3G0 AUSTRALASIA. 



in tliis region of West Victoria, where volcanic cones are reckoned by the hundred 

 — some simple eruptive craters, others real mountains 2,000 feet high — belonging 

 to every successive period between paleozoic and tertiary times. Several of the 

 craters are perfectly circular basins now flooded by lakes of great depth, such as 

 the Blue Lake, which occupies the upper cavity of a volcano belonging to the 

 Gambler group in South Australia, and which is no less than 675 feet deep. 

 Others, which formerly discharged lava streams covering vast expanses, are now 

 mere grassy or wooded cirques. All the older volcanoes are on the mainland 

 except Tower Hill, near Warrnambool, which rises above the surface of the neigh- 

 bouring waters. 



Like the Australian Alps the Tasmanian mountains are formed of granites and 

 Silurian deposits. But geologists have hitherto failed to determine the presence 

 of volcanoes properlj- so-called, although in many places eruptive rocks have 

 formed transverse barriers over which the running waters fall in cascades down 

 to the plains. Nearly the whole island is covered with irregular mountain masses, 

 which attain their greatest elevation in the north-west, here culminating in Cradle 

 Mountain (5,065 feet). Several other peaks exceed 4,600 feet, but the land falls 

 towards the south-east, where the seaboard is penetrated by deep fjords. 



Viewed as a whole Tasmania presents the outlines of half an oval, eroded on the 

 north side facing Australia in the form of a regidar concave curve. Here the 

 intervening waters of Bass Strait were at some former epoch undoubtedly replaced 

 by an isthmus connecting both regions, and of which nothing now survives except 

 a few granite islets. But immediately east of the strait the marine abysses plunge 

 into depths of over 2,500 fathoms. From the geological standpoint Wilson's 

 Promontory, the southernmost point of the Australian continent, is an island like 

 those scattered over the shallow waters of the strait. Were the mainland to 

 subside some 300 feet the two inlets to the west and east of the headland would 

 be connected by a second marine channel. 



North of the Australian Alps the highlands skirting the seaboard ramify into 

 several parallel chains, the main range running at a mean distance of 45 or 50 

 miles from the Pacific. Each chain and each transverse ridge has its separate 

 name, while the whole system is sometimes designated by the common appellation of 

 the Blue Mountains, a term more specially applicable to the mountains lying to the 

 west of Sydney, and long regarded by the early settlers as an unsurmountable ram- 

 part towards the interior of the continent. Although the highest peaks, such as 

 Sea-view, west of Port Macquarie towards the north of New South Wales, scarcely 

 exceed 6,000 feet, while most of them fall below 5,000 feet, they have in many 

 places been carved by erosive action into rocky cirques with vertical walls of an 

 imposing aspect. 



The ranges fall precipitously seaward, while on the opposite side they frequently 

 present the appearance rather of a gently inclined tableland, the ground sloping 

 somewhat uniformly in the direction of the plains watered by the Murray. Exten- 

 sive cavities, where the rivulets now escape through breaches in the periphery, 

 appear to have formerly been lacustrine basins. Such amongst others on the 



