24 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



The coal-measures are underlaid by a series of sandstone beds, 

 with some beds of shale. The thickness of the sandstone, in some 

 places, exceeds 2000 feet ; but to the west of the Little Entrance 

 it is much thinner ; and, finally, when it approaches the granite 

 ridge that lies between the Great Entrance and St. Anne's Harbour, 

 it has thinned out. The sandstones, with their superincumbent 

 coal-measures, are very uniform in their dip to the north-east. 



Next to the sandstone is the limestone ; and this accompanies 

 the sandstone very uniformly, along the whole course of its out- 

 crop, from the southern branch of Sydney Harbour to the Granite 

 ridge west of the Great Entrance. On both branches of Sydney 

 Harbour, and at George's River, the limestone dips distinctly be- 

 neath the sandstone. The shore, from George's River to Long Island, 

 gives the following Section, 



Section II. 

 Long Island to the Coal Measures East of George's River. 



Long Island. Round Island. 



Porphyry 



Micaceous Beds. 



/ 



First we have the limestone (e) ; then a low, flat space of half a 

 mile, where the stratification cannot be observed ; then beds of a 

 red and brown micaceous slaty rock, dipping at high angles in 

 various directions between south and west. - 



The base of Round Island is of the same kind of rock ; but the 

 Isle is capped with a limestone which, to judge from its fossils, 

 is quite different from the limestone * above described beneath the 

 sandstone. Long Island, on its eastern side, is 200 feet high, and 

 very precipitous ; but, in a westerly direction, it slopes gradually 

 to the water. It is composed principally of Porphyritic rocks. 



On the opposite side of the channel, the shore exhibits the 

 following section : — 



Section HI. 



First, the sandstone (/) which underlies the coal-measures, and 

 can be traced to within a few hundred yards of Roe's Point. 



At Roe's Point the limestone (containing here Productus Lyelli) 

 shows itself, having an easterly dip. This limestone, both in its 

 local position, dip, and general appearance, corresponds with the 

 limestone on the other side of the channel, at George's River ; 



* This limestone contains Terebratula dongata, and a Modiola. 



