THE SOCIETY ISLANDS. 139 



Lesson's views of the relations^hip existing between the outer coral reefs 

 and the central nucleus of volcanic islands seem to have escaped the atten- 

 tion of naturalists. He says/ speaking of the central mass of Bora Bora : 

 "Or a ce noyeau primitif et central s'adjoint une lisiere plus ou moins 

 large, tres plate, pen elevee au dessus de I'eau, qui repose sur une base 

 de corail. 



" Les isles basses, ou iMotous, qui paraissent quelquefois a une distance 

 assez notable de Vile principale, ont ete elevees indubitablement sur I'irra- 

 diation de quelques chaines du noyeau volcanique central. Jamais en effet les 

 bancs de coraux ne s'etendent au large, et toujours ils sont la dependance 

 de I'lle qu'ils entourent." 



From what precedes it is natural that Lesson should consider, as he does, 

 the passes leading into the lagoons as primordial volcanic valleys. Lesson^ 



Assembly House, .Teavanui Village, Bora Bora. 



imagines that when the submarine volcanoes do not reach the surface, corals 

 will grow on the submerged edge of the craters, the interior presenting an 

 immense lagoon. 



We may compare the reefs of Tahiti with those of Mauritius and the island 

 of Mehetia with Bourbon, both of which, having no platform of submarine 

 erosion, though in an area where corals grow in great abundance, yet are 



' Voyage autour dii Monde siir la Corvette la Co(iuille, Vol. I., par P. Lesson, Paris, 1S39. 

 '■' I.oc. cit., p. 4 76. 



