at the bottom
from which the band runs vertically for
over ;300 feet to a sharp bend at the top,
and so on in a series of parallel pleats,
the same band being bent until it occurs
only a few yards from the continuation of
itself in the neighboring folds. These are
wonderful instances of isoclinial folding—
a very rare type.

Many of rhe mountains of the West
Coast appear to have their outline go
vorned by overturned folds. The gen
tie slope up one side followed by a sheer
face on the nther is often, although not
necessarily, an indication of an over¬
turned fold. Although none of this type
of folding has been recorded it is al¬
most certain that the twisted rocks of
the west can provide many examples

In addition to a simple folding, se¬
condary folds are often superimposed
on the original ones; in fact, this is the
general rule. In the rock® near Cooee.
mentioned above, there are three series
noticeable. First, there has been a
major folding resulting in a series of
great folds.

Many Miles Across,

and probably several thousand feet deep.
These themselves consist of a succession

06 )

['HE TASMANIAN NATURALIST

of small folds ten to twenty feet across.
Again another folding has taken place
in a direction normal to the others: that
is, while the first have the succession of
anticlines and synclines in a vertical
succession the series shows waves in
the strata in a horizontal direction, that
is, along the surface of the ground.

At Cradle Mountain an even more in
tense folding is evident. Large folds
are apparent in all the cliff faces; that
at the head of Crater Lake, for example.
Rut in addition to these, the rock has
been folded in every possible direction
and in many degrees until the smallest
gives it the appearance of a succession
of ripple marks. These can be the re¬
sult of one intense compression and may
have been caused at; relatively the same
time; but often it is evident that they
have been the result of successive earth
movements. Thus, in the Mt. Lyell
district the rock was first folded into a
saucer-like shape; then later the edges
of this were pleated by a series of
minor folds. Most of the mineral hear¬
ing regions of the West Coast have been
subjected to at least two series of fold
ing movements separated by a very
great length of time.

Another type of fold, called by Mr.
E. C. Andrews the drag fold, occurs
at Broken Hill. Here there were two
layers of very hard rock about four
miles apart, and separated by beds of
soft rock. During compression these
bard layers moved horizontally and one

Dragged or Rolled

the soft rock against the other hard
layer. No instance* of this has yet
been reported from Tasmania.

This intense folding in probably every
case occurred in the zone of flowage.
These beds of rock have been let down
so deep into the earth that the particles
under inconceivable pressure and heat
thereby generated have become plastic,
and when the folding movements have
occurred the rocks have yielded as if
they were putty. A mile or so west of
the Leven at I'l verst one there is a bed
of what was originally a conglomerate
of round stones, the size of cricket balls,
set in a fine matrix. This has been
folded, but so great was the pressure
and so pliant had the particles become
that these embedded stones have stretch¬
ed or been compressed in exact confor¬
mity with the rest of the rock until now,
what were at one time round water
worn pebbles, have been stretched out
for, in seme cases, eight ecu inches, a* d
have been bent round following the lines
of the fold without breaking. The pres¬
sure necessary to do this cannot be
imagined.

Folding of all possible types can be
seen wherever the older rocks occur in
Tasmania. Anywhere west of a line
from Cradle Mountain southwards, in
many places along the shore of the
North Coast from Cape Grim to the
Tamar, around Beaeonsfield. south of
Sheffield, west of Fitzgerald, and in
many places round Gladstone and from
Fingal to Richcno, every variety of fold¬
ing may be seen.

Section 8.

Faults and

As we have seen, vvnile the strata In
the zone of flowage normally folds in re-
spose to pressure, that in the zone of
fracture normftly breaks. The formation
of block mountains implies a series of
such breaks on a large scale. But besides
these, the surface of the earth is always
having to adjust itself in a smaller or a
greater degree to varying conditions be¬
low. and there is a continual movement
between blocks oi the surface rock: some
rising, others sinking.

Now, if we have an extensive bed of
strata under half of which the crust is
gradually sinking or rising, while the
other half is stationary, a stage is readi¬
ed when something must give way. If the
movement is very slow and the rock soft.

Earthquakes

or under considerable pressure, it will tend
to drag and gradually to bend at the
junction between the moving and the
stable portion until a more or less uni¬
form curved slope connects the two. I his
resembles one side of an ordinary fold,
and is called a “monodinal fold.’ But a
tnonoclinal fold approximates rather to a
fault than to a fold. The best example
of such a feature is to be found in the
Blue Mountains east of Sydney, where
the level sandstones bend from the top
of the mountains to the plains 2000-3000
feet below without breaking.

If, instead of a gradual movement the
sinking or elevation is rapid the tendency
will be for the bed of rock to

( 17 )

THE TASMANIAN NATURALIST

Break at the Junction.

This will allow the moving portion to
respond to the influences from below
freely, and the result will be that in one
dace strata will be found at a different
evel from strata elsewhere that was ob¬
viously laid down at the same time; but,
besides this difference of level, showing
no signs of compression or other earth
movements. This break is called a
“fault/'

A simple break is termed a normal
fault, and its existence is indicated by
this fact that any given layer of rock
when followed along to the fault suddenly
stops there, the other side of the fault
being rock of a different layer, or even
of quite a different series. A break
caused as described above is seldom a
simple fracture. More usually there is
an area of broken rock with many small
faults. Sometimes the rock is so broken
that its structure has been destroyed,
and in extreme cases it may be reduced to
rubble. This is known as “fault breccia."

In very hard rock the fault in ay be a
fine, straight crack, and the sides may
be polished by the force of the slipping
rock. This polishing is known as “slick-
enside." Sometimes it can be seen that
there has been continual movement up
and down along a fault line. Sometimes
the edges of the strata adjacent to a fault
are dragged round towards the other
block.

These are the features exhibited when
a bed of rock is broken by portion sink
ing or rising in relation to the rest. Some¬
times faults may be occasioned by lateral
pressure in the same way as folding. In
this case, when the pressure has come on
the

Side of a Bed of Rock

instead of folding it has broken. Often
it will bend in the middle and then break.
This form is common amongst our sand¬
stones throughout Southern Tasmania.
At other times when the rock breaks
one portion is forced over the other. This
is termed an “overthrust fault.” Often
the edges are dragged round into a mono-
clinal fold. Faults may have a displace¬
ment or as it is called a “throw.” of any
number of feet, from great tectonic faults,
showing a movement of several thousand
feet down to ones of hafdly perceptible
throw'. Many of these smaller faults are
mere local adjustments, penetrating only
a few layers of rock and may be called
“creep faults.”

