ANNIVERSARY ADDRESS. 69 
time, as that ancient river had only just succeeded in cutting its 
channel down to the level of the top of the Hawkesbury Sand- 
stone. Then followed the gradual folding of the earth’s crust 
along the Lapstone monocline, accompanied by more or less 
extensive volcanic eruptions, in the neighbourhood of Prospect, 
Pennant Hills etc., in the coastal strip, and The Valley, Euroka 
Creek etc. in the Blue Mountains. The erosion of the lower 
portions at any rate of the valleys of the Blue Mountains dates — 
from the formation of the monocline, since which time they 
have been deepened to the extent of six hundred feet or more. 
While the monocline was forming the coastal strip was slowly 
subsiding ;.and in the now submerged valleys along the seaward 
margin of this strip were laid down the sands and gravels succes- 
sively of Pleistocene and Recent Age. It would be of importance 
to ascertain by means of accurate measurements whether the 
subsidence is still in progress. My thanks are specially due, for 
information supplied me for this paper, to the following :—T. F. 
Furber, 1.g., H. Deane, m.a., ‘M.LGE., F.L.S8., W.S. Dun, and A. J. 
Prentice, B.A. 
Norss. 
1. It is stated in this address that the Sandstone plateau of the 
Blue Mountains attains an elevation of about 4,000 feet. It is 
questionable, however, whether any portion of the Blue Mountains 
proper attains a greater elevation than about 3,800 feet. 
2. While the proofs of this address were being revised, I have 
been able to obtain further evidence which shows that the coal, 
disrupted by the volcanic neck at Euroka Farm, (Diagram 2, 
Plate 3) was probably derived from the Hawkesbury Sandstone 
rather than from the Permo-Carboniferous coal-measures. 
