TRANSACTIONS OF SECTION E. 807 



purpose to note tlie fact tliattbe^cqastal ranges of North America and the principal 

 chain of the Andes were all elevated in Tertiary times. It may be remarked, 

 further, that from the Mesozoic period down to tlie present the Pacific borders of 

 America have been the scene of volcanic activity far in excess of what has been 

 experienced on the Atlantic sea-board. 



Geographically the Asiatic coasts of the Pacific offer a strong contrast to those 

 of the American borders. The latter, as we have seen, are for the most part not 

 far removed from the edge of the continental plateau. The coasts of the mainland 

 of Asia, on the other hand, retire to a great distance, the true margin of the 

 plateau being marked out by that great chain of islands which extends from 

 Kamchatka south to the Philippines .and New Guinea. The seas lying between 

 those islands and the mainland occupy depressions in the continental plateau. 

 Were that plateau to be lifted up for 6,000 or 7,000 feet the seas referred to would 

 be enclosed by continuous land, and all the principal islands of the East Indian 

 Archipelago— Sumatra, Java, Celebes, and New Guinea — would become united to 

 themselves as well as to Australia and New Zealand. In short, it is the relatively 

 depressed condition of the continental plateau along tlie western borders of the 

 Pacific basin that causes the Asiatic coast-lines to diU'er so strikingly from those of 

 America, 



From a geological point of view the differences are less striking than the 

 resemblances. It is true that we have as yet a very imperfect knowledge of the 

 geological structure of Eastern Asia, but we know enough to justify the conclusion 

 that in its main features that region does not differ essentially from "Western North 

 America. During Mesozoic and Cainozoic times the sea appears to have over- 

 flowed vast tracts of Mauchooria and China, and even to have penetrated into 

 what is now the great Desert of Gobi. Subsequent crustal movements revo- 

 lutionised the geograpliy of all those regions. Great ranges of linear uplifts came 

 into existence, and in these the younger foi-mations, together with the foundations 

 on which they rested, were squeezed into folds and ridged np against the nuclei of 

 Palaeozoic and Archaean rocks which had hitherto formed tlie only dry land. The 

 latest of these grand upheavals are of Tertiary age, and, like those of the Pacific 

 slope of America, they were accompanied by excessive volcanic action. The long 

 chains of islands that flank the shores of Asia we must look upon as a series of 

 partially submerged or partially emerged mountain-ranges, analogous geographi- 

 cally to the coast ranges of North and Central America, and to the youngest 

 Cordilleras of South America. The presence of numerous active and recently 

 extinct volcanoes, taken in connection with the occurrence of many great depres- 

 sions which furrow the floor of the sea in the East Indian Archipelago, and the 

 profound depths attained by tlie Pacific trough along the borders of Japan and the 

 Kurile and Aleutian Islands — all indicate conditions of very considerable instability 

 of the lithosphere. We are not surprised, therefore, to meet with much apparently 

 conflicting evidence of elevation and depression in the coast-lands of Eastern Asia, 

 where in some places the sea would seem to be encroaching, while in other regions 

 it is retreating. In all earthquake-ridden and volcanic areas such irregular coastal 

 changes may be looked for. So extreme are the irregularities of the sea-floor 

 in the area lying between Australia, the Solomon Islands, the New Hebrides, and 

 New Zealand, and so great are the depths attained by many of the depressions, 

 that the margins of the continental plateau are harder to trace here than any where 

 else in the world. The bottom of the oceanic trough throughout a large portion 

 of the Southern and Western Pacific is, in fact, traversed by many great mountain 

 ridges, the summits of which approach the surface ay:ain and again to form the 

 numerous islets of Polynesia. But notwithstanding the considerable depths that 

 separate Australia from New Zealand there is geological evidence to show that a 

 land connection formerly linked both to Asia. The continental plateau, therefore, 

 must be held to include New Caledonia and New Zealand. Hence the volcanic 

 islets of the Solomon and New Hebrides groups are related to Australia in the 

 same way as the Liu-kiu, Japanese, and Kurile Islands are to Asia. 



Having rapidly sketched the more prominent features of the Pacific coast-lines, 

 wo are in a position to realise the remarkable cor.trast they present to the coast- 



