368 AUSTEALASIA. 



islands ; at another they are mere quagmires reflecting the glittering mirage, or 

 else argillaceous tracts covered with white saline efflorescences. During protracted 

 droughts these so-called lakes may be crossed on horseback, provided the traveller 

 avoid the bays and inlets of the periphery, where the treacherous muds and bogs 

 are longest maintained by the underground waters filtering through from the 

 surrounding lands towards the lateral creeks. 



From the disposition and outlines both of Lake Eyre, and of Lake Torrens, 

 which forms its southern continuation in the direction of Spencer Gulf, it seems 

 probable that these now isolated basins were formerly marine inlets communicating 

 freely with the South Pacific. The terminal depression, however, which is certainly 

 the lowest cavity on the Australian continent, still stands some 65 or 70 feet above 

 the present sea-level. Another depression towards the centre of Australia is occu- 

 pied by " Lake " Amadeus, alternately a shallow lagoon, morass, or saline waste. 

 In the arid region of West Australia there also occur several depressions of like 

 character, which are commonly designated by the name of lakes. 



In the thoroughly explored basins, such as that of the Darling, the fluvial 

 discharge is so slight compared with the rainfall that some observers have sought 

 for an explanation of the discrepancy in the existence of underground rivers 

 flowing beneath the surface clays, and carrying either to the sea or to some 

 subterranean reservoirs the greater part of the running waters. Some portion, 

 however, of the rainfall, instead of being carried off in river beds, remains on the 

 groimd in certain shallow basins, which in the Darling pasturages are known by 

 the name of " gilgies." On these level tracts, where the rains spread out in stag- 

 nant sheets without the force required to excavate a fluvial channel, the only 

 depressions where the water can be collected are the fissures formed in the arid 

 soil during the dry season. Under the action of the heavy downpours the sides of 

 these crevasses are washed away, the bed of the cavities thus formed is levelled, 

 and water-holes are gradually developed, which vary in depth from 4 to 5 or 6 

 feet, and in size from a few feet to over a hundred yards in circuit. Some of 

 these natural gilgies have even been enlarged by the natives, and converted into 

 reservoirs capable of containing considerable quantities of water. 



♦ 

 Climate. 



The climate of Australia is written on the surface of the land, its more salient 

 features being clearly indicated by those bare rocks, those treeless plains and 

 waterless depressions which occupy the greater part of the continent. Although 

 surrounded by marine waters, Australia is of too massive a form to enjoy an insular 

 climate, such as that of Europe with its deeply indented seaboard. Owing to the 

 dryness of the atmosphere, due to the slight relief and the monotonous contours 

 of the coastline, the meteorological conditions are essentially of a continental 

 character. 



Lying half within the tropical and half in the south temperate zone, this 

 region presents, from the York Peninsula to the terminal point of Tasmania, a 



