1847.] JUKES ON AUSTRALIA. 243 



unimportant beds in an economic point of view. Abundance of black 

 silicified wood strewed the road where it crossed these coal-measures, 

 and I have no doubt whole trees might be extracted with compara- 

 tively little cost and trouble. 



3. Of the alternations of shales and sandstones above the coal, I 

 can say nothing more, than that Mr. Clarke recognized them as re- 

 sembling beds he knew in the valley of the Hunter, to the northward, 

 which had the same position with regard to the coal. They were 

 about 400 feet in thickness. 



2. The thick mass of sandstone above them was called by Mr. 

 Clarke provisionally *Hhe Sydney sandstone." It consists of very 

 thick beds of white and light yellow sandstones, in some places fine- 

 grained, at others coarse, and containing small quartz pebbles. Litho- 

 logically it resembles the millstone-grit and the sandstones of the 

 lower coal-measures of the north of England. Its beds are parted 

 occasionally by thin bands of shale and contain no organic remains, 

 so far as is known. Its thickness is fully 700 or 800 feet. 



1. The upper shales contain a few small fragmentary vegetable 

 impressions and bits of leaves, and I believe also some fossil fish. 

 Their thickness must be at least 300 feet, but may be much more. 

 The most conspicuous member of this series in the country around 

 Sydney is No. 2, the Sydney sandstone. The districts composed of 

 it are always rocky and barren, with a level or gently sloping outline 

 when viewed from a distance, but when traversed are found to be 

 eaten into or furrowed in every direction by innumerable ravines. 

 These have almost invariably steep if not perpendicular sides, with 

 projecting and overhanging ledges of rock. They are narrow m pro- 

 portion to their length and depth, the latter often very great, and when 

 the sandstone rises any height above the sea, becomes enormous*. 

 The same character still continues however even below the sea-level, 

 as it is this which gives their peculiar form to the harbours of Port 

 Jackson and Broken Bay, with their many long winding ri^rrow arms 

 bounded by precipitous rocky cliffs. 



The upper shales, as might be expected, form a countiy with very 

 different characters, namely gently undulating plains and round-topped 

 lumpish hills. This is shown in all the district between Paramatta 

 and Emu Plains, Windsor and Campbelltown. 



In a good physical map, such as Sir T. Mitchell's map of New 

 South Wales, these characters become so distinctly marked, as to 

 enable us to give at once a rough approximation to the boundary of 

 the countries occupied by the two kinds of rock. 



By this aid and by the description given me by the Rev. W. B. 

 Clarke, joined to my own cursory observations, I am enabled to state 

 that the country lying between Campbelltown, Paramatta, Windsor, 

 and the Nepean River, forms a flat basin, being composed of the 

 upper shales, from beneath which the Sydney sandstone rises out in 



* See Mr. Darwin's description of two of the most celebrated valleys of this 

 kind on the slope of the Blue Mountains (Darwin's Journal). Mrs. Meredith 

 also descrihes them in her account of New South Wales. 



