314 CORALS AND CORAL ISLANDS. 



XIV. THE OCEANIC CORAL ISLAND SUBSIDENCE. 



Coral islands have been shown to be literally monuments 

 erected over departed lands ; and, through .the evidence from 

 such records, it is discovered that the Pacific has its deep-water 

 mountain chains, or lines of volcanic summits, not merely 

 hundreds, but thousands of miles in length. Some of the 

 ranges of high islands are proved by such records to have an 

 under-water prolongation, longer than that above water : the 

 Hawaian Islands for example, which have a length of only 

 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. 170° E. and lat. 

 19° N;, north of the Ralick and Radack (or Marshall) groups, 

 are in Hnear ranges.; and they have, along with the equally 

 linear ranges of high islands just south, a nearly uniform 

 trend, curving into north-west and north-north-west at the 

 western extremity. The coral islands consequently cap the 

 summits 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 280, 

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

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



