512 THE DISTRIBUTION, ETC , OF ALKALINE ROOKS, 



period, relics of Atlantis, of the Brasilio-Ethiopian Continent, of 

 (rondwana-land, of Antarctica, of Angara, and of Lemuria. 



In this connection it would be interesting, though perhaps nob 

 very profitable, to discuss the bearing of Jean's theory of a pear- 

 shaped earth on the occurrence of alkaline lavas in the Sandwich 

 Islands. 



How far the alkaline areas coincide with or distance them- 

 selves from the old eroded mountain-chains becomes a more 

 difficult problem, and one of less immediate interest I know of 

 no exact identity of an alkaline area with the core of an old 

 mountain-chain, yet the alkaline belts often lie very close to 

 eroded ranges There appear to be no true alkaline intrusives 

 in the old Carboniferous chain which runs along our coast to the 

 south of the Shoalhaven River, nor in the heart of the old eroded 

 ranges of Victoria, nor in the New England ranges, nor in the 

 old Barrier and Cobar ranges. The tinguaites of Kosciusko 

 occupy a different position, being situated in a block mountain, 

 which may have been continental all the time from Ordovician 

 or early Silurian to the present. 



The Situation of Alkaline Rocks with Regard to Faults. 



It has already been shown that alkaline rocks are often abun- 

 dant in highly faulted areas, but not in those areas where 

 faulting is due to compression and mountain-building. They are 

 always associated with trough-faults, block-mountains and 

 senkungsf eld-areas due to contraction. No foyaitic rocks occur 

 in the immense overthrust regions of Scotland, but in the frag- 

 mented region of the Hebrides they are met with. Throughout 

 the area of mythical Atlantis,* destroyed by mighty subsidences, 

 they abound. Throughout that intensely fragmented portion of 

 Gondwana-land now situated in the Indian Ocean between 

 Madagascar, Arabia and Abyssinia, they are equally plentiful. 

 Throughout Antarctica, which has been similarly fragmented, and 

 in which the Scott Expedition observed faulted cliffs, the faces of 



* " Atlantis r ' by Ignatius Donnelly. 



