92 Remarks on a Tertiary Deposit 



consider to be portions of the same elsewhere, let me briefly 

 describe the evidence they afford. We know that the land 

 is rising at present, and we have fossiliferous rocks of the 

 present period where the water has recently receded. These 

 are our latest Australian tertiaries. Our earliest in South 

 Australia are, as far as we know, the beds previously alluded 

 to as Eocene. While these latter were forming, the land was 

 sinking, and we obtain the knowledge of that fact by many 

 reasons, such as the following I now give. Darwin has justly 

 remarked that very thick fossiliferous beds are only formed 

 during subsidence, and this is borne out by the thinness of 

 the beds lately formed during a period of upheaval. The 

 same illustrious geologist has proved that the whole bed of 

 the Pacific is sinking, and that the subsidence is giving rise 

 to coral islands far away from land. Now at this part of 

 South Australia we have very thick beds, and those too of 

 coral, which I have traced 100 miles inland without any 

 break or sign of land during the epoch of their formation. 

 I think there can be little question that the sea bed must 

 have subsided where any great thickness of coral is found, 

 because it will not live below 30 fathoms, and must soon have 

 perished unless the lowering of the bottom kept pace with its 

 building operations, or at all events would not give rise to 

 thick strata, unless during subsidence. We have, then, evi- 

 dence of subsidence and upheaval. Between these periods 

 we find beds deposited from a deep sea current, which have 

 afterwards been washed away, probably by the denudation 

 they were exposed to during their uprising. I apprehend, 

 therefore, the series of changes which have taken place to 

 be somewhat in the following manner : the land was sinking 

 slowly during the Eocene period, and the coral animal made 

 up for the subsidence by its continual labours, just as it does 

 now in the Pacific. Though this would prevent any very 

 deep water being found on the site of the former land, yet 

 the subsidence would, of course, remove the reef further and 

 further away from the land, and render it more exposed to 

 the action of the sea. Extensive changes in the relative 

 position of the land would give rise to changes of temperature, 

 and new ocean currents would be the result. Now the coral 

 would not have stopped building as long as the animal could 

 keep pace with the subsidence, but any current bearing sedi- 

 ment would kill it speedily. Darwin, and other voyagers, 

 give many instances of this ; but a stream of sediment, did, 

 according to the evidence we have, break over the coral and 



