TRUE VOLCANOES. 373 



Leopold von Bach, ami with Flores and Graciosa, according 

 to Count Bedemar. It is this absence of volcanic action in 

 New Caledonia, where sedimentary formations with scams 

 of coal have lately been discovered, that the great develop- 

 ment of living coral reefs on its shores is ascribed. The 

 Archipelago of the Viti, or Fcejee Islands, is at once basaltic 

 and trachytic, though distinguished only by hot springs in 

 the Savu Bay on Vanua Lebu.* The Samoa group (Navi- 

 gator's Islands), northeast of the Fecjee Islands, and nearly 

 north of the still active Tonga Archipelago, is likewise ba- 

 saltic, and is moreover characterized by a countless number 

 of eruption craters linearly arranged, which are surrounded 

 by tufa-beds with pieces of coral baked into them. The Peak 

 of Tafua, on the island of Upolu, one of the Samoa group, 

 presents a remarkable degree of geognostic interest. It must 

 not, however, be confounded with the still enkindled Peak of 

 Tafua, south of Amargura, in the Tonga Archipelago. The 

 Peak of Tafua (2138 feet), which Dana first f ascended and 

 measured, has a large crater entirely filled with a thick for- 

 est, and crowned by a regularly rounded ash-cone. There is 

 here no trace of any stream of lava ; yet on the conical mount- 

 ain of Apia (2576 feet), which is likewise on Upolu, as well 

 as on the Peak of Fao (3197 feet), we meet with fields of 

 scoriaceous lava (Malpais of the Spaniards), the surface of 

 which is, as it were, crimped, and often twisted like a rope. 

 The lava-fields of Apia contain narrow subterranean cavities. 

 Tahiti, in the centre of the Society Islands, far more tra- 

 chytic than basaltic, exhibits, strictly speaking, only the ruins 

 of its former volcanic frame-work, and it is difficult to trace 

 the original form of the volcano in those enormous masses, 

 looking like ramparts and chevaux-de-frise, with perpendicu- 

 lar precipices of several thousand feet in depth. Of its two 

 highest summits, Aorai and Orohena, the former was first 

 ascended and investigated by that profound geologist Dana. J 

 The trachytic mountain, Orohena, is said to equal -ZEtna in 

 height. Thus, next to the active group of the Sandwich Isl- 

 ands, Tahiti contains the highest rock of eruption in the 

 whole range of the ocean between the continents of America 



Plutonic and sedimentary strata. But these rocks may have made 

 their appearance above the surface of the sea on the first volcanic up- 

 heaval of the island from the bed of the ocean. No traces are said to 

 have been found of fiery eruptions or of extinct volcanoes. 



* Dana, p. 313-3*0. t Dana, p. 312, 318, 320, and 323. 



X Leop. von Buch, p. 383 ; Darwin, Vole. is/., p. 25 ; Darwin, Coral 

 Reefs, p. 13,8 ; Dana, p. 28G-305 and 3G4. 



