Land-tracts during the Secondary and Tertiary periods. 169 



Australia in the examination of their geological features. The 

 similarity of these features over a large tract, coupled with the 

 exhibition of similar features wherever exploring vessels have ex- 

 amined the eastern sea border, favours the inference that the 

 whole of Eastern Australia is one geological system composed of 

 disrupted palaeozoic formations, and having a strike throughout 

 from north to south. The resemblance of this structure to that 

 of the Appalachian and Rocky-Mountain chains is striking. 

 Here, as there, the Devonian and carboniferous deposits have 

 been broken up into numerous parallel ridges from north to 

 south, showing the origin of the system to be subsequent to the 

 carboniferous period, but prior to the deposit of the coal-bearing 

 strata of this continent, which, like those of India, appear to be 

 of secondary age, these coal-bearing strata resting in Australia 

 unconformably on the true carboniferous and older palseozoic 

 strata*. 



The schistose system of New Zealand seems evidently due to 

 the same elevatory action as that which formed the Australian 

 system, since the coast-line of that island is almost identical with 

 the opposite shore of Australia in a somewhat lower latitude. 



Lastly, we have the grandest mountain system of the world — 

 the Andes — exhibiting similar features to the other systems 

 above discussed. This chain exhibits the greatest constancy of 

 direction of any, and in its extent it is unrivalled. The reports 

 and sections published of this chain, the latest of which is the 

 elaborate memoir of Dr. Forbes, show that this system, although 

 still in the height of its activity, had its origin as far back as the 

 oolitic period f, if indeed it do not eventually prove, as there is 

 reason to believe, to have been brought into existence, like the 

 Oural and the other systems to which I have adverted, at the 

 close of the carboniferous epoch. The activity of this volcanic 

 chain during the secondary period is shown by the forma- 

 tions of that period being interstratifled with porphyries and 

 other volcanic rocks ; and the direction of the volcanic band is 

 shown to have been, during the period, coincident with that of the 

 present chain, by the circumstance that these secondary deposits, 

 so interstratified with volcanic rocks of contemporaneous date, 

 lie in a band from north to south between the palseozoic forma- 

 tions of the central or higher region of the Cordillera and the 

 Pacific, forming a subordinate division of the chain of lower ele- 

 vation, and comprising within it the greater part of the existing 

 volcanoes of the Cordillera. It is worthy of remark also, as 

 showing the identity of this system with that of the Rocky 

 Mountains, that Dr. Forbes in the one, and Dr. Hector in the 



* See Selwyn, Quart. Journ. Geol. Soc. vol. xiv. p. 533. 

 t See Darwin's ' South America/ p. 247. 



