12G 



sive plains are composed in tlie upper part cliiefly of loams, 

 calcareous clays and clayey sands, and in the deeper and mar- 

 ginal portions of sands and gravels. But the thick deposits of 

 the Port Wakefield and Port Augusta basins show interstrati- 

 fications of carbonaceous muds with driftwood and very thin 

 lignites, none of which, however, are of tlie character or mag- 

 nitude to justify a special exploration. The indication at 

 present known to us which is best worthy of further investi- 

 gation, and to which I drew attention in the early part of 

 1878, is that of a bituminous shale discovered in a well sinking 

 at Border Town. It yields paraffin on distillation, and has 

 been proved for a thickness of 40 feet at a depth of 91 feet. 

 The overlying rock is a diatomaceous earth of fresh-water 

 origin, and the whole may prove to be the filling-in of a lake 

 depression during Pliocene time. 



PROSPECTIXft rOR COAL. 



The method of investigation pursued by the skilled geological 

 surveyor in a search for coal is identically that for petro- 

 leum, though more definite results will be obtained in the first 

 case than in the latter, because of the less diversihed conditions 

 under which it has been formed. AVorld-wide experience has 

 taught the scientific miner that coal originated as a terrestrial 

 vegetation, and that the period of its growth does not extend 

 very far back in geologic time. Our chief supplies are drawn 

 from the Carboniferous rocks of Primary age, and no coal is 

 known in rocks of older date. Some good coals are derived 

 from Secondary formations, and inferior coals and lignite from 

 Tertiary strata. The stratigraphical occurrences of coal in 

 Australia are Carboniferous, as in Tasmania ; Carboniferous- 

 Permian, as in New South AVales ; Carbonaceous (? Jurassic), 

 at Cape Paterson, A^ictoria ; and Miocene at Lal-Lal, near 

 Oeelong, Victoria. 



This province south of the latitude of Lake Eyre is occupied 

 by Pre-Sihirian, Silurian, and Tertiary rocks, the hist covering 

 fully three -fourths of the whole area. 



Among our Pahpozoic rocks we can have no expectation of 

 finding coal, as they were deposited as marine sediments untold 

 ages before the epoch of the earliest coal vegetation. 



As to the probability of finding coal in tlie bulk of the 

 strata classified as Mioc(?ne, there can be but one opinion, inas- 

 much as throughout the great extent of* country occupied by 

 the system, the beds are of marine origin, and therefore the 

 occurrence of coal among them is not to ])e looked for — the 

 necessary physiographic conditions having been wanting over 

 the entire area. (This is roughly defined in my *' Outlines of 

 South Australian (leology," Trans. Koy. Soc, Ui., ]). li.) The 



