70 president's AD»RE88 — SECTION C. 



of the shore-line to the south-west, the latter being composed 

 of highly folded and foliated Silurian rocks. 



This volcano appears to have been formed at the time of 

 the cessation of the prolonged subsidence of the floor of the 

 Permo- Carboniferous ocean between Ulladulla and Raymond 

 Terrace, the subsidence being due to this part of the earth's 

 crust being loaded with over 2000 feet of Lower Marine and 

 5000 feet of Upper Marine sediment. 



The older lavas of the Canobolas, near Orange, may also 

 have been erupted about this date. Near Rylstone, and in 

 the Murrurundi District, in New South Wales, there is abun- 

 dant evidence of volcanic action being continued into the age 

 of the Middle, and, perhaps, even into that of the Upper 

 Permo-Carboniferous Coal Measures, the volcanoes in each 

 case being situated in close proximity to the shore-lines of the 

 Permo-Carboniferous ocean. 



At the close of the Permo-Carboniferous period an addi- 

 tional 3000 feet of sediment had been added in some localities 

 to the 7000 feet of Permo-Carboniferous rocks already 

 deposited, and in the succeeding basement beds of the 

 Hawkesbury series there is evidence of a return of volcanic 

 activity on a small scale, in the shape of contemporaneous 

 tuffs, which occur on various horizons in the Hawkesbury 

 Series up to a level of about 2000 feet above the top of the 

 Permo-Carboniferous Coal Measures. 



With the deposition of the Hawkesbury sandstone and of 

 the Wianamatta shales the exceptionally heavy sedimenta- 

 tion of the Permo-Carboniferous period and of the Lower 

 Mesozoic rocks was brought to a close ; and there is no 

 evidence of a return of volcanic activity to New South 

 Wales, or, at all events, to the eastern portion of it, until 

 Tertiary time, unless, perhaps, the small sheets of leucite 

 basalt at Byrock and El Capitan may be referred to some 

 time about the close of the Mesozoic era. It is a remark- 

 able fact that there are no sediments of any thickness in that 

 portion of New South Wales which intervenes between the 

 Cordillera and the ocean older than early Mesozoic, and 

 during the long period of time which intervened between the 

 formation of the last of the Hawkesbury rocks and the 

 commencement of the Tertiary era the eastern portion of 

 New South Wales was not again visited by volcanic out- 

 bursts. 



In the Lower Mesozoic rocks of Queensland of Triassic 

 or Lower Jurassic age, Mr. Jack describes the occurrence 



