25 
pressure, without any movement in the mass taking place on cooling, they still 
retained their bedded character, although changed into granitic or schistose rocks, 
whilst any limestone beds were changed into marble, and coal into graphite 
(plumbago). 
During this cooling, or at a subsequent period, cracks and fissures were formed, 
into which thermal water found its way, depositing the mineral matter it held in 
solution on the sides of the fissure in layers, which would cause the banded 
appearance which is so commonly met with in veins, filling it by degrees in the 
same manner in which water heavily charged with lime gradually chokes up a pipe. 
Veins are fissures or faults which have been infilled by mineral matter in 
solution, either from small cross fissures and leaders, or directly, when the strata 
is pervious, from the side of the vein itself, which has been mostly the case in this 
colony, where, as a rule, the reefs have one good wall coated with a greasy impervious 
casing, whilst on the other side the country is much broken, and many small veins 
and leaders or feeders strike away from it into the country, the rock on this side 
being as a rule more pervious. 
In what state the metals were held in solution it is impossible to say, as we 
have no means of experimenting with them at the enormous temperature, and 
under the tremendous pressure that existed when they were deposited; but it is 
highly probable that they were in the form of double sulphides, whilst the silica 
was probably in the form of soluble sodic silicate. 
Although mineral veins occur mostly amongst the older rocks, metal occurs in 
minute quantities throughout the whole geological series, and water in some places 
contains an appreciable quantity of them in solution. It was upon this fact that 
the theory of the lateral infilling of mineral veins was based, as previously their 
presence could only be accounted for by the theory that all lodes were filled from 
below, the vein stuff being thrown up in a molten state. But now that we know 
that they are all soluble under certain conditions, it is very probable that higlily- 
bcated water, charged with certain salts, would dissolve the metals from out of 
the rock through which it passed, depositing them in the fissures. 
GEOLOGY OF THE COLONY. 
Hitherto it has generally been imagined that the formations to be found in 
Western Australia were limited iu number, and that the rocks mostly were either 
granite or sand; but that this was quite erroneous will be seen by examining the 
table of strata given below, which shows the various formations now known, and 
which will probably be much extended when all the country has been thoroughly 
examined. 
Table op Geological Formations. 
.s 
6 
£ <! 
o* 
Recent ( Holocene ) 
Pleistocene. 
Pliocene. 
Miocene. 
Eocene. 
Sedimentary. 
f Alluvium of lake basins and river valleys, river 
gravels, estuarine deposits, gypsum and salt 
bods, sand dunes, sand plains, raised beaches 
and shell marls and gravels, brick earth, man¬ 
grove swamps, ferruginous sandstones, nodular 
claystoncs, and clay, &e. 
f Ancient river gravels and lake beds. 
< Lower estuarine deposits, shelly limestones and 
( sandstones of the coast. 
/ <c Pindan 55 sands and gravels (often cemented 
\ by oxide of iron), gravel and ironstone. 
1 Ferruginous sandstones and variegated clays, 
( with beds of lignite. 
Not known. 
r Coralline and chalky limestones with flints, 
} calcareous 
( grits. 
and ferruginous sandstones and 
