GEOLOGY. The Great Dividing Range is corn posed mainly of Silurian beds, with, however, large areas of Carboniferous formation, while in the neighborhood of Sydney and Ipswich, New South Wales, are large areas of what arc proh ably .Jurassic beds. Throughout the range in trusions of granite are abundant. The Darling Range, on the west coast, is composed of more recent beds, probably Jurassic. East of this range, stretching far into the interior, the coun try is overlaid irregularly with granite, and the same rock appears in many, if not most, of the ranges of the interior, breaking through the Tertiary and Cretaceous beds which floor the plains and plateaus of this region. The distribution of these last two formations in the interior may he broadly characterized by the statement that the interior portions of Queens land and New South Wales are underlain main ly by Cretaceous beds, while the interior of Western and South Australia is mainly covered with Tertiary formations. There are, however, considerable tracts in the interior which are cov ered by older rocks. Thus, in the southern part, north of Silencer Gulf and the Gulf of Saint Vincent, is a large area of Pakeozoie beds ex tending inland as far as Lake Eyre, while from the head of the Gulf of Carpentaria an area of the same age extends southward. Tasmania is
composed mainly of Silurian strata; Carboni ferous and Jurassic beds and older crystalline rocks appear, however, both in the interior and on the east coast. Gold-bearing rocks and other valuable mineral deposits are widely dissemi nated throughout Australia.
There are no active volcanoes on the continent, but there are several areas of extinct volcanoes. They are very numerous in the State of Vic toria in the southeast, where they have had much to do with shaping the present conforma tion of the land. There are but few in New South \Vales, although outflows of basalt through low vents were numerous and extensive in that colony during Tertiary times. In Queensland the volcanic area is extensive, espe cially in the interior. In South Australia is the well-known volcanic group which has Mount Gambier for its central figure.