As we have shown, the western por¬
tion of Tasmania gives us every possible
example of folding. The eastern portion
on the contrary show's little folding, but
is broken in every direction by faults of

all descriptions and sizes. It is probab¬
ly impossible to follow a bed of rocK in
southern, central, northern or eastern las-
mania for a mile in any direction witn-
out meeting a Fault of some description.

We have first the major block faults.
The country is broken into segments, at
all different altitudes from sea level to
5000 feet. The edges of these various
blocks are all huge faults—whatever the
cause. For example, rock of the same
original bed occurs. At sea level at Ho¬
bart, and on the slopes of Mt. y el ling-
ton, not four miles away, it is to be seen
at an

Elevation of 3300 Feet.

Similarly the faces of the Western Tiers.
Ben Lomond, the East Coast mountains,
Mt. Field, the mountains south of the
Huon and all the lesser hills in south-
cistern Tasmania, show displacements of
the beds of rock to an equal extent.

Then these beds, each at its own height,
have been broken by many faults of lesser
size. Probably the Derwent is working
down one of these, as evidenced by the
cliffs at the rocks near New Norfolk, at
Bedlam Walls, near Risdon, and at the
Bluff, at Bellerive. The Tamar is also
probably following a fault line, up the
side of which the main line climbs be¬
tween Launceston and Evandale Junc¬
tion*

Our whole coast is probably determined
by three large faults, but certainly many
of the details are fixed by small ones.
Buss Strait is probably a block of land
dropped below the general level by a
series of faults running along the Tas¬
manian and Victorian coasts. These
coastal faults have not been a clean break,
but a series of minor criss-cross faults, in¬
tersecting each other and running at an
angle to the general line of break.

In addition to all these, our rocks are
broken by innumerable smaller faults.
Especially is this true of our coal fields
—coal measures being particularly fragile
rock and notoriously broken. These
small faults have been the greatest hin¬
drance to coal mining in Tasmania, and
at least one good colliery— Sandfly—was
forced to close solely on account of

The Innumerable Faults.

hen a seam is being mined and a fault
is met with the coal-bearing layer on the
other side of the fault is lost, and much
unprofitable work is necessary to pick it
up again. If this occurs too often a
stage is reached when the quantity of coal
won will not pay for the work of cut¬
ting out barren rock to get at it.

In Tasmania the common sandstone ori¬
ginally rested 500 feet above the common

( 18 )

THE TASMANIAN NATURALIST

blue and brown limestone. Very fre¬
quently these rocks may now be seen
alongside each other. This occurs on
the Huon-road, in Lenuh Valley, in Glen-
orchy Valley, and on the New Norfolk-
road east of Sorell Creek. This always
indicates the existence of a fault. All our
mining fields are bounded, limited and
traversed by faults, and every one of the
bulletins of the geological survey de¬
scribe many. Faults are by no means con¬
fined to the block mountain regions of
the east. The folded rocks of the west
have their share.

EARTHQUAKES.

These catastrophies are merely the ap¬
parent results of movements in the earth's
crust. When a fault occurs, or when,
during folding, beds of strata break, the
adjacent surface suffers an earthquake.
The causes are the causes that produce
folding and faulting, and have been sufli-
cientl.v discussed. Earthquakes are com¬
mon today wherever mountain building
i* going on; for example, all round the
outer edge of the land bordering the Paci¬

fic. They also occur through minor ad¬
justments of stresses after the building
processes are complete.

If the strata are very resistant the
strain will be resisted until it becomes too
great, when the rock will give way with
considerable displacement and
A Great Earthquake
like the recent one at Tokio w'ill result.
If the rock is not resistant it will give
gradually, a little at a time, as strain
comes on it and minor earth tremors only
will be the result. In Tasmania moun¬
tain building movements are fortunately
completed for the time being, and we are
not subjected to earthquakes on a large
scale; but Bass Straits is decidedly an
earthquake zone, and small tremors are
recorded from there nearly every year.
These are probably caused by slight slip-
pings along a fault line, a few inches at
a time, and due to adjustments of stresses
after a period in the recent past of con¬
siderable earth movements. No place or.
the earth’s surface can be said to be
definitely immune from the possibility of
earthquakes.

Section 9.

Volcanos, Geysers and Hot Springs

It has already been explained that these
activities are merely incidental phenomena
of mountain building processes, due to the
forcing of molten material close to the sur¬
face. A volcano is merely a vent from a
magma reservoir to the surface and a
geyser, or hot spring, is merely a vent from
a supply of water accompanying molten
rock or reaching it from the surface.

Many volcanos have commenced acti¬
vity within historic times, and under
scientific observation. The first sign is
usually a fissure traversing comparatively
level country, from which molten rock lias
appeared to flow (really it has been
squeezed). This molten rock, or lava,
consolidating round the vent soon builds
up a considerable mountain through which
these subsequent eruptions burst.

These fissures can all be traced to the
lines of great earth movements, aud cor¬
respond with folding or block faulting of
the underlying segments of the crust. In
all the most intensely active volcanic re¬
gions of the world the volcanic cones
or vents are all arranged in lines corres¬
ponding to these fissures, with the largest
volcanos where two fissures cross.

Fissure Eruptions.

The grandest of all volcanic eruptions
have been those in which the entire length

and breadth of the fissure have been the
passage way for the upwelling lava. These
have provided the great lava flows of an¬
tiquity which we can still trace today.
Their origin is due to the qualities of molt¬
en material accumulated below the sur¬
face, and the pressure generated by earth
stresses sufficiently powerful to eject such
a mass of material. Along the whole of
our north coast are huge flows, many of
over 100 square miles in area, of unbrok¬
en lava. In Victoria well over 20,000
square miles is covered in tins way. These
great flows are the result of a series of fis¬
sure eruptions, and are signs of earth
movements of a major degree. Throughout
Tasmania many smaller areas are covered
with ancient lava flows, and yet there are
very few places in which it can be de¬
finitely said that a volcano existed. Basalt

a rock that was once lava -stretches from
Pont vi lie to Bridgewater, and is found at
the back of Kingston, and around Sorell
and Richmond and in many other places
without the slightest trace of the previous
existence of a volcano. These occurrences
are probably the result of fissure eruptions
on a small scale.

