442 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 11, 



ing the usual woody sound wlien struck. They ignite readily by a 

 lighted match. The section exhibits an escarpment of 500 feet of 

 Hawkesbury rocks resting on 800 feet of Coal-measures, which exhibit 

 various distinguishing differences when compared with the Newcastle 

 beds, and are supported by the Upper Marine beds, which rise in a 

 dome-like form, and exhibit an approach rather to the beds immedi- 

 ately below the Muree series than to those of that place, reminding 

 one of the deposits near Harper's Hill, where basalt, as in the neigh- 

 bourhood of WoUongong, intrudes into and disturbs them, and where 

 they are succeeded by just such beds as mark the base of the Coal- 

 measures under Mount Keira. Certainly the Newcastle coal-seams 

 are not represented in the Illawarra section ; but the evidence is 

 perfectly distinct as to the inflammable beds belonging to the upper 

 part of the Upper Coal-measures. 



A view has been taken by some observers, of the connexion of the 

 Illawarra and Lower Hunter coal-beds, which would place them in 

 the same angular relation with the axis of the basin. This I believe 

 to be altogether erroneous. A considerable portion of the eastern 

 side of it has been entirely swept away; and traces of former surfaces 

 which must have belonged to a wider area are now apparent on the 

 summit of insulated points along the coast, that can only be accounted 

 for by admitting the destruction of considerable masses. This ex- 

 planation was offered by myself many years ago, and has been con- 

 firmed by more recent observations. Others have adopted this opinion; 

 but they have not coupled it with the fact, which I consider capable of 

 clear establishment, that the Illawarra and Newcastle beds are not 

 in the same plane. The coast-line is not that of the axis of the 

 basin, but cuts it obliquely ; so that different portions of the same 

 series of beds are represented in what would otherwise be about the 

 same longitudinal horizon. Looking at the matter in this way, the 

 strike of the Illawarra beds would appear to be full 25 miles to the 

 eastward of Newcastle, which will account for the existence of beds 

 in the former district which are not represented in the latter, but 

 which were once continuous over them. A further deduction from 

 this view is, that parts of the Coal-measures of the Illawarra, the 

 Shoalhaven, the Wollondilly, and the Cox river-basins are unques- 

 tionably the uppermost portions of the great eastern coal-field, the 

 middle and lower parts of which are so abundantly developed in the 

 basins of the Page, Goulbourn, and Hunter river-basins. 



Were it possible here to enter into a close investigation of this 

 subject, by reference to the evidence of the fossils collected from 

 the different members of the series, it could be shown that the cha- 

 racteristic species of the upper beds are not altogether those of the 

 middle and lower, although, generally speaking, there are the same 

 genera in all. 



5. River Nattai. — The Upper Coal-measures extend along the 

 heads of the creeks forming the Nattai Eiver ; these creeks run in 

 deep ravines, cutting the series from the Hawkesbmy rocks down to 

 the Upper Marine beds, which come in (as at the same distance in 

 the Illawarra, ascending Mount Keira) about 250 feet beloAV the lowest 



