J. D. Dana — Origin of Coral Reefs and Islands. 99 



pango Bay, in which we anchored in 174 feet water, has a length 

 of three miles. The coral reefs are of the fringing kind where 

 anv occur. .Upolu, a few miles west, has bold shores and 

 small or no reefs for fifteen miles of its north shore, east of 

 its middle ; but elsewhere there are broad reefs — mostly 5000 

 to 8000 feet in width — and a very gentle slope (three to 

 six degrees) in the land above — which is about the slope 

 of its underlying lava streams. The great width of the 

 reef seemed to be evidence of subsidence. But the absence 

 on the north side of the island of a channel in the reef 

 deep enough for any craft larger than canoes made it es- 

 sentially a great fringing reef. A calculation from the width 

 and land-slope gave about 260 feet for subsidence ; but I add 

 (on page 332 of my Report) my doubt as to any subsidence. 

 The facts known are against any elevation. 



Savaii, the largest island of the group, is a gently sloping 

 volcanic mountain, much like its name-sake, Hawaii, in its 

 features, with lavas looking as if not long out of the fire. It has 

 a broad reef for only 6 or 7 miles of its east shore ; elsewhere 

 on the east and northeast sides the reefs are fringing or want- 

 ing ; and on the southern and western sides mostly absent. No 

 evidence of elevation, and nothing certain as to subsidence, has 

 been reported from the island. 



The large Feejee Group bears abundant evidence of subsi- 

 dence in its very broad reef-grounds, barrier islands, and atolls. 

 Fringing reefs, or barriers with very narrow channels, occur 

 about some of the islands of the group ; but in view of the 

 facts that have been stated, these are useless as evidence either 

 way. 



Thus the conclusions as to the changes of level about these 

 large Pacific groups south of the equator are not far from Dar- 

 win's, although fringing reefs and the volcanic character of the 

 islands are thrown out of consideration, and other conditions 

 exist of varied interpretation. 



But cases of actual elevation occur in the Central Pacific 

 about several smaller islands as proved by elevated coral reefs. 

 These occur in the Austral and Hervey Islands south and 

 southeast of Tahiti, and in the Tonga or Friendly Islands. In 

 none of these, however, thus far reported is the elevation over 

 300 feet: and the amount varies greatly in adjoining islands of 

 the same group, some affording proof of no elevation. Hence 

 only local changes of level, not a general elevation, can be in- 

 ferred. 



To the north of the equator at the Sandwich Islands some 

 elevated reefs occur. But the amount of elevation is small and 

 is not general in the group. Moreover, the reefs are small, 

 where any occur, and the largest island of the chain, volcanic 