Lava Flows.

These may be distinguished petrologic-al¬
ly by the nature of the rock as will be

( 19 )

THE TASMANIAN NATURALIST

explained in a later chapter. They can
also be distinguished in the held by typical
characteristics. When a mass of crystaline
rock can‘be seen filling up a valley, and
overlying oldef rocks, it is safe to assume
that it must have flowed there as lava.
Very often by tracing such a rock the
course of ancient river valleys down which
the lava flowed can be discovered. As
this rock is invariably very hard it some¬
times happens that, if the original valley
sides were composed of soft rock, these
have later been weathered away, and the
lava flow which originally occupied the
lowest portion of the valley is left as a
ridge.

Usually the mechanical effect of flowing
molten material has left its mark on the
subsequent solid rock; that is, you can see
at a glance by its existing arrangement
that it once flowed to its present position.
Often it picks up blocks of other rock
as it travels, and these can now be found
embedded in a rock now much harder,
and often pieces of lava which have solidi¬
fied sooner than the mass, have been
broken off, and cun be found also embed¬
ded in the later cooled masses of the same
rock. Air bubbles are frequent in lavas,
and show in the solidfied rock as holes or
resides. These may at times show the
direction of flow, and sometimes they may
tend to become elongated in the direction
the lava originally moved.

As the flow cools cracks are formed
generally normal to the cooling surface.
These indicate the position of the original
surface long after this has been removed.
As the top or bottom of the flow is usual¬
ly the cooling surface these cracks tend
to develop vertically, and to divide the
rock into columns. These columns are
often very perfect, and are a very com¬
mon feature of solidified lava flows. They
are to be seen par excellence at the Burnic
breakwater, and in the quarry behind it.
where also the fall of the lava over the
former sea bank can be traced in the now
solid rock. Columns are also well de¬
veloped in the Jordan Valley, just north
of Bridgewater, at New Norfolk, just west
of the Derwent Bridge, and in many other
places. If the lava fell into water a cha¬
racteristic form is seen known as “pillow
lava,” the columns being divided by hori¬
zontal ioints. making a form resembling
a pile of square pillars, piled one on top of
the other.

Volcanic Cones.

Seldom does a volcano emit lava ’alone
from its crater. Much water aceompan
ies the magma ns an original constituent,
and much more is collected from surface
soakage. What pressure is released by
the molten lava reaching the surface,
this water converts into steam, and when

the pressure generated by this steam is
greater than the containing pressure of the
liquid lava, an explosion results. During
an eruption these explosions are more or
less constantly occurring in proportion to
the quantities of water present, and the
viseocitv of the lava. This has two re¬
sults, firstly, molten rock, instead of
flowing out of the crater as lava is hurled
in blocks high into the air, and secondly,
the lava itself is broken by smaller ex¬
plosions to an ash or a froth, which in
turn is ejected by larger explosions, and
spread round the country side. Most of
these blocks of disintegrated lava, and
the ashes so ejected fall close to the crater
mouth, and thus in time build up a
mountain, or volcanic cone, at the top of
which is to be found the crater. Most
lava flows are inter-stratified with layers
of ash and scoria (the “lava-froth”). ,
These are very common in Tasmania
around the remnants of ancient volcanos,
and can be found in many places along
both sides of the Derwent and through
the Midlands and along the North U'oast.
Cornelian Bay Cemetery and the recreation
ground at Lindisfarne—to give but two :
examples—consist of beds of volcanic ash ?
and scoria. A cloud often descends the ^
slope of the volcano during an eruption. t
This was once thought to be steam, but -
during the eruption of Mount Pelee such r
a cloud exterminated a whole town. Such
phenomena were then more carefully stud¬
ied, and were found to he in icroseonie frag¬
ments of white-hot lava shattered by ex¬
plosion, and instantly fatal to any form
of life.

Plugs and Necks.

These volcanic cones are usually com¬
posed of loose ash and boulders of bro¬
ken lava, and unless protected by sub¬
sequent lava flows do not long withstand
the attack of the weather. Thus, al¬
though nil the typical volcanos of today
have this form there are few definite
cones preserved from the much greater
eruptions of antiquity. But often lava
wells up through the crater and even¬
tually consolidates there. When the soft
ae 1 * of the cone is washed away this
solid core remains, often as a hill of
considerable height. At Mt. Pelee such
a Plug was pushed many thousands of
feet into the air by the great eruption.

Lava Mountains.

Although lava usually flows like a
molten river, down the nearest valley or
spreads in a sheet over a plain, some¬
times owing to the viscosity through be¬
ing nearly solid when erupted or through
containing minerals that solidify very
quickly (these and their effect will be

( 20 )

1/ H

THE TASMANIAN NATURALIST

discussed later under Petrology), the lava
does not flow or spread, but piles up into
ridges and hills near the crater. Many
of our so-called basaltic hills, as those at
Droughty Point, Bream Creek and round
York Plains appear to have been due to
this. Sometimes solid lava covers, and
so protects, a volcanic cone, at other
times it may partly cover a bed of loose
ash, the portions so covered being pro¬
tected and standing out as ridges and
hills when the unprotected portions are
removed.

Minerals from Volcanos.

Volcanoes seldom possess the requisites
necessary for the formation of minerals
in commercial proportions, but some¬
times large quantities of sulphur are
trapped in a crater or ash bed. Sulphur is
obtained from these sources in New Zea¬
land. Various forms of lime are occa¬
sionally so deposited and are very use¬
ful when found. The great diamond mines
of South Africa are all located in deep
volcanic pipes, anl the intense heat ap¬
pears to have been largely responsible
for the formation of the gems.

Hot Springs.

When water in quantities accompanies
a volcanic eruption, it may reach the sur¬
face in a heated condition, and the exist¬
ence of volcanic activity below the sur¬
face may raise the temperature of ordi¬
nary underground water so that the nor¬
mal spring water is hot.

