528 GEOLOGY OF THE CLARENCE RIVER BASIN, 



both were borne to the ocean by the main artery, the present 

 Clarence. For the water courses were now determined, and the 

 great river now swept into the sea somewhere near its present 

 mouth. But the relative levels of land and water were very 

 different. It is likely enough that the river was swift and 

 turbid, with a rocky bed, and a rocky sea shore on which to 

 disembogue. The miserable eminences of rock which now break 

 the level of the sea coast dunes were then high crags, hundreds of 

 feet above the water, and connected by rocky ranges, which are 

 now reefs, at almost an equal elevation. Somewhere under 

 the sand hills which now impound the inland waters there was a 

 deep valley or pass through which the river sped in its outward 

 course. But the river bed of that time must lie not less 

 than five hundred feet below the level of the present. For 

 another oscillation had yefc to take its turn. The land once 

 more began to sink, the currents to slacken, channels 

 to shoal, rivers to spread, swamps to form, forests to be 

 flooded, to die, and be buried as they lay in the accumulation 

 of sediment. In short the present period of subsidence had begun. 

 This action is still continuing, and, if it be directly connected with 

 the submergence of the N. E. Coast, and the growth of the Barrier 

 reef, is likely to go on, at whatever time it may have com- 

 menced, to far remote eras of Geological time. That allu- 

 vium is still accumulating upon the surface is obvious. 

 For the river banks are considerably higher than the 

 ground behind, which falls away into swamps, salt marshes, and 

 lakes ; and this elevation of the banks is of course due to the 

 deposit of detritus in inundations. Twenty years ago, when a 

 wall of rich tropical jungle rose directly from the waters edge, the 

 turbid waters were strained of their sediment, by filtering through 

 the matted underbrush and forest rubbish which then covered the 

 ground, so that the ultimate overflow into the back lands consisted 

 of comparatively clear water. Hence while the river was con- 

 tinually though slowly rising, by the increment which each 

 flood contributed so as to embank it with natural levees, 

 these back lands were kept more nearly at their original 



