Page:A sketch of the physical structure of Australia.djvu/74

62 much superior country to that of the white sand, the roads are hard and firm, and the ground far more fertile. The sandstone seemed often argillaceous or marly, and in some cases seemed to contain beds of hard grey gritstone and ferruginous concretions. In lithological character it resembled a good deal the new red sandstone of England. I never found any fossils in it, but it appeared every where to be horizontal and conformable to the white limestones and sands above it. These latter are certainly tertiary, as they in some places contained shells of the genera area and venus apparently of species now existing on the coast, and certainly of very recent and unaltered aspect. I am inclined to believe, that the brown sandstones below, with ferruginous concretions, as they are certainly conformable to these tertiary beds, may in reality be a lower part of the same formation.

On approaching the foot of the hills on the road from Perth to York, we pass at once from the horizontal brown sandstone to a steep slope of granite, above this to another of greenstone, and then to granite again. The surface of this plateau of rock, here about 800 feet above the sea, was gently undulating, covered with one wide forest of a large eucalyptus, called here mahogany. For a few feet below the surface the rock was a singular concretionary ferruginous compound, which looked like a clay or sandstone that, being highly ferruginous, had formed itself into a mass of small balls and irregular concretions of a black oxide of iron or hæmatite. Below this "ironstone" (which is its name in the colony), wherever the rock was exposed, it appeared for many miles to be granite, or some granitic compound. At a place about twelve or fifteen miles from the edge of the hills, in the descent of a lateral valley of the Swan, I passed, in the space of a mile, over the following rocks:

1st. A thin capping of "ironstone," forming a line of small crags.

2nd. A band of coarse granite.

3rd. Fine rather soft chloritic schist, green with a silvery lustre.

4th. A very hard crystalline greenstone, passing here and there into sienite.