ANNIVERSARY ADDRESS. 37 
the mountains must have required violent convulsions in the 
earth’s crust for their formation. But if we examine the rocks 
on all sides of the valley, we see no breaks nor signs of violent 
disturbance as suggested. The various beds of rock in horizontal 
strata may be seen to continue uninterruptedly around the sides 
of the valley, and the succeeding layers of rock, as we descend 
one side of the ravine, gradually approach the corresponding layers 
ou the other side, until at the bottom, in the bed of the water- 
course, we find that they actually join, which they would not do 
if the sides of the ravine had been violently torn asunder. We 
perceive, therefore, that the various outcropping strata must once 
have been continuous right across the valley or ravine, and that 
they have been removed by some agency without disturbance of 
the underlying beds. What then is this agency? Not volcanie 
fire but running water.” The above passage makes it clear that 
Mr. Wilkinson was of opinion that the valleys of the Blue Moun- 
tains were due to subaerial erosion only, and that they were not, 
as Darwin thought, original depressions, deeply indenting sub- 
marine banks, the sides of which had subsequently been rendered 
precipitous, partly by marine, partly by fluviatile erosion. 
One of the most important statements about the geology of the 
Blue Mountains is the following by the same observer! :—“ It will 
thus be seen that this locality (Port Hacking), is over a very deep 
portion of the coal basin. The eastern portion of this basin has 
been apparently faulted and thrown down beneath the waters of 
the Pacific Ocean, the precipitous coast, and a line about twenty 
miles east from it, marking approximately the lines of dislocation. 
The deep soundings immediately beyond this would seem to favour 
this view, so that here the bed of the ocean probably consists of 
the old land surface which once formed a continuation of that 
upon which the city of Sydney now stands, and which has been 
faulted to a depth of over 12,000 feet ; the length of the faulted 
area is not yet known, but it probably does not extend along the 
coast beyond, if so far as, the north and south limits of the Colony. 
1 Mineral Products &c. of New South Wales. By Authority, oe 
1882, p. 52. (In Second Edition 1886, p- 70.) 
