No. IV.
LIST OF GEOLOGICAL SPECIMENS, COLLECTED IN THE DISTANT INTERIOR DURING THE FIRST EXPEDITION, WITH THEIR LOCALITIES AND THEIR RELATIVE DISTANCES FROM EACH OTHER.
It may be necessary to observe that the height of the Cataract of the Macquarie River above the sea, was ascertained by barometrical admeasurement to be 650 feet. The country subsequently traversed is considerably lower. The specimens refer only to the geological formation of the distant interior.
Schorl Rock.—Colour blueish grey, fine grained, extremely hard. Composed of Tourmaline and Quartz. Forms the bed of the Macquarie at the Cataract, 75 miles to the N.W. of Wellington Valley.
Decomposed Mica Slate.—Colour white; yields to the knife; adheres strongly to the tongue.
Decomposed Feldspar.—Colour pale rose-pink; very fine grained; easily scratched with the knife; adheres strongly to the tongue.
Both specimens immediately succeed the Schorl rock at the Cataract, in large smooth-sided masses.
This formation may be said to terminate the rocks connected with the dividing ranges, since it is the last that occurs at their western base.
A little below the Cataract, the county undergoes a remarkable change, and becomes extremely depressed.
Porphyry with Feldspar.—Colour dull red, with white spots, or grey with red spots; very hard, compact, sonorous, magnetic. (See pp. 27 and 115.) Composition of Mount Harris, a hill called by Mr. Oxley, elevated about 170 feet above the level of the plains. It lies 65 miles to the N.N.W. of the Cataract, and is about 16 miles distant from the first of the marshes of the Macquarie.