The especial significance of these ther¬
mal activities is due to the fact that
heated water, often under pressure and
fa:- above boiling point, is able to dis¬
solve minerals from the rocks through
which it travels much more readily than
cold water, and that when it drops in
temperature, on reaching the surface
if. deposits these minerals. We thus get
very pure beds of the various minerals so
deposited, and the wonderful effects
characteristic of a hot spring are so
formed. The pink and white terraces of

Lake Rotomahana, in New Zealand, were
splendid examples of what a hot spring
can build by depositing different layers
of minerals in this way.

At Geilston Bay, in places behind Sand>
Bay, and in Upper Burnett street, West
Hobart, there are traces of existence of
ancient hot springs in the vicinity of Ho¬
bart. In these places there are deposits
of a very pure limestone (travertin), which
shows unmistakable signs of deposition
from a hot spring. In the deposit at
Geilston Bay leaves of trees growing near
have been preserved in the lime water
flowing from the spring.

Hot springs are usually the last phase
ot volcanic activity, and are found when
the actual craters have become extinct,
but the deeper regions of the earth are
stil* sufficiently hot to warm up water
percolating down to them. In periods of
fill’ volcanic activity the water mingles
with the lava and causes steam pockets,
explosions and ash rather than coming to
the surface merely as a hot spring. The
so-called hot spring near the Kimberley
railway station, between Deloraine and
Latrobe, has not had its waters heatql
(75 deg. F. is its usual temperature) by
thermal action, but by the chemical ac¬
tion of decomposing limestone below.

Geysers.

These spectacular phenomena are mere¬
ly perversions of the normal type of hot
spring. When, through a restriction in
the channel, or from another cause, the
column of water forming a hot spring
can become heated at unequal tempera¬
tures throughout its length there is a
possibility of lower parts of this column
of water being converted into steam
which then ejects the water column above
it This column of water is‘known as a
geyser. Hot springs may become geysers,
and active geysers in time usually re¬
move the obstruction which Causes their
existence as such and become hot springs
again.

A. N. Lewis.

( 21 )

THE TASMANIAN NATURALIST

“Some Tasmanian Reptiles”

Snakes are undoubtedly the represen¬
tatives of this division of our fauna to
which most attention is paid by the
casual observer, yet, strange to say, very
little regard is given to their classifi¬
cation, and Tasmania is credited often
with numerous species which it does not
possess.

There are but two classes of snakes* in
Tasmania, the ordinary venomous land
snakes, and the rare (as fa • as our island is
concerned) sea snakes. The number >f
species is very limited, as the land snakes
have but three representatives, whilst
but two species of sen snakes occasional¬
ly wander as far South as the Tasmanian
coast.

There are no harmless snakes in Tas¬
mania, nor have we any tree snakes, py¬
thons or death adders. The three ter-
rcstial Tasmanian snakes

Arc All Poisonous.

but these constitute the sole danger in the
bush. The various species of lizards
which are referred to so often as “death
adders/’ “blood suckers,” or other such
designations, are, in reality, quite harm¬
less. The most evenly distributed, as well
as the most dangerous Tasmanian reptile,
is the tiger snake (Noteehis sentatus).
Care must always be taken when dealing
with the tiger snake, especially in the early
summer, which is the breeding season. This
species, as with others, shows very con¬
siderable variation as regards coloration,
and the various vernacular designations
which have been given to the color varie¬
ties has tended to confuse matters. For
instance, bush dwellers usually refer to
the dark colored snakes as black snakes,
and the lighter forms as carpet snakes.
Both terms are incorrect, as neither the
true black snake, which has paired >-au-
dals, nor the true carpet snake, occur in
Tasmania. The typical tiger snake has the
body scales in 15 to 18 rows, ventral
plates 150 or more, and the sub caudals
which are entire, 40 to 60. The central
scale^ on the head

Is Shield Shaped.

almost as broad as long. This feature
alone immediately distinguishes it from
the other species. In the typically mark¬
ed specimens the body color is golden
brown, crossed by almost 50 bands of dark
brown. The average length is 5 feet, and
there is one specimen in the Tasmanian

Museum which measures no less than 6
feet inches.

The only other Tas .anian snake which
ur. all approaches the t.ger snake in size
7a the superb snake (Denisonia superbar
This species is also known as the copper
headed snake, the large scaled snake, and
the diamond snake. The last designation
ta totally incorrect, as the true diamond
snake is a python and a variety of the
carpet snake which (loci not occur in
Tasmania. In the superb snake the cen¬
tral shield in tho head is approximately
twice as long as broad. The color varies
from black to reddish brown, whilst the
average length is from three to five feet,

As regards the color of the Tasmanian
snakes in general, it is parri mUrly ne¬
cessary to remember that this shows
great variation. For instance although

A Typical Tiger Snake

is golden brown on the body, crossed by
bands of dark brown, yet they are occa¬
sionally met with almost black, or even
in sandy country almost white, and the
superb snake, although lacking the band¬
ed coloration, has similar changes as re¬
gards the general color.

The third land snake is the small white-
lipped whip snake, which can be immedi¬
ately identified owing to the white mark¬
ings on its lips, and the central scale
of the head, which is thee finite? as long
as broad. The whip snake is plentiful-
ay distributed over Tasmania* and is
found not only near the sea shore, but
also particularly plentiful on the moun¬
tain summits.

The two sea snakes which occasionally
teach Tasmanian waters are the wander¬
ing sea snake, a species which grows to
about 3ft. in length, having a body col¬
oring of olive and a number of encircl¬
ing black rings; and the

Spotted-tailed Sea Sanke,

in which the scales are laid edge to edge
and which is black above and yellow
below, eho tail being yellow, spotted
with black.

A Stray Turtle.

There is another representative which
is grouped in the reptilian class, although
of quite distinct order, namely, the leath¬
ery turtle, which is occasionally met
with in Tasmanian waters; but it is only
on very rare occasions that it is found
so far south, and as the whole turtle

< 22 )

THE TASMANIAN NATURALIST

group is but a relic of a bygone fauna,
such visitors tend to be less and less in
the progress of the years.

Lizards and the Harmless Dragon.

Returning to the land fauna, there
are some interesting examples amongst
the numerous lizards which occur in the
island. For instance, the several moun¬
tain dragons which are commonly met
with under rocks, etc., especially on the
hillsides. These interesting little ani¬
mals, which are repulsive-looking in
some ways.

