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ANNIVERSARY ADDRESS. 4] 
upon with such awed delight, the vast forest-clad landscape stretches 
away and breaks up into dark cobalt blue hills, wherein is repeated 
the same unique scenic character.” 
A brief description may now be introduced of the physical © 
geography and geology, including the probable mode of origin, of 
the Blue Mountains as far as at present known. 
1. Physical Geography—A. Boundaries.—The geographical 
do not agree with the geological boundaries, the area to which the 
term Blue Mountains is applied embracing only a small portion 
of the great geological formation of which the mountains are built. 
On the west the Blue Mountains are bounded by the well-marked 
escarpment over which the western railway runs at the Great 
Zigzag above Lithgow ; on the east they are bounded by a well- 
_ marked monoclinal fold crossed by the western railway at Lapstone 
Hill at the Little Zigzag between Emu Plains and Glenbrook. 
While the east and west boundaries are sharply defined at the 
above mentioned localities, they become less and less clear when 
traced respectively to the north and south of the western railway 
line, and it is a matter of uncertainty as to where the exact 
boundary line of the Blue Mountains should be drawn on the 
south and on the north. The southern boundary line is usually 
fixed at the valley of Cox’s River and that of the Warragamba 
River ; and the northern boundary at the Capertee valley and 
Colo valley. [See Plate 1.] 
The geological boundaries, however, are co-terminous with those 
of the Hawkesbury series, and extend from the Cambewarra 
Ranges, near Nowra, on the South, to at least as far as the Liver- 
pool Ranges on the north; and from the head of the Talbragar 
River on the west, to probably the edge of the continental shelf, 
about twenty miles east of the present coast line, on the east, 7.¢., 
for a distance of about two hundred miles from north and south, 
and one hundred and fifty miles from east to west. | 
B. Relief.—Geologically, as well as geographically, this larger 
area may be divided into. three portions, (1) the plateau of the 
