Page:A Voyage of Discovery and Research in the Southern and Antarctic Regions Vol 2.djvu/435



following general description of the geological and physical features of this beautiful portion of Australasia is chiefly derived from observations made in the vicinity of Hobart Town; and during a rapid excursion I made across the island, from the banks of the Derwent to the embouchure of the Tamar in Bass's Strait, including a short visit to Port Arthur and Tasman's Peninsula.

The general aspect of the country is mountainous, the main chain intersects the island from N.E. to S.W. in a somewhat zigzag course, attaining an altitude of about five thousand five hundred feet above the level of the sea, forming ranges or isolated peaks, intersected by the most fertile plains and valleys, which are watered by numerous streams and rivers, and richly clothed with woods and forests.

Five or six large lakes occupy the higher regions, at an elevation of between three and four thousand feet. The prevailing rocks are basalt and greenstone, occasionally passing into amygdaloid and other modifications of the trappean series; and are variously associated with those of the sedimentary class, calcareous, arenaceous, and argillaceous; these are in many places much inclined, disturbed, and dislocated (as evinced by the numerous faults in the coal formation at Port Arthur), by the intrusion of the igneous rocks at different periods of time. A kind of greywacké is widely distributed.

Basalt and greenstone enter very largely into the composition of the mountain range, cresting it in many places,