Are Quite Harmless,

although generally credited with being
dangerous “blood-suckers,” and numbers
are often killed by those who do not un¬
derstand the true place of these lizards

in the scheme of Nature. There are aho
the several rock lizards occasionally re¬
ferred to as “death adders,” and credit¬
ed with being possessed of many poison¬
ous qualities, which they do not have.

Two species >f the large blue-tongued
lizard are met with in Tasmania, and
they are often referred to as “goannas”
or ‘iguanas,” but such designations are
misleading, as iguanas are much larger
reptiles, of a different character, and
which occur on the mainland.

In addition to the foregoing there arc
a large number of species of the small
lizards, which occur in such numbers,
not only in the bush, but in suburban
gardens. Most of these lack vernacular
designations, although they have natur¬
ally been duly classified .with regard to
their scientific titles.

Clive Lord.

Section 10.

The Attack °f the Weather

In the previous sections we have seen
how masses of the earth’s crust may be
raised above the general level, and so
form land and how these masses may
be added to But immediately a section
of land appears above (he level of the
ocean and even before it is attacked by
various processes which modify the ef¬
fect of the building influences, impose
the details of topography on the land¬
scape and generally tend to level the
surface of the country. Indeed, they
arc at work long before the building
processes are complete. The more pro¬
nounced the building movements and
the greater the elevation given to the
landscape by them the greater the
powr of the levelling agents; so wher¬
ever these agents have been at work
for long the bolder futures imparted by
(he building movements have to be level¬
led to rolling plains. This genera! level¬
ling of the surface of the landscape is
spoken of as erosion.

Agents of Erosion.

The agents by which erosion may wear
away the rocks of the surface of the
earth may be grouped under three main
heads: —

(a) The weather.

(b) Water.

(c) Life.

The effect of the various agents in
these groups to some extent overlap.
For example, it is difficult to fix a point
where rain ceases to have the erosive
effects peculiar to the weather, and to

attain these grouped under the heading
“running water.” Again, the weather
may so effort running water as to turn
it into a flow of ice which presents very
different characteristics. Also life de¬
pends directly on climate, and the ab
sence or otherwise of the erosive form .
due to life may be considered a sub-divi¬
sion of the heading “weather.”

The Weather.

Under this heading we group the ef
feet that (1) The atmosphere; (2)
changes of temperature: (3) frost; and
(4) wind have on the landscape.

The weather effects all portions of the
earth's surface. While a river may pre¬
sent more visible evidence of the work
it i s doing in wearing down the country
side, its work is confined largely to its
channel; but the weather is at work
always. Night and day it is slowly, but
certainly, disrupting the rocks of the
earth’s crust. Naturally this effect is
more powerful on the summits of high
mountains, or on exposed rock faces, but
it penetrates everywhere, and no depth
of soil or covering of vegetation is a com
plete protection. Also the weather very
materially assists the other agencies.

Air.

The air has very little erosive effect
of itself. If the atmosphere contained
throughout the year relatively the same
degree of moisture, varied little in tem¬
perature, and was comparatively still,
it would scarcely affect the rocks at all

( 23 )

THE TASMANIAN NATURALIST

But no region with a climate absolute¬
ly so constituted exists. It is only as
the bearer of moisture and the vehicle
of change of temperature and varying
air current-s or winds that the air is of
importance in this regard. The chemi
cal effect on the rocks i s considerable,
but this is only possible through the
agency of water, and will be discussed
in the next section.

Changes of Temperature.

In most parts of the world the change
of the average temperature during the
year is considerable, and there is also
an even greater change in between the
day and the night temperature. In fact
only those portions of the globe which
are permanently under ice escape the ef¬
fects of this change. When the tem¬
perature is high, the particles constitut
ing the rocks or soil expand, and when
it drops they contract. This, although
slight, is regular and the mechanical
effect is very powerful. It tends to
loosen the grains in the cementing ma¬
terial which binds them together, or to
disrupt the particles themselves. It
subjects the rocks to a series of tiny
strains which, as the process continues
develops into cracks which present a
weakness for water, frost and wind to
act on.

This process is the most active agent of
erosion in the desert portion of Austra¬
lia, where the temperature often rises
from nearly freezing to over lOOdeg. F. in
an hour after sunrise. And it must be
remembered that it is the direct rays of
the sun that beat on the rocks, and that
tlie action is again increased by the fact
tliat rocks diffuse heat more quickly than
the atmosphere does. In Tasmania the
.action of this agency is obscured by the
action of frost, with us a much more
powerful erosive; but on a hot summer’s
day the bare rocks of our mountain tops
become unpleasantly hot, and the tem¬
perature there falls to the vicinity of
freezing point within a few hours of sun¬
set.

FROST.

When the change of temperature ex¬
tends to its maximum range the lower limit
descends below freezing point. Then, as
well as the mechanical effect of the ex¬
panding and contracting rock particles,
another agent of erosion comes into play.
Water percolating through the rock is
frozen as the temperature drops below
freezing noint, and is thus made to ex¬
pand. This tears the rock grains apart,
and widens and looseus joints and cracks.
Hie power of ice is very considerable, and
no rock can resist it. Its effect, is, of
course, felt very slowly, but it is very

sure. When the ice thaws again, the
joints and cracks are left open for more
water to accumulate, and the ice, after
each succeeding freeze, has greater power,
until it finally tears the particles apart.

Frost makes its effect felt all over
Tasmania during some parts of the year.
Its maximum work is done in places where
water freezes every night, and thaws again
next day. This occurs for about nine
months of the year on our higher moun¬
tain tops. It also occurred around the
edge of the ancient glaciers, and its effect
there will be discussed at greater length
later.

On most of our mountains capped with
diabase, water has entered the joints
which traverse the rock vertically, and the
regular effect of frost has been to tear
this solid rock in blocks from the parent
mass, and split it off in great columns.
Near the edge of the top of the moun¬
tain these appear as “organ pipes, and
on the tops of the ridges as accumulations
of boulders usually referred to as “Plough¬
ed Fields/' Anyone familiar with our
mountain tons knows this tyne of coun¬
try only too well, and its peculiar fea¬
tures are due almost entirely to the action
of frost on a rock with regular, vertical
points, in which the water can accumulate.

