114 J. T. JtUson: 



largely or mainly responsible for the slow gravitative drift of 

 detritus over the lowlands. 



Portions of the lowlands liave been changed by erosion into the 

 rock- and silt-Hoofed channel-like arms of the lake; and between 

 the arms sand ridges have been built up. Detritus, due mainly to 

 Tain action and forming the continuation of the surface of the low- 

 lands, underlies the sand ridges, but it has been entirely stripped 

 •off, and the bed-rock has been denuded, in the arms. The floors of 

 such arms are not therefore merely ** resurrected " surfaces; and 

 they have probably been cut during the formation of the sand 

 ridges. 



The rock floors of tlie lake, its arms, the rock basins, tlie rock 

 cliffs, and the low cliffs of the truncated piedmont plains are 

 believed to be dominantly due to wind action. 



The lake and pi'obably the whole adjacent topographic system are 

 regarded as migrating Avestwards. and the relations of the com- 

 ponent parts of the system to one another are unique and without 

 a known parallel elsewhere. 



General Description of the District. 



The main physical features are : — 



(1) Three small belts of " bigh " lands consisting of hard 

 resistant '* greenstones," dissected by small early mature valleys, 

 Avith a maximum depth of about 100 feet. 



(2) The '* lowlands,*' Avliich consist chiefly of decomposed basic 

 schists and form rather extensive areas (as compared Avitli the 

 *' high " lands) of flat or gently sloping sui-face. They form with 

 the "high" lands a north-north-west trending belt of country. 



(3) The " dry " lake, or playa. known as Lake Goongarrie, which 

 lies to the east of (and about 100 feet below) the township, and also 

 to the east of the " high " lands and '* lowlands," and of the 

 mining township of Comet Vale, eight miles to the north. This 

 playa is about eleven miles long in a north-south direction, with a 

 greatest width from east to Avest of about six miles. It has rock 

 cliffs and rock floors on the Avestei'n and sands on the eastern side,' 

 and, in' addition, possesses (especially in the south-Avestern portion) 

 Tiunerous islands, sand ridges, arms and quartz reefs and " bloAvs," 

 A long " peninsula " projects eastAvard betAveen Comet Vale and 



I The jrreater portion of the eastern side of the lake has not been traversed by the writer, 

 but from the' parts actually examined and fii-oni distant views, it is ]iractically certain that the 

 vhole side has practically similar characters, that is, low sandy stiores free fro n rock cliflf.s 

 and rock Moors. <. .. ■ ■. 



