ON ITS EXTERIOR. VOLCANOES. 369 



place in 1821 covered the whole Island of Bourbon 

 with these glassy threads. 



In the great Terra Incognita of Madagascar, we know 

 only of the wide distribution of pumice at Tintingue, 

 opposite to the French He Sainte Marie, and basalt 

 showing itself south of the Bay of Diego Suarez, near 

 the northernmost Cap d'Ambre, surrounded by gneiss 

 and granite. The height of the southern central range 

 of the Ambohistmen mountains is estimated, probably 

 with great uncertainty, at between ten and eleven thou- 

 sand feet. To the west of Madagascar, at the northern 

 outlet of the Mozambique channel, the largest of the 

 Comoro islands has a burning volcano (Darwin, Coral 

 Eeefs, p. 122). 



The small volcanic island of St. Paul (in 38 38' S.), 

 south of Amsterdam, is called volcanic not only on 

 account of its shape which vividly recalls that of San- 

 torin, Barren island, and Deception island in the New 

 Shetland group, but also on account of the repeatedly 

 observed eruptions of fire and vapour in recent times. 

 The very characteristic drawing given by Valentyn, in 

 his work on the Banda Isles, on the occasion of the 

 expedition of Willem de Vlaming (Nov. 1696), agrees 

 perfectly, as does also the assigned latitude, with the 

 drawings in the Atlas of Lord Macartney's expedition, 

 and with Captain Blackwood's survey in 1842. The 

 crater-shaped circular bay, almost an English mile 

 broad, is every where surrounded (with the exception of 

 one narrow opening through which the sea flows in at 

 high tide) by a high rocky escarpment, having a verti- 

 cally precipitous face internally, and a gentle and 

 gradual declivity externally. ( 502 ) 

 VOL. iv. B B 



