360 COSMOS. 



The lavas contain glassy feldspar, and are therefore rather 

 trachytic than basaltic. The shower of ashes frequently con- 

 tains olivin in long, fine threads, a phenomenon which like- 

 wise occurs at the volcano of Owhyhee. A violent eruption 

 of these glassy threads, covering the whole island of Bour- 

 bon, occurred in the year 1821. 



All that we know of the great neighboring terra incog- 

 nita of Madagascar is the extensive dispersion of pumice at 

 Tintingue, opposite the French island of St. Marie, and the 

 occurrence of basalt, to the south of the Bay of Diego Sua- 

 rez, near the northernmost Cap d'Ambre, surrounded by 

 granite and gneiss. The southern central ridge of the Am- 

 bohistmene Mountains is calculated (though with little cer- 

 tainty) at about 11,000 feet. Westward of Madagascar, in 

 the northern outlet of the Mozambique Channel, the largest 

 of the Comoro Islands has a burning volcano (Darwin, Coral 

 Reefs, p. 122). 



The small volcanic island of St. Paul (38 38 7 ), south of 

 Amsterdam, is considered volcanic, not only on account of 

 its form, which strongly reminds us of that of Santorin, Bar- 

 ren Island and Deception Island, in the group of the New 

 Shetland Isles ; but likewise on account of the repeatedly- 

 observed eruptions of fire and vapor in modern times. The 

 very characteristic drawing given by Valentyn in his work 

 on the Banda Islands, relative to the expedition of Willem 

 de Vlaming (November, 1696), corresponds exactly, as do 

 also the statements of the latitudes, with the representations 

 in the atlas of Macartney's expedition and Captain Black- 

 wood's survey (1842). The crater-shaped, circular bay, near- 

 ly an English mile across, is every where surrounded by pre- 

 cipitous rocks which fall perpendicularly in the interior, witli 

 the exception of a narrow opening, through which the sea 

 enters at flood-tide ; while those which form the margin of 

 the crater fall away externally, with a gentle slope.* 



The island of Amsterdam, which lies 50' of latitude far- 

 ther toward the north (37 48 X ), consists, according to Val- 

 entyn's representation, of a single, well-wooded, somewhat 

 rounded mountain, from the highest ridge of which rises a 

 small cubical rock, almost the same as at the Cofre de Pe- 

 rote, on the higher plains of Mexico. During the expedition 

 of D'Entrecasteaux (March, 1792), the island was seen for 

 two whole days entirely enveloped in flames and smoke. 



* Valentyn, Bescliryving van Oud en Nieuw Oost Indicn, Deel iii., 

 (1726), p. 70 ; Hct Eyland St. Paulo. (Compare Lyell, Pr/wc., p. 44G.) 



