104 
Geology of Sydney. 
seen all the leading characteristics of the Hawkesbury 
series. This formation underlies nearly the whole of 
the Sydney district, and consists of thick and thin 
horizontal beds of white and brownish yellow sand- 
stone, passing occasionally into grits and conglomerates, 
with a few interstratified lenticular beds of shale 
resembling the Wianamatta shales. These shale-beds 
were formed in small saucer-like hollows, and may be 
considered as miniature precursors of the Wianamatta 
formation which filled a wide depression caused by 
the elevation of the surrounding portions of the 
Hawkesbury formation.” 
The character of the Sandstones on the Mountains 
differs very little from the rock as seen round Sydney, 
that is, as far as its composition and intimate structure 
are concerned. The cementing matter holding the 
grains together is the same. The materials of the 
grains themselves — quartz — are the same. The beds 
are divided by bands of shale, but naturally there 
is a very great difference in the cohesion of the 
various beds of sandstone. A bed may be found 
quite friable or so divided into layers by ^cross- 
stratification ” as to be useless for a building-stone. 
Examples of this cross- stratification are very charac- 
teristic of the sandstones, and localities where the 
structure is very pronounced are too numerous 
to mention. The cliffs north of Bondi Bay furnish 
some very good examples. But, as a matter of fact, a 
pleasure trip in any direction, even to Manly, will 
