On the Formation and Growth of Coral Reefs and Islands. 45 



ON THE FORMATION AND GROWTH OF CORAL REEFS AND 

 ISLANDS. 



BY S. STUTCHBURY. 



Being a Paper read lefore the Philoso})fiical and Literary Society of Bristol, 

 March, 1832. 



In attempting to embody in a popular form, the following brief outline 

 of the history of coral reefs and islands, it will be necessary to premise the 

 subject by stating, that the greater portion of the matter will be found to 

 assimilate very closely to that of various published authorities, but cor- 

 roborated by personal observations made among the Islands of the South 

 Pacific, particularly those denoted on the charts by the name of the Dan- 

 gerous Archipelago, and situated between the latitudes 12 and 27 degrees 

 south, longitude 130 and 155 west, forming a part of that division of the 

 world entitled Eastern Oceanica, or Polynesia. 



The particular groupe of islands to which we shall call attention, is 

 named by the natives Paumotus, literally signifying low islands, Pau in 

 the Tahitian language meaning low, and Motu an island. 



In speaking of the material of coral, to which it will be necessary con- 

 tinually to allude, we mean that hard cretaceous substance, formed by 

 myriads of minute marine animals, called saxigenous (or rock making) 

 polypiers, of which there exist an amazing variety. 



Note. — Our motive in appending the following abstracts from the published ac- 

 count of the voyage of Captain Flinders, in the form of a note, is, that although it 

 has already been often quoted, and although we diflFer from it in very many par- 

 ticulars, yet we still think it highly deserving of being perpetuated and brought for- 

 ward, as a beautiful and popular view of these highly interesting formations. 



Captain Flinders, when upon the coast of New Holland, made the following 

 observations on the formation of coral islands; speaking of those in Torres straits, 

 he says, " These islands, or banks, are in diilerent stages of progress ; some have 

 become islands, but not yet habitable ; some are above high water mark, but desti- 

 tute of vegetation ; whilst others are overflowed with every returning tide." He 

 goes on to say : — 



" It seems to me, that wjien the animalcules which form the corals at the bottom 

 of the ocean, cease to live, their structures adhere to each other, by virtue either of 

 the glutinous remains within, or of some property in salt water ; and the interstices 

 being gradually filled up with sand and broken pieces of coral washed by the sea, 

 which also adhere, a mass of rock is formed. Future races of these animals erect 

 their habitations upon the rising bank, and die in their turn to increase, but princi- 

 pally to elevate, this monument of their wonderful labours. The care taken to work 

 perpendicularly in their early stages, would mark a surprising instinct in these diminu- 

 tive creatures. Their wall of coral, for the most part in situations where the winds 

 are constant, being arrived at their surface, affords a shelter, to leeward of which 

 their infant colonies may be safely sent forth ; and to their instinctive foresight it 

 seems to be owing, that the windward side of a reef, exposed to the open sea, is 

 generally, if not always, the highest part, and rises almost perpendicular, sometimes 

 from the depth of two hundred and perhaps more fathoms. To be constantly covered 



