PRESIDENTIAL ADDRESS — SECTION E. 233 



perished there might have been a remnant of Leichardt's band. 

 It therefore offered Mr. McPhee £500 to undertake the work ; 

 but that gentleman thought that the sum named was insuffi- 

 cient, and the society, having no more funds available for the 

 purpose, has reluctantly abandoned the task for this season. 



In March last Mr. Tietkins, F.R.G.S., described an ex- 

 pedition led by himself, which, starting from the overland- 

 telegraph line at Alice Springs, travelled due west for about 

 three hundred and ninety miles. He discovered a salt lake 

 about a hundred square miles in area, which lies directly under 

 the Tropic of Capricorn, and close to the West and South Aus- 

 tralian borders. This sheet of water has since been christened 

 Lake Macdonald. 



The surrounding country is chiefly a Spinifcx desert ridged 

 with long, low, flat-topped ranges of red sandstone. From their 

 appearance it is probable that these ranges are the remnants 

 of a sandy Cretaceo-tertiary lake-bed, whose surface, once con- 

 tinuous, is now broken up by the drainage-basins scooped out 

 of it as the waters flowed away to lower levels. 



The course of the principal river — the Finke — runs trans- 

 verse to these ranges, cutting directly tln-ough them in deep 

 narrow chasms, and this probably indicates that the present 

 drainage-system is older than the mountain-feo.tures of the 

 country. And if the American geologists are justified in their 

 theory that the bed of the Great Salt Lake of Utah was flexed 

 or arched upwards into low hills as it was relieved of the 

 weight of water which once rested upon it, we too may specu- 

 late upon similar changes of level having occurred hereabouts 

 to create a synclinoriura, or broad regional uplift, in an area 

 which at a still more remote period was the most depressed 

 part of a vast lake-basin. The past history of this part of 

 Australia when it is traced out should shed some additional 

 light upon the interesting subject of the oscillations of the 

 earth's surface, so exhaustively treated of last year by Pro- 

 fessor Hutton. 



The discovery in the same region of an underground river 

 recently reported by Mr. Brown, Government Geologist, is a 

 fresh indication that the aridity of the region is a modern 

 condition, for it is not easily conceivable that the present rain- 

 fall of between 2in. and lOin. per annum could flush the rocks 

 with subterranean waters in quantity copious enough to per- 

 forate the limestone rocks with passages which are large 

 enough to rival the Jenolan Caves, or those recently discovered 

 at Waitomo, in New Zealand. 



The beautiful map of this region which has been engraved 

 by Stanford for the Eoyal Geographical Society of Australia 

 is a valuable addition in the cartography of this country. Mr. 

 Tietkins after discovering Lake Macdonald turned back to 



