in South Australia. 93 



terminate its existence. This deposit was, therefore, stopped 

 by a new one taking its place, -which was of quite a different 

 nature, being that which we find at Guichen Bay. How 

 long after this the land continued to subside cannot be guessed, 

 for we do not, and cannot, now know the extent of the beds 

 formed subsequently. "We see, however, that a change came 

 at last, and upheaval followed, but so slow that coast action 

 had time to remove successively, except in one or two places, 

 all that the deep water current had thrown down, leaving 

 only the dead coral exposed to view. All the facts given 

 above bear out the correctness of these views, but of course I 

 am far from claiming adhesion to them as perfectly certain. 

 Indeed I have rather occasion to warn the Institute that 

 neither my attainments nor habits of inquiry at all constitute 

 me an infallible guide, and I shall consider myself fortunate 

 if future and more experienced enquirers find nothing to 

 correct in my theories. With regard to the nature of the 

 rocks at Guichen Bay, I will just remark that though ocean 

 currents generally seem to be clear water on the surface, they 

 must carry sediment along the bottom, and that wherever 

 soundings have been taken in them, the bottom has been 

 found to consist of shells and fine sand. Sometimes, how- 

 ever, currents are found charged with sediment at the sur- 

 face, such as those proceeding from the mouths of rivers, and 

 then the water occasionally has a muddy tinge even at great 

 distances from the coast. 



I would extend this paper beyond reasonable limits, were 

 I to give all the facts I have noticed connected with the sub- 

 ject. I will, therefore, conclude by calling attention to the 

 vast operations of nature which are here disclosed. It is not 

 alone the enormous subsidence which at first caused a deep 

 coral reef and then an open sea (which must have maintained 

 for ages to give rise to such a thickness of sedimentary rock), 

 which must excite surprise. Nor is it the long period of up- 

 heaval. But the immense amount of denudation which has 

 removed hundreds of square miles of thick beds of rock, is 

 certainly a work of such magnitude as to excite wonder and 

 amazement. At all events there is a fine agricultural country 

 over the spot where such changes were operated, and the 

 Mount Gambier volcano is a witness as to the cause which 

 rescued land from sea. Many interesting questions remain 

 to be asked, which can only be answered by very extended 

 investigation. We might enquire whether the subsidence 

 was very general in Australia. Also, whether the bed of the 



