Journals of Two Expeditions of Discovery in North-West and Western Australia, Volume 2Grey, George
History
Journals of Two Expeditions of Discovery in North-West and Western Australia, Volume 2
Grey, George
Natural history -- Australia -- Western Australia; Western Australia -- Discovery and exploration
After visiting Longwood and Napoleon's tomb we rode to Flagstaff Hill to
search for fossil shells. The whole soil that I saw was composed of
decomposed old volcanic rocks; but I saw no rock but basalt in different
stages of decomposition; sometimes it assumed the form of porphyry. I
also saw veins of quartz, gypsum, and jasper. On a part of Flagstaff Hill
there was a thin stratum of calcareous earth, in which shells are found.
My hip was so painful that I could not climb to the point where these
were, but an artillery soldier ascended and brought down some, and of
these I had several specimens given me; they are found associated with
bones which are apparently those of birds. None of these bones were given
to me but I saw and examined several specimens. The shells are very
numerous at this point.
On returning into town I found several specimens of dead land shells,
apparently recent; these lay on the sides of the hills, partly buried in
the soil, and bore the appearance of having been washed into this
position by the heavy rains.
July 22.
Rode over in the morning to Longwood, and then proceeded to Gregory's
Valley, lying between Longwood and The Barn. This valley, nearly 1700
feet in depth, appears at one period to have been the scene of great
volcanic disturbances. The lowest rock I saw was a compact porphyritic
one. The upper strata of basalt were in a state of rapid decomposition;
but the whole of the valley was traversed by basaltic dykes in every
direction; these crossed one another in such a way that it was easy to
tell their relative ages; for instance several of them were in the form
of:
So that one had been forced from its position by another long
subsequently to its formation.
The general form of Gregory's Valley is a large basin bounded by a lofty
precipitous mountain on one side called The Barn, and having a very
narrow opening seaward, through which a small stream has cut its way. A
remarkable circumstance connected with the basaltic dykes is that they
are composed of a more compact basaltic rock than the basalt which they
penetrate, so that whilst the rock has mouldered away these basaltic
dykes have remained standing; and, as in the progress of their decay they
split up, they present the appearances of walls built by human hands,
with regular layers of stones, and which traverse the ravines of the
island in all directions.
As might be expected, I found regular basaltic crystals in this valley,
and also a variety of quartz ore, and other crystals, in the veins
traversing the basalt. I also found the following remarkable section:
This was in a side valley or ravine leading from Gregory's Valley in a
southerly direction.
On going down to the sea I found many species of starfish. I brought away
three species of these with me. Two Species Pentagonal; one species
Quadrilateral.
First species Pentagonal length of side 0.55 inch.
Second species Pentagonal length of side 0.50 inch.
Quadrilateral length of side 0.55 inch.
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