Page:A sketch of the physical structure of Australia.djvu/65

53 comes to plains of clay and sand, covered by angular fragments of quartz rock, ironstone, and granite, (p. 180.) Mount Arrowsmith, in lat. 30&deg; 5', the southernmost hill of the next range called Grey's Range, he describes as having indurated quartz and pieces of gypsum, (p .219), a compact sandstone with blocks of specular iron ore scattered over it, highly magnetic, (p. 231.) He describes the hills about Mount Poole, lat. 29&deg; 35', as composed of compact white quartz, split into innumerable fragments in the form of parallelograms (p. 240), and says the same white quartz continued throughout the Grey range, the neighbouring plains being covered with its fragments, (p. 259.) Near the Depôt, however, on Preservation Creek, he found large slabs of beautiful slates traversed by veins of quartz. We have here then, evidently, two north and south ranges of hills of moderate elevation, being together about 180 or 200 miles in length, and composed of old igneous and metamorphic rocks. A little N.W. of the extremity of Grey range, Captain Sturt describes the Bawley Plains, the basis of which he says is sandstone, on which rested thin layers of clay, with ridges of loose sand reposing on the clay. Thence he penetrated into the interior for about 400 miles, generally in a N.N.W. direction till he reached lat. 24&deg; 30', long. 137&deg; 59'. For the whole of this distance the country was a desert of the most inhospitable character. The arid plains were covered with bare ridges of drift sand, often 80 to 100 feet