CHAPTER XII. 
ORIGIN OF THE MOUNTAINS. 
ORIGIN OF THE BLUE MOUNTAINS — THE MOUNTAINS 
FROM SILURIAN TO TRIASSIC TIMES — THE SCULPTURING 
OF THE MOUNTAINS — THE WORK OF RUNNING WATER. 
In looking back through the long ages of geological 
time, the earliest glimpses we get of the area now 
covered by the dividing chain, west of Sydney, is in 
Silurian times. We see a wide expanse of ocean, the 
nearest dry land being probably a pre-Silurian con- 
tinent, remnants of which are found in the McDonell 
Ranges, Yorke’s Peninsula, and Tasmania. Alter the 
deposition of the series of sediments that go to make 
up our Silurian rocks, vast earth movements caused 
the stratified rocks to be thrown into great folds, so 
that beds ten miles long were so compressed as to 
occupy but one half that length. This folding pro- 
duced elevated ridges in the earth’s crust, with a 
general north and south trend, and we have here the 
first indication of a mountain region — a condition 
that did not, however, long continue. The Silurian 
sediments are thus the oldest rocks we know of 
on the Dividing Chain. But it must not be taken 
for granted that the present mountains were there- 
fore formed in Silurian times. We date the age of 