The summit of Mt. La Perouse is cov¬
ered with sandstone, which frost has
flaked into broad, flat slabs no thicker
than a school slate, and which now lie
over the whole surface of the mountain.
Many quartzite mountains of the West
have had the rock of their tops broken
into tiny sharp chips like the chipped
marble often spread over graves. Several
mountain tops around Cradle Mountain
are covered with this. Frost is the re¬
sponsible agent.

Frost is active to a lesser extent in the
lower country, but is always at work dur¬
ing the winter months on every exposed
rock surface.

WIND.

Wind drives particles of rock separat¬
ed from the mass against other portions
of still solid rock. These have a power¬
ful erosive effect. This is very noticeable
in desert country, where the wind-blown
sand carves typical forms from protrud¬
ing beds of rock. These are identifiable,
ns they could not hare originated in any
other wav. They often assume fantastic
figures. In Tasmania we have many ex-
nmrdes of this weathering Tts greatest
effects are to be seen on rljff faces. Most
of the small caves above high-water mark
round the coasts and the numerous caves
in the sandstone and mudstone cliffs in¬
common in the sandstone cliffs on the

( 24 )

THE TASMANIAN NATURALIST

land are due to wind. These caves are
slopes of Mount Wellington, on the moun¬
tains on the east of the Derwent, and
throughout the Midlands. On the floor
of caves formed by wind is usually found
a deposit of line particles worn from the
rock from which the cave has been weath¬
ered, and the way the wind attacks the

soft layers in a cliff face is most notice¬
able.

The effect of wind seen thus to its great¬
est advantage on cliff faces is also pre¬
sent wherever a bare face of rock is ex¬
posed to alternating or even to regular
breezes.

A. N. Lewis.

Some Tasmanian Parrots

Parrots are always interesting, even
to those who take very little interest in
bird life. Their usually bright colora¬
tion makes them conspicuous, and as
they make good ease birds they are often
kept as pets. Their paired feet and
stout bills are characteristic of the whole
parrot order. Specimens of one species
or another are to be met with in most
parts of Tasmania, although with the ad¬
vance of settlement certain of the more
terrestrial species are becoming rare.

Amidst the tall timber of the moun¬
tains the piercing notes of the black or
white cockatoo often may be heard,
whilst amidst the smaller timber the
green parrot is common. Amidst the
more open timbered plains tlie brightly-
colored rose IIas are common, whilst the
brush-tongued parrots or lorikeets often
are to be seen in flocks in the flowering
eucalypts.

Three species of lorikeets, or brush-
tongued parrots are met with in Tas¬
mania, the most conspicuous of these
beinf the rainbow lorikeet, which has its
head, throat, and abdomen blue, chest
red, whilst the upper plumage is green.
'I his species is to be met with usually
in flocks, particularly among

The Tall, Flowering Eucarypis.

Tlie birds are very fast fliers, and cover
large areas of country in search of food.

The commonest lorikeet in Tasmania
is the musk lorikeet. The general color
of this species is green, whilst the fore¬
head is red and there is a distinctive
red streak behind the eye, which, to¬
gether with the pronounced yellowish
patch on each side of the lower breast,
serve as distinctive features. This lori¬
keet is noted, not only for its loud
screeching amidst the eucalypt blossom,
but also for its excursions into the orch¬
ard and gardens of the cities. The
smallest bruRh-tougued lorikeet found in
Tasmania is the little lorikeet, which in

bow. it is the smallest of the purely
size is only about half that of the rain-
Australian family loridae. The red col-
oiatiou of the forehead and sides of the
lace, the absence of the red streak be¬
ll iml the eye, and the general small size
oi the bird, form easy points for iden¬
tification.

As a contrast to the foregoing small
example, the black cockatoo may be
mentioned, as it is the largest of the
Psittaciformes, and is well distributed
over the island. The identification is
easy, owing to its large size, general
black plumage, with the yellow ear cov¬
erts and the distinctive yellow band on
the tail .fl This species is particularly

Fond of White Grubs,

which are to be found in decaying wood,
or under the bark of their trees. With
the aid of its very powerful bill the
black cockatoo can tear open the dead
bark, or make a veritable burrow into
decaying beech (the so-called “myrtle*')
logs.

The gang gang cockatoo has a plum¬
age of slate grey, whilst the male has a
prominent red crest. It is seldom notic¬
ed in Tasmania, but it is common ou
King Island. The white cockatoo <f
pure white plumage, but. with a distinc¬
tive yellow' crest, is found in many parts
of the country. This cockatoo is very
intelligent, and when a flock descends in
a fanner's grain paddock a sentinel is
usually posted to warn if danger ap¬
proaches. This sentinel is relieved at
regular intervals.

The galah, or rose-breasted cockatoo,
was not noticed in Tasmania until recent
years, but as several small flocks have
escaped from captivity they will probably
increase in numbers.

There is but one record of the occur¬
rence of the cockatoo parrot (a small
brown form with a prominent crest), and
this bird was probably an escapee.

( 25 )

THE TASMANIAN NATURALIST

One of the

Best Known Specimens

in Tasmania is the green parrot, or green
rosella, which is also known as the moun¬
tain parrot. The general color of this
species is green, the forehead red, cheeks
blue, with the under parts yellowish
This species is confined to Tasmania,
where it is fairly common, particularly
amidst the smaller eucalypts which fringe
the larger forests. It is also met with
high up oil the mountain, for which rea¬
son it has obtained one of its common
vernacular names.

Another well-known species is the white-
cheeked rosella, the distinctive plumage
of which serves to immediately identify
the bird which is to be met with throng-
out Tasmania wherever conditions ui.j
suitable. On King Island there is an ad¬
ditional form, the Crimson rosella.

Two very interesting green parrots or
parakeets occur in the island, the blue¬
winged, which is widely distributed, and
the orange-breasted both of which occur
here. The former species can be recognis¬
ed by the blue band on forehead, blue
wing, and the entire greenish yellow color
of the under surface; whilst the orange-
breasted species has under surface of an
orange yellow with distinctive orange mark¬
ings, the upper plumage is green, whilst
there are blue markings on the wing and
forehead. The frontal hand of this
species is usually much paler than in the

blue-winged form, and serves as an easy
distinguishing mark apart from other con¬
siderations. As with all forms which fre¬
quent the ground'these species are feel¬
ing the extension of settlement and arc
much rarer than formerly.

