THE HAWKESBURY SANDSTONE. 101 
_ not truly horizontal ; but they are horizontal enough to be called, 
as they are by Darwin, Clarke, and Mr. Tenison-Woods himself, 
Indeed, allow the action of water in swamps or pools, and in 
, Of which action the shales intercalated in the sandstone give 
frequent, indications. They have been, he says, deposited in the 
ps, and subsequently eroded by the creeks, And this would 
‘ecount for many, but not for all of the phenomena presented. 
quote Darwin again: “In several 3 of the sandstones I no- 
iced patches of shale, which might at the first glance have been 
mistaken xtraneous fragments ; their horizontal lamine, 
Af the successive layers of sandstone were de xam) 
‘milar erosion are common ; an excellent one occurring in a 
‘Marry to the west of Rushcutter’s Bay, which is duplicated by a 
cues parallel section at the foot of the cliff to the east of Wol- 
loo. The evidence in favour of the existence of strong 
: Surrents of water is unmistakable. They have cut channels 
- through sands and shales, and filled them up again, sometimes 
_ Mth stuff derived from the immediate neighbourhood, containing 
frgments of the already indurated beds, and sometimes with clean 
“ud whi may have been drifted some distance. Such rivers are 
ound in a system of sandhills, unless the dunes be 
by the river, or intervene between it and the sea. 
