IKJliN liXPEDlI'lUN NAKliATIVE. 



iu;j 



;iii<l Oniiistou Crueks, fui'ijiiiig the uuiiu sourccb ut' the Fiiike, were ruuniug, roac n 

 long ridge ut' Oixluvieiiiu Quartzite. 



Climbing over the liinestoiie hills a little distance tu the iiuilh of our eaiii}) 

 we eaine upon tin; lledbauk Creek, running soutii, just as it emerged from the 

 gorge in which it passes through the lofty quartzite ridge from which, innuediately 

 to tlie west of the ''ovje, rises Mount Sonder. 



The waterslied lies well to the north of the line along which are now the 

 highest peaks such as Mounts Soinler, Zeil, Jleuglin and (Jihs, and the creeks 

 have in course of time cut tlu'ir way in deej) gorges througli the ridge which forms 

 the southern boundary of the Pre-Candjrian area. 



The accompanying diagram will serve to give a general idea of the main 

 physiographic features of the region. It is supposed to represent a section cut 

 from north to south from the Burt Plains, which lie to the north of the main 

 McDonnell Range to the James llange in tlie south. Starting in the south we 

 tlnd tiie Missionary Plains, which vary considerably in widtii, gradually narrowing 

 from about twenty miles at the western end to perhaps a mile or two at tiie 

 eastern end in the neighbourhood of Alice Springs.* Going north across these we 

 come to a series of low hills and then cross a distinct ridge with a steep northern 

 escarpment and so descend into the Horn Valley, which is at most only about a 

 quarter of a mile in width. Crossing another distinct ridge bounding tiie Horn 

 Valley on the north we come into another broad valley, perhaps half a mile across, 

 lying at the Ijase of the main McDonnell llange. The latter consists of a series 

 of low jumbly liills with a main ridge in the southern part the whole running east 

 and west for some 400 miles. This general arrangement of parallel valleys and 

 ridges all running east and west, with the main river channels cutting across them 

 from the watershed in the north, is the striking |.ihysiographic feature of the 

 Higher .Stej>jje region. 



* Thc\ are nut called the llissioiiai-y Plains except in the liioad part uut to the west eni.I, bvit tlie \alle.v is 

 reall.v dii-cctly continuous from east to west and is gradually narrowed in eastwards as the .James llange (here 

 usually called the Waterhouse) trends north-east so as to aii|iroach the Ihdlonnells. 



