154 New South Wales. paet i. 



stated) that a comparatively small amount of subse- 

 quent erosion would form them into cliffs: that the 

 waves have power to form high and precipitous cliffs, 

 even in land-locked harbours, I have observed in many 

 parts of South America. In the Eed Sea, banks with 

 an extremely irregular outline and composed of sedi- 

 ment, are penetrated by the most singularly shaped 

 creeks with narrow mouths : this is likewise the case, 

 though on a larger scale, with the Bahama Banks. 

 Such banks, I have been led to suppose, 1 have been 

 formed by currents heaping sediment on an irregular 

 bottom. That in some cases, the sea, instead of spread- 

 ing out sediment in a uniform sheet, heaps it round 

 submarine rocks and islands, it is hardly possible to 

 doubt, after having examined the charts of the West 

 Indies. To apply these ideas to the sandstone plat- 

 forms of New South Wales, I imagine that the strata 

 might have been heaped on an irregular bottom by the 

 action of strong currents, and of the undulations of an 

 open sea ; and that the valley-like spaces thus left un- 

 filled might, during a slow elevation of the land, have 

 had their steeply sloping flanks worn into cliffs; the 

 worn-down sandstone being removed, either at the time 

 when the narrow gorges were cut by the retreating sea, 

 or subsequently by alluvial action. 



Van Diemen's Land. 



The southern part of this island is mainly formed of 

 mountains of greenstone, which often assumes a syenitic 



1 See the * Appendix ' (2nd edit. pp. 251 and 255) to the ' Part 

 on Coral Beefs.' The fact of the sea heaping up mud round a sub- 

 marine nucleus, is worthy of the notice of geologists : for outlayers 

 of the same composition with the coast-banks are thus formed ; and 

 these, if upheaved and worn into cliffs, would naturally be thought 

 to have been once connected together. 



