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with porcelain cappings situated within the MacDonnells near 

 the Elder River. I saw numerous hills of a like character 

 throughout the ranges in my travels. At the extreme head of 

 the Petermann Creek resting on fossiliferous Silurian limestone, 

 and on the Walker Creek resting on mudstone, it may be seen. 

 As a rule the hills are cone-shaped, very white, composed of clay- 

 grit, and always horizontally disposed. There is a diiference of 

 2,000 feet in altitude between the counterpart of these hills in 

 the neighbourhood of Lake Eyre. The interesting joroblem is, 

 were these hilh formed by wind-drift ? or were they formed be- 

 neath the sea ? If from wind-drift, their great elevation is easily 

 accounted for ; if on the contrary a marine deposit, it is quite 

 evident Australia was beneath the sea at no very distant geologi- 

 cal data. Following on this version, what has become of this 

 immense deposit ? and to where has it gone ? and by what way 1 

 It is so friable that as the waves of the sea gently receded it 

 would be lapped away, and by ocean currents carried to the 

 bottom of some other ocean. But why was Lake Eyre and its 

 basin not filled ? or more correctly, why is it a depression ? 

 Should not this formation fill it to overflowing ? To this may be 

 added that it is evident pre-Silurian and Silurian rocks form the 

 bedding to Lake Amadeus not many feet beneath the blue clay, 

 and farther to the east granite outcrops occur near the western 

 watershed of the Finke. It is possible an ocean current swept 

 through and along this valley, and coming in contact with the 

 Flinders Range rocks carried off all sediment collected on the 

 way, and much of what was already in Lake Eyre basin, which 

 great vortex was probably formed at the close of the Silurian 

 epoch. What treasures of wealth that basin holds can only be 

 told by the diamond drill, but from the fact that coal has been 

 struck at Leigh's Creek, and that the rocks surrounding it on the 

 north and north-west dip into it, it is possible that coal may be 

 found in many places around its edge. To come to a 



Conclusion. 



The fact is everywhere apparent that rapid degradation is 

 going on throughout Central Australia, especially where the hard 

 rocks are more exposed on the high-lands. The extremes of heat 

 by day, and almost invariably cold nights, cause much contraction 

 and expansion, and the rocks break up. When sufficiently broken 

 the wind, which throughout the summer months blows from the 

 east, carries the sand along and forms sandhills as even as ocean 

 waves. The wicd is here a great factor in the transport of 

 eroded rocks, much greater than flood-waters. So porous is the 

 soil that moisture sinks beneath the surface at once in the sandy 

 country, and flows to lower levels. In a few instances an anti- 



