28th September (Sunday).
Walked out from the camp to a low hill about one mile south-south-east.
It was composed of granite at the base and capped with horizontal strata
of sandstone, some of the beds containing large water-worn pebbles, and
the superstratum highly ferruginous. To the south-west of this hill the
rock was slate, the strata nearly vertical; the strike north and south,
but much contorted, and large pebbles of porphyry, quartz, slate,
granite, sandstone, and agate formed banks in the bed of the river. The
country, as seen from the hill, was generally level in appearance, but
consisted of numerous low ridges and detached hills of granite, with
sandstone on the summits. The valley of the river extended to the east
and south, and a large branch appeared to join from the south about ten
miles lower down, as a valley and some ranges of hills trended in that
direction. The whole face of the country had an arid and desolate aspect,
as there were no large trees except along the principal watercourses, and
many of the hills appeared destitute of any other vegetation besides
small acacias and scrub trees, the bare rock showing through its scanty
covering.
29th September.
At 7.15 a.m. again steered east up the river, the country level and
timbered with stringybark, box, bloodwood, leguminous ironbark, and rusty
gum; the soil a red sandy loam, thinly grassed; at 10.30 a.m. came to low
hills and ridges of granite and porphyry, timbered with box, leguminous
ironbark, terminalia, and the grass somewhat improved. Altered the course
at 11.0 a.m. to the south to close in with the river; but after crossing
a great number of dry watercourses, and even steering west, only reached
the bank of the river at sunset. The channel was dry, and all the
vegetation had disappeared, only a barren waste of coarse sand and gravel
180 yards wide, with bare rocky banks, showed that it had once been a
running stream. A few small hollows in the rocks retained water from the
late rain, but not sufficient for our horses, and though we found a small
pool in the sand, it was insufficient for the supply of the party.
Encamped at 6.0 p.m. The geological structure of this portion of the
country is wholly dissimilar to any other part of North Australia we have
yet traversed. Granite, porphyry, and slate are the prevailing rocks. The
whole appear to have been subjected to considerable disturbance, as the
slate is much broken and contorted, and in several parts altered by
contact with the porphyry, and no definite strike or dip appeared to
exist. The porphyry is of a red-brown colour, consisting of grey paste
with crystal of felspar and angular fragments of slate and granite
sometimes one foot in length. The granite contains little mica, and the
quartz frequently is arranged in rhomboidal crystals nearly parallel to
each other; it readily decomposes, and from the predominance of quartz
forms a coarse gritty soil. Quartz-rock forms large beds and veins in the
granite, and has a general trend north and south. It often contains
crystals of mica, and therefore not likely to contain metals. In washing
the sand of the river near Camp 83, only a small quantity of titaniferous
iron remained after the removal of the quartz and mica. It was in this
locality that the Gilbert Gold Field was afterwards discovered.
Latitude by e Pegasi 18 degrees 25 minutes 33 seconds.
30th September.
Moved the camp about one mile higher up the river to some small pools of
water, and then with Mr. H. Gregory ascended the hills to the south of
the camp. From the highest ridge the course of the river was visible for
nearly twenty miles, trending first seven miles south-south-west and then
south-south-east; at the bend a branch appeared to join from
west-south-west, in which direction the country appeared very flat for
fifteen or twenty miles, as only a few distant hills were visible; from
north round to south-east the country was very broken and hilly, rising
highest to the north-east, but the view was limited to eight or ten
miles; south-east a valley opened through hills, and more distant ranges
were indistinctly seen beyond. The whole aspect of the country was
barren, rock forming the principal feature. Returning to the camp,
collected a quantity of the clustered figs on the bank of the creek; this
fruit is rather insipid.
1st October.
Steering an average south-south-east course from 7.40 a.m. till 2.40
p.m., camped on the right bank of the river, which first came from
south-west and then from south-east, throwing off two branches to the
south-west, and was thereby diminished to 100 yards wide at our camp;
only one creek and some gullies joined from the east, although the
country in that direction was hilly; the bed of the river was still dry
and sandy; water very scarce. Slate, quartz, schist, granite, and trap
are the principal rocks, and by their decomposition do not produce a soil
favourable to vegetation, the country becoming more desolate as we
advanced. The only trees which retain their verdure are those which grow
on the banks of the river.
Latitude by a Cygni 18 degrees 40 minutes 29 seconds.