48 



to about half the depth of the side, and there the schists buttress 

 it up, having their own slope covered with a talus formed of the 

 fallen quartzite rocks. Standing on the ridge, the quartzite can 

 l^e traced for miles to the limit of vision on either side. Varying 

 little in apparent height, sometimes straight, sometimes sinuous, 

 this thin red line holds its own in a general direction of east and 

 west. Distinctly visible from this elevated position, the mass of 

 upland country collectively termed the Macdonnells are seen to 

 1)6 composed of other ridges, all parallel and narrow, and inclined 

 like the first. The rock tints and scarped edges leave no room 

 for doubt as to their identical composition, and that they are 

 situated along the edges of a line of faults which bring the same 

 series and sequence of rock beds into view. Looking northward 

 the country rises, and the quartzite ridges are but little elevated 

 above the plain which extends to the Reynolds Range. Passing- 

 through Heavitree Gap, and following the telegraj^h line, Alice 

 Springs is situated on a boss of coarse red granite, which has 

 greatly disturbed the country. To the north ridge, beyond Bond 

 Springs cattle-station, we pass over numerous intrusive dykes of 

 diorite, wdiich have faulted the granite and schists. Plates of 

 mica two and three inches squai'e occur in the granite. A descent 

 of only 40 feet from the north ridge leads down to the tertiary 

 alluvial covering of the plain. The system of diorite dykes, 

 which are met with north-east of Alice Sj^rings, do not continue 

 beyond the Mount Ben stead ridge, the last one being met with at 

 Mount Benstead well, where the dyke, by forming a bar across 

 Love's Creek, dams back the soakage waters, and atfords a limited 

 supply to the well. 



East of Alice Springs, the Macdonnells are formed of two nearly 

 2:)arallel ridges, the Undoolya and Benstead, which dip south and 

 strike nearly east and west. The Hart Ranges, with which they 

 converge and junction, have also two main ridges, the Georgina 

 or Bald Hill ridge and the Hart Range j^roper. This system 

 runs E.S.E., and dips northerly. Load's Creek and the Ross 

 drain the first two ridges, and the Hale or Elder the two latter. 

 From the chaotic jumble of mountains which are caused at the 

 i unction of the Benstead and Georgina Ranges, a range which I 

 liave called the Elder Range runs south-eastward, and has been 

 traced by me to lat. 24" S. A section drawn through the system 

 from the Ross Creek across through the ruby-fields to the Plenty 

 River shows a great anticlinal axis, with four main faults indi- 

 cated by the four ridges mentioned. At the Ross, the limestone 

 series is surmounted by a fissile purple sandstone, apjDarently 

 identical with that found on the Mount Charlotte ridge. It forms 

 a ridge with a steep escarpment on the north side, and with the 

 limestones ascending about half-way up. Proceeding up the 



