TRUE VOLCANOES. 383 



the peninsula of Malacca, or of the Birman country to the 

 east coast of Africa, thus inclosing in its northern division 

 the Bay of Bengal and the Arabian and Red Seas. We 

 pursue the chain of volcanic activity in the Indian Ocean in 

 the direction from north-east to south-west. 



Barren Island, in the Bay of Bengal, a little to the east 

 of the great Andaman Island (lat. 12 15'), is correctly con- 

 sidered an active cone of eruption, issuing out of a crater of 

 upheaval. The sea forces its way through a narrow opening 

 and fills an internal basin. The appearance presented by 

 this island, which was discovered by Horsburgh in 1791, is 

 exceedingly instructive for the theory of the formation of 

 volcanic structures. We sec here in a complete and per- 

 manent form what nature exhibits in only a cursory way at 

 Santorin, and at other points of the earth's surface. 76 The 

 eruptions in November 1803 were, like those of Sangay in 

 the Cordilleras of Quito, very distinctly periodical, recurring 

 at intervals often minutes (Leop. von Buch in the Abhandl. 

 der Berl. Akademie, 18181819, s. 62). 



The island of Narcondam, to the north of Barren Island, 

 has likewise exhibited volcanic action at a former period, as 

 has also the cone-mountain of the island of Cheduba, which 

 lies more to the north, near the shore of Arracan (10 52'). 

 (Silliman's American Journal, vol. xxxviii, p. 385). 



The most active volcano, judging from the frequency of 

 the lava-eruptions, not only in the Indian Ocean but in 

 almost the whole of the south hemisphere between the meri- 

 dians of the west coast of New Holland and the east coast 

 of America, is that on the island of Bourbon in the group 

 of the Mascareignes. The greater part of the island, parti- 

 cularly the western portion and the interior, is basaltic. 

 Recent veins of basalt, with little admixture of olivine, run 

 through the older rock, which abounds in olivine ; beds of 

 lignite are also enclosed in the basalt. The culminating 

 points of the Mountain Island are the Gros Mornr and the 

 Trois Salazes, the height of which La Caille over-estimated 

 at 10,658. The volcanic action is now limited to the southern- 

 most portion, the " Grand pays brule." The summit of the 



7 fi Leop. v. Buch, in the Abhandl. der Akad. der Wiss. zu Berlin, 

 1818 and 1819, s. 62; Lyell, Princ. of Geology. (1853), p. 447, where a 

 fine representation of the volcano is given. 



