Commander North-West Australian Expedition.
Perth, 6th February, 1862.
APPENDIX.
Adopting the course which I have found most convenient on similar occasions, I now proceed to offer a few remarks on the general features, productions, and natural capabilities, etc., of the country traversed by the Expedition, which could not, without disadvantage, have been introduced into the foregoing narrative. These remarks have already appeared at the conclusion of my report published on the 18th November, 1861, but are equally applicable to the present publication.
Commencing with its geographical and geological peculiarities, that portion of the country that came under our observation consists of a succession of terraces, rising inland for nearly 200 miles, more or less broken up by volcanic hills towards the coast. The first belt averages from ten to forty miles in width from the sea, and is a nearly level plain, slightly ascending to the southward, with an elevation of from 40 to 100 feet, the soil being generally either light loam or strong clays, according as it is the result of the disintegration of the granite rocks that occasionally protrude above its surface, or of volcanic rocks of black scoria that frequently interrupt the general level; hills of this nature also constitute the greater portion of the more elevated islands off the coast, Cape Lambert, and the promontory that shelters the western side of Nickol Bay. The generality of these rocks do not, however, yield so rich a soil as might be expected from their origin. This is owing to the absence of actual lava, the eruptive heat having nearly been sufficient to convert the superincumbent primary and tertiary rocks into a vitreous scoria, having a specific gravity of 3.2, and is highly indestructible in its texture.
Proceeding inland for the next fifty or sixty miles is a granite country that has been originally capped with horizontal sandstones, and has an elevation of about 1000 feet. This range terminates to the southward in level plains of good soil, the produce of the next series of more elevated country, while towards the northern edges the granite and sandstones have undergone great changes through the action of numerous trap dykes, that have greatly disturbed its surface, producing metamorphic rocks, some resembling jasper, and others highly cellular and scoriaceous.
In about latitude 22 degrees, on the meridian of Nickol Bay, we came upon another and more elevated range trending away to the south-east, having an altitude of 2500 feet above the sea. This, unlike the last section, has a southern escarpment of 500 or 600 feet, and consists of horizontal sandstones and conglomerates, which have comparatively undergone little change, and has an average breadth of eight or ten miles, the southern flank being bordered by fertile valleys of strong loamy clays, merging gradually to the southward into stony ridges and hills, some having an elevation of nearly 4000 feet, the culminating point being attained at Mount Bruce, in latitude 22 degrees 30 minutes.
From this point the country gradually falls to the Ashburton, the bed of which river, in the same meridian as the bay, is about 1600 feet above the sea, and the adjoining ranges not above 2200 feet, or about the same as the country on the Gascoyne, Lyons, and Upper Murchison.
Of minerals I was unable to discover any traces, except iron. Quartz reefs occasionally traversed the country in a north-north-east and south-south-west direction, or nearly the same as the mineral lodes at Champion Bay; but I could not find any instance in which this rock offered much to indicate the probable existence of gold, it being far surpassed in this respect by the rocks on the Upper Murchison. Coal does not appear likely to be found within the limits of the country passed over, unless towards the easternmost point attained by the Expedition.