38 PLANT HABITS AND HABITATS IN THE 



rens, and for much of the way skirts the western base of the FHnders. 

 As seen from the railway line, the mountains rise fairly abruptly from 

 the plain. This is due, according to Howchin, to faulting connected 

 with the formation of the great central valley of South Australia. 

 Near Beltana the line enters the hills and at Copley (Leigh's Creek) it 

 runs in the valley separating the smaller western range from the main 

 ranges to the east. The highest altitude given by Howchin of the 

 northern Flinders is 3,120 feet (Freeling Heights), and among the 

 prominent elevations is Mount Serle, east of Copley, to which refer- 

 ence will be made later. It has already been mentioned that in the 

 north the Central Highlands assume the rugged appearance character- 

 istic of mountains in an arid land. This implies also the presence of 

 canyons cut deep by water-courses. Such stream-beds are dry, how- 

 ever, a large part of the year. 



For the most part the Central Highlands are of lower Paleozoic 

 (Cambrian) age. The exceptions to this have already been referred to. 

 There are occasional structures which are of great interest to the geolo- 

 gist, as, for example, the circumclinal fault known as Wilpena Pound, 

 where a great basin was formed, access to which can be had at one 

 point only, and the glacial "till," supposedly pre-Cambrian, which can 

 be seen at Depot Flat, near Quorn, as well as at other places. 



From the present standpoint the leading interest in the highlands of 

 South Australia lies in their effect on the climate. The isohyets 

 and isotherms are pushed considerably northward by the central 

 land elevations and with this, and because of it, an extra-regional 

 distribution of plants occurs by which those of the cooler and more 

 moist south are projected far north, into the midst of a region that is 

 remarkably hot and dry. 



The lowlands of South Australia may be said to consist mainly of 

 the basins, great and small, in which the lakes in the northern portion 

 of the state more especially are situated, and, in addition, the region 

 along the course of the Murray River. They are the Lake Eyre Basin, 

 that of Lake Fromme, Lake Torrens, and Lake Gairdner. In addi- 

 tion are the coastal plains, of which the one between Port Augusta and 

 Port Pirie needs only be mentioned. The positions of these basins 

 are given in figure 10. 



The Lake Eyre Basin is a part of the great artesian basin of central 

 Australia, which is estimated by Taylor (1914:108) to have an area of 

 676,000 square miles. Only a relatively small proportion of the total, 

 however, is in South Australia. The deepest portion of the basin 

 centers in Lake Eyre, the bottom of which is estimated to be 60 feet 

 below the level of the sea. Where the railway crosses the southern 

 extremity of the lake the altitude is 3 feet below the sea. The basin 

 is a closed one, but the evaporation-rate is so great that much of the 

 area which constitutes the lake is dry most of the time, being covered by 



