INTRODUCTION. XXi 



mode of formation of the recent corals around the base of the elevated 

 volcanic mass. 



The want of continuity of the atolls of the eastern Paumotus, of the 

 EUice, Gilbert, and Marshall Islands, their separation by considerable dis- 

 tances and great depths, would seem to preclude the idea of the formation 

 of tertiary limestones over great areas. The existence of these discon- 

 nected and isolated limestone islands would suggest their formation upon 

 mounds or ridges elevated to very different heights below the surface of 

 the ocean, — the mounds and ridges consisting of volcanic or other rocks 

 elevated by the volcanic agencies we know to have been active over 

 very extensive areas of the Pacific from tertiary times to the present 

 day. In some of the Pacific archipelagoes the areas covered by the ter- 

 tiary limestones are of considerable extent, as, for instance, the plateau of 

 the northwestern Paumotus, of the Tonga Islands, and that upon which 

 the eastern islands of the Fiji Archipelago rise : the so-called Lau or Wind- 

 ward group of Fiji. Conditions similar to those under which the central 

 Pacific tertiary limestones were deposited must have been of wide geograph- 

 ical range ; they appear in the Philippines, the Loyalty, the New Hebrides, 

 and Solomon Islands, in New Caledonia, in the China Sea, the East Indian 

 Archipelago, at Christmas Island in the Indian Ocean, the Red Sea, and 

 the West Indian area. 



Dana very justly remarks : " It is important to have in mind that the 

 coral-reef era probably covered the whole of the Quaternary and perhaps the 

 Pleiocene Tertiary also, and hence the local elevations that have taken place 

 in the ocean were not crowded events of a short period." ^ 



The boring at Funafuti will show us the character and age of the rocks 

 underlying the mass of recent material of which the land rim, not only 

 of that atoll, but probably also that of the other atolls of the Ellice and 

 of neighboring groups, is composed ; though of course we can only judge 

 by analogy the probable character of the underlying base from that of 

 the nearest islands where it has been ascertained. The bore at Funafuti 

 reached 1114 feet; it passed at first through the modern reef rock 



1 Dana, J. D., Origin of Coral Reefs and Islands. Am. Jour. Scien., XXX., September, 1885, 

 p. 173. 



