THE OCEANIC CORAL-ISLAND SUBSIDENCE. 365 



four hundred miles from Hawaii to Kauai, and five hundred 

 and thirty to Bird Island, the western rocky islet of the group, 

 stretch on westward, as the coral registers show, even to a dis- 

 tance of two thousand miles from Hawaii, or, as far as from 

 New York to Salt Lake City ; and how much farther is un- 

 known, as the line of coral islands here passes the boundary 

 of the coral reef seas, or the region where coral records are 

 possible. 



Other ranges of submerged summits are shown to extend 

 through the whole central Pacific, even where not a rocky 

 peak remains above the surface; for all the coral islands from 

 the eastern Paumotus to Wakes' Island, near long. 1 70° E. 

 and lat. 19° N., north of the Palick and Padack (or Marshall) 

 groups, are in linear ranges ; and they have, along with the 

 equally linear ranges of high islands just south, a nearly uni- 

 form trend, curving into northwest and north-northwest at the 

 western extremity. The coral islands consequently cap the sum- 

 mits of linear ranges of elevations, and all these linear ranges 

 together constitute a grand chain of heights, the whole over five 

 thousand miles in length. Thus, the coral islands are records 

 of the earth's submarine orography, as well as of slow changes 

 of level in the ocean's bottom. 



This coral island subsidence is an example of one of the 

 great secular movements of the earth's crust. The axis of the 

 subsiding area — the position of which is stated on page 326, 

 has a length of more than six thousand miles — equal to one- 

 quarter of the circumference of the globe; and the breadth, 

 reckoning only from the Sandwich Islands to the Friendly 

 Group (or to Tongatabu) is over twenty-five hundred miles, 

 thus equalling the width of the North American continent. 

 A movement of such extent, involving so large a part of the 

 earth's crust, could not have been a local change of level, but 



