xliv. 



the successional arrangement is sufficiently clear to leave little 

 room for question. 



These rocks are the chief repositories of our mineral wealth, 

 including ores of copper, lead, silver, bismuth, iron, and gold. 

 They exhibit little disturbance, and the absence of faults is 

 noteworthy ; however, along the line of the anticline, from 

 Hallett's Cove to the Stockade, and along the G-awler hills, 

 well marked examples of highly contorted strata are to be 

 seen. 



Mr. Selwyn has given an approximate measure of the thick- 

 ness of the strata in the Cape Jervis promontory between 

 jNormanville and Encounter Bay. He states that " the dip of 

 the beds appears to be very regularly and constantly to the 

 south-east, at an average angle of not less than 30 degrees, and 

 consequently, unless some very extensive faults occur — of 

 which I could see no evidence — there is a constantly ascending 

 series, exposing a vertical thickness of nearly 30,000 feet of 

 strata." In this connection Mr. Selwyn records an observa- 

 tion that is confirmatory of my opinion of the prevailing super- 

 position of the mica slate and gneiss : — " From the highly 

 metamorphic character of nearly the whole of these rocks, and 

 particularly of those portions that, from the dips, Avould appear 

 to be the highest beds of the series, it is often exceedingly difficult 

 to determine whether the dip observed is really that of the 

 beds, or only that of the cleavage." There cannot be a doubt 

 that the thickness of these fundamental rocks is much greater 

 in those portions of the central chain near Adelaide than in 

 the Cape Jervis promontory ; indeed, Mr. Scoular has led us 

 to infer that 90,000 feet in vertical measure are displayed in 

 the South Para river, and that this thickness is not a moiety of 

 the whole ; and I trust that our curiosity in this particular will 

 soon be satisfied by the jmblication of an extended horizontal 

 section from the Gawler Plains eastward, which, we know, our 

 zealous corresponding member has long been engaged in 

 preparing. 



Mr. Selwyn was at first inclined to the opinion that the 

 slaty rocks, which underlay unconformably the sandstones, 

 purple and grey shales, and siliceo-calcareous beds which 

 occupy the whole country from Mount Remarkable and Port 

 Augusta, north-east of Mount Serle, belonged to a superior set 

 of beds than those which occupy the whole of the country to 

 the south ; but he afterwards thought " it just possible that no 

 such natural divisions exist in the rocks of the South Austra- 

 lian chain, and that the difference in general mineral and 

 lithological characters observed between the northern and 

 southern rocks is entirely due to metamorphic influence." In 

 the absence of fossil evidence that geologist hesitates to ex- 



