368 REACTION OF THE INTERIOR OF THE EARTH 



times, as has also the still more northerly conical moun- 

 tain of the Island of Cheduba (18 52' N.), near the 

 coast of Arracan (Silliman's American Journal, vol. 38, 

 p. 385). 



The most active volcano, if the abundance of lava 

 poured forth be made the criterion, not only in the 

 Indian Ocean but almost in the whole of that part of 

 the southern hemisphere which lies between the meri- 

 dians of the west coast of New Holland and the east 

 coast of America, is the volcano of the Island of Bour- 

 bon in the group of the Mascareignes. The greater 

 part of the island, in particular the western and inland 

 portion, is basaltic. More recent basaltic dykes, poor in 

 olivine, intersect the older rock which is rich in olivine ; 

 and beds of lignite are enclosed in basalt. The culmi- 

 nating points of the mountainous island are Le Grros 

 Morne and Les Trois Salazes whose height was over- 

 estimated by Lacaille at 10,000 French feet (10,658 

 English). The volcanic activity is now confined to the 

 south-eastern part of the island, Le Grand Pays Brule. 

 The summit of the Volcano of Bourbon, which almost 

 every year sends forth, according to Hubert, two streams 

 of lava, which often reach the sea, is, according to 

 Berth's measurement, 8000 feet high.{ 501 ) It shows 

 many cones of eruption to which distinct names have 

 been given, and of which sometimes one and sometimes 

 another sends forth eruptions. The summit itself does 

 so but rarely. The lavas contain glassy felspar, and are 

 therefore trachytic rather than basaltic. The showers 

 of ashes often contain olivine in the form of long and 

 fine threads, a phenomenon which is also found in the 

 Volcano of Owyhee. A great eruption which took 



