10 
of the regular tropical rains, which do not seem 
to extend their influence further south ; and 
this, combined with the level sandy nature of 
the surface, sufficiently explains why the water 
courses descending into the interior never attain 
any considerable magnitude or importance. 
The upper stratum of rock forming this level 
tract is a ferruginous sandstone, the superficial 
beds of which are formed by the aggregation of 
small concretionary masses, which are easily 
separated, and form an ironstone gravel, which 
is remarkably frequent on the western coast, 
gradually diminishing to the eastward. This 
rests on a coarse sandstone, varying from 50 to 
300 feet in thickness. 
The decomposition of this rock has covered 
its surface with sand of a red colour, and the 
whole country would have been one vast tract 
of desert had not the continued action of cur- 
rents of water excavated immense valleys, and 
thereby exposed the lower rocks. 
Immediately below the sandstone, thick beds 
of soft shale exist, and these so readily decom- 
pose into soft clay that when once exposed to 
the action of the weather, by the removal of the 
superincumbent sandstone, the whole bed is 
quickly washed away by the heavy tropical rains, 
leaving many isolated portions which, being still 
protected by portions of the superincumbent 
sandstone, form hills with steep sides and flat 
summits surrounded by low cliffs, giving a re- 
markably regular and monotonous outline 
to the features of the country throughout the 
whole tract where these rocks prevail. 
Beneath the shales, beds of chert, passing into 
silicious limestone, were observed wherever the 
upper beds were removed. But though lime- 
stones are usually rich in fossil remains, I was 
unable to detect any which would afford a clue 
to the relative age of this rock. Near the Gulf 
of Carpentaria, it approaches so closely in 
character to the celebrated lithographic lime- 
stone used for printing, that there can be little 
doubt that it is equal to that procured from the 
German quarries. 
The strata of this limestone are nearly hori- 
zontal, but not always quite conformable with 
the upper sandstones, and in the valley of the 
Victoria River it rests on, or passes into a hard 
jasper rock, veined with red and white, capable 
of receiving a high polish. 
The next rock in the descending series is a 
hard white sandstone, of so compact and even 
texture as to almost resemble quartz. The 
stratification is so indistinct that it is scarcely 
possible to ascertain the dip of the beds, but it 
seems to rise unconformably through the upper 
rocks, and forms low ridges of a very rugged 
character. No fossils were observed, but veins 
of sulphate of pyrites were -very frequent. 
Basalt is largely developed in the valleys of 
the upper part of the Victoria River ; it also 
appears at the head of Sturt’s Creek which flows 
into the desert interior, and on the Raper 
River, on the shores of the Gulf of Carpentaria. 
There are also small tracts of basalt along the 
edge of the table land towards the Gulf, but not 
forming very important features of the country. 
The relative age of this rock is distinctly re- 
ferable to the period immediately preceding the 
deposition of the highest beds of the upper 
sandstones, as it is often exposed as interstrati- 
fied. The lower beds, much altered by the 
contact of the melted rock and those above, 
shew traces of being partly derived from the de- 
composition of the basalt. 
The beds of Basaltic Rock are nearly hori- 
zontal, and the general form of the surface of the 
country does not indicate any great change since 
the fluid rock filled the valleys. 
No trace of slates or schistoze rock of any kind 
was observed, and in three isolated cases where 
granite was exposed it was in immediate contact 
with sandstone. 
After travelling over nearly 1000 miles of the 
table land just described, the extreme monotony 
of feature is suddenly intercepted at the 143rd 
meridian, and the eastern division of tropical 
Australia being entered, the boundless plains 
and sandy deserts are exchanged for bold ranges 
of hills of granite, slate, porphyry, and trap 
rocks, in the relative positions of which the 
effect of great disturbance is everywhere 
evident, but the limits of this paper will not 
admit of more than a general view of their 
geological arrangement. 
The ranges of hills are nearly north and 
south, the western acclivity is usually easy and 
the eastern slope abrupt, while each succeeding 
range as we proceed eastward rises to a greater 
elevation ; thus the range between the head of 
the Lynd River and the Gulf of Carpentaria is 
2500 feet above the sea level, that between the 
Lynd and Burdekin Rivers or the watershed 
line is nearly 3000, while some of the ranges on 
the east coast are 5000 feet in elevation, forming 
the boldest features of the Australian coast. 
Granite, though frequent, especially on the 
eastern slopes, is not so largely developed as the 
superincumbent slates, which are so much dis- 
turbed that it is scarcely possible to generalize 
the dip of their strata. 
These slates are very variable in character, 
some parts a fine blue roofing slate with even 
and fine cleavage, while in other parts it assumes 
more the appearance of a sandstone rock inter- 
sected in all directions by thin veins of quartz. 
Interstratified with the slate there are thick 
beds of quartz, which sometimes form small 
hills, but it is not a rock favourable to the de- 
velopment of metallic minerals, such as gold, 
silver, or copper, for though to the general ob- 
server there is no difference in the appearance 
of bed and vein quartz, they are geologically 
totally distinct, the latter being the description 
which accompanies the gold of Victoria and 
New South Wales. 
Vast masses of porphyry have been erupted 
through the slate, and this rock frequently con- 
tains fragments of granite and slate embedded 
in it, clearly indicating a more recent date than 
either of the rocks of which it contains the 