One form of the parrot tribe, concern¬
ing which there has been much discus¬
sion with regard to its exact classifica¬
tion in tlie family group, is the Swift par-
lot. This species is often found in com¬
pany with the lorikeets, which it resembles
greatly in some general respects. Swift
parrots can be distinguished by the

Swiftness of Their Flight,

the red forehead and throat and the blue
on the crown of the head. In certain
years this species is to he found in great
numbers in some districts, but they are a
semi-migratory form and appear to travel
large distances.

The final representative of the parrot or¬
der in Tasmania is the interesting ground
parrot which is a purely terrestial spe¬
cies now becoming rare on account of its
numerous enemies, more particularly in¬
troduced cats which take such a heavy
toll of our bird life in general. The
ground parrot can be easily recognised by
its distinctive plumage which is green
barred black and gold. This interesting
form has always been of interest to natu¬
ralists. It was first described in 1702.
The French exnedition which visited Tas¬
mania in 1703 fully described this interest¬
ing form, and published illustrations of it.

Clive Lord.

’ £ Some Notes

The ordinary naturalist has not many
opportunities to study these gigantic ce¬
taceans. Possibly, during the course of
his sea voyages, lie may have seen them
at a distance. A few skeletons have
been noticed in museums, and if by chance
one* has been observed stranded on the
shore, especially if it has been there some
time, the average person is only too anxi¬
ous to get as far away as possible. Whales
are. therefore, rather difficult to study.
They cannot, as a class, be handled and
examined such as butterflies, or even
birds.

Nevertheless, whales are of great in¬
terest, and many facts have yet to be
leaned concerning not only their habits,
lit more especially the part which they
play in the evolutionary trend of animal
life in general. One question which is
of interest to naturalists has been the
elucidating of the problem concerning

on Whales ”

the animals from which whales evolved.
It must be remembered that a whale is
a true mammal, and not a fish as it is
sometimes termed. Many consider that
whales originated from one of

The Most Primitive Families
of the Carnivora, but their aquatic habits
throughout untold generations have entire¬
ly changed these animals so much in
character that a vast amount of pains¬
taking research has been necessary in or¬
der to gain the knowledge which is pos¬
sessed by the world today, and a very
great deal yet needs to be done in this
as in other branches of science.

Whales have become essentially adapted
j’or an aquatic existence. The tail has
become tlie main means of locomotion,
whilst the hind limbs have practically
disappeared, although vestiges are found
in certain species, whilst the fore-limbs
have been reduced to mere paddles.

( 26 )

THE TASMANIAN NATURALIST

Life in the water and the resultant con¬
stant pressure on the head, together yith
the fact that tue head is held practically
motionless while swimming, has had a
modifying effect upon the skull and the
neck bones of the wlmle. As with all
mammals with one or two minor excep¬
tions the neck bones, or cervicle verte¬
brae, are seven in number, and they be¬
come compressed to such an extent that
they are proportionately shorter than in
any other animal, and in some species the
majority are fused together.

To describe the changes which have
taken place in the Cetacean skull would
entail the use of more time and more
technical language than is possible in the
present instance; but, nevertheless, the
subject of the various changes is a study of
great interest.

To turn to more general matters the fact
m iy be recalled that whales generally

Are Remarkably Uniform

in shape, although they vary in size; in
fact, the first essential of a whale is like
the snake, to be large whenever the matter
is discussed without undue attention to
scientific accuracy. The giant of the
ocean—the Blue Whale—may reach 100
feet m length.

As regards the classification of whales
they naturally fall into two sub-orders—
the whale-bone whales (Mystacoceti) and
the toothed whales (Odonticeti) the latter
including the dolphin family.

The whalebone whales (Mystacoceti)
are naturally the more valuable group
commercially. Owing to the cosmopoli¬
tan nature of the Cetacean order as a
whole it is a matter of difficulty to say
with any degree of certainty exactly which
species occur in Tasmanian waters.

The origin of whalebone obtained from
whales is often misunderstood. This is
not “bone” in the true sense of the word,
but is evolved from the hard palate.
Owing to this wonderful structure the
teeth have atrophied, and in certain whales
have become rudimentary, and only ap¬
pear in early life. As these early teeth
degenerate they are replaced by long tri¬
angular -plates of whalebone, set at an
angle, and frayed on the inner side of the
jaw. This arrangement allows the whale
to progress through the water and sieve
out the small animalculae, commonly call¬
ed the whale food of “Brit,” upon which
these huge creatures feed. The animal
elevates the tongue, and thus drains off
the liquid through the plates of whalebone,
the fringes cut out of the inner edges
retaining the essential portions of the
whale's diet, after which the mouth is
closed, and the food swallowed.

The toothed whale (Odontoceti) are
by far the larger group, and the division
contains forms ranging from the
Huge Sperm Whale

to the small dolphins. An interesting
fact is that the skull of the toothed whales
is always more or less asymetrical.

The beaked whales (Ziphidae) form an
interesting group of the toothed whales.
Such forms as Hvperodon Mesoplodon and
Ziphius occur in Tasmanian waters, but
they are seldom obtained, and there is not
a great deal known about them.

The family J)elphi»idae, includes the
fierce “killers" and the smaller dolphins.
The latter are usually called “porpoises” by
Tasmanian fishermen, but they are, strictly
speaking, dolphins. The dolphins can
be distinguished by the deep grooves on
the palatal surface of the maxillaries, and
by the larger number of teeth.

Clive Lord.

Section 11.

Erosion by Running Water

Tn the last section we showed how the
weather is continually at work breaking
down the rocks of the surface of the
world. A far more important agent in
the process of levelling: the landscape is
running water. The action of the wea¬
ther merges into that of runnig water,
for which rain falls in any quantity the
surface soil cannot absorb it all, and
some runs a greater or less distance over
the surface, and even portion of the
water that soaks into the soil or rocks
emerges at a lower level to run in
streams over the surface. While the wea¬
ther is at all times engaged in wearing

away exposed surfaces, water only affects
certain restricted channels; but the re¬
sult is far stronger and pogsc.9ses much
greater power than the slow effect of
the weather. So much so that frequently
the result of a single shower is apparent.
The effect of the weather may be

Compared to Decay.

whilst that of running water resembles
wear, and is often referred to as “abra¬
sion.” The weather affects the whole
surface similarly if with differing inten¬
sity; but running water affects the land¬
scape in an almost infinite varieties of

( 27 )

THE TASMANIAN NATURALIST

ways, and so must be dealt with at
greater length, alth ugh here only the
broad principles can be referred to. It
is difficult to give particular examples
here because they exist everywhere- In
a day’s walk along any river, creek, or
natural rainwater channel, all the fea¬
tures here described may be seen.

