STRZELECKl's N. S. WALES AND VAN DIEMEN'S LAND. 559 



mineralogy ; but the materials he met with for this purpose were 

 too few and too little important to satisfy his curiosity, and he 

 turned therefore to the wider field of investigation presented by 

 its geological structure, and has endeavoured by a map, coloured in 

 a certain sense geologically, by a number of sections, and by de- 

 scription, to communicate information on this subject. The map 

 includes a district of about 150 miles in New South Wales, mea- 

 suring inland from the sea-coast from the 30th to the 39th degrees 

 of south latitude, and the whole of Van Diemen's Land, the author 

 stating that he was induced to continue his investigations south- 

 wards into that island, and include it in his geological survey, in 

 consequence of the great similarity of its general structure to that 

 of the main land. — We shall endeavour in the present article to 

 deduce a general account of the geology of the district without 

 confining ourselves to the exact order of arrangement adopted by 

 the author. 



The physical features of the eastern coast of Australia appear 

 to be derived from a great number of sharply-defined elevations, 

 producing a multitude of ridges which have a general direction 

 from N. E. to S. W., and which are sometimes broken through 

 and occasionally connected by transverse ridges. Very numerous 

 and prominent spurs project as it were on the eastern face of 

 these principal lines of elevated ridges, and the natural result of a 

 conformation so peculiar is the existence of many yawning chasms, 

 deep winding gorges and frightful precipices, forming an endless 

 labyrinth of almost subterranean gullies, exceedingly difficult to 

 penetrate, and rendering the whole tract intricate and broken. 

 A similar structure is said to extend also to the west of the 

 mountain range. 



The altitudes of the higher points of these ridges, which are 

 for the most part peaks of striking shape and lofty elevation, 

 range in the more northern district, as in latitude 30°, from 2400 

 to 4700 feet. Towards the south, in the district known as the 

 Australian Alps, one peak called Mount Kosciuszko attains the 

 height of 6500 feet, and the chain there trends greatly towards 

 the west until it turns again southwards and terminates in the 

 sea at Wilson's Promontory. The same structure is however con- 

 tinued across Bass's Straits, by a chain of islands, and forms a lofty 

 and picturesque mountain district in the north-eastern extremity 

 of Van Diemen's Land. 



The central axis of the whole district thus remarkably charac- 

 terised consists, it would appear, invariably of igneous rocks, and 

 chiefly of granite, syenite, and quartz rock. Of these granite is de- 

 scribed as constituting " nearly the entire floor of the western 

 portion of New South Wales, to the complete exclusion of mica 

 slate and gneiss, and extending far into the interior of New Hol- 

 land, in masses of mammillary, tuberous, globular or botryo'idal 

 form." (p. 85.) 



The forms of the mountain summits mark by their deep, jagged, 

 dentated, and serrated outline the nature of the rocks which crown 



r p 2 



