The island of Tasmania is connected, as it were, with the continent of Australia by two chains of islands, the lines of which are afterwards continued in the mountain-syatems both of Tasmania and Australia. The Tasmanian systems pass from north to south in a strangely zigzag course, throughout which the mineralogical character of the rocks varies considerably. The land, therefore, may be presumed to have once presented a very different line of contour to what it does at the present day.