Page:A sketch of the physical structure of Australia.djvu/73

61 usual forest of the country, and producing fruits and vegetables in considerable quantities in the gardens of the colonists. It consists partly of grains of quartz and partly of calcareous grains, probably rolled fragments of shells and corals. In several places it passes into the state of a rather soft friable limestone, sufficiently firm to be used for building stone. In other places are seen rising from the sand what appear to be trunks of fossil trees, having not only the external form of trees, but much even that resembles their internal structure. These occur throughout the colony in places wherever this white sand is found, and they have been frequently described at King George's Sound, where Mr. Darwin believed them to be calcareous concretions formed in the hollows left by decayed trees. In a little cliff near Fremantle, however, near the entrance of the Swan, I saw some of these dendritic masses fully exposed, and from their peculiar structure and conformation I believed them to be nothing more than stalactites formed in the sand by the percolation of rain water dissolving and taking up the carbonate of lime found in the sand, and re-depositing it in fantastic forms wherever a predisposing cause happened to determine it. I believe the limestone in these sands likewise to be formed in the same way, as the bedding had frequently a rather highly inclined or contorted dip, evidently not due to movements of elevation, but the result of their original formation. In this case I suppose rain to have sank through the sand, dissolving the carbonate of lime in its passage, till it at length became saturated or could sink no farther, and that, as it evaporated, the carbonate of lime was deposited in a crystalline condition, binding up all the adjacent grains into a more or less solid stone.

At the foot of Mount Eliza, near Perth, some beds of a close red sandstone may just be seen beneath these white sands and limestones, and a few miles further east, just on reaching the ferry to Guildford, the upper white rock ends in a little escarpment, and the red sandstone crops from under it, and forms the remainder of the country in the neighbourhood of the Swan River up to the foot of the hills. This red sandstone forms a