Mechanism of Stream Erosion.

As soon as water commences to flow
over the surface of the earth, either
after a fall of rain or from a spring, it
starts to wear away portion of the sur¬
face. Its work is seen as the excavation
of its channel. In the earlier stages
such runnels form only after a shower.
The weight of the water removes par¬
ticles of loose sr.i! and carries them with
it down the slope, until its power is
checked by the exhaustion of the sup¬
ply or by the disappearance of slope suffi¬
cient to enable it to obtain momentum
The many trickles towards the top or a
slope will one by one unite, and thus
gain greater volume and hence power un¬
til finally a permanent stream grows
from innumerable small runnels. The
stream carries out its own function in
the erosion process, as will be explained,
but it is only the result of many stream¬
lets, and is only working in the lower
portion of a larger valley. The tiny tri¬
butaries erode the sides and the head
of the main valley, and do the real work
of removing the bulk of the landscape.
The amount they can perform depends
on (1) the volume of water; (2) the slope;
and (3) the hardness of the rocks.

The Volume of Water.

It is obvious that if the nrst motive
power possessed by the streamlet is its
own weight, then as the weight of water
running over the surface increases so
will its erosive effect increase, and the
streamlet with the most water will wear
out the larger channel. But mere vol¬
ume of water, except in the first in¬
stance, has very little effect of itself. It
must be realised that pure water nas
little power to wear away rock; its power
is given by the particles it carries with
it, in much the same way that the patter
portion of a piece of sandpaper has
little use in smoothing a piece of wood,
but merely carries the grains of emery
which tear away the fibres of the wood.
Tn both eases the naper and the water
only carry the sand grains which do c.
real work.

But, taking the simple case of a rain¬
water channel formed in soil after a
shower, the greater the volume of water
the greater tjie weight of soil which it
can move down the slope. This gives

the stream its first start, and until the
soil and broken surface rock are re¬
moved volume alone is all that is required
to wear out a channel. And it is this
tiny streamlet formed after a passing
shower that is the moet active and per¬
sistent of all the factors that are en¬
gaged in levelling the landscape. The
work of ouc is slight, but there are so
many, and they are so readily formed,
and are at work so universally that they
are continually Washing the loose mate¬
rial separated by the action of the wea¬
ther from the surface of the hills down
to the valleys from which places the
streams remove it.

In this early stage the volume of water
usually depends on the amount of ram
falling in a given time. The heavier the
shower, the less of it the soil can ab-
soib, and the more it has to run down
the hill side. Also the more frequent
the showers the more frequently will-
water run in the courses of the stream¬
lets.

The Slope.

Water, of course, can only move when
there is a certain slope, and it requires
no mental effort to realise that the steep
ev the slope the greater the speed with
which the water will run, and hence
its greater erosive and transporting
power. If the rate of How of a stream
is doubled, the weight of material it
can ear 13 increases to times. So

while rain fulling on level ground either
sinks into the soil or lies as stationary
pools, and has little mechanical effect
on the landscape, rain which mils on a
hillside in any quantities scours chan¬
nels in the soil, which vary in size with
the slope of the hill. In their earliest
stages these rain water streams merely
carry off as much soil as the volume of
water, and by the velocity imported by
slope gives them capacity. But if the
process is at all regular, the surface
soil is soon removed from their channels,
and they commence to wear away the
solid rock below.

Hardness of the Rocks.

Now the third factor comes into play.
Naturally the softer the. rock the easier
this work will be. In the case of a
sandstone, for example, the streamlet
will in a short time erode a consider¬
able channel, but if the rock is a com¬
pact,- igneous mass it will have very lit¬
tle effect. Where a piece of country
contains small areas of rocks, varying
in hardness, the streams will wear deep,
and broad channels in the softer ones,
and gradually divert the fallen rain from
the areas of harder rock, which will m
time be left ns ridges and spurs. Thus

( 28 )

THE TASMANIAN NATURALIST

we see so many of the hills and spurs
of our hilly^ country capped with the
hard rock diabase — these portions being
more elevated simply by the removal of
softer beds of rock surrounding them.

Rain Water Channels.

When the area drained by any given
watercourse is large enough, a stream
will be formed that is perennial, and
not dependent merely on a passing
shower; but it is the small rain water
runnels that largely build up the stream.
The stream with its greater regularity
and power develops special characteris¬
tics, but it must be borne in mind that
it is only at work in its own channel at
the bottom of a valley. In the course
of time these valleys work further ami
further into the tableland, whence they
rise, and are continually widening their
own valleys. This headward and lateral
u erosion is the most powerful agent at
work levelling the landscape, and this
work is accomplished, as has been ex-
[- plained, by the rain water channels
: worn by the water from each shower
*' that cannot be absorbed where it falls.

■ These channels, therefore, must he put
first as the most active agents of ero¬

sion. Much of the erosive mechanism
of streams and rivers, to be described
next, can be traced in these small wa¬
tercourses, and all the features present¬
ed by a great river may often be seen
within a few yards along the course of
one of these rain channels.

Vegetation Control of Erosion.

We have explained that the most pow¬
erful agent at work reducing the land¬
scape to a level rounded topography was
the number of tiny runnels and storm¬
water streamlets formed after rain at
the heads and sides of the main streams.
It is appropriate here to notice a very
important modification given to the

natural action of these streamlets by the
hand of man. Left to themselves, these
storm water gutters very soon erode
away the side of the hill, until a slope
is attained over which water can just

flow.

As explained before, if the slope is
greater than this, the power of the
streams is increased enormously, and

hence they very soon reduce the slope

to a gentle grade.

A. N. Lewis.

(To be Continued.)

i

( 29 )

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