1883.] 479 [Crosby. 



coral islands that the depth of the Polynesian sea has increased 

 at least 10,000 feet, or two miles, in comparatively recent geolog- 

 ical times. The present average depth of this part of the Pacific 

 is probably not more than three miles. Consequently, when the 

 great coral island subsidence began the average depth was about 

 one mile. Now no one can doubt that the elevation of Polynesia 

 by two miles would bring into existence hundreds, perhaps thous- 

 ands, of new islands and greatly extend the area of those now 

 existing, probably uniting whole groups into one or two large 

 islands, and thus giving Polynesia the aspect of a larger Malaysia. 

 Mr. Wallace has shown very clearly that the Malay Archipelago, 

 like the West Indian Archipelago, is a vast area of half-sub- 

 merged continental land. But probably its appearance is no 

 more continental now than was that of Polynesia before the coral 

 island subsidence began. 



The western islands of Polynesia are the largest, and parallel 

 with this we have the fact that the subsidence, as indicated by 

 the coral monuments and the heights of the volcanic land, in- 

 creases eastward ; so that it seems entirely an arbitrary matter 

 as to where we draw the line between the two great archipela- 

 goes of Malaysia and Polynesia. Professor Dana has directed 

 attention particularly to the fact that the trend of the whole of 

 Polynesia, and of each of the Polynesian groups, is exactly 

 parallel with the Malaysian trend, which is continued through 

 Australia to New Zealand. 



The largest and most western islands of Polynesia, like the 

 still larger islands of the Malay Archipelago, include both the 

 older and newer stratified formations, as well as volcanic rocks. 

 But as we pass toward the east and north the islands not only 

 become smaller, indicating a more profound subsidence in that 

 direction ; but the older stratified rocks disappear and the islands 

 are composed entirely of volcanic materials and coral formations. 



That Sumatra, Java, Borneo, etc., have been a part of the 

 Asiatic continent in very recent geological times few will ques- 

 tion. That Australia and New Guinea have, at an earlier period, 

 been connected with this great Asiatic peninsula is almost equally 

 certain. And that New Zealand, New Caledonia, the Salomon 

 group and New Ireland were, in like manner, once joined to Aus- 

 tralia hardly admits of doubt, in view of the fact that they are, in 



